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1
Hill, Andrew Jason. "Monitoring and modeling the hydrology of a forested sinkhole wetland on the Tennessee Highland Rim : a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online version, 2007. http://proquest.umi.com/pqdweb?index=77&did=1445039661&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1255094472&clientId=28564.
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Rawal, Kishor. "Exploring the Geomechanics of Sinkholes: A Preliminary Numerical Study." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1480069621108946.
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Khadka, Suraj. "A Numerical Study of the Coupled Geomechanical Processes in Sinkholes." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1532970968316002.
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4
Gooch, Bradley Tyler. "Improving Ground Penetrating Radar Resolution of Features of Active Sinkholes." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1646.
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Ground penetrating radar (GPR) is widely used to identify locations of sinkholes in covered karst terrain in Florida. Some sinkholes serve as hydraulic conduits between the surficial and underlying aquifers. Their role is critical in determining the surficial aquifer response to pumping in deeper aquifers. Improved methods for discriminating between hydraulically active sinkholes and plugged sinkholes could help regional water management. In the covered karst of west-central Florida a clay-rich weathering horizon forms over the limestone. The clay-rich layer is in turn overlain by surficial sands. Ground penetrating radar profiles typically show a strong reflector from the top of clay-rich horizon as well as internal layering within sands. Active sinkholes are expected to have sandy conduits that broach the clay layer, and perhaps layering in the overlying sand indicative of ongoing subsidence. Three dimensional simulations of GPR profiles over sinkhole with and without conduits were run with the finite-difference time-domain (FDTD) program GPRMAX. Results from the synthetic surveys were then processed with standard techniques, including migration. The modeling confirms that conduits appear in GPR records primarily as gaps in the return from the clay layer. The modeling also shows that non-traditional survey geometries (varying antenna spacing and orientation) are unlikely to recover more information than traditional proximal transmitter-receiver separation. Also examined are GPR profiles and 3D grids over a set of active and inactive sinkholes in Tampa, Florida. Results from these surveys showed decent structural recovery of a small sinkhole similar in structure to that of the modeled ones. Indications of active subsidence and possible conduit structure were apparent from this data. Finally, the dense surveys served as a benchmark to compare interpretations taken with the same surveys at lower spatial resolutions and profiles with 2D-only processing methods in order to understand errors in analysis and interpretation that are possible from 2D surveys. Two-dimensional surveys, 2D processed and migrated, showed some similarity to the 3D results previously mentioned but contained more complexities and artifacts, which led to poorer interpretation ability.
5
Avutia, Daniel John. "Analytical and numerical study of dolomite sinkholes in Centurion South Africa." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9076.
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Includes bibliographical references.Sinkholes encompass the withdrawal of shallow sediment into deep hollow compartments located in karstic stratum. These subsequent surface openings associated with karst geology have inhibited multiple infrastructure developments. Sinkholes are triggered by the alteration of the existing groundwater level which erodes weathered altered dolomite (WAD) residuum into karst cavities. Substantial literature has explored the stability of sinkholes, with reliance on limit analysis and empirical data, to quantify the strength of the porous karst residuum. In this study, the appraisal of sinkhole propagation was facilitated with the geological data acquired along the Gautrain route through Centurion, South Africa. Sinkhole development was analysed through analytical theories and the application of numerical methods. The analytical study conceptualized the ‘angle of draw’ of dolomite overburden layers into cavities, with Terzaghi’s arching in soil equation. The analytical results illustrated constant vertical drawdown in the WAD and incremental cavity propagation in the frictional chert residuum.
6
Stocks, Lee. "A spatio-temporal analysis of land use and land cover change and sinkhole development in Opequon Creek Watershed, West Virginia 1984-2009 /." [Kent, Ohio] : Kent State University, 2010. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1271287859.
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D'andrea, Joy Marie. "A Statistical Analysis of Hurricanes in the Atlantic Basin and Sinkholes in Florida." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6077.
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Beaches can provide a natural barrier between the ocean and inland communities, ecosystems, and resources. These environments can move and change in response to winds, waves, and currents. When a hurricane occurs, these changes can be rather large and possibly catastrophic. The high waves and storm surge act together to erode beaches and inundate low-lying lands, putting inland communities at risk. There are thousands of buoys in the Atlantic Basin that record and update data to help predict climate conditions in the state of Florida. The data that was compiled and used into a larger data set came from two different sources. First, the hurricane data for the years 1992 – 2014 came from Unisys Weather site (Atlantic Basin Hurricanes data, last 40 years) and the buoy data has been available from the national buoy center. Using various statistical methods, we will analyze the probability of a storm being present, given conditions at the buoy; determine the probability of a storm being present categorically. There are four different types of sinkholes that exist in Florida and they are: Collapse Sinkholes, Solution Sinkholes, Alluvial Sinkholes, and Raveling Sinkholes. In Florida there are sinkholes that occur, because of the different soil types that are prevalent in certain areas. The data that was used in this study came from the Florida Department of Environmental Protection, Subsidence Incident Reports. The size of the data was 926 with 15 variables. We will present a statistical analysis of a sinkholes length and width relationship, determine the average size of the diameter of a sinkhole, discuss the relationship of sinkhole size depending upon their soil types, and acknowledge the best probable occurrence of when a sinkhole occurs. There will be five research chapters in this dissertation. In Chapter 2, the concept of Exploratory Factor Analysis and Non-Response Analysis will be introduced, in accordance of analyzing hurricanes. Chapter 3 will also address the topic of hurricanes that have formed from the Atlantic Basin from 1992 – 2014. The discussion of the probability of a storm being present (also categorically) will be addressed. In Chapter 4 a study of sinkholes in Florida will be addressed. In Chapter 5 we will continue our discussion on sinkholes in Florida, but focus on the time to event between the occurrences of the sinkholes. In the last chapter, Chapter 6, we will conclude with a future works and projects that can be created from the foundations of this dissertation.
8
D'Andrea, Joy. "A Statistical Analysis of Hurricanes in the Atlantic Basin & Sinkholes in Florida." Thesis, University of South Florida, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10103862.
Full textAbstract:
Beaches can provide a natural barrier between the ocean and inland communities, ecosystems, and resources. These environments can move and change in response to winds, waves, and currents. When a hurricane occurs, these changes can be rather large and possibly catastrophic. The high waves and storm surge act together to erode beaches and inundate low-lying lands, putting inland communities at risk. There are thousands of buoys in the Atlantic Basin that record and update data to help predict climate conditions in the state of Florida. The data that was compiled and used into a larger data set came from two different sources. First, the hurricane data for the years 1992–2014 came from Unisys Weather site (Atlantic Basin Hurricanes data, last 40 years) and the buoy data has been available from the national buoy center. Using various statistical methods, we will analyze the probability of a storm being present, given conditions at the buoy; determine the probability of a storm being present categorically. There are four different types of sinkholes that exist in Florida and they are: Collapse Sinkholes, Solution Sinkholes, Alluvial Sinkholes, and Raveling Sinkholes. In Florida there are sinkholes that occur, because of the different soil types that are prevalent in certain areas. The data that was used in this study came from the Florida Department of Environmental Protection, Subsidence Incident Reports. The size of the data was 926 with 15 variables. We will present a statistical analysis of a sinkholes length and width relationship, determine the average size of the diameter of a sinkhole, discuss the relationship of sinkhole size depending upon their soil types, and acknowledge the best probable occurrence of when a sinkhole occurs. There will be five research chapters in this dissertation. In Chapter 2, the concept of Exploratory Factor Analysis and Non-Response Analysis will be introduced, in accordance of analyzing hurricanes. Chapter 3 will also address the topic of hurricanes that have formed from the Atlantic Basin from 1992–2014. The discussion of the probability of a storm being present (also categorically) will be addressed. In Chapter 4 a study of sinkholes in Florida will be addressed. In Chapter 5 we will continue our discussion on sinkholes in Florida, but focus on the time to event between the occurrences of the sinkholes. In the last chapter, Chapter 6, we will conclude with a future works and projects that can be created from the foundations of this dissertation.
9
Koby, Peter J. "Spatial Analysis of Ancient Maya Settlement Near Karst Sinkholes at Xuenkal, Yucatan, Mexico." Kent State University Honors College / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1335809783.
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10
Mehrotra, Neeta. "An automated method for locating sinkholes in Montgomery County, Virginia, using digital elevation models." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-08222009-040435/.
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Marinuzzi, Natalie Romina. "LOCATION OF SINKHOLE CONFINING BREACH USING GROUNDWATER FLOW PATTERNS DERIVED FROM CONE PENETRATION TESTING." Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4442.
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Dynamic forces in the hydrologic cycle move underground water through Florida's carbonate rocks dissolving chemical components of the rocks, leaving behind caves, solution pipes, and other voids that result in a karst terrain. Ravelling is the common subsidence mechanism throughout most of Florida where unconsolidated materials filter downward into voids in the underlying limestone. A cavity in the overburden develops and enlarges over a period of many years. The enlarged cavity is also known as sinkhole. The investigations of sinkhole characteristics and potential involve studying the regional geology, hydrology and mapping historic sinkholes that have occurred in the area. Use of Cone Penetration Test (CPT) soundings, in conjunction with conventional soil borings are becoming more common in the assessment of subsurface soil conditions in the vicinity of sinkhole-related ground surface. The penetration resistance data by CPT can determine the presence and extent of raveled soil zones characteristic of sinkhole features, and the penetration pore water pressure data can be used to determine the integrity of the clay confining unit at each test sounding location. The objective of this study is to identify the possible location of the confining breach at a sinkhole in Seminole County. The methods used in the assessment of the sinkhole's subsurface conditions were Standard Penetration Test (SPT), which provided information that helped to identify the location of the ravelled zones within the soil profile, and Cone Penetration Test that gave information of the piezometric water levels obtained from the pore pressure dissipation curves. The total head was calculated from the piezometric water levels corresponding to the different elevations. The data were found to exhibit a downward behavior of the total head, starting at around elevation 50 feet, NGVD that extended towards lower elevations. The SPT boring log identified a ravelled zone starting at 31 feet approximately. From both information it was possible to establish that the hydraulic head was influenced by the proximity of the ravelled zones, where the head precipitated rapidly as the elevation decreased. From the result of this study, it was concluded that the location of the breach in the confining layer started at 61.8 feet deep below the ground surface. Potentiometric contour lines at elevation 24.40 feet denoted flow patterns of water from the surroundings of the depression towards the approximate location of the center, which is the existing of subsurface cavity.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil and Environmental Engineering
12
Dinsmore, Michael A. "Origin and Evolution of Sinkholes on the Bellevue-Castalia Karst Plain, North-Central Ohio." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1320933862.
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13
Fasesin, Kingsley. "Improving Sinkhole Mapping Using LiDAR Data and Locating Sinkhole Hotspots in Johnson City, TN." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etd/3511.
