Journal articles on the topic 'Red Soil - Collapse Behaviour'

Abstract. A mechanistic understanding of how tropical-tree mortality responds to climate variation is urgently needed to predict how tropical-forest carbon pools will respond to anthropogenic global change, which is altering the frequency and intensity of storms, droughts, and other climate extremes in tropical forests. We used 5 years of approximately monthly drone-acquired RGB (red–green–blue) imagery for 50 ha of mature tropical forest on Barro Colorado Island, Panama, to quantify spatial structure; temporal variation; and climate correlates of canopy disturbances, i.e., sudden and major drops in canopy height due to treefalls, branchfalls, or the collapse of standing dead trees. Canopy disturbance rates varied strongly over time and were higher in the wet season, even though wind speeds were lower in the wet season. The strongest correlate of monthly variation in canopy disturbance rates was the frequency of extreme rainfall events. The size distribution of canopy disturbances was best fit by a Weibull function and was close to a power function for sizes above 25 m2. Treefalls accounted for 74 % of the total area and 52 % of the total number of canopy disturbances in treefalls and branchfalls combined. We hypothesize that extremely high rainfall is a good predictor because it is an indicator of storms having high wind speeds, as well as saturated soils that increase uprooting risk. These results demonstrate the utility of repeat drone-acquired data for quantifying forest canopy disturbance rates at fine temporal and spatial resolutions over large areas, thereby enabling robust tests of how temporal variation in disturbance relates to climate drivers. Further insights could be gained by integrating these canopy observations with high-frequency measurements of wind speed and soil moisture in mechanistic models to better evaluate proximate drivers and with focal tree observations to quantify the links to tree mortality and woody turnover.

Very few experimental data on the mechanical behaviour of unsaturated soils exists, particularly on the collapse behaviour under general stress states, because of the technical difficulties and time-consuming nature of measuring suction and deformation. This paper presents the results of a series of controlled-suction triaxial tests on the collapse behaviour of an unsaturated compacted clay with different initial dry densities and suctions. The collapse behaviour here includes deformation characteristics, such as volume changes, and hydraulic characteristics, such as saturation changes. It is found that the wetting-caused collapse mainly depends on the mean net stress and the initial density, and that the volume decrease reaches a maximum when the specimen is under the initial yielding mean net stress. It is also found that the soil-water characteristic curve in terms of suction and degree of saturation shifts upwards with increasing specimen density. The soil-water characteristic curve of a compacted soil mainly depends upon the current density, not directly upon the stress state. In addition, experimental data show that the collapse occurs mainly in an intermediate range of suction levels, which are neither very high nor very low, and that the wetting-caused volume decrease is accompanied by an increase in the degree of saturation.Key words: unsaturated soil, density, triaxial test, suction, collapse, degree of saturation.

Unsaturated pyroclastic soils originated by Vesuvius volcano show a collapsible behaviour upon wetting with a significant reduction in volume and rearrangement of solid skeleton. The paper investigates the role played by vegetation on wetting-induced collapse behaviour (namely, collapsibility) of reconstituted unsaturated soil specimens through two series of wetting tests in a standard oedometer. The first series of tests was performed on bare soil specimens, as to resemble the site conditions. The second group of tests was conducted on the same soil previously vegetated for 20 weeks with perennial graminae species, which are frequently used as a nature-based solution for contrasting surface erosion along slopes in different geo-environmental contexts. First, an initial small vertical net stress was applied on partially saturated specimens having similar initial saturation degree, then collapse was induced by flooding the specimens with distilled water and final vertical displacements were measured. As main outcome, soil porosity is highly reduced by the growth of grass roots. Consequently, the potential wetting collapse in the rooted soils is inhibited by low values of porosity. For similar initial soil porosity, in both bare and vegetated specimens (after root growth), a further reduction of the volumetric collapse magnitude is observed.

Retaining walls may be required in a location where gypsum may present in soil in large percentages .The behavior of retaining walls on ordinary soils is well known but the behavior of retaining walls resting on gypseons soils may be not well understood as the case of ordinary soils.In this study it is intended to reflect the behavior of gravity retaining wall resting on collapsible soil. And to do so a small prototype model (600mm*500mm*200mm) is used with soil mixed in presumed percentages with different gypsum percentages (5%, 20%, 30%, 50%). In addition to a model with 30% gypsum and treated with 2.7% Cement dust mixed with soil founded retaining wall structure. After preparing the foundation gypseous soil, a small glass made retaining wall filled with sand, which represent gravity wall, is put over such bed and backfilled with ordinary sandy soil. Dial gauges are placed to side and top of wall to measure the rotation settlement behavior and collapse of system. 4kPa stress are applied to backfill soil as to accelerate collapse with leaching process commenced. Data are recorded and analyzed completely, which shows the behavior of such structures embedded with different gypsum content.The improvement in rotation settlement and collapse for the retaining wall model reaches more than 89%, was gained after treating the embedded gypseous soil layer, with 2.7% cement dust.

This work aims to evaluate the water effect on the soils collapse potential. The laboratory tests based on the soils samples preparation determined the soils properties. Parameters such as water content, dry unit weight, degree of saturation, voids ratio and particles size distribution were determined. The collapse potential was analysed indirectly according to various researchers criteria. The results confirmed the high vulnerability of the study area to collapse. The oedometer tests determined the values of the collapse potential showing the conventional relationship between the collapse potential and the water content. It is noted that increasing water content leads to decrease soils strength to collapse, and the increasing progress of collapse poses a risk to constructions on silty sand. The collapse potential decreases with the increase in the relative density keeping the water content constant. This collapse potential caused by soil water content variation can be reduced from compaction.

Slope failure is a complex process which depends on several factors concerning nature and properties of soil, slope morphology and structure, past stress history, groundwater regime, boundary conditions, and their changes. As a consequence, the mechanism of slope failure is typically characterized by the development of a highly non-uniform strain field, which does not allow an easy prediction of the failure conditions. Usually, the process which will bring the slope to final collapse starts with local soil failure, which then leads to formation and propagation of a shear zone, and finally to general slope failure. This mechanical process is called progressive failure. However, in spite of the progresses in the knowledge of the slope behavior, a complete framework about the progressive failure is still missing; in particular, information about the response of granular unsaturated sloping soils is very poor. This paper reports the results of a couple of small-scale experiments on slopes reconstituted with unsaturated pyroclastic soils and subjected to continuous rainfall. The use of miniaturized sensors and optical fibers provided useful data to read some aspects of the mechanics of failure.

