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1
Hamad, Asal Mahmud, e Mahmood Gazey Jassam. "A Comparative Study for the Effect of Some Petroleum Products on the Engineering Properties of Gypseous Soils". Tikrit Journal of Engineering Sciences 29, n. 3 (15 ottobre 2022): 69. http://dx.doi.org/10.25130/tjes.29.3.7.
Testo completoAbstract (sommario):
Gypseous soils are considered problematic soils because the soil cavities happen during receiving the water or this type of soil and solving gypsum materials and contract in a soil volume. In this study, three types of gypseous soils are used; soil1, soil2, and soil3 with gypsum content (28.71%, 43.6%, and 54.88%) respectively, petroleum products (engine oil, fuel oil, and kerosene) are added to the soils with percentages (3%, 6%, 9%, and 12%) for each product. The result showed that specific gravity, liquid limit, optimum moisture content (O.M.C), and maximum dry density decreased with an increased percentage of product for all types of products. The direct shear (dry and soaked case) results show that increasing the (angle of internal friction and the soil cohesion) for soil1, soil2, and soil3 by adding engine oil and fuel oil. Still, when the soils were treated with kerosene, the angle of internal friction increased while cohesion decreased. The collapse potential for the treated soils increases with increasing gypsum content for all petroleum products. The collapse potential (CP) for (soil1) decreased by 47% when using 6% of the engine oil, 48.8% when using 9% of the fuel oil, and 55% when using 9% of the kerosene. The same percentage of the petroleum products (engine oil, fuel oil, and kerosene) decrease the collapse potential for (soil2), (47%, 46%, and 50%) respectively and decrease the collapse potential for (soil 3), (51%, 47.7%, and 52%) respectively. In the unconfined compressive test applied on (soil1) using maximum density, the results show that the soil strength increased (26% and 10%) when using 6% and engine oil and fuel oil, respectively, while the soil strength decreased by 29% when treated with 9% of kerosene.
2
Aitken, RL, e PW Moody. "Interrelations between soil pH measurements in various electrolytes and soil solution pH in acidic soils". Soil Research 29, n. 4 (1991): 483. http://dx.doi.org/10.1071/sr9910483.
Testo completoAbstract (sommario):
Ninety soil samples (81 surface, 9 subsurface) were collected from eastern Queensland and soil pH (1:5 soi1:solution) was measured in each of deionized water (pH,), 0.01 M CaCl2, 0-002 M CaCl2 and 1 M KCl. Soil solution was extracted from each soil after incubation for 4 days at the 10 kPa matric suction moisture content, and pH (pHss) and electrical conductivity were measured. The objectives of this work were to investigate interrelationships between soil pH measurements in various electrolytes and soil solution pH in a suite of predominantly acidic soils. Although the relationships between pHw and pH measured in the other electrolytes could be described by linear regression, the fitting of quadratic equations improved the coefficients of determination, indicating the relationships were curvilinear. The majority of soils exhibited variable charge characteristics (CEC increases with soil pH) and the curvilinear trend is explained on this basis. At low pH, the difference between pH, and pH measured in an electrolyte will be small compared with the difference at higher pH values because, in general, at low pH, soils will be closer to their respective PZSE (pH at which electrolyte strength has no effect). Of the electrolytes used, pH measured in 0.002 M CaCl2 gave the closest approximation to pHs,. However, when soils with ionic strengths greater than 0.018 M were selected (predominantly cultivated surface soils), pH in 0.01 M CaCl2 gave the best approximation to pHss. For predicting pHss, the ionic strength of the electrolyte will need to be matched to that of the soils studied. For a suite of soils with a large range in soil solution ionic strength (as in this study), it is preferable to measure pHss directly.
3
Luo, Donghui, Jialun Li, Yongxing Cao, Bo Tan, Wei Li e Hanyu Wang. "Research on the Influence of Typical Soil Parameters on Critical Breakdown Field Strength and Residual Resistivity Based on Discharge Topography". Energies 14, n. 16 (6 agosto 2021): 4810. http://dx.doi.org/10.3390/en14164810.
Testo completoAbstract (sommario):
Partial discharge of soil occurs when a lightning current enters the ground, and the strength of partial discharge is closely related to the magnitude of its critical breakdown field strength. Therefore, how to accurately obtain the variation law of the typical soil critical breakdown field strength and residual resistivity is the key to realizing the safe operation of the grounding devices and cables in the ground. This paper first selects a variety of typical soils to study the influence of various factors on the morphology of the discharge channel, and then studies the calculation methods of the soil critical breakdown field strength and residual resistivity under the introduction of different discharge channel morphologies and structures, and further discusses the reason why typical soil media factors have a small impact on the critical breakdown field. The experimental results show that under the same conditions, the critical breakdown field strengths of different soils from small to large are sand soil, loam soil and Yellow cinnamon soil. The largest ratio of residual resistivity to initial resistivity of the three soils is sand soil.
4
Eid, Hisham T., Ruslan S. Amarasinghe, Khaled H. Rabie e Dharma Wijewickreme. "Residual shear strength of fine-grained soils and soil–solid interfaces at low effective normal stresses". Canadian Geotechnical Journal 52, n. 2 (febbraio 2015): 198–210. http://dx.doi.org/10.1139/cgj-2014-0019.
Testo completoAbstract (sommario):
A laboratory research program was undertaken to study the large-strain shear strength characteristics of fine-grained soils under low effective normal stresses (∼3–7 kPa). Soils that cover a wide range of plasticity and composition were utilized in the program. The interface shear strength of these soils against a number of solid surfaces having different roughness was also investigated at similar low effective normal stress levels. The findings contribute to advancing the knowledge of the parameters needed for the design of pipelines placed on sea beds and the stability analysis of shallow soil slopes. A Bromhead-type torsional ring-shear apparatus was modified to suit measuring soil–soil and soil–solid interface residual shear strengths at the low effective normal stresses. In consideration of increasing the accuracy of assessment and depicting the full-scale field behavior, the interface residual shear strengths were also measured using a macroscale interface direct shear device with a plan interface shear area of ∼3.0 m2. Correlations are developed to estimate the soil–soil and soil–solid interface residual shear strengths at low effective normal stresses. The correlations are compared with soil–soil and soil–solid interface drained residual shear strengths and correlations presented in the literature.
5
Barzegar, AR, RS Murray, GJ Churchman e P. Rengasamy. "The strength of remolded soils as affected by exchangeable cations and dispersible clay". Soil Research 32, n. 2 (1994): 185. http://dx.doi.org/10.1071/sr9940185.