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Predicting infrastructure damage and economic impact of sinkholes requires high accuracy mapping distribution and development. The study mapped sinkholes and sinkhole hotpsots in Johnson City, TN using LiDAR-derived Digital Elevation Model (DEM) and a database of known sinkholes which were matched to LiDAR-derived depressions. For all matched depressions (n = 404), three metrics were calculated: circularity index, ratio of length to width of the Minimum Bounding Rectangle (MBR) and percent coverage of the MBR by the depression, and 3,634 new sinkholes were identified. Newly developed hotspots were identified in north Johnson City and other areas in the south near the Johnson City Medical Center. The methodology developed can be applied to identify hotspots in other small metropolitan cities and the hotspot map produced can be employed in hazard mitigation planning, resource allocation, and made available publicly to property owners and insurance companies.
14
Warren, Rachel H. Pauline. "Modifying Ohio’s DRASTIC ground water potential pollution model to account for karst limestone voids and sinkholes." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1556987810146683.
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15
Bumpus, Peter B. "Self-Potential Response to Rainfall Changes Over Plugged and Unplugged Sinkholes in a Covered-Karst Terrain." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1581.
Full textAbstract:
For the protection of wetland and water resources it would be beneficial to understand when collapse conduits function as recharge points to the underlying aquifer. Inexpensive, noninvasive methods to detect recharge are desirable. Previous studies show negative self-potential (SP) anomalies over sinkholes that correspond to the expected electrokinetic effects of groundwater flowing downward through a conduit. SP surveys are less labor-intensive than high-resolution 3D GPR and resistivity, and continuous long-term monitoring is possible. However, before SP surveys can be reliable indicators of flow, SP contributions from ET, conductivity changes, redox reactions, thermoelectric effects, cultural noise, and lateral flow must be understood. A year of continuous SP monitoring was combined with high-resolution 3-D GPR surveys, and intermittent water table monitoring over two small covered-karst sinkholes in Tampa, Florida. Positive and negative SP anomalies episodically manifested over conduits, suggesting that conduit flow is dynamic, not static. Three distinct SP flow regimes in the conduits are postulated: fast flow open to the aquifer, slow flow open to the confining layer through the collapse conduit walls, and a conduit, plugged high enough to behave like the rest of the confining layer. SP responses after rain events also appear to measure the effects of two moving Gaussian wetting front curves, one striking the monitoring electrode, one the reference. viii The wetting front volumes are differently dispersed by traveling different distances. By comparing curve shapes for all possible pairs of electrodes, it may be possible to establish surficial infiltration and flow patterns.
Temporal SP response clearly shows SP is also affected by soil conductivity, rainfall history, and cultural noise. Ultimately, SP changes too frequently to rely on measurements many hours or days apart. Over the course of the year, the electrodes became less responsive to rainfall and more erratic. Extremely wet and dry conditions seemed to affect responses. The porous faces of the electrodes or the bentonite clay gel used to enhance contact may decline. It appears a better design for electrodes and electrode contact needs to be developed.
To test the intermittent behavior hypothesis, more conduits need to be studied, and moisture and SP must be studied concurrently. Several reference electrodes placed in various topographic, vegetative, geologic, and climatic settings could help distinguish groundwater flow from other SP sources. SP is a valuable research tool; however external complexities such as cultural noise, sinkhole lithology, and the state of the unsaturated zone make SP data difficult to interpret without ancillary information.
16
Save, Neelambari R. "Ground penetrating radar technique to locate coal mining related features: case studies in Texas." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3204.
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The goal of this research project is to identify the efficacy of the ground
penetrating radar (GPR) technique in locating underground coal mine related subsidence
features at Malakoff and Bastrop, Texas. The work at Malakoff has been done in
collaboration with the Railroad Commission of Texas (RRC). RRC has been carrying
out reclamation of abandoned underground coal mines at Malakoff since the early
1990Âs. The history of the specific mining operations (at Malakoff and Bastrop) that
took place in the early 1900Âs has been difficult to ascertain; therefore, the use of a
geophysical techniques like ground penetrating radar to identify hidden voids and
potential subsidence features is vital for future reclamation process. Some of the
underground mine workings at the field site have collapsed over time affecting the
topography by creating sinkholes. GPR data, employing 25 MHz, 50 MHz and 100
MHz frequency antennae, have been collected in common offset patterns and azimuthal
pattern. GPR data indicate the mine tunnels possibly connecting existing sinkholes by
radargram hyperbolae that correspond with mine openings observed visually or during
reclamation. This study also denotes the importance of understanding the variable
physical properties of the stratigraphy, which could lead to false alarms by
misinterpretation of the radar signals. Natural and man-made above-ground structures
cause obstructions in data collection, and hence an optimal design is required for each
survey. RRC successfully ground-truthed the data during its reclamation process. In
turn, the acquired geophysical data helped to guide the reclamation. At Bastrop, GPR
data along with historical documentation led to the conclusion that coal mining did exist
in this region but is not a major concern to the immediate stability and safety of the field
site. It can be concluded from both the studies that the GPR technique identifies
anomalous shafts/tunnels possibly connecting potential failure.
17
Yactayo, Guido Andres. "Modification of the SWAT Model to Simulate Hydrologic Processes in a Karst-influenced Watershed." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34807.
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In the United States, karst ecosystems cover approximately 20 percent of the country and karst aquifers provide 40 percent of the water used for drinking. In karst-influenced watersheds, karst features such as sinkholes and sinking streams act as rapid pathways for carrying water and pollutants into streams and groundwater. Human activities on karst landscapes can present some special problems such as alterations to hydrologic regime, contamination of groundwater, ground subsidence, and damage to cave ecosystems. Modeling a karst-influenced watershed can provide a better understanding of the interactions between surface and ground water and how water quality is affected by human activities.
Several models were evaluated to determine their ability to model both discharge and nutrient transport in karst watersheds. The Soil Water Assessment Tool (SWAT) model was found to be appropriate due to its capability to represent almost all of the hydrological processes, its user-friendliness, and its ability to generate most of the parameters from available data. Moreover, SWAT can represent nitrogen transformations and transport processes and calculate nitrogen loadings, which is critical for karst watersheds. While it has been widely used and found to be an appropriate prediction tool, it does not explicitly include the capacity to represent specific features characteristic of karst-influenced basins. Baffaut and Benson (2008) modified the SWAT 2005 code to simulate faster aquifer recharge in karst environments, and this version was further modified here in the SWAT-Karst to represent karst environments at the HRU scale. A new parameter sink allows simulating the hydrology and nitrate transport in a sinkhole representing its unique landuse and soil characteristics, and a new parameter ss partitions nitrate transported with water that is lost from sinking streams.
The SWAT-KARST model was used to simulate discharge and nitrogen loadings within the Opequon Creek karst-influenced watershed, located in the Potomac and Shenandoah River basin in Virginia and West Virginia. In the Opequon Creek watershed, SWAT-karst using the HRU to represent sinkholes had a more notable impact in the watershed hydrology than SWAT-B&B using a pond to represent sinkholes.
Results of statistical evaluation show that SWAT-karst and the Baffaut and Benson (2008) version performed better than SWAT in predicting streamflow in a karst-influenced watershed. Although SWAT-karst showed almost the same performance as SWAT-B&B, SWAT-karst model offers the flexibility to represent the unique relationship between surface and ground water in karst features in an HRU.
Using an HRU to represent sinkholes can depict the associated variability of a karst landscape. The new variables sink and ss provide a mechanism to represent the nutrient transport through sinkholes and sinking streams. Sensitivity analysis showed that SWAT-karst was sensitive to the new parameter sink which can be used for model calibration and to represent water recharge and nutrient transport to aquifers outside the watershed boundary.Master of Science
18
Pattumma, Klairoong. "VEGETATION STRUCTURE, LIGHT AVAILABILITY, AND SEDIMENT DEPOSITION WITHIN SINKHOLE BUFFERS ASSOCIATED WITH TRACKED AND WHEELED VEHICLE TRAINING AT FORT KNOX, KENTUCKY." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/691.
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Heavy wheeled and tracked vehicle training has been conducted on portions of the landscape of Fort Knox, Kentucky for approximately 60 years. Fort Knox is located on the Kentucky Karst Plain and sinkholes are dominant features of this area. Sinkholes and karst terrain present an atypical problem in combination with this unique land use, potentially impacting downstream and local terrestrial environment. A study of the training area sinkhole complex was conducted as a first step toward mitigating the impact of military activities and reduces potential problems of sedimentation and water quality degradation. A total of 20 sinkholes within Training Areas 9 and 10 at the Fort Knox Military Reservation were randomly selected to represent the study area. The objective of this study was to determine the relationship between stand structural characteristics, understory light availability and understory vegetation in sinkhole riparian buffers and concentrated flow paths and with the amount of sediment entering sinkholes in the study area. Vegetation data were collected during the growing months of May and June in 2009. All regressions analyses for vegetative structures have r2 values between 0.000 to 0.308 indicating weak to no correlation among the variables. Light availability and percent herbaceous cover showed moderate and weak relationship in buffers (r = 0.547, p = 0.003) and flow paths (r = 0.164, p = 0.245). Sediment gained in splay areas showed no significant relationship to vegetation structure (r = 0.039 to -0.335). The relationship between sediment gained and mean percent herbaceous cover was not significant in flow paths (r = -0.172, p = 0.2341) or buffers (r = 0.130, p = 0.292). While the results of this study suggest the amount of the sediment depositing in the sinkholes was unrelated to observe variation in sinkhole vegetation, the relationship between overstory vegetation and understory vegetation within sinkholes was more noticeable. On site observations strongly suggest that concentrated flow paths were the primary conduits for sedimentation into splay areas. Therefore, management considerations pertaining to training areas should minimize flow paths leading to sinkholes. Best management practices for Fort Knox training areas should integrate these research findings, in addition to current knowledge of riparian buffers and training areas' management requirements.
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MacSwiney, GonzaÌlez MariÌa Cristina. "Ecology and conservation of bat assemblages associated with water-filled sinkholes (cenotes) in the Yucatan Peninsula, Mexico." Thesis, University of Aberdeen, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485386.