Biosurfactants are natural substances produced by several bacterial and fungal organisms that are amphiphilic and are extracellular (a part of the cell membrane). Biosurfactants can reduce the stress between solids and liquids on the surface and at the end. Biosurfactants have several properties, i.e. they are stable, less harmful, as well as readily degradable, and extremely eco-friendly. Biosurfactants also have a wide range of industrial uses because they are a versatile category of chemical substances. The principal justification for conducting such research was the isolation of possible biosurfactants containing bacteria. Sampling was performed for the isolation of bacteria producing biosurfactants from different oil-polluted sites That is to say, experiment for emulsification, test for oil spreading, test for drop collapse, and measure for hemolysis. The capability to produce biosurfactants was seen in 22 different isolates from polluted sites B1, B2, and B3. Through different biochemical tests and Gram staining, it was identified that isolated bacterial strains are Pseudomonas spp and that is Pseudomonas aeruginosa. The procedure used as characterizing biosurfactants was the TLC plate’s procedure, by using TLC plates process yellow dots emerged after spraying on silica gel plates with an throne and ninhydrin reagents. These yellow spots confirmed the presence and production of rhamnolipid in the biosurfactant. Hence, it was concluded that identified strains in the study can be helpful in the heavy metals, pesticides, and hydrocarbons bio-degradation and bioremediation. These may also be used as biological control agents to protect plants from various pathogens, resulting in improved crop yields. Introduction Biosurfactants are natural substances produced by several bacterial and fungal organisms that are amphiphilic and are extracellular (a part of the cell membrane) (Chen et al., 2007; Ghayyomiet al., 2012). Main purpose of the bio-surfactantsgeneration or production is a consequence of financial availability (Van Dyke et al., 1993 It is reported that almost 50 percent of the world's surfactants are used because of the need for cleaning agents as well as the rate of growth grows every day (Deleu and Paquot, 2004). Appropriate use of bio-surfactants will control environmental emissions what these are the most dangerous, constantly rising gradually and disrupting the routine maintenance of life every day. Awareness campaign initiatives have been introduced and also increase for environmental laws, various innovative approaches need to be implemented and even the issue of pollution focused entirely. Developing appropriate advanced technologies to help clear up chemicals and toxins from the ecosystem, like hydrocarbons (both inorganic and organic). Studies on biosurfactants are being launched by scholars and researchers with significant health issues like adverse environmental effects, air contamination, environmental change, and waste management (Makkar and Cameotra, 2002 Biosurfactants contribute to expanded demand for such microbial products as alternatives to chemical surfactants (Benatet al., 2000). Microbes seem to have the capability to degrade contaminants, but their biodegradation is limited leading to hydrophobicity, low solubility in water, and inadequate bioavailability, of such pollutants (Patil, et al., 2012). GhayyomiJazeh, Mishraet. al (2001) those bacteria that produce biosurfactants were isolated from the site of petroleum spills and afterward, 160 strains and as well as 59 strains were able to produce biosurfactants have shown better performance in a test for hemolysis of blood, and 45 strains with positive findings within oil spread experiment were applied in the laboratory to isolate and segregate the media cultured Banat process (Rahman et al., 2002) These were observed and researched that biosurfactants of Pseudomonas aeruginosa spp are most likely to disrupt the bonding of hydrocarbons like nonadecane, octa, Hexa, and hepta, in marine Water contaminated with oil spills up To approximately 47%, 53%, 73% and 60%(Abrar et al., 2020). Current study concluded that the isolated strain having the ability to degrade hydrocarbon as well as the ability to degrade the heavy metal. The strain also can protect the plant from various diseases. The present research found that the isolated strain is capable of degrading hydrocarbon while also being capable of degrading the heavy metal. As well as the strain does have the capability to defend plants from different diseases. Material And Methods Area of Study The investigation was conducted at HazaraUniversity(HU) Microbiology Laboratory, MansehraPakistan. Assemblage of Samples Thehomestay area of the city Mansehra Pakistan which is named as a township, where oil spills arose, oil spills soil samples were obtained as well as sampling from various Mansehra automobile workshops were also done. Sterilized bags of polythene were being used to collect samples of the soil, after thatthe sample was taken towards the Hazara University (HU) Mansehra Microbiology Laboratory to examine and extract bacterial strains that could develop biosurfactants. The soil temperature at the time of sample selection was around 30 ° C. The pH was also verified by Galvano science companies at the time of selection by pH meter, and the pH being reported was 7. Preparation of Media 15 x 100 mm Petri dishes were being used to prepare the media. Agar plates were thoroughly cleaned with water from the tap and then carefully covered in aluminum foil following cleaning then placed within autoclave at 121°C for about 15 min at 15 psi for sterilization. The nutrient agar which contains 0.5% NaCl, 0.3% beef extract, 0.5% peptone, and 1.5% agar, in 500 ml of distilled water, 14 g of the nutrient agar media (Merck) were dissolved. The nutrient level used mainly for the production of non-fastidious species. Nutrient agar is widely known as it's capable of growing a variety of bacteria types and provides nutrients required for the growth of bacteria. Upon sufficient dissolution of such nutrient agar in distilled water, these were then sterilized by autoclaving for 15 min at 15 psi in the autoclave and held at 121 °C Upon autoclaving, pouring of the media was done in laminar flow hood, and then packed and placed for yet more use in a fridge at 4°C. 2.4 Preparation of serial dilution The bacteria are isolated using the serial dilution process. During this process, 10 test tubes were taken and distilled water (9ml) was added in each tube. After that tubes were put for 15 minutes in the autoclave machine at 121°C. After that 1gm of a crude oil sample from the soil was added in a test tube containing distilled water. Further, 1 ml of the solution was taken from the first test tube and poured to the adjoining tubes for the preparation dilution as under . Afterward, 10μl of the solution was pipetted from both the dilution of and shifted for spread culture techniques, then incubated the plates at 37°C for 48hrs. Biosurfactants extraction Firstly, in nutrient broth solution theculture of bacteria was added and inoculated with oil, the bacterial colony was then incubated at the temperature of 25°C in a shaking incubator just for 7 days. Incubation after seven days of trembling. Thebacterial Crop was then taken and centrifuged at 5000rpm at temperature 4°C for 20minutes. Following centrifugation, the supernatant was collected and then mixed in the equivalent amount in Methanol: Chloroform. White sediment was then retained and collected for further use . Bacterial Colonies Isolation 1 g of the soil polluted with oil was diluted serially up to 106 dilutions.10 μl of 104 and 106 dilutions for spread culture were transferred to the MSM agar plates and nutrient agar. The plates were then incubated at 37°C for 48hrs. Twenty-two morphologically separate colonies were separated for further specific examination just after the incubation and processed by using the technique of streak plate. Screening of Isolates’ Biosurfactants Behavior To check the activity of biosurfactants produced by the bacterial species the following methods of screening were done. Hemolytic Activity of Biosurfactants for Erythrocytes Blood agar containing 5% of blood was prepared as after the fresh isolates were added and inoculated on blood agar plates, then the plates were taken and placed in the incubator at temperature 37°C for 48hrs (Rashediet al., 2005). Thereafter the observation of clear zone in the colonies indicated the existence of bacterial species that produce biosurfactants. This experiment was undertaken to control the ability of isolated bacteria to induce blood agar hemolysis. Three forms of hemolysis usually involve; alpha, beta, and hemolysis of the gamma. The agar underneath the species is dark greenish, then it is Alpha, the yellowish color produced in beta hemolysis and gamma hemolysis does not affect the bacterial sppwhichadded on the plates (Anandaraj and Thivakaran, 2010). Bio-surfactant identification with process of CTAB MSM (Mineral salt agar medium) with (2%) of glucose serving both as carbon source, (0.5 mg / ml) acetyl-tri-methyl-ammonium-bromide (CTAB), and methylene blue (MB: 0.2 mg/ml) are used to detect anionic bio-surfactants (Satpute et al., 2008). For this method, thirty microliters (30μl) of cell-free supernatant were added to each of the wells of the methylene blue agar plate that comprises of borer (4 mm in diameter). after that, the incubation of the plates was done for 48-72 hrs at 37°C. Just after incubation in each of the wells, a dark blue halo zone was being used to show the successful anionic bio-surfactant production. Table 1: Composition of MSM Media S. No Ingredients Amount (gm/L) I Potassium dihydrogen phosphate (KH2PO4) II Magnesium Sulfate (MgSO4) III Iron Sulfate (FeSO4) IV Sodium Nitrate (NaNO3) V Calcium Chloride (CaCl2) VI Ammonium Sulfate (NH4)2SO4 Technique for Spreading of Oil A sufficient number of isolated bacteria were inoculated into a solution of 100ml nutrient broth. Over 3 days, the culture was incubated at 37 ° C in a rotating shaker incubator (150 rpm). After that biosurfactants synthesis was checked in culture suspensions (Priya and Usharani, 2009; Anandaraj and Thivakaran, 2010). For this process, thirty milliliters (30ml) of distilled water was added in a Petri dish. In the middle of the distilled water, 1 milliliter (1ml) of diesel oil was added, and then a