Testo completoAbstract (sommario):
The tensile strengths of remoulded samples of five Australian soils with differing clay type, texture and shrink-swell potential were measured as a function of exchangeable cations (Na, Ca and Mg) and exchangeable sodium percentage (ESP). Spontaneously and mechanically dispersible clays were also determined as a function of ESP. The tensile strength changed with the nature of the exchangeable cation, clay content and amounts of spontaneously and mechanically dispersible clay. In Ca-soils, the tensile strength was highly correlated with clay content and CEC. Regression analyses of data for soils containing various amounts of exchangeable sodium showed that mechanically and spontaneously dispersible clay were individually correlated with the tensile strength of remoulded soils. However, multiple regression analyses of these data indicated that spontaneously dispersible clay alone was a major predictor of the tensile strength of remoulded sodic soils. This suggests that measurement of spontaneously dispersible clay adequately accounts for the differences in tensile strengths of dry remoulded soils as influenced by ESP values. Analysis of variance of data for all the soils with varying ESP values showed that spontaneously dispersible clay was strongly correlated with clay content. Analyses of data for individual soil type showed that spontaneously dispersible clay was highly correlated with ESP. For each soil studied, increase in ESP resulted in increase of dispersible clay and hence in tensile strength. Although tensile strength increased with ESP, the rate of change of strength with ESP was different for each soil. Soil with the highest clay content gave rise to the greatest rate of change. The effect of exchangeable magnesium on tensile strength was similar to calcium. However, in two of the soils, exchangeable magnesium, in the presence of sodium, increased the strength slightly more than calcium, confirming the ionic radius effect of these elements.
6
Misra, RK, e CW Rose. "An examination of the relationship between erodibility parameters and soil strength". Soil Research 33, n. 4 (1995): 715. http://dx.doi.org/10.1071/sr9950715.
Testo completoAbstract (sommario):
Erosion rate of soil by the impact of raindrops and overland flow of water is often considered to be affected by the shear strength of surface soil. Physically based erosion models indicate a link between defined erodibility parameters and soil strength. The objectives of this paper are to determine erodibility parameters with the process-based erosion model GUEST for a. krasnozem soil of two contrasting strengths, and to examine the influence of soil strength on erodibility parameters. Soil beds of width 1 m and length 5.8 m, with and without compaction, were exposed to simulated, constant rate rainfall. A range of slopes was used. Detachment trays of width 300 mm and downslope length 200 mm containing soils of identical strength were placed at the same slope and exposed to the same rain in order to determine the effects of rainfall-driven processes alone on erosion. Soil strength was measured with a hand vane tester and a pocket penetrometer to determine whether compaction was effective in modifying soil strength. Temporal variation in sediment concentrations (c) for the large soil beds and detachment trays was measured for each slope and soil strength. The settling velocity characteristic of soil, with and without exposure to rain, was determined with the modified bottom withdrawal tube technique. Values of c decreased with increase in soil strength. The relationship between c and slope was influenced by soil strength in a manner consistent with the theoretical expectation of the role of soil strength in controlling erosion. Rilling during erosion was absent only when the soil was compacted. The average settling velocity of the soil exposed to rain (i.e. its depositability) was significantly lower than for the same soil not subjected to rain, indicating a breakdown of soil aggregates as a result of raindrop impact. Rainfall detachability parameters (estimated with GUEST) Were lower when soil strength was high. Runoff-driven erodibility parameters, namely the specific energy of entrainment (J), increased and the approximate erodibility parameter (�) decreased with increase in soil strength. The Variation in these erodibility parameters with soil strength was consistent with the theory implemented in GUEST. Detailed analysis of the relative contribution of rainfall- and runoff-driven processes to c at varying stream powers and soil strengths indicated that, at high soil strength, uncertainty in the values of J and � is high because of the higher contribution to c of rainfall-driven rather than runoff-driven processes. The adequacy of in situ measurement of soil strength as an indicator of soil erodibility is discussed in relation to the results presented.
7
Li, Xinming, Haoyang Zhang, Yanrui Guo, Song Yin e Kebin Ren. "Effect of Dry-Wet Cycles on Strength Properties and Microstructure of Lime-Metakaolin-Modified Soil". Advances in Civil Engineering 2022 (29 settembre 2022): 1–14. http://dx.doi.org/10.1155/2022/1296288.
Testo completoAbstract (sommario):
To explore the feasibility of replacing natural hydraulic lime (NHL) with lime-metakaolin (L-MK) in the restoration of soil sites, the samples of L-MK-modified silty sand (hereinafter L-MK-modified soil) underwent 0, 5, 10, and 15 dry-wet cycles and were then tested for mass loss, unconfined compressive strength, and splitting tensile strength. Some samples were tested using XRD, TG and SEM microscopic tests to study the strength mechanism for L-MK- and NHL-modified soil. The results showed that the mass loss ratios of the L-MK- and NHL-modified soils after 15 dry-wet cycles were within 2%. The compressive and tensile strengths of the L-MK-modified soil decreased with more dry-wet cycles, but the tensile strength decreased sharply initially and then to be stable after five dry-wet cycles. The attenuation characteristics were different obviously for the failure mode of compressive and tensile strength and the unevenness of the specimen caused by dry-wet cycles. The compressive and tensile strengths of L-MK-modified soil were significantly higher than those of NHL-modified soil after the same dry-wet cycle, and the decreased range of compressive and tensile strength was smaller than that of NHL-modified soil. The strength formation and attenuation characteristics of L-MK-modified soil are closely related to the influence of dry-wet cycles on the hydration products (e.g., CSH and C4AH13) generated by hydration reaction. The mix proportion of 6% L + 4% MK can effectively replace 8% and 10% NHL to protect soil sites.
8
Dolling, PJ, e GSP Ritchie. "Estimates of soil solution ionic strength and the determination of pH in West Australian soils". Soil Research 23, n. 2 (1985): 309. http://dx.doi.org/10.1071/sr9850309.
Testo completoAbstract (sommario):
The average ionic strength of 20 West Australian soils was found to be 0.0048. The effects of three electrolytes (deionized water, CaCl2 and KNO3), three ionic strengths (0.03, 0.005 and soil ionic strength at field capacity, Is) and two soil liquid ratios (1:5 and 1:10) on the pH of 15 soils were investigated. pH measurements in solutions of ionic strength 0.005 differed the least from measurements made at Is. The differences that occurred in comparisons with distilled water or CaCl2 of ionic strength 0.03 (0.01 M) were much greater (20.4 pH units). An extractant with an ionic strength of 0.005 may provide a more realistic measure of pH in the field than distilled water or 0.01 M CaCl2 for West Australian soils.