Full textAbstract:
In the Yucatan, cenotes or water-filled sinkholes fonned by the dissolution of limestone and surrounded by a characteristic dense layer ofheterogeneous vegetation, are the main sources of water for humans and animal assemblages. I investigated the importance of cenotes and their surrounding vegetation for bats by comparing the assemblage structure and diversity between forest and pastureland, with and without cenotes. I set ground level mist nets, sub-can.6py nets and harp traps and recorded the ultrasonic calls of flying bats for 96 nights in 2003-2005. Capture and acoustic methods recorded a total of 37 species in six families. Accumulation curves demonstrated that I sampled most of the species likely to be recorded. Forest sites had a greater bat species diversity and abundance than pastureland, as well as more rare and threatened species. Forest sites with and without cenotes had a similar bat assemblage structure and diversity, whereas in pastureland there was a greater species diversity and abundance and number of rare and threatened species at cenotes than at sites without cenotes. Cenotes in the pastureland landscape attracted an abundance of frugivores which fed on 27 plant species from 13 families. In addition, the highest number of passes and feeding buzzes of insectivorous bats was recorded at cenotes in pastureland. One species, Pteronotus personatus, represented a new record for the Yucatan bat fauna. Chrotopterus auritus and Micronycteris schmidtorum, both of which are listed by the Mexican government as threatened species, together with Eptesicus furinalis, Eumops underwoodi and P. personatus, were recorded only at cenotes. In Yucatan's agricultural landscapes, protection of cenotes and their characteristic vegetation is, essential not only for the conservation of bat diversity but also because they represent potential seed sources for the regeneration of the lowland forest, in which bats play key roles as pollinators and seed dispersers. Key words: Chiroptera, deforestation, echolocation, forest, frugivorous bats, insectivorous bats, habitat use, pastureland, pollination, seed dispersal, water resources.
20
Kleinhans, Ilse. "Rehabilitation of sinkholes and subsidences on Dolomitic Land Ekurhuleni Metropolitan Municipal Area of Jurisdiction Gauteng South Africa." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/63306.
Full textAbstract:
Extensive research has been done on the investigation, evaluation, development and
management of land underlain by dolomite to prevent the formation of sinkholes and subsidences.
Little emphasis is, however, given to the various processes and methodologies with respect to
the investigation and rehabilitation of sinkholes or subsidences.
In South Africa most sinkholes and subsidences have been recorded on dolomite of the Malmani
Subgroup of the Chuniespoort Group on the Far West Rand and in an area south of Pretoria
within the City of Tshwane, with numerous studies done on the occurrence of sinkholes and
subsidences in these two areas. However, a large number of sinkholes and subsidences have
also been recorded on the East Rand in the Ekurhuleni Metropolitan Municipal area, which is the
focus of this research.
Very little is published on the occurrence of sinkholes and subsidences, the related geological
models, investigations and rehabilitation work done in the Ekurhuleni Metropolitan Municipal area.
It has been attempted with this thesis to document the various processes and methodologies
applicable to the investigation and rehabilitation of dolomite-related sinkholes and subsidences
within a non-dewatering environment. This is based on experience gained during the investigation
and rehabilitation of various sinkholes and subsidences within the Ekurhuleni Metropolitan
Municipal area on the East Rand, over the past ten years.
Various methods of investigation, including non-intrusive and intrusive methods have been tried
and tested to determine the extent of subsurface erosion within an affected sinkhole or
subsidence area. The gravity geophysical method in association with the drilling of percussion
boreholes; exposure of the affected area by means of excavation and the use of the Dynamic
Probe Super Heavy (DPSH) method, in areas not accessible for a drilling rig where gravel,
cobbles and boulders are absent in the subsurface profile; is the most appropriate methods for
sinkhole or subsidence investigations on the East Rand. The gravity method is, however, not
always successful in delineating narrow grykes in a shallow dolomite environment. The use of a
specific method or methods of investigation is prescribed by the accessibility of a site. Accessibility
constraints within a build-up area, may lead to the use of an investigation method other than what
is generally preferred.
The specific method or combination of methods used to rehabilitate a sinkhole or subsidence will
depend on the available funds, current and proposed land use, subsurface conditions,
accessibility constraints caused by existing infrastructure for equipment and the impact of the
rehabilitation procedure on existing infrastructure.
The various sinkhole and subsidence rehabilitation methods used on dolomite in South Africa and
their applications are discussed, including: the Inverted Filter Method, Dynamic Compaction
Method, combination of the Inverted Filter and Dynamic Compaction Methods, Compaction
(backfill) Grouting Method, Combination of the Inverted Filter and Compaction Grouting Methods, Combination of the Dynamic Compaction and Compaction Grouting Methods and the use of Self-
Compacting Concrete or Soil-cement Mix.
Nearly half of the Ekurhuleni Metropolitan Municipal area is classified as dolomite land. A total of
241 ground movement incidents had been recorded, since 2005 to mid-2013. The Ekurhuleni
Metropolitan Municipal area of jurisdiction is divided into three regional areas, namely:
Southern Regional area: More than 50% of the region is directly underlain by dolomite and
chert of the Monte Christo Formation of the Malmani Subgroup of the Chuniespoort Group.
A total of 141 ground movement incidents had been recorded, with all dolomite-related
sinkholes and subsidences caused by ingress of water. Approximately 85% were caused by
sewer lines, 7% by leaking water lines and valves, 4% by surface water ponding and 3% by
concrete stormwater lines.
Northern Regional area: The northern portion of the region is directly underlain by dolomite
of the Malmani Subgroup; from west to east by, chert-poor dolomite of the Oaktree
Formation, chert-rich dolomite of the Monte Christo Formation, chert-poor dolomite of the
Lyttelton Formation and chert-rich dolomite of the Eccles Formation. Dolomite of the Monte
Christo Formation is also encountered in the south-eastern portion of the region. A total of
83 ground movement incidents had been recorded. Ground movement incidents are related
to both ingress of water and dewatering of dolomite groundwater compartments including the
Bapsfontein, Elandsfontein and Sterkfontein-East Dolomite Groundwater Compartments and
Sub-Compartment.
Eastern Regional area: More than 50% of the region is regarded as dolomite land, with large
portions of dolomite of the Monte Christo Formation and the Oaktree Formation of the
Malmani Subgroup covered by the Karoo Supergroup. Dolomite of the Monte Christo
Formation also occurs in the south-western portion of the regional area. A total of 17 ground
movement incidents had been recorded. None of the recorded ground movement incidents
are, however, related to dolomite. Incidents are related to poorely backfilled old wet services,
natural erosion of subsurface soils, collapse of shallow coal workings and collapse of mine
shafts and ventilation shafts.
The sinkhole and subsidence rehabilitation method mostly used in the Ekurhuleni Metropolitan
Municipal area is the Inverted Filter Method accounting for 85% of rehabilitation work, 10% for
compaction grouting and 5% for the use of the Dynamic Compaction Method.
The sinkhole and subsidence rehabilitation method should not be prescriptive, given the vast
number of variables involved. A comprehensive understanding of the affected area is essential
although for cost effective and practical rehabilitation measures.
A site specific set of criteria for the rehabilitation of the features and affected infrastructure must
be developed to ensure proper stabilisation and safe future use of the area. Basic principles can
however be applied to each sinkhole or subsidence, such as: Ensuring the trigger of the sinkhole
or subsidence has been identified and removed; the position and extent of the receptacles have
been determined as best as possible and erosion paths sealed; the known eroded area, possible voids and cavities properly backfilled and densified; a proper impervious or engineer designed
earth mattress created; ensuring that all affected subsurface wet services are replaced and
comply with industry standards; and that proper surface drainage exists.Thesis (PhD)--University of Pretoria, 2017.
Geology
PhD
Unrestricted
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Zerkel, Brent Matthew. "GEOPHYSICAL RECONNAISSANCE OF KARST FEATURES ASSOCIATED WITH SINKHOLES ON THE ANTIOCH UNIVERSITY CAMPUS IN YELLOW SPRINGS, OHIO: WESTERN AREA." Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1186020252.
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Schwartz, Benjamin Farley. "Hydrogeophysical quantification of infiltration and recharge through soil-filled sinkholes using Time Domain Reflectometry and Electrical Resistivity Tomography." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29748.
Full textAbstract:
This dissertation presents the results of a detailed physical and hydrogeophysical study of two soil-filled sinkholes mantled by ancient New River fluvial terrace deposits. Research was performed at the Virginia Tech Kentland Experimental Farms in Whitethorne, Virginia, USA between fall 2003 and spring 2007, and focused on characterizing infiltration, deep drainage, and recharge through soil-filled sinkholes. Using hydrogeophysical methods, the spatial and temporal distribution of soil moisture was modeled and potential recharge was quantified in two soil-filled sinkholes.
Access-tube time domain reflectometry (TDR) was used to derive one-dimensional (1-D) soil moisture profiles. During access-tube installation, 470 soil samples were obtained from depths between 0.3 and to 9.0 m and characterized both physically and chemically. Using these data, a TDR calibration method was developed. Physio-chemical, TDR moisture, and 1-D electrical resistivity tomography (ERT) data were used to derive a numerically optimized form of Archieâ s Law which was used to convert ERT measurements into volumetric soil moisture. These results led to development of 2-D ERT-derived distributions of soil moisture in three transects across the two sinkholes in two terraces. Potential recharge was quantified using time-series ERT data with comparison to modeled cumulative potential evapotranspiration (PET) and cumulative precipitation between May 17 and October 9, 2006. The patterns of ERT-derived potential recharge values compared well with those expected from PET and precipitation data. Over the monitoring period from late spring to early fall during this study, results showed that a period of intense rain followed by a 31-day period of consistent rain, in which the rate of precipitation was equal to or exceeded PET, were the only periods in which significant amounts of potential recharge occurred (from 19 to 31% of cumulative precipitation during the study). Spatial distributions of ERT-derived moisture clearly revealed that significant amounts of infiltration occurred on sinkhole flanks and bottoms. Runoff during periods of intense rain flowed to the topographically lowest point in the sinkholes where it infiltrated and resulted in localized zones of enhanced infiltration and potential recharge to the water table.Ph. D.
23
Huang, Hsin-Hui 1976. "Geomorphologic investigations on karst terrain : a GIS-assisted case study on the island of Barbados." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101144.
Full textAbstract:
Maintaining a safe water supply is particularly crucial for karst islands such as Barbados. In order to take proper measures to prevent and reduce saltwater intrusion and to safely extract the right fraction of recharge, karst characteristics must first be fully understood. Geomorphologic investigations of karst surface features of the Porters & Trents groundwater catchments (Barbados) employed GIS technologies to explore the development and distribution of sinkhole features. Contour-based digital elevation models, surface geology, lithology, and remote sensing images were incorporated in this investigation. Seventy-six sinkholes were investigated and occupied approximately 1% (0.16 km2) of the total area (16.41 km2) under study. It was found that age of karstification is not related to age of a terrace. The middle terrace was the one found to be most karstified. Yet, degree of karstification within a terrace is age related. Also, cluster density increases with age of coral within the middle terrace. Density of sinkholes within a cluster also increases with age of coral within the middle terrace.Finally, this study shows that sinkhole long axis, cluster elongation direction, sinkhole alignment and karst lineament all have a tendency to a northeast alignment. This supports the idea that underlying coral rock fracture and conduits have a northeast orientation.