centrifuged twenty microliter (20μl) culture was introduced to the middle of a plate, which was isolated from oil spilled soil or local oily groundwater. The species producing the bio-surfactant displace the hydrocarbons and disperse it even in the water. Then it was calculated and analyzed within 1 mint (Ali et al., 2013). Technique for Drop collapse In this process, 96-wellsformed in each of the plates of nutrient agar. Afterwards, all the 96-wells of microliter plates was then filled withmineral oil of about 2ml. Then stabilized the plate at 37oC for 1 hour, after which the oil surface was filled with 5μl of supernatant culture. Therefore, the drop shape was taken to be observed on the oil surface after 1min. The drop which was collapsed, generated by the supernatant culture which is used to signify positive(+ive) outcome and the drops which stayed the same and displayed no changeindicates negative(-ive) outcome. And was taking distilled water as a control(Plaza et al., 2006). Emulsification index The emulsification index was calculated, as stated by the process followed by Cooper and Goldenberg (1981) In this process, 2 ml of kerosene oil was taken and inserted in each of the test tubes to the same amount of cell-free supernatant, and then homogenized for 2 min in a vortex at high speed and allowed for 24 hours to stand. The emulsification steadiness was then determined after the 24 hours, and the emulsification value was estimated by measuring the emulsified layer height by the total liquid layer height, then multiplied by 100. Quantification for the Dry weight of Biosurfactants The bacterial colony was inserted and inoculated in the nutrient broth medium, followed by oil and centrifuged at 5000rpm and after that, the supernatant was clutched and treated with chloroform and methanol and mixed. The white colored deposits were taken and used for the furtherprocess of dry weight. Afterwards, took the clean Petri plate and determined the empty plate weight. Next, the sediment was poured onto Petri plates. Now, for the drying process the hot air oven was used and set the 100ºC of temperature for 30minutes and the plates were put in the oven. After the drying process, the plates were weighted again. The dry weight was calculated for the biosurfactants using the formula which described below: Selected strains Identification and their characterization Instead, various basic biochemical methods were used to identify the isolated bacterial strains. Various biochemical tests, such as Gram staining, Oxidase test, Urease test.Catalase test, Methyl red test, Motility test, Indole test, Starch hydrolysis, Citrate test, Spore staining, Gelatin hydrolysis. Then afterwards, for the preliminary characterization of the biosurfactant, the thin layer chromatography process was used. Physical characterization of the strains selected Gram staining First, on the slide, using the wire loop the bacterial pure culture was taken, and smear was prepared on the slide, and then a drop of purified water was applied. Then, the sterile loop or needle was correctly mixed the bacterial colony and purified water, then mixed up until it is somewhat turbid. Then, spirit lamp was used to fixed the bacterial smear on slide and cooled to room temperature. With this glass slide was loaded with solution of crystal violet and stood for 1minute anddistilled water was applied on slide. Meanwhile the slide was submerged for 1 minute with the iodine solution, and then flushed and rinsed with water. Therefore, decolorizer of about 1 to 2 drops(5 percent acetone and 95 percent alcohol) were added to the slide’s smear and stand for 30seconds, and then treated with water. After then slide was rinsed with safranin for 60seconds, and then treated with water anddry in air. Microscopic analysis was done with 100x objective lenses using emersion oil on smear. Cell morphology The isolates of the bacterial cell were gram stained on slides and then the slides were observed under the light microscope, showing the shape and color of the cells. Biochemical characterization of the selected strains Catalase test Aim of this study is to identify, evaluate and examine that, whether or not the microbes are capable of producing catalase enzymes, while catalase is a protective enzyme, i.e. catalase has the potential to protect against the lethal chemicals known as (H2O2). In this study a bacterial culture that was clarified overnight was used. This culture has been smeared on a glass slide, and 3 percent hydrogen peroxide (H2O2) has been applied and observed on smear. Effects have been observed for bubble formation. Citrate test This study was performed to check the amount or ingest the citrate as the carbon and energy supply for growth and metabolism. Medium containing bromothymol blue and sodium citrate as pH indicator, bacterial was introduced. Ammonium chloride is also present in this medium used as a nitrogen source. Results were noted with variations of color from green to blue. Urease test The capability of urease enzyme for degrading urea was calculated in this bacterial capacity test. Bacterial culture was taken and inoculated for 48 hours at 37 ° C in urease broth, and then color was observed. Methyl red test Through using the process known as mixed acid fermentation which is used to evaluate the bacteria's acid production. The bacterial culture was taken and introduced in the broth of MR-VP and then incubated for 3days at a temperature of 37°C. Two (2) to three (3) drops of Methyl red were added in the broth medium after the incubation period. The change in broth color was observed for final results after a few seconds. Indole test Through using the process to assess the bacteria 's capability to crash indole from tryptophane molecules. After the 24 hours of incubated, taken the fresh inoculum of bacteria and then inserted into the tryptone medium, 24 hours of incubation of about 30oC, 2ml of the tryptone broth medium was added into a sterile test tube. Kovac's reagent was taken to be added (few drops) in sterile test tube and stimulated for a few minutes, and variations of color were detected. Gelatin test It is the approach assess to figure out the use of enzymes known as gelatins from bacterial organisms that precipitate the gelatin. Fresh inoculum of bacteria was taken after 24 hours, and inserted into the media of gelatin agar. This was incubated for around 24 hours, so the temperature did not exceed 30 ° C. Media was observed after incubation time. Starch hydrolysis Several of the micro-organisms that use the starch as a carbon energysource. Therefore, this method has been used to assess whether or not bacteria may use starch as a source of carbon. The bacterial fresh inoculum was spread on the petri starch agar plates, and after that the plate was incubated for 24 hours andmaintained the temperature at 30 to 35 ° C, then gradually applying the supplements of iodine to the plates to flow the change, and then examining the plates. Preliminary characterization of the strains selected Experimental characterization of the bio-surfactant was performed by using the process of TLC (Anandaraj et al., 2010). On a silica gel plate, crude portion of the rudimentary bio-surfactant was separated using Methanol: Chloroform: water (CH3OH: CHCl3: H2O) in the ratio of as an eluent with a different color producing reagents. Ninhydrin reagent (0.5 g ninhydrin in 100ml anhydrous acetone) was used to find bio-surfactant lipopeptide as red spots and anthrone reagent (1 g anthrone in 5ml sulfuric acid combined with 95ml ethanol) as yellow spots to identify rhamnolipid bio-surfactant (Yin et al., 2008). Results and Discussion Isolation of bacteria At first, twenty-two (22) strains from a polluted soil sample were isolated from nutrient agar media.Mixed culture provided by these colonies, so they were taken and smeared on the plates of nutrient agar and then fresh inoculum was collected and stored at temperature of 4oC for the further analysis. Bio-surfactants (surface-active compounds)are formed by a variety of amphiphilic bacterial and fungal organisms that are extracellular (a part of the cellular membrane) (Chen et al., 2007). Screening of Isolated strains for biosurfactant producing colonies Different experiments were carried out to identify, isolate and screen bacteria that are capable of generating bio-surfactants and that is Oil spreading technique(OST), blood hemolysis test(BHT), CTAB test, Emulsification operation. There were twenty-two distinct isolates observed in the current research. And the B1, B2 and B3culture were taken and selected from the twenty-two (22) strains isolated from the polluted spot, which were found to produce biosurfactant. And the oil spreading technique showed promising results for these strains. And strain B2 showed a greater displacement of oil and this is 4 mm. Oil spreading method is quick and often easy to handle, and this technique requires no particular equipment, only a very small amount of sample is used. This approach can be applied when the production and quantity of biosurfactant is small (Plaza et al., 2006) and (Youssef et al., 2004) Only bacterial cultures have been allocated and screened for bacterial species that can generate or use biosurfactants. Just three (3) strainsamong them presented the best results.Those 3 strain,s (B1, B2 and B3) were selected as an additional analysis. Blood hemolysis test On the petri plates of blood agar, the . Isolated bacteriaof B1, B2 and B3 were taken andstreak at the temperature about 37°C for 48 hours. Strain B1 demonstrated β (Beta) hemolysis after the incubation cycle and B2 and B3strains demonstrated γ (Gamma) hemolysis. The B1 strain had an emulsification index of about 74 percent and that was very high as compared to 70 percent for B2 and about 53 percent for B3 respectively. Around the same time, B1 strain showed β (Beta) hemolysis and γ (Gamma) hemolysis was shown bystrains B2 and B3 on the platesof bloodagar. The β hemolysisshowed by the strain B1 in the blood agar test, and the strain B2 and B3 showed γ (Gamma) hemolysis. It is determined that 20 percent strains that are the bestproducer of rhamnolipid have not fully lysed the blood, because the ability of the producer strains capacity not be responsible for the hemolytic activity. According to many researchers, who have shown that this is not such an effective tool for biosurfactant detection due to many bioproducts that may also