9
Fredlund, D. G., Anqing Xing, M. D. Fredlund e S. L. Barbour. "The relationship of the unsaturated soil shear strength to the soil-water characteristic curve". Canadian Geotechnical Journal 33, n. 3 (2 luglio 1996): 440–48. http://dx.doi.org/10.1139/t96-065.
Testo completoAbstract (sommario):
The measurement of soil parameters, such as the permeability and shear strength functions, used to describe unsaturate soil behaviour can be expensive, difficult, and often impractical to obtain. This paper proposes a model for predicting the shear strength (versus matric suction) function of unsaturated soils. The prediction model uses the soil-water characteristic curve and the shear strength parameters of the saturated soil (i.e., effective cohesion and effective angle of internal friction). Once a reasonable estimate of the soil-water characteristic curve is obtained, satisfactory predictions of the shear strength function can be made for the unsaturated soil. Closed-form solutions for the shear strength function of unsaturated soils are obtained for cases where a simple soil-water characteristic equation is used in the prediction model. Key words: soil suction, soil-water characteristic curve, shear strength function, unsaturated soil.
10
Zhang, Xiao Ming, Qian Jin Liu e Xing Xiu Yu. "Differences of Shear Strength between Undisturbed and Remolded Soils of Lands for Agriculture and Forestry in Menglianggu Watershed of Linyi City". Advanced Materials Research 599 (novembre 2012): 815–19. http://dx.doi.org/10.4028/www.scientific.net/amr.599.815.
Testo completoAbstract (sommario):
To find the effects of pedoturbation on soil erosion of lands for agriculture and forestry in Menglianggu watershed of Linyi city from soil mechanics, shear strengths of 3 typical land uses (6 different soils) which are undisturbed and remolded respectively were measured by direct shear apparatus. Effects of particle size and binding materials on shear strength were analyzed by comparing shear properties of undisturbed and remolded soils with the same dry density, water content and vertical loads. The results show that all the angle of internal friction ( ) and most of soil cohesion ( ) of undisturbed soils are bigger than that of remolded soils; The final shearing stress also comply with the law above; The main factors affecting shear strength are soil particle size and binding materials.
11
Habibullah, Hafiy Syafiqy, Min Lee Lee e Soon Yee Wong. "Correlation between undrained shear strength and liquidity index of soils in Malaysia". E3S Web of Conferences 347 (2022): 03004. http://dx.doi.org/10.1051/e3sconf/202234703004.
Testo completoAbstract (sommario):
Accuracy of soil undrained shear strength measurement is often governed by the quality of undisturbed soil sampling. Numerous previous attempts have been made to establish correlations between the undrained shear strength and various soil physical parameters. This paper aims to determine a correlation between the undrained shear strength (cu) and liquidity index (IL) based on 34 soil samples collected from selected sites in Peninsular Malaysia. Sieving, hydrometer analysis and Atterberg limit tests were performed to determine physical properties of the soils. The undrained shear strengths were determined using the Unconsolidated Undrained (UU) triaxial test. An attempt was made to correlate the undrained shear strength with liquidity index of all the soil specimens. However, the correlation was found to be considerably weak (r2 = 0.47). The correlation was improved significantly (r2 = 0.82) by limiting the data to soils with fines content of more than 65% only. The proposed equation was in the form cu = a exp(-bIL) where the values of constants a and b were determined empirically as 72.9 and 1.95, respectively.
12
Dai, Lei, e Xiao Xuan Deng. "The Relationship between Calcium Hydroxide Concentration in Pore Solution and the Strength of Stabilized Soils". Advanced Materials Research 989-994 (luglio 2014): 19–22. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.19.
Testo completoAbstract (sommario):
Under the same cement content, the stabilized soils, made of the soils with similar physical properties, may be significant difference in the strength. In this research, three groups of soils were selected, and the soils in each group are similar in physical properties. Strength and ions concentration in pore solution of the stabilized soils were investigated. The result reveals that calcium hydroxide (CH) concentration in pore solution of the stabilized soils might not reach to saturation due to soil consuming Ca2+and thus cause calcium silicate hydrates gels (C-S-H) and calcium aluminates hydrates gels (C-A-H) to form less. The cementitious hydrates are the main strength contributors of the stabilized soils. The Strengths of stabilized soils, the soils bearing similar physical properties, were almost identical as long as the CH concentrations in pore solution were saturated. The effect of chemical factors of soil on the strength of stabilized soil can be briefly attributed to the change of CH concentration in pore solution, and be further attributed to the influence of CH concentration on the amount of C-S-H and C-A-H formed in stabilized soils.
13
Saad, Ahmed Hassan, Haslinda Nahazanan, Zainuddin Bin Md Yusoff, Muskhazli Mustafa, Mohamed Hamdy Elseknidy e Angham Ali Mohammed. "Evaluating Biosedimentation for Strength Improvement in Acidic Soil". Applied Sciences 11, n. 22 (16 novembre 2021): 10817. http://dx.doi.org/10.3390/app112210817.
Testo completoAbstract (sommario):
Marine clay soils are problematic soils in the construction industry when they are subjected to construction loads. When these soils are loaded, they lose their structure. This leads to the soil being unable to withstand loads of any magnitude without exhibiting significant, permanent deformations. In order to stabilize the marine soil, new methods for soil improvement were built upon biogrouting by incorporating physical, biological and chemical treatments into the soil. However, the biggest challenge of this method is the bacteria migration through the soil medium. To overcome this issue, the electrokinetic phenomenon can be utilized alongside biogrouting to prevent the bacteria migration. In this regard, the present study applied electrobiogrouting stabilization to investigate the improvement of acidic marine clay soil with a pH of 3.69. To accomplish this, two large-scale physical models with dimensions of 500 × 300 × 1200 mm were fabricated to examine the influence of two different treated distances between the inlet and outlet—450 mm (D45) and 600 mm (D60)—on the stability of the treated soil. It was observed that the shear strength of the treated soil improved significantly. The shear strength at the D45 treated distance increased from 3.65 kPa (untreated soil) to 28.14 kPa (treated soil). However, the strength increased by increasing the treated distance. In addition, compressibility and soil electrical conductivity were reduced significantly, and the Atterberg limits were significantly enhanced from OH to OL. The reasons for the enhancement of treated soil were the formation of CaCO3, which filled the soil voids, and that the water content was reduced. To address issues with marine clay soil, this study aims to minimize the high cost of a special foundation system and the use of non-environmentally friendly materials such as calcium-based binders, aside from the reduction of deformations caused by loading. The findings of this study can be used for acidic soils and the improvement of soil’s geotechnical behavior in general.