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Julio, Amdan Abelardo Andrés. "Modelación Numérica de Erosión Interna de Suelos." Tesis, Universidad de Chile, 2012. http://repositorio.uchile.cl/handle/2250/102749.
Full textAbstract:
El estudio se enmarca en un análisis numérico orientado a determinar la distribución de
tensiones efectivas que se generan en un medio poroso cuando el gradiente hidráulico
se aproxima al gradiente hidráulico crítico, condición que gatilla la migración de finos en
medios porosos de estructura inestable. Este fenómeno ha sido crítico en los suelos de
transición y núcleo pertenecientes a la presa W.A.C. Bennet, la cual presentó serias
anomalías con manifestaciones de “sinkholes” en varios puntos del coronamiento, luego
de 30 años de funcionamiento.
Para estos efectos, se ha desarrollado un modelo numérico que utiliza el programa
computacional que resuelve las ecuaciones de un medio continuo vía diferencias finitas,
para reproducir las trayectorias de esfuerzos verticales obtenidas en probetas de suelos
durante la etapa de flujo, i.e., los ensayos efectuados en el permeámetro de grandes
dimensiones del laboratorio de UBC. Un aspecto relevante que requiere la solución del
fenómeno, se refiere a modelar la pérdida de esfuerzos verticales en el suelo, producto
del roce generado en el contacto suelo – permeámetro.
Se contempla la implementación de dos alternativas que permiten evaluar por separado
dicha pérdida. Éstas corresponden a una interfaz, con propiedades de fricción y rigidez
y a la distribución del módulo de deformación, expresada en función del nivel de
confinamiento del suelo. La primera solución establece que la interfaz es capaz de
provocar la pérdida de los esfuerzos verticales, independiente del módulo de
deformación del suelo utilizado. La segunda, que no usa interfaz, requiere del ajuste del
parámetro que controla la expansión lateral en el modelo (Modulo de Poisson), en
cuanto permite que el suelo se “cuelgue” de las paredes del permeámetro para provocar
la pérdida deseada. Debido a que ambas aproximaciones corresponden a diferentes
formas de modelar el mismo problema, se establece que la mejor solución corresponde
a la alternativa que considera la distribución del módulo de deformación en la probeta.
El presente estudio incluye conceptos como línea de falla hidromecánica que, en
definitiva, entrega el marco geotécnico requerido para generar una solución que se
aproxime al problema de inestabilidad interna, por lo que el programa computacional
desarrollado en esta tesis es una útil herramienta práctica en el análisis de estabilidad
interna de presas de tierra.
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Hyland, Sara Elizabeth. "Analysis of Sinkhole Susceptibility and Karst Distribution in the Northern Shenandoah Valley, Virginia: Implications for Low Impact Development (LID) Site Suitability Models." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33148.
Full textAbstract:
Increased stormwater runoff due to urban development in the northern Shenandoah Valley (NSV) region of Virginia has prompted local officials and representatives to consider Low Impact Development (LID) as a stormwater management technique. LID is based on infiltrating stormwater runoff at the source through practices such as bioretention, rain gardens, and grass swales. The karst terrain that underlies the Shenandoah Valley presents a major barrier to the use of LID. Infiltration of surface runoff in karst landscapes may threaten groundwater quality and the stability of the bedrock. In 2004 the Center for Geospatial Information Technology (CGIT) at Virginia Tech developed an LID site suitability model for the NSV region incorporating karst as a key component in distinguishing unsuitable from suitable conditions for LID. But, due to the difficulty of mapping karst, the karst layer used in the site suitability model is very coarse in resolution, based primarily on carbonate versus non-carbonate rock.
This study uses a 1:24,000 scale sinkhole map derived from sinkhole boundaries identified by geologist David Hubbard (1984) of the Virginia Department of Mines and Minerals (DMME) to develop a more detailed karst map for a sub-watershed of the NSV region. The analysis uses geospatial techniques to determine the relationship between sinkhole distribution and four major landscape factors: bedrock type, soil depth to bedrock, proximity to geologic faults, and proximity to surface streams. The analysis identified three major trends in sinkhole occurrence: (1) sinkholes are more abundant in relatively pure carbonate rocks of Ordivician age; (2) sinkhole occurrence increases with proximity to fault lines; and (3) sinkholes are sparse near streams, most abundant 600 to 1400 feet away from surface streams. Based on these findings a sinkhole susceptibility index was produced using weighted overlay analysis in ArcGIS. The sinkhole susceptibility index provides a more detailed karst layer for the LID site suitability maps and can be used by the NSV region as a predictive tool for future sinkhole occurrence.Master of Science
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Fasesin, Kingsley, Ingrid Luffman, Eileen Ernenwein, and Arpita Nandi. "Improving Sinkhole Mapping Using LiDAR Data and Assessing Road Infrastructure at Risk in Johnson City, TN." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/asrf/2018/schedule/30.
Full textAbstract:
Improving Sinkhole Mapping Using LiDAR Data and Assessing Road Infrastructure at Risk in Johnson City, TN.
Kingsley Fasesin1, Dr. Ingrid Luffman 1, Dr. Eileen Ernenwein 1 and Dr. Arpita Nandi1
1 Department of Geosciences, College of Arts and Sciences, East Tennessee State University, Johnson City, TN;
Abstract
Predicting infrastructure damage and economic impact of sinkholes along roadways requires mapping of sinkhole distribution and development of a model to predict future occurrences with high accuracy. The study is carried out to define the distribution of sinkholes in Johnson City, TN and risks they pose to roads in the city. The study made use of a 2.5 ft Digital Elevation Model (DEM) derived from Light Detection and Ranging (LiDAR) data acquired from Tennessee Geospatial clearing house (TNGIS) and an inventory of known sinkholes identified from topographic maps. Depressions were identified using the LiDAR-derived DEM by subtracting a filled-depressions DEM from the original study area DEM. Using a spatial join, mapped sinkholes were matched to depression polygons identified from the LiDAR-derived DEM. For all matched sinkhole-polygon pairs, three indices were calculated: circularity index, area ratio of minimum bounding rectangle, and proximity to train tracks and roads. The dataset was partitioned into training (70%) and validation (30%) subsets, and using the training dataset, thresholds for each index were selected using typical values for known sinkholes. These rules were calibrated using the 30% validation subset, and applied as filters to the remaining unmatched depression polygons to identify likely sinkholes. A portion of these suspected sinkholes were field checked. The future direction of this research is to generate a sinkhole formation model for the study area by examining the relationship between the mapped sinkhole distribution, and previously identified sinkhole formation risk factors. These factors include: proximity to fault lines, groundwater and streams; depth to bedrock; and soil and land cover type. Spatial Logistic Regression analysis will be used for model development, and results will be used to generate a sinkhole susceptibility map which will be overlain on the road network to identify the portions of interstate and state highways at risk of sinkhole destruction.
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Al-Halbouni, Djamil [Verfasser], Torsten [Akademischer Betreuer] Dahm, Torsten Gutachter] Dahm, Francisco [Gutachter] [Gutiérrez, and Eoghan P. [Gutachter] Holohan. "Photogrammetry and distinct element geomechanical modelling of sinkholes and large-scale karstic depressions / Djamil Al-Halbouni ; Gutachter: Torsten Dahm, Francisco Gutiérrez, Eoghan P. Holohan ; Betreuer: Torsten Dahm." Potsdam : Universität Potsdam, 2019. http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-432159.
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Al-Halbouni, Djamil Verfasser], Torsten [Akademischer Betreuer] Dahm, Torsten [Gutachter] Dahm, Francisco [Gutachter] [Gutiérrez, and Eoghan P. [Gutachter] Holohan. "Photogrammetry and distinct element geomechanical modelling of sinkholes and large-scale karstic depressions / Djamil Al-Halbouni ; Gutachter: Torsten Dahm, Francisco Gutiérrez, Eoghan P. Holohan ; Betreuer: Torsten Dahm." Potsdam : Universität Potsdam, 2019. http://d-nb.info/1218404973/34.
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Al-Halbouni, Djamil [Verfasser], Torsten [Akademischer Betreuer] Dahm, Torsten [Gutachter] Dahm, Francisco [Gutachter] Gutiérrez, and Eoghan P. [Gutachter] Holohan. "Photogrammetry and distinct element geomechanical modelling of sinkholes and large-scale karstic depressions / Djamil Al-Halbouni ; Gutachter: Torsten Dahm, Francisco Gutiérrez, Eoghan P. Holohan ; Betreuer: Torsten Dahm." Potsdam : Universität Potsdam, 2019. http://d-nb.info/1218404973/34.
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Nxomani, Clifford David. "Genetic characterization of conspecific populations of Tilapia Sparrmanii (A.Smith 1840) in the dolomitic sinkholes and springs of the North-West Province (South Africa), and their comparison to Tilapia Guinasana (Trewavas 1936)." Thesis, Rhodes University, 2002. http://hdl.handle.net/10962/d1007452.