induce red blood cell lysis, that is not so sufficient to be the surface-active molecule (Youssef et al., 2004). (Rashedi and others, 2005). Table2 Blood Hemolysis Test CTAB agar plate test This test confirms the anionic biosurfactants development. After plate incubation at a temperature of 37 ° C for 72 hours, dark blue hollow zone was existedaround each of the B1 strains wells, which clearly indicated the positive (+ive) development of anionic Biofactant. In addition, the B1 and B2 strains showed positive (+ I ve) results and, in the CTAB analysis, the B3 strain was found to be negative (-ive). The growing microorganisms when secreted the anionic biosurfactants on the plates of CTAB (cetyl-tri-methyl-ammonium-bromide) and methylene blue, then as a result the dark blue-purple insoluble ion pairs formed on the plates. The halo zone around each of the colonies was developed that can recognize rhamnolipid production and that was dark blue in colour, and could correlate with production of rhamnolipid (Siegmund et al., 1991). As indicated in (Fig1) Fig1: B1 positive on CTAB agar plate Oil Spreading Technique The oil was displaced by B1, B2and B3 strains in this test strain and showed a zone that was so clear. The bacterial strains capable of developing biosurfactant were tested and separated from the sample of soil which was oil spilled and brought from the District of Mansehra, Pakistan and from automobile workshops of Mansehra. As shown in (Fig.2). Fig.2: Results of Oil Spreading by B1, B2 and B3Table 3;.Test for oil spreads Bacterial culture Formation of zone (mm) Readings B,1 B,2 B,3 Drop-collapse technique During this process the drop shape was observed at the oil surface. As seen in Fig 3, the collapsed drop was provided by the supernatant culture B1 , B2 and B3.. Emulsification index Emulsification stability was measured with the use of kerosene oilin this test, and then observed the results. Since this emulsification index was calculated by dividing the height of the emulsion layer by the total height of the liquid layer and then multiplying by 100, as shown in the formulation below. Emulsification index Emulsification stability was measured with the use of kerosene oilin this test, and then observed the results. Since this emulsification index was calculated by dividing the height of the emulsion layer by the total height of the liquid layer and then multiplying by 100, as shown in the formulation below. Fig 3: Result of Drop-collapse test Table 4: The activity of Biosurfactant emulsification Dry weight of bio-surfactants In this examination, white-colored sediment was collected. Then measured the weight of the sterile Petri plate which was empty in the first step. Then, the sediment was poured into plates. The plates were taken and weighted after 30 minutes of drying on a hot air oven, following the process of drying. The weight of biosurfactants (dry weight) was measured using the following formulations: Fig 4: Dry weight of biosurfactants Table: 5: Dry weight of the biosurfactants Bacterial Culture Weight of the plate (g) biosurfactant in The plate after drying (g) Dry weight of Biosurfactant (g) B,1 B,2 B,3 Identification of selected strains and their characterization Gram staining For structural applications, and stroke analysis gram staining method was used.(Fig.5) shows findings from the process of gram staining. Fig 5: Microscopic view of Gram staining Biochemical identification of bacterial strains and their characterization Specific biochemical studies were performed to identify the species for further recognition and characterization. The bio-surfactant producing microorganism was found to be Pseudomonas aeruginosa after conducting various characterizations and the biochemical tests(Eric Deziel et al., 1996), Which can be used to further analyze and study the industrial development of the biosurfactant. Rhamnolipid is also isolated and produced from the Pseudomonas aeruginosa species on the silica gel plate (Rashedi et al., 2005), a form of biosurfactants highly recommended for processes of bioremediation. All the findings collected from biochemical testing were labeled as Berge 's Manual and it revealed that the protected microorganism was (Pseudomonas aeruginosa). Results of biochemical test were tabulated in (Table.5) Table 6: Bacterial strain identification Tests B1 B2 B3 Gram staining Negative Negative Negative Oxidases Positive e Positive Positive Catalase Positive Positive Positive Indole Positive Negative Negative Citrate Positive Negative Negative Urease Negative Positive Negative Nitrate Positive Positive Positive Motility Positive Positive Positive Gelatin hydrolysis Positive Negative Negative Lactose Negative Positive Positive Methyl red Negative Positive Positive Voges Proskauer Negative Negative Negative Fig 6: Results of biochemical tests(A) Methyl red and Voges Proskauer tests (b) catalase tests (c) oxidase tests (d) indole tests (e) citrate tests (g) lactose tests (h) urease tests Preliminary bacterial strain’s characterization The plates showed yellow dots, when sprayed with anthrone reagent. It indicated the existence of biosurfactants of rhamnolipid in the organism on the plate of TLC as seen in theFig.7 Fig 7: Biosurfactant characterization by TLC Conclusion Biosurfactant development is exciting and perceptible across industries to clean up oil waste and pollutants, particularly in the ecosystem.Compared with chemical surfactants, the biosurfactants are less harmful. It plays an important role in defining the advantages and the importance of industrial applications. Therefore, it is not possible to disregard the growing role and importance of biosurfactants in environmental sustainability.Biosurfactant formulations which can be used for bacterial, fungal, and viral organisms as growth inhibitors. Such biosurfactant inhibition properties can make them components that are applicable to Numerous illnesses that are used as medicinal agents. Therefore it was decided that the described strain could be used as a potential source for heavy metal bioremediation pesticide and hydrocarbon polluted sites. And also used as shielding the plant from different pathogens, contributing to improved crop yields. There is no doubt that the biosurfactants are a multifunctional, advanced, versatile, long-lasting and updated type not only for the twenty-first century but beyond. Conflict of interest The authors declared that they have no conflict of interest and the paper presents their own work which does not been infringe any third-party rights, especially authorship of any part of the article is an original contribution, not published before and not being under consideration for publication elsewhere. References Ali, S.R.; Chowdhury, B.R.; Mondal, P. and Rajak, S. “Screening and characterization of biosurfactants producing microorganism from natural environment (Whey spilled soil)”. Nat. Sci. Res. 2013, 3(13), 34–64. Anandaraj, B. and Thivakaran, P. “Isolation and production of biosurfactants producing organism from oil spilled soil”. Biosci. Tech. 2010, 1(3), 120–126. Banat, I.M.; Makkar, R.S. AND Cameotra, S.S. “Potential commercial Application of Microbial Surfactants”. Applied MicrobialBioethanol. 2000, 53, 495-508. Cooper, D. G, Zajic, J. E. and Denis, C. J. Am. Oil Chem. Soc. 1981, 58, 7780. Deleu, M. and Paquot, M. “From Renewable Vegetables Resources to Microorganisms: New Trends in Surfactants”C.R. 2004, 7, 641-646. Eric, Deziel.; Gilles,Pauette.; Richars, Villemur.; Francois,Lepine.; and Jean-Guy, Bisaillon. “Biosurfactants Production by a Soil Pseudomonas Strain Growing on Polycyclic Aromatic Hydrocarbons”. Applied and Environmental Microbiology. 1996, 62(6), 1908-1912. Ghayyomi, J.M.; Forghani, F.; Deog, Hwan, Oh. “Biosurfactant production by Bacillus sp. Isolated from petroleum contaminated soil of Sirri Island”. Ame. J. Appl. Sci, 2012, 9(1), 1-6. Makkar, R.; & Cameotra, S. An update on the use of unconventional substrates for biosurfactant production and their new applications. Applied microbiology and biotechnology. 2002, 58(4), 428-434. Mishra, S.; Jyot, J.; Kuhad, R. C.; & Lal, B. Evaluation of inoculum addition to stimulate in situ bioremediation of oily-sludge-contaminated soil. Environ. Microbiol. 2001, 67(4), 1675-1681. Patil, T. D.; Pawar, S.; Kamble P. N. & Thakare, S. V. “Bioremediation of complex hydrocarbons using microbial consortium isolated from diesel oil polluted soil”. Der ChemicaSinica Journal of Biotechnology. 2012, 3(4), 953-958. Plaza, G.; Zjawiony, I.; and Banat, I. “Use of different methods for detection of thermophilic biosurfactants producing bacteria from hydrocarbon contaminated bioremediation soils”. Petro. Sci. Eng. 2006, 50(1), 71–77. Priya, T.; Usharani, G. “Comparative study for bio-surfactant production by using Bacilus subtilis and Pseudomonas aeruginosa”. Res. Int. 2009, 2(4), 284–287. Rahman, K.S.M.; T.J. Rahman.; S, McClean.; R, Marchant.; and I, M. Banat. “Rhamnolipid biosurfactants production by strains of pseudomonas aeruginosa using low-cost raw materials”. 2002, 18, 1277-1281. H.; Jamshidi, E.;Mazaheri, Assadi. M.; and Bonakdarpour, B. “Isolation and production of bio-surfactant from Pseudomonas aeruginosa isolated from Iranian southers wells oils”. Int. Environ. Sci. Tech. 2005, 2(2), 121–127 Satpute, S.K.; Bhawsar, B.D.; Dhakephalkar, P.K.; and Chopade, B.A. “Assessment of different screening methods for selecting bio-surfactant producing marine bacteria”. Indian J. Marine Sci. 2008, 37, 243–250. Shafeeq, M.; Kokub, D.; Khalid, Z. M.; Khan, A. M.; Malik, K. A. (1989). MIRCEN J. Appl. Microbiol. Biotech. 1989, 5, 505–510. Siegmund, I. and Wagner, F. “New method for detecting rhamnolipids excreted by Pseudomonas species during growth on mineral agar”. Tech. 1991, 5, 265–268. Van Dyke, M. I.; Couture, P.; Brauer, M.; Lee, H. and Trevors, J. T. "Pseudomonas aeruginosa UG2 rhamnolipid biosurfactants structural characterization and their use in removing hydrophobic compounds from soil". J. Microbiol. 1993, 39, 1071-1078. Yin, H.; J, Qiang.; Y, Jia.; J, Ye.; H,Peng.; H, Qin.; N, Zhang. B. “Characteristics of bio-surfactant produced by Pseudomonas aeruginosa S6 isolated from oil containing water”. Process Biochemistry. 2008, 44: 302–308. Youssef, H.; Duncan, El.; Nagle, P.; Savage, N.; Knapp, M.; McInerney, J. “Comparison of methods to detect biosurfactant production by diverse microorganisms”. Microbiol Methods. 2004, 56, 339-347.