14
Harper, R. J., e R. J. Gilkes. "The effects of clay and sand additions on the strength of sandy topsoils". Soil Research 42, n. 1 (2004): 39. http://dx.doi.org/10.1071/sr03063.
Testo completoAbstract (sommario):
The clay contents of sandy soils in south-western Australia are often modified, either intentionally or inadvertently, as a result of management practices and erosion. Although the strength of sandy surfaced soils has previously been shown to be related to clay content, in natural soils the effects of induced changes in clay content on soil strength have not been assessed.Increasing amounts of subsoil clay were added to their respective topsoils in increments ranging from 5 to 20% by weight, and these systematically increased soil strength. A strong log–log relationship between clay content and soil strength explained 69% of the variation, with soil strength further affected by sodicity. This enhancement of soil strength has implications for the practice of claying water-repellent soils, particularly where non-uniform application or poor incorporation results in high concentrations of clay, where very high rates (e.g. 300 t/ha) of application are used, or where clayey subsoils are brought to the surface by deep cultivation or the removal of topsoils by erosion.Drift sand, with a clay content of around 1% and negligible strength, was added in increasing increments to typical topsoils, over the range of 0–100% by weight to replicate the effects of wind-induced deposition and winnowing of clay particles. Increasing additions of drift sand systematically decreased soil strength, with a log–log relationship between clay content and strength of the mixtures explaining 81% of the variation. This suggests that wind erosion, and the winnowing of clay or deposition of drift sand, permanently destabilises soil surfaces by reducing soil strength. It is feasible that strategic applications of sand on the surfaces of soils affected by hardsetting may reduce soil strength and encourage soil structure development and seedling emergence.
15
Harrop-Williams, Kingsley, e Samuel Ejezie. "Stochastic description of undrained soil strength". Canadian Geotechnical Journal 22, n. 4 (1 novembre 1985): 437–42. http://dx.doi.org/10.1139/t85-063.
Testo completoAbstract (sommario):
The probabilistic description of the undrained strength of cohesive soils is important in the reliability analysis of short-term slope stability. In this paper the undrained strength is derived to be identically beta-distributed with depth. The approach is through consideration of particle-to-particle effects in the soil and the overall contribution of both cohesion and friction to the undrained strength. The final result confirms experimental investigation in these soils.
16
Mielke, L. N., W. L. Powers, S. Badri e A. J. Jones. "Estimating soil water content from soil strength". Soil and Tillage Research 31, n. 2-3 (agosto 1994): 199–209. http://dx.doi.org/10.1016/0167-1987(94)90080-9.
Testo completo
17
Hivon, E. G., e D. C. Sego. "Strength of frozen saline soils". Canadian Geotechnical Journal 32, n. 2 (1 aprile 1995): 336–54. http://dx.doi.org/10.1139/t95-034.
Testo completoAbstract (sommario):
This paper summarizes an extensive laboratory program undertaken to study the influence of soil type, temperature, and salinity on the strength of three different frozen soils under conditions of unconfined constant strain rate tests. Since the effects of temperature and salinity can be unified by studying the variation of unfrozen water content, measurements of unfrozen water at different temperatures were carried out using the time-domain reflectometry (TDR) method. The stress–strain behavior is influenced by the presence of fine particles in the soil, and an increase in temperature and salinity (unfrozen water content) causes a significant loss of strength. For each soil tested, a predictive model of its strength in terms of salinity and temperature (unfrozen water content) is presented. Key words : frozen soil, saline, unfrozen water, strength.
18
Lawrence, David M., e Julia M. Slingo. "Weak Land–Atmosphere Coupling Strength in HadAM3: The Role of Soil Moisture Variability". Journal of Hydrometeorology 6, n. 5 (1 ottobre 2005): 670–80. http://dx.doi.org/10.1175/jhm445.1.
Testo completoAbstract (sommario):
Abstract A recent model intercomparison, the Global Land–Atmosphere Coupling Experiment (GLACE), showed that there is a wide range of land–atmosphere coupling strengths, or the degree that soil moisture affects the generation of precipitation, amongst current atmospheric general circulation models (AGCMs). Coupling strength in the Hadley Centre atmosphere model (HadAM3) is among the weakest of all AGCMs considered in GLACE. Reasons for the weak HadAM3 coupling strength are sought here. In particular, the impact of pervasive saturated soil conditions and low soil moisture variability on coupling strength is assessed. It is found that when the soil model is modified to reduce the occurrence of soil moisture saturation and to encourage soil moisture variability, the soil moisture–precipitation feedback remains weak, even though the relationship between soil moisture and evaporation is strengthened. Composites of the diurnal cycle, constructed relative to soil moisture, indicate that the model can simulate key differences in boundary layer development over wet versus dry soils. In particular, the influence of wet or dry soil on the diurnal cycles of Bowen ratio, boundary layer height, and total heat flux are largely consistent with the observed influence of soil moisture on these properties. However, despite what appears to be successful simulation of these key aspects of the indirect soil moisture–precipitation feedback, the model does not capture observed differences for wet and dry soils in the daily accumulation of boundary layer moist static energy, a crucial feature of the feedback mechanism.
19
Wang, Yong, Jun Jiang, Ren-kou Xu e Diwakar Tiwari. "Phosphate adsorption at variable charge soil/water interfaces as influenced by ionic strength". Soil Research 47, n. 5 (2009): 529. http://dx.doi.org/10.1071/sr08181.
Testo completoAbstract (sommario):
The effect of phosphate adsorption on zeta potential of the colloids of variable charge soils and the effect of ionic strength on phosphate adsorption by the soils were investigated using batch experimental method. The presence of phosphate resulted in the decrease in zeta potential and isoelectric point (IEP) of the colloids of the soils, which further suggested that the phosphate was adsorbed specifically by these soils. The effect of phosphate adsorption on zeta potential was correlated with the content of free Fe/Al oxides in the soils; the higher the content of Fe/Al oxides in a soil the greater was the decrease in zeta potential and IEP of the soil colloids. The intersection of phosphate adsorption–pH curves at different ionic strengths (a characteristic pH) was obtained for 2 Oxisols. Above this pH, the adsorption of phosphate increased with increasing ionic strength, whereas below it the reverse trend occurred. The intersect pH was 4.60 for the Oxisol from Guangdong and 4.55 for the Oxisol from Yunnan, which was lower than the values of PZSE (point of zero salt effect) of these soils, but near the PZNC (point of zero net charge) of the soils. The effects of ionic strength and pH on phosphate adsorption by these soils were interpreted with the help of an adsorption model developed previously by Bowden et al. The results of zeta potential suggested that the potential in an adsorption plane became less negative with increasing ionic strength above the soil PZNC and decreased with increasing ionic strength below the soil PZNC. These results support the hypothesis of the adsorption model that the potential in the adsorption plane changed with ionic strength with an opposite trend to the surface charge of these soils. The phosphate adsorption by these soils was related not only to the ionic strength but also to the types of electrolytes present. K+ induced a greater increase in phosphate adsorption than Na+ due to the greater affinity of the soils to K+ than Na+.