Full textAbstract:
This study was undertaken to investigate the genetic relationships of allopatric populations of the cichlid fish, Tilapia sparrmanii (A. Smith 1840) inhabiting the sinkholes and springs of the North West Province, South Africa. It also examined the genetic relationships of T sparrmanii to its polychromatic sister species, Tilapia guinasana (Trewavas 1936) which is endemic to the Guinas sinkhole in Namibia. Finally, the study investigated whether there is a genetic basis for T guinasana's colour polymorphism. The research was prompted by the concern of conservation authorities about the possible loss of unique fauna given the high demand for use of the subterranean waters for agricultural, domestic and industrial purposes. Such demands have the potential to drain these habitats. Further concerns related to habitat destruction and the introduction of alien species in the ecosystems inhabited by both fish species. Three approaches were adopted in attempting to answer the above questions. First was the investigation of Sodium dodecylsulphate (SDS)-Polyacrylamide Gel Electrophoresis (PAGE) of total cellular proteins as a fast and relatively inexpensive indicator of genetic relatedness between the fish populations. Secondly, genetic differentiation between the T sparrmanii populations and its relationship to T guinasana were assayed using restriction endonuclease analysis of Polymerase Chain Reaction (PCR)-amplified regions of the cytochrome b gene and the d-Ioop of mitochondrial DNA, coupled with Temperature Gradient Gel Electrophoresis (TGGE) analysis of the same regions. The third approach involved the use of Random Amplified Polymorphic DNA (RAPD) fingerprinting of the populations ofT sparrmanii as an indicator of genetic differentiation between them. RAPD fingerprinting was further used to investigate the genetic relationships between T sparrmanii and T guinasana and to probe the genetic basis of the polychromatism of the latter. SDS-PAGE did not reveal any genetic differentiation between the T sparrmanii populations, nor could the analysis detect variation within them. It however clearly distinguished at a species level between T sparrmanii and T guinasana as well as between these and other fish species, thus indicating its possible utility as an indicator of genetic relatedness at a species level. Mitochondrial studies employing the Restriction Fragment Length Polymorphism (RFLP) of Polymerase Chain Reaction (PCR)-amplified cytochrome b (1.1 kb) and d-Ioop regions (0.9 kb) with six and five restriction enzymes respectively, failed to reveal genetic differences within and between the allopatric populations. TGGE of500 bp of the d-Ioop and 400 bp of the 12sRNA PCR-amplified fragments did not reveal any differences between the populations of T. sparrmanii, nor did the analysis reveal any differences between T. sparrmanii and T. guinasana. The lack of differentiation between the T. sparrmanii populations by these mitochondrial Dna analysis techniques, despite habitat fragmentation, indicated a recent origin of the populations from a common ancestral population. Failure to distinguish between T. sparrmanii and T. guinasana may be related to the sensitivity of the techniques utilized. RAPD fingerprinting analysis indicated that the populations are genetically differentiated from each other. Using a measure of coefficient of variation, the population with the highest variation was the Wondergat population (13.99%), followed by the Klerkskraal popUlation (8.29%), the Malmani and Marico Oog populations (each with 5.88%) and the least variation (4.95 and 4.83%) was with the Amalinda and Molopo Oog populations respectively. This high degree of intra population similarity points to the fact that this differentiation is still confined within the limits of con specificity. The genetic distances between all of the T. sparrmanii populations across all primers ranged from 0.09 to 0.234 and averaged 0.146, a value that falls in the upper end of conspecific population differentiation. Such results indicate populational sub-division below the species level. RAPD fingerprinting therefore proved more sensitive than protein or mitochondrial studies. The differentiation it detected between the populations is a reflection of their adaptation to local conditions of the unique ecosystems they inhabit. A comparison with a subset of primers between T. guinasana and T. sparrmanii confirmed the separate species status of the former from the latter. The mean genetic distance between the T. sparrmanii populations was 0.136, compared to that between T. sparrmanii and T. guinasana which was found to be 0.374. Statistical analysis of the difference between the mean genetic distances indicated significance with 95% confidence. The polychromatism of T guinasana was investigated to determine whether there were significant differences between its five colour morphs. RAPD fingerprinting indicated with 95% confidence that there were significant differences between the colour forms based on the genetic distances computed between them. These genetic differences appeared to correlate with the observed assortative mating between the colour forms of the species. The manifestation of the polychromatism at sexual maturity in T guinasana probably indicates that colouration plays an important role in the breeding process. The genetic uniqueness shown here between the populations of T sparrmanii and the colour forms of T guinasana indicate for protective measures to be put in place if the genetic resources of the isolated fish populations are to be preserved. These must be coupled with a thorough assessment of the temporal and spatial distribution of genetic variability of the populations as a guide to a long-term management strategy for the fish populations and the ecosystems they inhabit. This study therefore has shown that the allopatric populations of T sparrmanii in the sinkholes and springs of the North-West Province are genetically unique, as well as show that the colour forms of T guinasana are genetically distinct.
31
North, Leslie A. "Application and refinement of the karst disturbance index in west-central, Florida." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002147.
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Mccrackin, Charles W. "Quasi 3-Dimensional Electrical Resistivity Mapping of Air-filled Karst Conduits and Policy Implications." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4151.
Full textAbstract:
This study assesses the capability and practical applications of quasi 3-Dimensional (3D) electrical resistivity surveying (ER) for mapping air-filled karst conduits. Vadose zone caves within the Brooksville Ridge of West Central Florida are relatively similar in architecture, with N-S elongation, and do not consist of an interconnected network of conduits. A high resolution quasi-3D ER survey was performed over two mapped cave systems on the Brooksville Ridge. The resultant survey verified the general effectiveness of quasi-3D ER in locating the two known near-surface cave features. Several other locations in the survey show similar or stronger resistivity anomalies trending in a N-S direction; these are interpreted to represent previously unknown voids. The quality of inversion results were tested by comparing results against the known void locations and by computing cross-over errors from surveys conducted at the same point with different orientations. Our results show that 3D inversions of multiple adjacent parallel profiles produces higher quality results (lower cross-over errors, better fit to cave locations) than 2D inversions. The data indicate that no single value of resistivity can be used as a reliable indicator of the presence of a void, presumably due to variable void size and the complexity in resistivities in the host rock. With sinkholes continuing to be of concern to residential and urban development in West Central Florida, the results of this research show the necessity of applying geophysical techniques in order to reduce the potential hazards posed by karst terrain.
33
Rönnqvist, Hans. "Predicting surfacing internal erosion in moraine core dams." Licentiate thesis, KTH, Hydraulic Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-14084.
Full textAbstract:
Dams that comprise broadly and widely graded glacial materials, such as moraines, have been found to be susceptible to internal erosion, perhaps more than dams of other soil types. Internal erosion washes out fine-grained particles from the filling material; the erosion occurs within the material itself or at an interface to another dam zone, depending on the mode of initiation. Whether or not internal erosion proceeds depend on the adequacy of the filter material. If internal erosion is allowed, it may manifest itself as sinkholes on the crest, increased leakage and muddy seepage once it surfaces, which here is called surfacing internal erosion (i.e. internal erosion in the excessive erosion or continuation phase). In spite of significant developments since the 1980s in the field of internal erosion assessment, the validity of methods developed by others on broadly graded materials are still less clear because most available criteria are based on tests of narrowly graded granular soils. This thesis specifically addresses dams that are composed of broadly graded glacial soils and investigates typical indicators, signs and behaviors of internal erosion prone dams. Based on a review of 90+ existing moraine core dams, which are located mainly in Scandinavia as well as North America and Australia/New Zealand, this thesis will show that not only the filter’s coarseness needs to be reviewed when assessing the potential for internal erosion to surface (i.e., erosion in the excessive or continuing phase); in addition, the grading stability of the filter and the core material as well as non-homogeneities that are caused by filter segregation need to be studied. Cross-referencing between these aspects improves the assessment of potential for internal erosion in dams of broadly graded soils and furthermore it provides aid-to-judgment.
QC 20100715
34
Veni, George. "Effects of Urbanization on the Quantity and Quality of Storm Water Runoff Recharging Through Caves into the Edwards Aquifer, Bexar County, Texas." TopSCHOLAR®, 1985. http://digitalcommons.wku.edu/theses/1842.
Full textAbstract:
Eighty-nine caves and sinkholes were investigated in the Edwards Aquifer recharge zone in Bexar County, Texas. The study examined their hydrogeologic and topographic origins and distribution, relationships to major fracture traces, quantity of recharge into the aquifer and degree of sensitivity towards degradation of the aquifer’s water quality. Groundwater traces were attempted to determine aquifer flow routes, time of groundwater travel, groundwater volume within conduits, and the aquifer’s capacity for dilution and dispersion of recharged contaminants. Trends in water quality were examined to quantify the volume and variety of contaminants recharged into the aquifer and to determine the effects of urbanization upon the Edwards Aquifer. The Edwards recharge zone was hydrogeologically assessed to rate the sensitivity of its areas. Socio-political impacts on recharge zone development were also examined.
Based on the results of the above outlined research method, the conclusions of this investigation are that caves and sinkholes contribute substantial recharge into the Edwards Aquifer, rapidly transmit that recharge to the aquifer and are sensitive sites for potential contamination. The entire recharge zone was determined to be very sensitive to contamination. No significant differences were found between areas within the recharge zone to scale their degree of sensitivity. Major conduit flow networks were found to exist within the aquifer and their groundwater flow paths could be traced. Urban development of the Edwards recharge zone was shown to decrease the volume of recharge and degrade the aquifer’s water quality. No significant detrimental effects on the aquifer were observed. The volume of diminished recharge and the concentration of recharged contaminants that were necessary to produce significant adverse effects on the aquifer were not determined due to lack of precipitation during the study period and inconclusive groundwater tracings. It was recommended that further development of the recharge zone be suspended until the effects of urbanization are quantified.
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Breyl, Jacobus. "Sinkhole formation due to subsurface erosion above undermined ground." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/73464.
Full textAbstract:
In November 2016, 38 sinkholes formed due to subsurface erosion above undermined ground on Donkerhoek farm near Sasolburg. The fact that the sinkholes formed more than 24 years after mining in the area ceased, emphasised the need for a method to predict the likelihood of sinkhole formation due to subsurface erosion. This is especially relevant for mining houses required to quantify their mine closure risks.
The purpose of this study was to investigate the mechanisms and soil properties involved in the formation of the 38 sinkholes on Donkerhoek farm through a fieldwork and laboratory testing programme and develop a method to predict the likelihood of sinkhole formation.
Three areas were selected for test pit excavation: an area with large sinkholes, one with small sinkholes and a third with no sinkholes but with a history of subsidence crack formation. The same mechanism of sinkhole formation was observed in both the large and small sinkhole areas: at the soil-rock interface, soil was being eroded into a subsidence crack in the rock, resulting in an upwards migrating cavity and the eventual formation of a sinkhole on surface when the cover over the cavity collapsed. This was the first time that this mechanism was observed in the Sasolburg area, having previously only been identified in the Secunda area.
The laboratory tests, carried out on samples obtained during the fieldwork, included foundation indicator, dispersivity, XRF and XRD, soil water retention curves, consolidated undrained triaxial and permeability tests. By comparison of the results from the different study areas, it was concluded that the larger sinkholes form in areas with highly dispersive soils, higher clay content, higher swell potential and a higher capacity to retain suctions when wetted.
The following soil properties and factors were identified as the main contributors to sinkhole formation:
• The strength of the lid, which is highly influenced by the unsaturated behaviour of the lid material. The lid strength determines the sinkhole diameter;
• The erodibility of the material which is influenced by dispersivity and the material obtaining a crumb structure due to desiccation;
• The activity of the soil, which influences the volume changes during drying and thereby the width and depth of desiccation cracks; and
• The thickness of the soil layer overlying the rockhead.
With the critical factors identified, the Van der Merwe method to predict sinkhole size was used as basis to develop an index method to predict the likelihood of sinkhole formation due to subsurface erosion above undermined ground. The method considers combinations of the following factor groups to express a high or low likelihood of the formation of large or small sinkholes in a particular area:
• The strength of the lid material, mainly influenced by the unsaturated behaviour of the soil;
• The capacity for cavity formation (CCF), which combines the dispersivity, erodibility and activity of the soil; and
• The influence of the thickness of the soil layer overlying the rock, evaluated by calculating the ratio between crack width in the rock and the soil layer thickness.Dissertation (MEng)--University of Pretoria, 2019.
Civil Engineering
MEng (Geotechnical Engineering)
Unrestricted
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Montane, Juana Maria. "Geophysical Analysis of a Central Florida Karst Terrain using Light Detection and Ranging (LIDAR) and Ground Penetrating Radar (GPR) Derived Surfaces." FIU Digital Commons, 2001. http://digitalcommons.fiu.edu/etd/42.