By embedding water content sensors and pore water pressure sensors inside the red clay slope on-site in Guiyang, Guizhou, shear tests were performed on soil samples at different depths of the slope under different weather. The changes of water content, pore water pressure, and shear strength index of the slope inside the slope under the influence of the atmosphere were tracked and tested, and the failure characteristics and evolution of the red clay slope were analyzed. It is believed that the depth of influence of the atmosphere on red clay slopes is about 0.7 m, rainfall is the most direct climatic factor leading to the instability of red clay slopes, and the evaporation effect is an important prerequisite for the catastrophe of red clay slopes. The cohesion and internal friction angle of the slope soil have a good binary quadratic function relationship with the water content and density. The water content and density can be used to calculate the cohesion and internal friction angle. Failure characteristics of red clay slopes: the overall instability failure is less, mainly surface failure represented by gullies and weathering and spalling, and then gradually evolved into shallow instability failure represented by collapse and slump. The damage evolution law is as follows: splash corrosion and surface corrosion stage⟶ fracture development stage⟶ gully formation stage⟶ gully development through stage⟶ local collapse stage⟶ slope foot collapse stage.

Virtually all investigation of liquefaction has used undrained tests, and it has become common to represent the undrained strength in terms of a collapse surface or collapse stress ratio described by an effective friction angle. A difficulty with undrained tests is that they only allow observation of the interaction of elastic and plastic strain because of the imposed boundary condition (i.e., no drainage or zero volume change), precluding a proper understanding of an effective stress criterion for maximum undrained strength. Drained triaxial tests do not suffer from this shortcoming, and stress–dilatancy of dense sands in drained shear is well established as a fundamental aspect of sand behaviour, based on micromechanical considerations. It is particularly interesting to consider the stress–dilatancy behaviour of very loose sands in the context of soil liquefaction. Although there are some data in the literature on loose sand behaviour in drained triaxial compression, the majority of data are actually for sands markedly denser than sands showing static liquefaction in undrained tests. This paper therefore reports some laboratory testing of very loose sands, together with comparative undrained liquefaction data, and compares the loose behaviour to that of dense sand. These data are reduced to stress–dilatancy form so that the fundamental aspects of loose soil behaviour can be seen and compared to flow rules used in constitutive models. The stress–dilatancy of very loose sand shows no limiting stress ratio markedly less than that of the critical state. Moreover, the stress–dilatancy trends of very loose sand are the same as those of dense sand. There is no evidence of "structural collapse" of the particulate arrangement of very loose sands, contrary to speculation associated with collapse surfaces in the literature. Explanations of sand liquefaction must seek other physical explanations of the soil behaviour.Key words: sand, constitutive relations, plasticity, liquefaction.