20
Zhou, Yan-Ming, Zong-Wei Deng, Zi-Jian Fan e Wen-Jie Liu. "Shear Strength Deterioration of Compacted Residual Soils under a Wind Turbine due to Drying-Wetting Cycles and Vibrations". Advances in Civil Engineering 2021 (13 dicembre 2021): 1–10. http://dx.doi.org/10.1155/2021/8628842.
Testo completoAbstract (sommario):
The soil beneath a wind turbine withstands not only environmental impacts but also continuous vibrations transmitted from the superstructure. This paper presents an experimental study of the deterioration characteristics of shear strengths of residual soils affected by drying-wetting cycles and continuous vibrations. A series of triaxial tests were performed on compacted residual soil specimens after various drying-wetting cycles and vibrations. The influences of drying-wetting cycles and vibrations on the shear strengths of residual soils with different compaction degrees were analyzed. The results demonstrate that the shear strength and cohesion of compacted residual soils decreased as the number of drying-wetting cycles increased, and they tended to be stable after three drying-wetting cycles. The angle of internal friction decreased linearly with the reduction of compaction degree but was generally not affected by drying-wetting cycles. The shear strength of compacted residual soils also decreased because of continuous vibrations. After 10000 vibrations, the strength was stabilized gradually. Both the cohesion and angle of internal friction showed dynamic attenuation phenomenon. Finally, a modified Mohr–Coulomb strength equation considering the effects of drying-wetting cycles and vibrations was established. This equation could be used to predict the shear strength of compacted residual soils and further estimate the embedded depth of wind turbine foundations.
21
Schjønning, Per, e Karl J. Rasmussen. "Soil strength and soil pore characteristics for direct drilled and ploughed soils". Soil and Tillage Research 57, n. 1-2 (settembre 2000): 69–82. http://dx.doi.org/10.1016/s0167-1987(00)00149-5.
Testo completo
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He, Shi, Xinbao Yu, Aritra Banerjee e Anand J. Puppala. "Expansive Soil Treatment with Liquid Ionic Soil Stabilizer". Transportation Research Record: Journal of the Transportation Research Board 2672, n. 52 (23 agosto 2018): 185–94. http://dx.doi.org/10.1177/0361198118792996.
Testo completoAbstract (sommario):
Calcium-based stabilizers such as lime and cement control swell and shrinkage behavior and enhance strength properties for expansive soils through the formation of pozzolanic components. However, sulfate-bearing subgrade soils stabilized with calcium-based stabilizers might cause excessive swelling and shrinkage due to the formation of highly expansive minerals like ettringite and thaumasite. In this paper, one liquid ionic soil stabilizer (LISS) was evaluated as an alternative stabilizer used to control swelling and shrinkage behavior of expansive soils. A comprehensive laboratory experiment program including a linear shrinkage test, a one-dimensional swell test, and an unconfined compressive strength test, was designed and carried out on soils from Dallas, Texas before and after treatment. Three dosage levels of stabilizer and four different curing periods were investigated. Test results indicate that LISS is an effective stabilizing agent, which not only reduces swelling and soil plasticity but also increases soil strength. Furthermore, a similar type of LISS is utilized to treat the soil in Dallas via deep injection using a hydraulic pump. Field emission scanning electron microscopy results on the test soil showed that the stabilizing program is likely to work through clay flocculation and morphological variations in the clay particles.
23
Ezreig, Ali Muftah Abdussalam, Mohd Ashraf Mohamad Ismail e Khaled Ibrahim Azarroug Ehwailat. "Hydrophobic Effect of Soil Stabilization for a Sustainable Subgrade Soil Improvement". Materials 15, n. 9 (24 aprile 2022): 3087. http://dx.doi.org/10.3390/ma15093087.
Testo completoAbstract (sommario):
The chemical process of using additives to stabilize soils is to improve soil that lacks strong engineering properties. In particular, the moisture susceptibility of subgrade soil through seasonal rains is still questionable. The presence of water in the construction is the cause of deterioration and premature distress of pavements and their supporting geotechnical structures. In this work, the chemical use of hydrophobic caltite (HC) in various amounts (ranging from 3%, 5%, to 7%) and 5% of cement to enhance laterite soils is investigated. The investigation includes the evaluation of soil properties, such as, unconfined compressive strength (UCS) by curing in air and under water, flexural strength (FS), and California Bearing Ratio (CBR) soaked and unsoaked. The addition of caltite with cement increases the strength characteristics with the UCS values of 2078–2853 kPa during the early curing stages (7th day), and 4688–4876 kPa after 90 days of curing. The added caltite in the cement soil samples shows a reduction index of strength loss underwater with the UCS values of 3196, 3334, and 3751 kPa for caltite cemented soil when compared with cement soil alone. FS results suggest that the inclusion of caltite in cement means that post-peak behavior can be enhanced, reducing the brittleness and increasing the ductility. The successful reaction with soil additives occurred in the curing period of 7 days. In terms of the microstructural analysis, results show that HC with cement reduces the porosity, voids, and cracking of laterite soils. Furthermore, new polymer globules, products from the reaction, appeared on the clay particle surfaces, thereby reducing the water absorption. The addition of hydrophobic-caltite to the soil–cement mixture results in increased strength and reduced water absorption in a soil–cement mix, thus achieving a given strength value.
24
Jiang, Huang, Ma e Luo. "Analysis of Strength Development and Soil–Water Characteristics of Rice Husk Ash–Lime Stabilized Soft Soil". Materials 12, n. 23 (23 novembre 2019): 3873. http://dx.doi.org/10.3390/ma12233873.
Testo completoAbstract (sommario):
With increased awareness of environmental protection, the output of traditional curing agents such as cement and lime is less and less, so it is urgent to develop new curing agents with high efficiency and environmental benefits. Thus, this study aims at investigating the application of rice husk ash (RHA) from agricultural waste to the soft soil stabilization. A series of tests are conducted to analyze the strength development process and soil–water characteristics of rice husk ash–lime (RHA–lime) stabilized soils. The results of the strength tests showed that by increasing the content of RHA, the unconfined compressive strength (UCS) and splitting strength of stabilized soils increased first and then decreased. The effective shear strength indexes of the three soil types (soft soil, lime-stabilized soil, and RHA–lime soil) are measured and compared. It is found that RHA can effectively improve the shear resistance and water resistance of stabilized soil. The results of methylene blue test demonstrated that RHA can also promote the reduction of the specific surface area and swelling potential energy of lime-stabilized soil. In addition, the influence of RHA on mineral composition and morphology change in stabilized soils is studied at the microscopic level. The X-ray diffraction tests and scanning electron microscope (SEM) tests showed that strength development and change of soil–water properties of RHA–lime stabilized soil are attributed to enhanced cohesion by cementation and pores filling with agglomerated mineral.