Full textAbstract:
Airborne LIDAR (Light Detecting and Ranging) is a relatively new technique that rapidly and accurately measures micro-topographic features. This study compares topography derived from LIDAR with subsurface karst structures mapped in 3-dimensions with ground penetrating radar (GPR). Over 500 km of LIDAR data were collected in 1995 by the NASA ATM instrument. The LIDAR data was processed and analyzed to identify closed depressions. A GPR survey was then conducted at a 200 by 600 m site to determine if the target features are associated with buried karst structures. The GPR survey resolved two major depressions in the top of a clay rich layer at ~10m depth. These features are interpreted as buried dolines and are associated spatially with subtle (< 1m) trough-like depressions in the topography resolved from the LIDAR data. This suggests that airborne LIDAR may be a useful tool for indirectly detecting subsurface features associated with sinkhole hazard.
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Quillen, Amanda Kay. "Diatom-Based Paleolimnological Reconstruction of Quaternary Environments in a Florida Sinkhole Lake." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/211.
Full textAbstract:
Despite lake sensitivity to climate change, few Florida paleolimnological studies have focused on changes in hydrology. Evidence from Florida vegetation histories raise questions about long-term hydrologic history of Florida lakes, and a 25-year limnological dataset revealed recent climate-driven effects on Lake Annie. The objectives of this research are (1) to use modern diatom assemblages to develop methods for reconstruction of climatic and anthropogenic change (2) to reconstruct both long-term and recent histories of Lake Annie using diatom microfossils. Paleoenvironmental reconstruction models were developed from diatom assemblages of various habitat types from modern lakes. Plankton and sediment assemblages were similar, but epiphytes were distinct, suggesting differences in sediment delivery from different parts of the lakes. Relationships between a variety of physical and chemical data and the diatoms from each habitat type were explored. Total phosphorus (TP), pH, and color were found to be the most relevant variables for reconstruction, with sediment and epiphyte assemblages having the strongest relationships to those variables, six calibration models were constructed from the combination of these habitat types and environmental variables. Reconstructions utilizing the weighted averaging models in this study may be used to directly reveal TP, color, and pH changes from a sediment record, which might be suggestive of hydrologic change as well. These variables were reconstructed from the diatom record from both a long-term (11,000 year) and short-term (100 year) record and showed an interaction between climate-driven and local land-use impacts on Lake Annie. The long-term record begins with Lake Annie as a wetland, then the lake filled to a high stand around 4000 years ago. A period of relative stability after that point was interrupted near the turn of the last century by subtle changes in diatom communities that indicate acidification. Abrupt changes in the diatom communities around 1970 AD suggest recovery from acidification, but concurrent hydrologic change intensified anthropogenic effects on the lake. Diatom evidence for alkalization and phosphorus loading correspond to changes seen in the limnological record.
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da, Silva Talia Simone. "Centrifuge modelling of the behaviour of geosynthetic-reinforced soils above voids." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274675.
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Understanding the deformation mechanisms of soils and geosynthetics in response to the formation of a void below a geosynthetic-reinforced soil is crucial to provide efficient designs of geosynthetic-reinforced soil systems such as embankments and landfill liners. Centrifuge modelling of the soil and geosynthetic behaviour was conducted using a trapdoor to simulate the formation of a void in a controlled environment at realistic stress levels. A plane-strain model allowed visual observations of the deformation mechanisms using Particle Image Velocimetry. Granular soils and model clay liners were tested, as would be relevant to embankments and landfills respectively. These soils were tested with and without the reinforcement to evaluate the benefit provided by the geosynthetic. Detailed analysis of the centrifuge test results showed that arching significantly reduces the stress at the base of the soil when a void forms; this mechanism is due to stress redistributions and not the formation of a physical arch. A new method to reliably predict this reduction was provided by calculating the coefficient of lateral stress on the failure plane based on the observations of a continuous convex arc of major principal strains above the void, and the assumption that this is indicative of the stress behaviour. The observed results were also used to address the limitations in the current design methods related to the fill behaviour. Expansion in the soil was confined to a parabolic zone above the void estimated from the soil dilatancy, rather than a single, unique coefficient of expansion in the deforming soil. The zone of subsidence was characterised by the combination of a vertical prism and funnel to the surface, with the surface settlement profile better described by a Gaussian distribution rather than the parabolic profile used previously. An adaptation to the design methods for use with compacted clay liners was proposed by considering the clay as a beam with the maximum strain related to curvature and not elongation, and calculating the applied stress on the geosynthetic ignoring the clay arching. Analysis and interpretation of the centrifuge tests has thus given new insight into the soil and geosynthetic behaviour based on visual observations relevant to how these systems deform in practice. This has allowed the recommendation of more efficient design procedures and consequently will facilitate better predictions of geosynthetic-reinforced soil behaviour above voids.
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Seale, Larry D. "Creation, analysis, and evaluation of remote sensing sinkhole databases for Pinellas County, Florida." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001339.
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Cervantes, Christian Alonso Vega. "Um sistema de detecção de ataques Sinkhole sobre 6lowpan para internet das coisas." reponame:Repositório Institucional da UFPR, 2014. http://hdl.handle.net/1884/38133.
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Orientador : Prof. Aldri Luiz dos SantosCo-orientadora : Profª. Michele Nogueira Lima
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Informática. Defesa: Curitiba, 18/08/2014
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Resumo: A Internet das coisas (IoT) é fruto de uma revolução tecnológica que representa o futuro da computação e da comunicação, sendo identificada como uma das tecnologias emergentes que mudará nossa forma de vida. As redes IoT são formadas por objetos heterogêneos (nós) com alguma inteligência, isto é, com capacidade de processamento que lhes permitem, entre outras tarefas, enviar e receber informações através da rede. Entretanto, cada vez mais objetos estarão interligados com aparelhos digitais, veículos e demais, e a presença deles tende a crescer em nossas vidas trazendo mais comodidade e facilidade. A IoT ligará todos esses objetos, assim como ligará outros que não pertencem à computação podendo ser fixos ou móveis. Visto que os objetos que compõem a IoT possuem recursos limitados, estes se tornarão vulneráveis a vários tipos de ataques, sendo o ataque sinkhole um dos mais destrutivos nas redes. Contudo, as soluções existentes para a proteção e segurança contra os ataques sinkhole geram um elevado consumo de recursos e usam mecanismos complexos para garantir um bom desempenho. Desta forma, este trabalho propõe um sistema de detecção de intrusão, chamado de INTI (Detecção Intrução contra ataques SiNkhole sobre 6LoWPAN para a InterneT das CoIsas) para identificar a presença de ataques sinkhole no serviço de roteamento na IoT. Além disso, INTI visa mitigar os efeitos adversos encontrados em IDSs que perturbam o seu desempenho como falsos positivos e negativos, também como os elevados consumos de recursos. O INTI combina o uso dos mecanismos como o uso de watchdog, reputação e confiança. O mecanismo de watchdog possibilita o monitoramento das atividades dos outros nós durante o encaminhamento de pacotes. A reputação e a confiança colaboram para determinar os dispositivos considerados confiáveis e não confiáveis na rede IoT. Estes mecanismos são utilizados para a detecção de ataques sinkhole, analisando o comportamento dos dispositivos. O sistema INTI foi avaliado em dois cenários realísticos de IoT, e nesses cenários os resultados obtidos mostram a eficácia do INTI em termos de taxa de detecção de ataques, o número de falsos negativos e falsos positivos e da eficiência na taxa de entrega, na latência e no consumo de energia. Palavras-chave: IDS, IoT, segurança, proteção, ataques sinkhole, watchdog, reputação.
Abstract: The Internet of Things (IoT) is the result of a technological revolution that represents the future of computing and communication, being identified as one of the emerging technologies that will change our way of life. The IoT networks are formed by heterogeneous objects (nodes) with some intelligence, that is, with processing capabilities that enable them, among other tasks, send and receive information across the network. However, more and more objects are interconnected with digital devices, vehicles and other equipment, and their presence tends to grow in our lives bringing more convenience and ease. The IoT will connect all of these devices as well as bind other objects that do not belong to the digital world and that can be fixed or mobile. Since the objects that make up the IoT have limited resources, they become vulnerable to various attacks, and the sinkhole attack is one of the most destructive in the networks. However, existing solutions for the protection and security against sinkhole attacks generate a high consumption of resources and use complex mechanisms to ensure good performance. Thus, this dissertation proposes an intrusion detection system, called INTI (intrusion detection against sinkhole attacks on 6LoWPAN for IoT), to identify the presence of sinkhole attacks on the routing services in IoT. Moreover, INTI aims to mitigate adverse effects found in IDS that disturb its performance, suck as false positive and negative as well as the high resource cost. The INTI system combines the use of mechanisms such as watchdog, reputation and trust. The watchdog mechanism enables the monitoring the activities of other nodes for packet forwarding. The reputation and trust mechanisms collaborate to determine the devices considered reliable and unreliable in IoT network.These mechanisms are used for detection of attackers, by analyzing the behavior of devices. The INTI system was evaluated in two realistic scenarios of IoT, and these scenarios the results show the effectiveness of INTI in terms of attack detection rate, the number of false negatives and false positives and efficiency in the delivery rate, latency and energy consumption. Keywords: IDS, IoT, security, safety, sinkhole attacks, watchdog, reputation.
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Seale, Larry D. Jr. "Creation, Analysis, and Evaluation of Remote Sensing Sinkhole Databases for Pinellas County, Florida." Scholar Commons, 2005. https://scholarcommons.usf.edu/etd/857.
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A database of likely sinkholes in Pinellas County, Florida, created using airborne laser swath mapping (ALSM a.k.a LIDAR for light detection and ranging), correlates poorly with other databases of likely sinkholes created from modern and historic aerial photographs. Urbanization appears to be the cause of the poor correlation. Buildings obscure much of the ground surface in urban areas, and many man-made depressions can be confused with natural sinkholes. Additionally, the lack of air photos contemporaneous with the ALSM data hinders ALSM analysis in rapidly developing areas.
Selecting a lightly-developed portion of the county for further study reduced the effects of urbanization. Air photos of this focus area, taken two years after the ALSM data were collected, image essentially the same surface as the ALSM data; therefore, ALSM and the air photos can be considered concurrent. While correlations among the two databases in the focus area were better than in the county-wide comparisons, the incongruencies were still numerous and the validity of the databases was unsubstantiated.
An additional database of likely sinkholes in the focus area, created using all available information, represents the most exhaustive search for sinkholes in Pinellas County to date. By assuming it is correct (i.e. it identifies true sinkholes), this composite analysis is used to assess the validity of the ALSM database and the air photo databases. Measuring the ALSM and air photo databases against the composite analysis reveals that, while ALSM outperforms the air photo methods, the ALSM and air photo analyses each fail to recognize true sinkholes more than 50% of the time. However, it also demonstrates that, while flawed, using the databases allows for a better-than-random chance of selecting a site free of sinkholes.