Benggang with steep collapsing walls is one of the worst soil erosion problems in South China. The collapse of walls is the most critical process in Benggang development. This is mainly due to the soil water properties. The soil water characteristic curve (SWCC) is a key indicator for analyzing soil moisture, but the SWCC and its mechanism of influence in collapsing walls remain obscure. A pressure plate meter was used for drying experiments to research the SWCCs of undisturbed soils of five layers (from top to bottom: red soil layer, transition layer I, sand soil layer, transition layer II and detrital layer) of two typical collapsing walls. The van Genuchten (VG) model can be fitted to the SWCCs for different layers (NSE ≥ 0.90). With increasing soil depth, the parameters a and θs first decreased and then increased, the parameters n first increased and then decreased, θr declined as the soil depth increased. These findings illustrate that soil water holding capacity decreases with increasing soil depth. The bottom of the soil is weak in water retention and water can easily reach saturation, resulting in a decline in soil stability, thus promoting soil collapse and finally inducing upper soil collapse. Furthermore, gravel content and particle morphology are factors that should not be neglected for SWCCs. The results of this study provide a theoretical basis for understanding the process of wall collapse in Benggang landforms in South China.

Two small-scale mock-up tests were carried out on a compacted mixture of bentonite and sand, one with saturation from the bottom only and the other with saturation from the top and bottom. Swelling pressure was monitored at different positions of the soil sample in both axial and radial directions. Results showed that the two-side saturation accelerates the swelling pressure kinetics by a factor of 4. The radial swelling pressure kinetics depends on the soil swelling, soil collapse, and interaction between the soil layers. Further analysis based on the relative humidity measurements in an infiltration test performed previously showed that the variations of swelling pressure with suction are similar to those found in literature, and that threshold points exist indicating the initiation of soil collapse. These threshold points appeared at higher suction when the soil was farther from the wetting face. The failure of the axial confining elements in the storage galleries was also simulated by releasing the piston and allowing a limited axial swelling of 20%. The radial swelling pressures decreased sharply upon the piston release and during the free axial swelling. A swelling pressure gradient was found from the bottom to the top with a higher value at the bottom. The density gradient was estimated based on the swelling pressure profile.

AbstractLime and cement are quite compatible for stabilizing clayey soils; changes in a thermal regime may inversely affect the advantages of stabilized soil. The present study interprets changes in the mechanical behaviour of frozen and unfrozen Himalayan soil samples through an unconfined compressive strength test. The soil was treated with ground eggshell powder (3%-9%) and alkali activator (Sodium chloride) (2%-6%); it was reinforced with arbitrarily distributed polypropylene fibers (0.05%-0.15%). Standard 7, 14 and 21-day-old soil specimens were tested in unfrozen conditions, while fresh 21-day-old soil specimens were tested after 3, 5 and 10 freeze-thaw cycles. The design of the experiments was based on the Taguchi technique and arranged in an orthogonal array. The results of the research clearly show that poultry waste (eggshell powder) and alkaline soil stabilizer improved the strength behaviour of the subject soil. On the other hand, the polypropylene fibers played an important role in changing the brittle behaviour of the stabilized soil to ductile behaviour. The sudden collapse of a structure may be avoided by using polypropylene fibers.

Recurrent freeze–thaw cycling is a powerful weathering process that subjects soil to frost heave and thaw settlement. The cycling significantly changes the soil structure and leads to particle recombination, ultimately causing deterioration of the soil's properties. Herein, we investigated the effect of freeze–thaw cycles on loess-like soil in seasonally frozen regions; specifically with respect to the engineering geological properties, such as changes in grain-size distribution, liquid–plastic limit and collapse behaviour. The results indicate that over the course of 20 freeze–thaw cycles, the soil samples’ dry density decreased, the particle diameter of each soil fraction changed in a bi-directional manner (large particles were broken into finer sizes and fine particles agglomerated into larger particles), and the liquid limit and plasticity index first increased and then decreased. An increase in the initial water content resulted in more significant changes. In contrast to the undisturbed soil samples, the freeze–thaw cycles caused non-collapsible remoulded loess-like soil to collapse. Furthermore, microscopic evaluation allowed us to determine the collapse mechanism. Essentially, after the freeze–thaw cycles, the quantity of micropores in the soil decreased, whereas that of medium pores and macropores significantly increased. In addition, a trellis structure, similar to the typical loess structure, was generated.

Depending on the state paths, loading–wetting of compacted unsaturated soils can exhibit complex volumetric behaviour, such as swelling, collapse, collapse followed by swelling, swelling followed by collapse, and swelling pressure development. Microscopically, these behaviours arise from complex interactions among applied stresses, air–water pressure deficit or suction at the water menisci, moisture content or degree of saturation in the voids, and the nature of the micro- and macrosoil aggregates of compacted soils that depend on the level of suction. While significant advances have been made in modelling hydromechanical behaviour of compacted unsaturated soils taking these interactions into account, input parameter determination requires advanced testing equipment and the testing processes can be very time-consuming. In 2012, a relatively simple and practical framework within the void ratio – moisture ratio (water volume / solid volume) – net stress space (referred to as the MPK framework) has been proposed by Kodikara to explain–predict these state paths. A desirable feature of this framework is that it identifies a direct link between the well-known compaction curve and the compacted soil constitutive behaviour. This paper presents a comprehensive series of tests on statically compacted soils, the results of which are in close agreement with this framework. Two soil types, namely lightly reactive kaolin and more reactive clay (referred to as Merri Creek soil), were used in the testing. The soils were prepared with different moisture contents from the dry state and statically compacted at constant water content to obtain void ratio – moisture ratio – net stress constitutive surfaces, as well as soil specimens for state path tests. The state path test results of yielding under loading, collapse under wetting, swelling pressure development, and change in yield pressure due to wetting are explained within this framework. In addition, some published data on a silty soil mixture were also analysed, highlighting that the framework is valid, regardless of the degree of reactivity of the soil. Suction was not measured in the authors’ experiments, as it was not required to explain the above state paths according to this framework. However, it is recognised that suction is the conjugate state variable to the moisture content. Therefore, in future experiments, suction will be measured and its role will be fully explained within the framework, adding more generality.

The effect of compaction pressure on subsequent soil behaviour during isotropic consolidation has been investigated by conducting controlled-suction triaxial tests on samples of an unsaturated compacted silty soil. A comprehensive set of laboratory experiments was carried out in a double-walled triaxial apparatus on samples of unsaturated soil that were prepared using two different compaction pressures. The axis translation technique was used for creating the desired suctions in the samples. In the experiments, the soil samples were subjected to isotropic consolidation under constant suctions. The results show that different compaction pressures produce different fabrics in a soil and therefore affect the behaviour of the soil. The results also show that the value of yield stress and the location of the loading–collapse (LC) yield curve are functions of soil fabric. Furthermore, it is shown that the slopes of normal consolidation lines for densely and loosely compacted samples differ in unsaturated conditions but are the same in saturated soils. A comparison is made between the behaviour of the dense and loose samples, and the difference in the behaviour is explained.Key words: suction, unsaturated soil, compaction, consolidation, soil fabric.

Soil improvement by foam is a key technique to control formation damage in shield construction. The half-life of three kinds foam was obtained by test self-developed foam and other two types. Meanwhile, their characteristics of stability and dissipation were analyzed. The physical-mechanical characteristic of red clay which was improved by foam was tested. Test result show that as the foam concentration increasing, the cohesion and plastic fluidity of soil increases firstly and then decreases, but the internal fiction angle decrease always. The permeability of red clay was measured by penetration test. The impregnation depth of foam in red clay was analyzed. The results provide key parameters for shield construction to prevent engineering accidents, such as, flowing, sand gushing, mud boiling, collapse and so on.

Abstract Collapsible soils present significant geotechnical and structural engineering challenges worldwide. They can be found in arid or semi-arid regions and are directly affected by the multi-step wetting procedure due to the reduction of soil suction. The main objectives of this paper are to investigate the volume change behaviour, collapse mechanism and deformation characteristics under the control of suction and net vertical stress. In this study, three types of collapsible soils were investigated such as natural soils of sandy gypseous, silty loess, and artificial soil of gypsum–sand mixture. A series of constant net stress-suction control (wetting and drying) tests using a combination of axis-translation and vapor equilibrium techniques were deployed to cover a wide range of applied suction. The test results show that large volume change and collapse deformation occur upon a stepwise suction decrease. On the other hand, shrinkage behaviour resulting from increases in imposed suction is observed during the drying path. The collapse deformation depends on the stress path and is a function of net normal stress, suction, dry density, and degree of saturation. The water content and the degree of saturation dramatically increase as the applied suction decreases from the initial high to zero values at the drying path.