25
Sivapullaiah, P. V., A. Sridharan e H. N. Ramesh. "Strength behaviour of lime-treated soils in the presence of sulphate". Canadian Geotechnical Journal 37, n. 6 (1 dicembre 2000): 1358–67. http://dx.doi.org/10.1139/t00-052.
Testo completoAbstract (sommario):
Lime has been used extensively to improve the shear strength of fine-grained soils. It has been recently reported that the presence of sulphate causes abnormal volume changes in lime-stabilized soil. The paper presents the strength behaviour of lime-treated montmorillonitic natural black cotton soil in the presence of varying sulphate contents after curing for periods of up to 365 days. Alteration of soillime reactions in the presence of sulphate affects the strength development by cementation. Consequently, the stressstrain behaviour effective stress paths of soil cured with sulphate are similar to those of normally consolidated soil rather than cemented soils. The reduction in shear strength due to a reduction in effective cohesion intercept occurs for lime-treated soil cured with sulphate for long periods.Key words: clays, cohesion, fabric, friction, shear strength.
26
Yi, Yaolin, Martin Liska, Cise Unluer e Abir Al-Tabbaa. "Carbonating magnesia for soil stabilization". Canadian Geotechnical Journal 50, n. 8 (agosto 2013): 899–905. http://dx.doi.org/10.1139/cgj-2012-0364.
Testo completoAbstract (sommario):
This paper investigates the potential for carbonating reactive magnesia (MgO) to serve as a more sustainable soil stabilization method by providing rapid and significant strength development of the stabilized soil through absorbing substantial quantities of CO2. Gaseous CO2 was forced through laboratory-prepared reactive MgO-treated soil samples in a triaxial cell set-up, and their resulting mechanical and microstructural properties were investigated using unconfined compressive strength, X-ray diffraction, and scanning electron microscopy. The results showed that adequately carbonated MgO-treated soils could, in a few hours, reach a similar strength range to corresponding 28 day Portland cement (PC)-stabilized soils. Hydrated magnesium carbonates, namely nesquehonite and hydromagnesite–dypingite, were the main products of the carbonated MgO in the soil, and were responsible for the significant strength development.
27
Moghaddasi, Hamed, e Arman Khoshghalb. "Elasto-plastic analysis of a multi-stage excavation in bonded geomaterials". E3S Web of Conferences 92 (2019): 16013. http://dx.doi.org/10.1051/e3sconf/20199216013.
Testo completoAbstract (sommario):
The deformation characteristics of braced and unbraced excavations in a dry structured soil are investigated numerically. A constitutive model based on the theory of bounding surface plasticity is used to predict the plastic deformation of the soil. A plastic cementation index is introduced in the hardening modules to capture soil degradation. In the model, the progress of the degradation is associated with the stress magnitude and the accumulated plastic deformation. The constitutive model is implemented in a finite difference code to analyse the lateral deformation of braced and unbraced excavations. The implemented model captures the strength increase of soils due to cementation, and predicts the subsequent debonding and strength degradation due to excavation. It is shown that soil cementation significantly influences the compression and tensile strengths of soils, and alters the deformation profile of the excavated face.
28
Atkinson, J. H., W. H. W. Lau e J. J. M. Powell. "Measurement of soil strength in simple shear tests". Canadian Geotechnical Journal 28, n. 2 (1 aprile 1991): 255–62. http://dx.doi.org/10.1139/t91-031.
Testo completoAbstract (sommario):
During a simple shear test the axes of stress rotate and, in a conventional apparatus in which the only stresses measured are the normal and shear stresses on horizontal planes, it is not possible to define the stress state completely. As a result, the measured failure stresses may not represent the true strength of the soil. Examination of possible Mohr's circles for soils at failure in simple shear tests demonstrates that the measured strength for a given soil depends on, among other things, the ratio of the horizontal and vertical effective stresses at failure. Results of laboratory tests on Cowden Till and on blue London Clay show the differences between strengths measured in simple shear and triaxial tests. A consequence of the conventional interpretation of the simple shear test is that effective stress failure envelopes have a false cohesion intercept with friction angles smaller than those measured in triaxial tests. Key words: clays, laboratory equipment, shear strength, shear tests, triaxial tests.
29
Gui, Meen-Wah, e Chun-Ming Yu. "Rate of strength increase of unsaturated lateritic soil". Canadian Geotechnical Journal 45, n. 9 (settembre 2008): 1335–43. http://dx.doi.org/10.1139/t08-065.
Testo completoAbstract (sommario):
Lateritic soil is a kind of residual soil that is widely distributed in Asia. The water table of the soil is normally very deep so the upper part of the soil is often unsaturated. The largest lateritic soil area in Taiwan is the Linkou terrace. Because the soil here is loosely cohered and consolidated, the problem of slope instability and landslides has always been a major concern. To evaluate the triggering mechanism of landslides, it is necessary to obtain the failure criterion that represents both the saturated and unsaturated conditions of the soil before any analysis is carried out. The parameter required to define such a failure criterion is the rate of shear strength increase, tan φb, which can be obtained via a series of laboratory strength tests in a modified triaxial system under various matric suction levels. Both the intact and remolded lateritic soils taken from Linkou terrace have been tested for this purpose. The results confirm that matric suction in the lateritic soil contributes significantly to the soil shear strength and that intact soil has a higher strength than remolded soil.
30
Budianto, Eko, Dina Limbong Pamuttu, Simon Tatai, Daud Andang Passalli e Hairulla Hairulla. "Analysis of Unconfined Compressive Strength in Clay Mixed with Sand". E3S Web of Conferences 328 (2021): 10009. http://dx.doi.org/10.1051/e3sconf/202132810009.