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Upton, Ethan A. "Sinkhole Lake Infiltration of Contaminants of Emerging Concern from Onsite Water Treatment Systems." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7977.
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The advancement in synthetic chemicals commonly referred to as contaminants of emerging concern (CECs) and their application has led to an increase in environmental pollution. The use of septic tanks otherwise referred to as onsite water treatment systems (OWTS), promotes the introduction of CECs into the environment while allowing little in the way of remediation. In order to study the impacts of CECs from OWTS as they infiltrate the environment and the aquifer system, water, sediment, and vegetation samples were collected around a sinkhole lake surrounded by residential housing using OWTSs. The main question of this research project is what is the fate of CECs from OWTSs effluent within the catchment of a sinkhole lake? Liquid chromatograph mass spectrometry was used to analyze the samples for the presence of CECs. It was found that the relative quantity of CECs in the individual constituents is dependent upon 1) the hydrophobicity and polarity of the individual compound, 2) the specific sampling site, 3) the topography gradient, and 4) for vegetation the connectedness of the sample type to the sediment. The implications derived from this study can be applied in environmental engineering, urban and suburban planning, environmental monitoring, and should be considered when residents use well water as their source of potable water.
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Ahmed, Jaleel. "Empirical Analysis of a Cybersecurity Scoring System." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7722.
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In the field of cybersecurity, the top-level management make use of metrics to decide if the organization is doing well to protect itself from cyber attacks or is in tatters leaving itself susceptible against the vast threats looming around. Not only that but metrics are even used to measure the performance of the security team. The aim of this thesis is to show how economics is closely related to cybersecurity and how metrics play an important role in policy making of an organization. Furthermore, I scrutinize one of the leading security score providers for the way they detect botnet infection. Botnet infection is a part of compromised system group in their score card categories that amounts to 55\% of the total security score. So, it becomes essential for the security score providers to have the right method of grading a company since it will have an impact on how they use their resources to protect itself from outside threat and the insurance premium they pay to cover any successful cyber attacks. I have found out that the data on which the botnet infection vector is graded has false positives. I shed light on security analyst and security team on a whole in their role in making decisions according to the security score. It is even the duty of the security team to work ethically, that is, the aim should not be to improve the security score rather the aim should be to protect the organization from outside attacks and if it happens to increase the security rating then be it so.
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Xavier, Neto Pedro. "Processamento e interpreta??o de dados 2D e 3D de GPR :aplica??es no imageamento de fei??es k?rsticas e estruturas de dissolu??o no campo de petr?leo de Fazenda Bel?m-CE." Universidade Federal do Rio Grande do Norte, 2006. http://repositorio.ufrn.br:8080/jspui/handle/123456789/18362.
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Previous issue date: 2006-05-05In Fazenda Bel?m oil field (Potiguar Basin, Cear? State, Brazil) occur frequently sinkholes and sudden terrain collapses associated to an unconsolidated sedimentary cap covering the Janda?ra karst. This research was carried out in order to understand the mechanisms of generation of these collapses. The main tool used was Ground Penetrating Radar (GPR). This work is developed twofold: one aspect concerns methodology improvements in GPR data processing whilst another aspect concerns the geological study of the Janda?ra karst. This second aspect was strongly supported both by the analysis of outcropping karst structures (in another regions of Potiguar Basin) and by the interpretation of radargrams from the subsurface karst in Fazenda Bel?m. It was designed and tested an adequate flux to process GPR data which was adapted from an usual flux to process seismic data. The changes were introduced to take into account important differences between GPR and Reflection Seismic methods, in particular: poor coupling between source and ground, mixed phase of the wavelet, low signal-to-noise ratio, monochannel acquisition, and high influence of wave propagation effects, notably dispersion. High frequency components of the GPR pulse suffer more pronounced effects of attenuation than low frequency components resulting in resolution losses in radargrams. In Fazenda Bel?m, there is a stronger need of an suitable flux to process GPR data because both the presence of a very high level of aerial events and the complexity of the imaged subsurface karst structures. The key point of the processing flux was an improvement in the correction of the attenuation effects on the GPR pulse based on their influence on the amplitude and phase spectra of GPR signals. In low and moderate losses dielectric media the propagated signal suffers significant changes only in its amplitude spectrum; that is, the phase spectrum of the propagated signal remains practically unaltered for the usual travel time ranges. Based on this fact, it is shown using real data that the judicious application of the well known tools of time gain and spectral balancing can efficiently correct the attenuation effects. The proposed approach can be applied in heterogeneous media and it does not require the precise knowledge of the attenuation parameters of the media. As an additional benefit, the judicious application of spectral balancing promotes a partial deconvolution of the data without changing its phase. In other words, the spectral balancing acts in a similar way to a zero phase deconvolution. In GPR data the resolution increase obtained with spectral balancing is greater than those obtained with spike and predictive deconvolutions. The evolution of the Janda?ra karst in Potiguar Basin is associated to at least three events of subaerial exposition of the carbonatic plataform during the Turonian, Santonian, and Campanian. In Fazenda Bel?m region, during the mid Miocene, the Janda?ra karst was covered by continental siliciclastic sediments. These sediments partially filled the void space associated to the dissolution structures and fractures. Therefore, the development of the karst in this region was attenuated in comparison to other places in Potiguar Basin where this karst is exposed. In Fazenda Bel?m, the generation of sinkholes and terrain collapses are controlled mainly by: (i) the presence of an unconsolidated sedimentary cap which is thick enough to cover completely the karst but with sediment volume lower than the available space associated to the dissolution structures in the karst; (ii) the existence of important structural of SW-NE and NW-SE alignments which promote a localized increase in the hydraulic connectivity allowing the channeling of underground water, thus facilitating the carbonatic dissolution; and (iii) the existence of a hydraulic barrier to the groundwater flow, associated to the A?u-4 Unity. The terrain collapse mechanisms in Fazenda Bel?m occur according to the following temporal evolution. The meteoric water infiltrates through the unconsolidated sedimentary cap and promotes its remobilization to the void space associated with the dissolution structures in Janda?ra Formation. This remobilization is initiated at the base of the sedimentary cap where the flow increases its abrasion due to a change from laminar to turbulent flow regime when the underground water flow reaches the open karst structures. The remobilized sediments progressively fill from bottom to top the void karst space. So, the void space is continuously migrated upwards ultimately reaching the surface and causing the sudden observed terrain collapses. This phenomenon is particularly active during the raining season, when the water table that normally is located in the karst may be temporarily located in the unconsolidated sedimentary cap
Esta tese apresenta resultados da pesquisa realizada no campo de petr?leo de Fazenda Bel?m-CE (Bacia Potiguar), com o objetivo de entender os mecanismos de gera??o de colapsos de terreno associados ? exist?ncia de um substrato carbon?tico intensamente fraturado e karstificado da Forma??o Janda?ra. A principal ferramenta utilizada foi o imageamento do karst soterrado com GPR (Ground Penetrating Radar). Dois eixos tem?ticos de pesquisa foram desenvolvidos: um eixo de natureza geof?sica, que consistiu no desenvolvimento de metodologias de processamento de dados de GPR, e um eixo de natureza geol?gica, que consistiu do estudo do karst Janda?ra e dos fatores condicionantes da sua evolu??o. Este segundo eixo foi fortemente apoiado no estudo de estruturas k?rsticas aflorantes e na interpreta??o de radargramas do karst soterrado. Um fluxo de processamento adequado para tratar dados de GPR ? proposto a partir da adapta??o de um fluxo usual de processamento s?smico. As principais modifica??es introduzidas est?o associadas com diferen?as fundamentais existentes entre GPR e S?smica, notadamente: pior condi??o de acoplamento entre fonte e solo, fase da wavelet (que ? mista, no GPR), grande n?vel de ru?do (inclusive a?reo), aquisi??o monocanal e maior import?ncia dos efeitos de propaga??o (principalmente dispers?o) na onda eletromagn?tica. A necessidade de um processamento adequado foi ainda mais premente em Fazenda Bel?m devido ? forte presen?a de ru?do a?reo, por se tratar de uma ?rea industrial, e grande complexidade das fei??es k?rsticas soterradas. A etapa chave do fluxo de processamento ? a corre??o dos efeitos de propaga??o. Em meios diel?tricos de perda baixa a moderada, verificou-se que a propaga??o do pulso de GPR impacta fortemente o seu espectro de amplitude, mas provoca muito pouca altera??o no seu espectro de fase. P?de-se assim corrigir os efeitos da propaga??o com uma aplica??o judiciosa de ganhos e balanceamento espectral. Os ganhos foram utilizados para recuperar a perda de amplitude e o balanceamento espectral, para recuperar as componentes da faixa superior de freq??ncia, que s?o mais fortemente afetadas pelos efeitos da propaga??o. Apesar da n?o estacionaridade do sinal do GPR, o balanceamento espectral promove um aumento de resolu??o, o que qualifica esta t?cnica como um bom substituto dos algoritmos de deconvolu??o, garantindo repetitividade e independ?ncia do meio geol?gico. A karstifica??o da plataforma carbon?tica Janda?ra est? associada a, pelo menos, tr?s eventos de exposi??o sub-a?rea relacionadas ?s discord?ncias do Turoniano, Santoniano e Campaniano. Em Fazenda Bel?m, a partir do Mioceno M?dio, o karst Janda?ra foi soterrado por sedimentos silicicl?sticos continentais. Este soterramento preencheu parte das cavidades de dissolu??o e fraturas e, assim, o desenvolvimento do processo de karstifica??o foi bastante atenuado, em compara??o com outros locais da Bacia Potiguar, onde o karst Janda?ra est? exposto. Nas condi??es vigentes em Fazenda Bel?m, identificou-se que os principais fatores condicionantes do surgimento das dolinas e do colapso de terreno s?o: (i) exist?ncia de uma cobertura inconsolidada espessa o suficiente para encobrir o calc?rio, por?m delgada o suficiente para que o seu volume possa ser acomodado nos espa?os vazios dessas estruturas; (ii) ocorr?ncia da interse??o de lineamentos estruturais SW-NE e NW-SE, que promovem um aumento localizado da condutividade hidr?ulica e condicionam a canaliza??o do fluxo hidr?ulico subterr?neo, facilitando a dissolu??o dos carbonatos; e (iii) exist?ncia de uma barreira hidr?ulica vertical, associada ? Unidade A?u-4, que condiciona a circula??o da ?gua subterr?nea a ser predominantemente lateral. Os colapsos de terreno em Fazenda Bel?m seguem o seguinte processo de evolu??o temporal. O fluxo de ?gua se infiltra atrav?s da cobertura sedimentar inconsolidada e promove sua mobiliza??o para o espa?o vazio das estruturas de dissolu??o na Forma??o Janda?ra. Este efeito ? iniciado na base da cobertura sedimentar, onde o fluxo aumenta o seu poder de abras?o, devido ? mudan?a brusca do regime laminar para o regime turbulento, ao entrar no karst. O material remobilizado vai preenchendo, as cavidades intra-acamamento e geram espa?o, de forma remontante, na cobertura sedimentar acima situada, que vai se afinando at? o ponto de colapso, quando ent?o ocorrem as dolinas. Este fen?meno ? especialmente ativo durante a esta??o chuvosa, quando o n?vel est?tico da ?gua, que normalmente est? situado dentro do calc?rio, pode estar temporariamente localizado dentro da cobertura sedimentar
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Estifanos, Biniam H. "Geophysical Mapping of Concealed Karst and Conduits north of Bellevue, OH." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1388079101.