Abstract A collapsible soil is composed essentially of a packing of mineral particles and a set of interparticle bonds holding the system together. Failure requires the bond system to fail and the soil structure to collapse. A natural hazard is presented. The soil structure may collapse inwards (consolidate), as in loess failure, or it may collapse outwards (disperse, disintegrate), as in the failure of quick-clays, some collapsing sands, some silty estuarine deposits, and in wind erosion of silty soils by saltating sand grains. Generalising about bonding systems allows two types of interparticle bond to be recognized: long range bonds and short range bonds. Long range bonds are found in clay mineral systems and allow the occurrence of plasticity. They are represented by c in the standard Coulomb equation. Short range bonds are found in inactive particle systems. These are soil systems where the constituent particles do not have a significant electrical charge. A slight deformation of a short-range bonded system causes much loss of strength. It is short range bonds which tend to dominate in collapsing soil systems, although in the complex case of loess the bond failure is initially mediated by long range bonds at the interparticle contact regions. A collapse failure involves a large scale remaking of the soil structure, and thus total failure of the bonding system. Generalising again- it can be claimed that five types of particle make up engineering soils: A active clay mineral particles (the smectites), B inactive clay mineral particles (e.g. kaolinite, illite), C very small inactive primary mineral particles (close to the comminution limit in size- mostly in the quick-clays), D silt (usually quartz silt), and E sand (usually quartz sand). The nature of type D particles contributes to the collapse of loess soils, the most widespread of the collapsing soil phenomena. The nature of type C particles controls the behaviour of quick-clays. C and D systems are essentially dominated by short-range bonds.

The collapse of soils under wetting is a major problem in Geotechnical engineering. The erection of structures on these types of soils, located in arid and semi-arid zones, needs careful treatment of these soils. Soil reinforcement techniques have been rapidly increased during these two decades because of their effectiveness in geotechnical engineering. The aim of this experimental work is to investigate the collapsible soil behaviour in order to improve its characteristics. To achieve this goal, Polyethylene fibers, and Sisal fibers were used as Polyethylene fibers content in mass are varied from 0% (unreinforced samples) to 15%; and Sisal fibers content from 0.5% to 1%. The fiber reinforcement is combined with other processing procedures such as compaction and the addition of CPA cement to decrease the collapse potential.

A detailed description of the volumetric behaviour of compacted unsaturated soils is essential for modelling compacted soil behaviour. It is more complex than when the soil is saturated, as unsaturated soils exhibit a range of responses, such as yielding under loading, swelling and collapse under wetting, and shrinkage and cracking during drying. In unsaturated modelling, (v, s, p) or (v, s, p′) is commonly used as the state space to describe volumetric behaviour, where v (= 1 + void ratio, e) is the specific volume; s is the soil suction; and p and p′ are the mean net and mean effective or skeleton stress, respectively. An alternative approach is to use (v, vw, p) space to describe volumetric behaviour, where vw is specific water volume. In either case, coupled water retention behaviour is needed to describe the overall macroscopic process more completely by including the fourth state variable (vw or degree of saturation, Sr, for the former and s for the latter). Following from work undertaken under one-dimensional conditions, the current paper presents the volumetric behaviour of compacted kaolin in (v, vw, p) space. A series of state path tests comprising various loading, unloading, and (or) wetting paths with nondecreasing degrees of saturation was carried out. The results show that a state boundary surface that is also the virgin compaction surface depicting the loosest state of soil takes control of the volumetric behaviour in (v, vw, p) space, which can be used as a more practical approach to modelling compacted soil behaviour, especially for analysing major wetting events.

AbstractWith red supergiants (RSGs) predicted to end their lives as Type IIP core collapse supernova (CCSN), their behaviour before explosion needs to be fully understood. Mass loss rates govern RSG evolution towards SN and have strong implications on the appearance of the resulting explosion. To study how the mass-loss rates change with the evolution of the star, we have measured the amount of circumstellar material around 19 RSGs in a coeval cluster. Our study has shown that mass loss rates ramp up throughout the lifetime of an RSG, with more evolved stars having mass loss rates a factor of 40 higher than early stage RSGs. Interestingly, we have also found evidence for an increase in circumstellar extinction throughout the RSG lifetime, meaning the most evolved stars are most severely affected. We find that, were the most evolved RSGs in NGC2100 to go SN, this extra extinction would cause the progenitor’s initial mass to be underestimated by up to 9M⊙.

The Brasília underground transportation system comprises 6.5 km of shallow tunnel excavated in a soft red soil known as porous clay that overlies harder residual soils. The tunnel diameter is 9.6 m. Settlement observations indicated that surface settlements were two to three fold the initially predicted value, although no indication of excavation instability was observed. Settlements reached, at one section, 500 mm without failure. Another striking feature was settlement amplification between the top of the excavation and the surface by a factor that averaged 1.2 but reached up to 4. This occured because of the collapsible nature of the porous clay, which presented a considerable reduction of volume as the tunnel face advanced. This paper describes tunnel design, construction, and instrumentation; and summarizes geology and soil properties from in situ and laboratory tests. Field measurements of settlements and horizontal displacements are described and analysed. The main cause of the large settlements was collapse of the porous clay structure. Key words: tunnelling, porous clay, settlements, collapse.

Unsaturated soil mechanics is of keen relevance when dealing with soil above the water table orcompacted soils. Barcelona Basic Model (BBM) is one of the most widely used constitutive models for describing unsaturated soil behaviour and is available as a soil model in software like PLAXIS and CODE_BRIGHT (developed by UPC). The present study demonstrates a numerical framework to implement BBM within the ABAQUS package as a user-defined soil model using a user subroutine called UMAT (User Material). The backward Euler integration scheme coupled with Newton Raphson iterative algorithm is used to construct the model. A convergence test is conducted to check the accuracy and stability of the integration. UMAT's inability to manage pore pressure led to proxy diffusion to depict suction variation. The heat equation is used as a proxy for diffusion in three-dimensional space and time. Anoedometer test is simulated in which the soil is allowed to consolidate and then set to saturate at constant vertical stress, which leads to wetting collapse. The results demonstrate a reasonable behaviour of wettinginduced compression of soil subjected to loading with varying saturation level.

The objective of the present study is to develop a biotechnological tool for a new application of silty sand soil as stabilized materials in linear works replacing chemical stabilizer (e.g. cement and lime) by natural cement, formed by precipitated calcium carbonate generated by microorganisms of the Sporosarcina family. For this purpose, it is conducted a chemical and mineralogical characterization and an examination of physical and geotechnical properties, being very important from the engineering standpoint. The results of different tests are presented here. The data show that the effects of bacteria are reducing the soil specific surface and increasing its plasticity. The reason for this result could be the addition of a plastic component to the natural soil, or the result of the more aggregated structure promoted during the treatment. The pore size distribution of the soil changes in an approximate range 3 - 30 µm, where the pore mode tends to disappear. The change in the pore density function is reflected in the mechanical behaviour of the treated soil, which presents typical features of a less dense soil with respect to the natural untreated one. The friction angle of the treated soil is slightly higher, and its compressibility is consistently lower than that of the natural soil. As the bacteria do not seem to produce any cementation effect on the soil skeleton, collapse upon wetting does not seem to be significantly affected by the treatment. On the contrary, comparison of collapse data shows that occurrence and amount of collapse are ruled by the as-compacted dry density. The tests performed seem to suggest that the microbiological technique may be effective to improve the mechanical characteristics of the compacted soil. For that, it is necessary to provide more energy in compacting the treated soil that it will be stabilized, so as to achieve a high initial dry density. From this viewpoint, it seems that higher compaction effort is even more effective than increasing the amount of bacteria introduced to stabilize the soil.