Testo completoAbstract (sommario):
Clay soils are soils that have high shrinkage potential and have good carrying capacity in water unsaturated conditions but poor in water-saturated conditions. Clay soil has a low carrying capacity, so to increase the carrying capacity of the soil it needs to be stabilized by using an added material which is sand. Land used for 100% disturbed soil, 95% disturbed soil + 5% sand, 90% disturbed soil + 10% sand, 85% disturbed soil + 15% sand, with curing time 3,7,14, and 28 days. The mixture was tested using aunconfined compressive strength test instrument with SNI 03-6887-2002 method. The results of the unconfined compressive strength test showed that the increase in maximum soil strength occurred in the addition of 90% disturbed soil + 10% sand at the age of 28 days curing, which reached 1,194 kg/cm2. But the results of unconfined compressive strength increased when the mixture of 85% disturbed soil + 15% of sand reaching 1,348 kg / cm2. Based on testing that the more amount of sand is added, the higher the value of unconfined compressive strength obtained.
31
Govers, G., e RJ Loch. "Effects of initial water content and soil mechanical strength on the runoff erosion resistance of clay soils". Soil Research 31, n. 5 (1993): 549. http://dx.doi.org/10.1071/sr9930549.
Testo completoAbstract (sommario):
Effects of antecedent water content and soil strength on the resistance to erosion by overland (rill) flow were tested for two clay soils of the eastern Darling Downs, Queensland. Both shear and unconfined compressive strength of wet soil (for soil wet to saturation immediately prior to application of rill flow) mere higher for soil with initially high water contents than for soil initially air-dry. Rates of runoff erosion did not show a simple relationship with soil strength across the two soils, though for each soil, higher strength was associated with much lower rates of erosion. The results show that variations in initial water content can be associated with large chang;es in soil erodibility. Particularly for the initially wet soils of higher strength, rates of runoff erosion were controlled by rates of detachment of sediment. From size distributions of wet aggregates and of sediment, and from measured water contents of wet soil, it can be suggested that the extent of incipient failure of aggregates on wet;ting was a major factor controlling ease of detachment by rill flow, as it can be inferred that detachment of sediment involved breakdown of aggregates. Consistent with this, rates of runoff erosion across the two soils showed a direct relationship with the amount of water uptake on wetting, which appears to be a useful measure of susceptibility to detachment by rill flow. Water uptake on wetting would be an indirect measure of incipient failure and, hence, of aggregate strength.
32
Lee, In-Mo, Sang-Gyu Sung e Gye-Chun Cho. "Effect of stress state on the unsaturated shear strength of a weathered granite". Canadian Geotechnical Journal 42, n. 2 (1 aprile 2005): 624–31. http://dx.doi.org/10.1139/t04-091.
Testo completoAbstract (sommario):
The effect of stress state on the unsaturated shear strength of a Korean residual soil was studied using modified triaxial tests. Experimental results show that the soil-water characteristic curve and shear strength of this soil are significantly affected by the change of net normal stresses. This effect should be taken into consideration in the model to precisely describe the shear strength envelope of unsaturated soils. Thus, a new model for estimation of unsaturated shear strength is proposed using the soil-water characteristic curve and the saturated shear strength parameters.Key words: prediction model, soil-water characteristic curve, matric suction, triaxial test, unsaturated shear strength.
33
Kraszewski, Cezary, Leszek Rafalski e Beata Gajewska. "Effect of Compaction Ratio on Mechanical Properties of Low-Strength Hydraulically Bound Mixtures for Road Engineering". Materials 15, n. 4 (19 febbraio 2022): 1561. http://dx.doi.org/10.3390/ma15041561.
Testo completoAbstract (sommario):
Road layers should be properly compacted to obtain an adequate bearing capacity and durability. Both the unbound and hydraulically bound mixtures used in the layers require compaction. After compaction and hardening, soil mixed with a binder acquires mechanical features that unbound soil lacks, including tensile strength (Rit) and unconfined compressive strength (Rc). The effect of the compaction ratio (DPr) of the low-strength cement-stabilised soils on these features has rarely been investigated. This study investigates the influence of the compaction ratio on the mechanical properties of hardened, stabilised mixtures of medium-grained sand with 5%, 6.5%, and 8% Portland cement. Cement–soil stabilisation tests showed that compressive strength depends exponentially on the compaction ratio, whereas tensile strength and the stiffness modulus depend linearly on the compaction ratio. For tensile strength and the dynamic stiffness modulus, the effect is not statistically significant, and the usual practice of ignoring compaction dependence is justified. For compressive strength, however, the effect is significant, especially when DPr = 98–100%. When the values of Rc and Rit strengths at various DPr were normalised by those at 100%, it was found that mixtures with higher strengths are the least resistant to changes in the compaction ratio. Knowing the percentage by which the value of a given parameter changes with compaction can be extremely valuable in engineering practice.
34
Karpenko, F. S. "Physico-chemical nature of clayey soils strength". Геоэкология. Инженерная геология. Гидрогеология. Геокриология, n. 5 (20 settembre 2019): 48–60. http://dx.doi.org/10.31857/s0869-78092019548-60.
Testo completoAbstract (sommario):
The principles of soil mechanics based on Mohr–Coulomb strength theory and Terzaghi effective stresses theory give us the idea about the nature of clay strength. However, these theories consider the clay as a solid body and do not take into account their internal structure. In the present paper, the problems in determining the strength of clayey soils are considered from the standpoint of the physicochemical theory of effective stresses. This theory is based on the ideas of the internal structure of clays. The main idea implies that the structure of clays depends on the contacts formed between mineral particles, where the external stresses transmitted to the soil are concentrating. Water in clayey soils not only fills the pore space but also interacts with the mineral particles forming hydrate films around them. The prevailing type of structural contacts in clays determines the properties of latter. Strength is an intrinsic property of soil determined by its composition and internal structure, independent of the conditions of load application to it and characterized by the actual effective strength value. The value of actual effective strength in clays is determined by the total strength of individual contacts. This is the maximal stress transferred to the soil contacts, the structure being ruined upon exceeding this value. The actual effective strength in soils with the same predominant type of contacts depends on the number of contacts. The numerical strength characteristics of contact types are determined for different clay soil varieties to characterize the actual effective strength. The parameters of relationship between the actual effective strength in clays and their strength characteristics are obtained from the soil testing by standard methods.
35
Ou, Ou, Xin Gui Zhang e Nian Ping Yi. "The Experimental Study on Strength of Subgrade Soil Treated with Liquid Stabilizer". Advanced Materials Research 194-196 (febbraio 2011): 985–88. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.985.
Testo completoAbstract (sommario):
The liquid soil stabilizer technology is a chemically modified method that can stabilize or reinforce those soils with weak engineering properties. In this paper, two typical high liquid limit soils ，which can not be directly used as subgrade materials，were treated with a new soil stabilizer and it were processed that serials of comparison test on the main engineer properties of soil that pre-and post-treated with soil stabilizer. Then the results show that the soil liquid stabilizer is effective to improve strength and moisture susceptibility for two selected soils. The liquid soil stabilizer technology opened up a new approach for soil improvement and ground treatment.