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Pisani, Luca. "Il controllo delle strutture tettoniche sul carsismo dei Gessi bolognesi: i casi di studio delle doline della Spipola e dell'Inferno." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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Le relazioni tra carsismo e strutture tettoniche sono indubbiamente uno dei campi dell'indagine speleogenetica più interessanti per comprendere le relazioni dei sistemi carsici con la geologia di una determinata area.
La struttura di un sistema carsico dipende infatti da molteplici fattori, il cui ruolo può essere sostanzialmente passivo (caratteristiche strutturali) o attivo (condizioni ambientali). Per quanto sia conosciuta l'indubbia relazione di controllo dei fattori passivi sullo sviluppo e l'evoluzione dei sistemi carsici, mancano ancora in letteratura dei testi dettagliati e focalizzati sul controllo che le strutture tettoniche hanno sul carsismo alla macro scala.
L'obiettivo di questa tesi è analizzare l'area carsica dei Gessi bolognesi attraverso indagini di rilevamento sia in esterno che in grotta per:
a) integrare e migliorare la già esistente cartografia geologica attraverso i dati reperibili direttamente dal sottosuolo;
b) delineare dei modelli sui principali meccanismi di controllo strutturale sulla speleogenesi dell'area in esame.
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Blazzard, Kimberly. "Geostatistical Analysis of Potential Sinkhole Risk: Examining Spatial and Temporal Climate Relationships in Tennessee and Florida." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etd/3426.
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Sinkholes are a significant hazard for the southeastern United States. Although differences in climate are known to affect karst environments differently, quantitative analyses correlating sinkhole formation with climate variables is lacking. A temporal linear regression for Florida sinkholes and two modeled regressions for Tennessee sinkholes were produced: a general linearized logistic regression and a MaxEnt derived species distribution model. Temporal results showed highly significant correlations with precipitation, teleconnection patterns, temperature, and CO2, while spatial results showed highly significant correlations with precipitation, wind speed, solar radiation, and maximum temperature. Regression results indicated that some sinkhole formation variability could be explained by these climatological patterns and could possibly be used to help predict when/where sinkholes may form in the future.
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Krumplytė, Kristina. "Žemės naudojimo tendencijos ir ypatumai Šiaurės Lietuvos karstiniame regione." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2007. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2007~D_20070808.112558-21266.
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Šiaurės Lietuvos karstinis regionas – vienas iš labiausiai komplikuotų ir probleminių regionų. Dėl gamtinių ypatybių jame ypač sunkiai suderinami ekologiniai, ekonominiai ir socialiniai teritoriniai interesai. Tai lemia gilėjančius kraštotvarkinius konfliktus šioje teritorijoje.
Problematiškiausia yra ta karstinio regiono dalis, kurioje tankiausias paviršinių karstinių darinių tinklas (Biržų, Pasvalio rajonai). Tai aktyvaus karsto zona, skirstoma pagal paviršinių karstinių darinių tankį bei jų atsiradimo intensyvumą. Tokį teritorijos suskirstymą lėmė ne proceso intensyvumas, bet problematiškas ūkinis panaudojimas. Šiaurės Lietuvos karstiniame regione per trumpą laiką atsiranda vis naujų reljefo formų, būna sunku ūkininkauti, tenka imtis specialių gamtosaugos priemonių, kurios skatina geriau pažinti karstinio reljefo raidos ypatumus.
Šio darbo tikslas – išryškinti žemės naudojimo tendencijas Šiaurės Lietuvos karstiniame regione bei numatyti žemės ūkio plėtros, žemės naudojimo perspektyvas, atsižvelgiant į gamtinius ypatumus.
Darbe analizuojami žemės ūkio paskirties žemės naudotojai, jų žemėnaudos dydis, siekiant numatyti žemės ūkio plėtros, žemės naudojimo perspektyvas. Išryškinti dirvožemio dangos savitumai, dirvų sukultūrinimas ir derlingumas (pagal ekonominius balus) skirtingo sukarstėjimo teritorijose. Analizei pasirinkta: Biržų rajono Širvėnos, Parovėjos, Pabiržės seniūnijos ir Pasvalio rajono Krinčino, Pasvalio apylinkių, Pušaloto seniūnijos. Ūkininkų ūkių veiklai... [toliau žr. visą tekstą]The sinkhole region of Northern Lithuania is one of the most complicated and problematical regions. It is difficult to co-ordinate ecological, economical and social interests in the region because of the peculiarities of land and nature in it. This causes many conflicts connected to organization of land exploitation in this region. The most problematic district of the sinkhole region is the one where the sinkhole derivatives are very dense (regions of Birzai and Pasvalys). It is the zone of an active sinkhole, which is allocated according to sinkholes density along the surface and the intensity of appearance of them. Such an allocation was not determined by the intensively of the process itself. It was determined by a problematic employment of the land in an agricultural way. An active perfunctonary sinkhole zones is called to be the most complicated territories for employment of nature and ecology. One needs to have an exceptional knowledge about the territories mentioned in a case to employ them for agricultural purposes. New forms of relief are to appear in a very short period of time in the sinkhole region of Northern Lithuania. This makes farming difficult, special safety measures need to be taken into consideration. This stimulates to find out more about the peculiarities of the evolution of sinkhole relief. In this paper there are the users of agricultural land and their land-tenure analyzed in case to preview the expansion of agriculture and the perspectives of... [to full text]
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Feeney, Thomas. "Mechanisms Responsible for Sinkhole Flooding on an Urbanized Karst Terrain: South Sunrise / Media Drive, Bowling Green, Kentucky." TopSCHOLAR®, 1986. http://digitalcommons.wku.edu/theses/2006.
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Sinkhole flooding on the urban karst area of Bowling Green, Kentucky, was studied by investigating past flood events in the South Sunrise/Media Drive Sinkhole. The actual flood levels of four floods were compared to levels calculated by an empirical runoff determination method. Outflow capacity tests and dye tracing revealed the nature of drainage within the karst depression.
The Soil Conservation Service runoff determination method and the three-hour maximum rainfall event were used to estimate the level of flooding. Three of the four flood events studied provided deviations between the actual and calculated flood levels of less than 0.26 feet (0.08 meters). The fourth event produced a deviation of 1.45 feet (0.44 meters) which was explained by the intense nature of the precipitation event.
Analysis of the data resulted in the conclusion that surface storm water runoff exceeded the outflow capacity of the sinkhole drains during all four flood events and that the peak flood elevations were not related to the level of the water table in the area. Evidence also suggested that drainage from the base of the South Sunrise/Media Drive Sinkhole occurs through interconnecting voids associated with a cave roof breakdown pile, and not through an efficient system of solution conduits.
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Kiflu, Henok Gidey. "Optimized Correlation of Geophysical And Geotechnical Methods In Sinkhole Investigations: Emphasizing On Spatial Variations In West-Central Florida." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4709.
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Abstract
Sinkholes and sinkhole-related features in West-Central Florida (WCF) are commonly identified using geotechnical investigations such as standard penetration test (SPT) borings and geophysical methods such as ground penetrating radar (GPR) and electrical resistivity tomography (ERT). Geophysical investigation results can be used to locate drilling and field testing sites while geotechnical investigation can be used to ground truth geophysical results. Both methods can yield complementary information. Geotechnical investigations give important information about the type of soil, groundwater level and presence of low-density soils or voids at the test location, while geophysical investigations like GPR surveys have better spatial coverage and can resolve shallow stratigraphic indicators of subsidence.
In GPR profiles collected at 103 residential sites in covered-karst terrain in WCF, sinkhole-related anomalies are identified using GPR and SPT methods. We analyze the degree to which the shallow features imaged in GPR correlate spatially with the N-values (blow counts) derived from SPTs at the 103 residential sites. GPR anomalies indicating sinkhole activity are defined as zones where subsurface layers show local downwarping, discontinuities, or sudden increases in amplitude or penetration of the GPR signal. "Low SPT values" indicating sinkhole activity are defined using an optimization code that searched for threshold SPT value showing optimum correlation between GPR and SPT for different optimal depth ranges. We also compared these criteria with other commonly used geotechnical criteria such as weight of rod and weight of hammer conditions.
Geotechnical results were also used to filter the data based on site characteristics such as presence of shallow clay layers to study the effectiveness of GPR at different zones. Subsets of the dataset are further analyzed based on geotechnical results such as clay thickness, bedrock depth, groundwater conditions and other geological factors such as geomorphology, lithology, engineering soil type, soil thickness and prevalent sinkhole type. Results are used to examine (1) which SPT indicators show the strongest correlations with GPR anomalies, (2) the degree to which GPR surveys improve the placement of SPT borings, and (3) what these results indicate about the structure of sinkholes at these sites.
For the entire data set, we find a statistically significant correlation between GPR anomalies and low SPT N-values with a confidence level of 90%. Logistic regression analysis shows that the strongest correlations are between GPR anomalies and SPT values measured in the depth range of 0-4.5 m. The probability of observing a GPR anomaly on a site will decrease by up to 84% as the minimum SPT value increases from 0 to 20 in the general study area. Boreholes drilled on GPR anomalies are statistically significantly more likely to show zones of anomalously low SPT values than boreholes drilled off GPR anomalies. We also find that the optimum SPT criteria result in better correlation with GPR than other simple commonly used geotechnical criteria such as weight of rod and weight of hammer. Better correlations were found when sites with poor GPR penetrations are filtered out from the dataset. The odds ratio showed similar result while the result varied with the depth range, statistics and threshold SPT value (low N- value with optimum correlation), with a maximum observed odds ratio of 3.
Several statistical results suggest that raveling zones that connect voids to the surface may be inclined, so that shallow GPR anomalies are laterally offset from deeper zones of low N-values. Compared to the general study area, we found locally stronger correlation in some sub-regions. For example, the odds ratio found for tertiary hawthorn subgroup were 25 times higher than the odds ratio found for the general study area (WCF).