Abstract Collapsed walls cause collapsed mounds, and the disintegration characteristics of collapsed walls are thus closely linked with the occurrence of collapsed mounds. The current study examines the disintegration characteristics and the physical and chemical properties of collapsed walls. A multilevel analysis was conducted by obtaining soil samples from four layers of a collapsed wall. The results showed that 1) the physical and chemical properties of the soil samples (red soil layer, sandy soil layer, debris layer, gravel and eluvial breccia) are closely related to the weathering degree of the crust; 2) gravel and eluvial breccia disintegrated in the shortest time, whereas red soil exhibited the slowest disintegration in the vertical section of the collapsed wall. The order of the disintegrating ratio of the layers is as follows: red soil layer < sandy soil layer < debris layer < gravel and eluvial breccia. Initial water content significantly influenced the disintegration ratio of the red soil layer and sandy soil layer, whereas its effect on the debris layer and gravel eluvial breccia is minimal; and 3) most of the physical and chemical properties of the collapsed wall are significantly correlated with the disintegration ratio of the soil sample. The following physical and chemical properties, which are positively correlated with the disintegration ratio, are arranged based on highest to lowest correlation coefficient: sand content, MgO, natural water content, K2O, CaO, exchangeable sodium, pH, porosity, Na2O, and cation exchange capacity. The following physical and chemical properties, which are negatively correlated with the disintegration ratio, are organized based on highest to lowest correlation coefficient: cosmid, Fe2O3, silt particle, Al2O3, TiO2, SiO2, organic matter, free iron oxide, and free alumina. Only exchangeable calcium, saturated water content, specific gravity of soil particles, and dry density of soil particles are significantly correlated with the disintegration ratio. The correlation coefficient indicates that the disintegration ratio and soil structure, as well as the chemical content of clay minerals, are closely correlated. The study helps explain the mechanism of wall collapse and provides references for developing protective measures against erosion.

Crop residues left on the soil function as a nutrient reservoir and as a ground cover in agricultural systems. The aim of the present study is to assess the chemical alterations in the soil after the decomposition of different amounts of straw from corn as second crop. The climate of the region is classified as hot tropical and the soil is categorized as Red-Yellow Latosol (Typic hapludox) in the cerrado-amazon ecotone. The experiment was set up in randomized blocks in September 2013 after harvesting the second crop corn, comprised of corn straw rates (0, 14.18 and 42.54 t ha-1) with six repetitions. The content of macronutrients, H+Al, pH and base saturation in the soil profile were assessed. The straw rates were added to litter bags and stored on the soil, where they were kept for 154 days throughout the rainy period. Subsequently, the soil characteristics were assessed in layers 0 to 0.05, 0.05 to 0.10, 0.10 to 0.15, 0.15 to 0.20 and 0.20 to 0.40 m. The Ca+2 and Mg+2 elements were only released by the straw on the first 0.05 m of soil. However, K circulated in the soil profile reaching depth of 0.40 m. There was reduction in K+ saturation in treatments without straw. No alterations were observed in the other nutrients and studied attributes. According to the results, it is important to distribute the cultural remains of maize homogeneously in the area during harvesting to avoid the appreciation of soil fertility spots, especially of K.

Abstract: Dying is a popular practice in textile industry which is prevalent at all parts of the world from the period of ancient civilization. Initially, natural dyes i.e. dye derived from natural resources like vegetables, flowers, minerals, plants etc. were used. Now-a-days, due to technological and scientific innovations synthetic dyes are processed at large scale in the laboratories as it is still one of the most profitable industry globally. However, the rapid utilization of chemicals in textile industry for production of synthetic dyes causes degradation of environment like soil pollution, water pollution etc. Hence, it is necessary to promote the utilization of natural dyes globally. In this paper, the exhaustion of dye extracted from red chillies, one of the most used vegetables same has been studied on cotton fabrics at different temperatures using UV-Visible light spectrophotometer. The colour strength of the fabric before and after application of soap therein are also studied experimentally. Keywords: Natural dye, red chillies, cotton fabrics, exhaustion of dye, absorption.

Soil mechanical behaviour is strictly related to its natural water content, which is primarily dependent on hydraulic boundary conditions. When soils are partially saturated, as frequently occur in river embankments, soil suction also turns into a fundamental variable worth of investigation and monitoring, both in laboratory and in the field, for a reliable interpretation of the related soil response to external actions. The case of earthen water retaining structures and their safety condition assessment towards local or global collapse mechanisms requires special attention for soil characterization and site measurement of unsaturated soil states. Moreover, strength and hydraulic models used for relevant stability analyses should be adequate for representing the site-specific behaviour of soil in terms of water content, pore water pressure and suction values, relying on the effective possibility to properly calibrate all required parameters. Nevertheless, these aspects typically receive only limited attention, especially in standard practice, leading to inaccurate estimates of flood hazard and related risk management. In this context, with the aim of comprehensively studying the strength and retention properties of a riverbank silty soil, a series of laboratory investigations – including oedometric and direct shear tests under suction-controlled conditions – have been performed. Laboratory tests are here used as the main direct source of information to model unsaturated soil behaviour, monitoring different state variables under suction-controlled conditions. The results have been then interpreted using both literature and soil-specific mechanical and hydraulic models, to be possibly implemented in integrated methodologies for the stability assessment of river embankments.

One of the most common causes of ground failure during earthquakes is the liquefaction phenomenon, which produces severe damage to property. Although methods are available for seismic analysis of pile foundations, most of them consider soil to be an elastic material. Collapse of piled foundations in liquefiable areas has been observed in most recent strong earthquakes despite the fact that a large margin of safety is employed in their design. Lateral spreading of gently-sloping deposits of liquefiable sand is a cause of much damage in earthquakes, reportedly more than any other form of liquefaction-induced ground failure. The present investigation finds the effect of earthquake induced lateral soil movement on lateral pile capacity. Parametric study is carried out on the same model by changing the ground surface to different slopes on the top of the non liquefiable layer and by changing the length of the pile in the bottom layer of the non liquefiable layer. The paper focuses on the behaviour of pile under lateral soil movement due to earthquake. The bending moment and displacement behaviour of pile is studied in detail for different slope conditions.

This paper summarizes the findings from an experimental program concerning the hydromechanical behavior of two smectite clays tested under high stresses. Increasing axial stress on the smectite samples under controlled relative humidity (suction) leads to collapse in the soil structure and increases the degree of saturation. Irreversible volume change is observed in samples tested under cyclic suction with constant axial load. Water-retention (adsorption and desorption) behavior of the smectite clays tested in this study is affected by particle size, initial void ratio, and confinement conditions during the tests. Laponite, which has a large specific surface area, tends to hold more water than hectorite at a given relative humidity. More water is adsorbed by samples compacted at lower axial stress.Key words: smectite clays, hydromechanical stresses, behavior, relative humidity and suction, water retention, degree of saturation.

Non-lethal parasite infections are common in wildlife, but there is little information on their clinical consequences. Here, we pair infection data from a ubiquitous soil-transmitted helminth, the whipworm (genus Trichuris ), with activity data from a habituated group of wild red colobus monkeys ( Procolobus rufomitratus tephrosceles ) in Kibale National Park, Uganda. We use mixed-effect models to examine the relationship between non-lethal parasitism and red colobus behaviour. Our results indicate that red colobus increased resting and decreased more energetically costly behaviours when shedding whipworm eggs in faeces. Temporal patterns of behaviour also changed, with individuals switching behaviour less frequently when whipworm-positive. Feeding frequency did not differ, but red colobus consumption of bark and two plant species from the genus Albizia , which are used locally in traditional medicines, significantly increased when animals were shedding whipworm eggs. These results suggest self-medicative plant use, although additional work is needed to verify this conclusion. Our results indicate sickness behaviours, which are considered an adaptive response by hosts during infection. Induction of sickness behaviour in turn suggests that these primates are clinically sensitive to non-lethal parasite infections.

The behaviour of sika and red deer during the rutting season is highly variable in relation to vocalization, habitat preference during the rut, and onset and termination of rutting. The red deer is a native species in Central Europe, but the areas where it lives in sympatry with the introduced sika deer have been increasing in the last three decades. Such situation can be found in the Doupovsk&eacute; hory Mts., where sika deer has been intensively spreading. Hybridization between the two species and changes in behaviour are the most important problems. In this study we prove the shift in the rutting period shown by both species. To evaluate the shift in the rutting season, we used a very extensive long-term data set on deer shot within the Military Training Area. These changes occur very slowly, however, and are very difficult to monitor and evaluate in the wild. Based on our results, the timing of the rutting season has converged at the mean rate of 0.62 day per year (rutting season starts later in the red deer and earlier in the sika deer). &nbsp;