36
Abidin, Akhmad Zainal, R. B. Emil Trisatya Nuriman, Narendra Afian Pradipto e Ridwan P. Putra. "Emulsion Polymers of Carboxymethyl Cellulose and Methyl Methacrylate with Sodium Dodecyl Sulfate Surfactant as Soil Stabilizer". Indo. J. Chem. Res. 9, n. 3 (30 gennaio 2022): 163–70. http://dx.doi.org/10.30598//ijcr.2022.9-abi.
Testo completoAbstract (sommario):
Polymer-based materials have gained considerable attention in the road construction sector due to their ability to improve the mechanical strength and durability of soil. In this study, carboxymethyl cellulose-methyl methacrylate (CMC-MMA) emulsion polymers were prepared from different MMA to CMC mass ratios with sodium dodecyl sulfate surfactant. The synthesized materials were homogeneously mixed with laterite soil, and their unconfined compressive strengths were measured using dry and wet methods on a universal testing machine. The results indicated that the polymers were obtained in high yields with optimum solids content. Characterization using Fourier transform infrared confirmed the homopolymerization probability of monomers in the materials with increased MMA fractions. In addition, the viscosity of the graft-copolymers measured at room temperature was in the range of 1.2-3.2 cP. The polymer-stabilized soils exhibited maximum unconfined compressive strengths of 564 and 162 psi, respectively, obtained from the dry and wet methods. In general, the rise of MMA fraction in the treated soils enhanced the compressive strength of the soil, with a slight increase in soil pH. This study unfolds the potential of cellulose-based materials that can be implemented in soil reinforcement technology.
37
Rahardjo, H., T. T. Lim, M. F. Chang e D. G. Fredlund. "Shear-strength characteristics of a residual soil". Canadian Geotechnical Journal 32, n. 1 (1 febbraio 1995): 60–77. http://dx.doi.org/10.1139/t95-005.
Testo completoAbstract (sommario):
Shallow landslides in natural residual soils slopes are common all over the world. The slip surfaces associated with these landslides are often situated above the groundwater table. Therefore, it is important to quantify the contribution of negative pore-water pressure to the shear strength of soil. The shear-strength characteristics of residual soil from the Jurong Formation in Singapore were assessed using multistage, consolidated drained triaxial tests. These tests involved shearing under either a constant net confining pressure and varying matric suctions or under a constant matric suction and varying net confining pressures. An extended form of the Mohr–Coulomb equation was used to interpret the test results. The test results show that for matric suctions up to 400 kPa, the angle of internal friction associated with the matric suction, [Formula: see text], is similar to the effective angle of internal friction, [Formula: see text], which averages 26° for the residual soil of the Jurong Formation. The residual soil can maintain a high degree of saturation for matric suctions as high as 400 kPa. Examples involving stability analyses of a residual soil slope with varying pore-water pressure profiles indicate that soil suction contributes significantly to the factor of safety, particularly for shallow slip surfaces. Key words : residual soil, unsaturated soil, matric suction, shear strength, multistage triaxial test, slope stability.
38
Zhang, Deheng, Fenqiang Xu, Yan Zhang e Fang Li. "Study on Strength and Deformation Characteristics of Expansive Soils Treated with Lime-biomass Ash". Journal of Solid Waste Technology and Management 47, n. 4 (1 novembre 2021): 653–58. http://dx.doi.org/10.5276/jswtm/2021.653.
Testo completoAbstract (sommario):
This paper investigates the strength deformation of the lime-biomass ash treated expansive soils. The unconfined compressive strength, one-dimensional compression of the modified expansive soil of compaction were studied. The results showed that the maximum dry density and optimum moisture content of expansive soil decreased with the increase of lime and biomass ash content; The unconfined compressive strength test results show that there is no remarkable change in the unconfined compressive strength of the soils immediately treated with biomass ash, but the sample after 7 days of curing period of strength has been greatly improved, especially after the addition of lime is more obvious; the compression coefficient, the rebound coefficient of the saturated expansive soil with lime-biomass ash is significantly smaller than saturated expansive soil. The compressive modulus of the modified expansive soil increases with the increase of vertical pressure, which reflects the hardness of the improved expansive soil.
39
Lu, Youqian, Guoqing Cai e Chenggang Zhao. "The Shear Strength of Granite Weathered Soil Under Different Hydraulic Paths". Applied Sciences 10, n. 18 (22 settembre 2020): 6615. http://dx.doi.org/10.3390/app10186615.
Testo completoAbstract (sommario):
At present, there is no clear understanding of the influence of differences in soil mineral composition, particle size grading, and hydraulic paths on the shear strength of unsaturated soil, and the related strength models are not applicable. The shear strength characteristics of different saturation specimens under different hydraulic paths were studied on two granite weathered soils. The experimental results show that the shear strength index of the prepared specimen is “arched” with the increase of saturation, and the dehydration specimen decreases linearly with the saturation. As considering the cementation of free oxides in soils and the interaction among soil particles at different saturations, it is assumed that there are three different contact modes among soil particles: direct contact, meniscus contact, and cement contact. The difference in contact modes will reflect the different laws of shear strength. A shear strength model capable of distinguishing between the capillary effect and the adsorptive effect was established. The model predicted and verified the shear strength data of granite weathered soil under different hydraulic paths well, and then theoretically explained the evolution law of the shear strength of granite weathering soil under the change of saturation.
40
Que, Xinzhe, Zhao Jin, Yixuan Hou, Yongchao Zhou e Yiping Zhang. "Experimental Study on the Time-Dependent Characteristics of MLPS Transparent Soil Strength". Materials 15, n. 14 (18 luglio 2022): 4990. http://dx.doi.org/10.3390/ma15144990.
Testo completoAbstract (sommario):
The time-dependent characteristics of transparent soil strength, composed of magnesium lithium phyllosilicate, is important for applying a thixotropic clay surrogate. The gas injection method was employed to obtain the strength, represented as cracking pressure, which was then correlated to variables including rest time, disturbance time, and recovery time. Three concentrations (3, 4, and 5%) were tested. The results show that the strength was directly proportional to the rest time, recovery time, and concentration while the disturbance time reversed. The calculated limit strengths for 3%, 4%, and 5% transparent soils were 3.831 kPa, 8.849 kPa, and 12.048 kPa, respectively. Experimental data also showed that the residual strength for higher concentration transparent soil was more significant than the lower ones. The elastic property immediately generated partial strength recovery after disturbance, while the viscosity property resulted in a slow recovery stage similar to the rest stage. The strength recovery rate was also sensitive to concentration. Furthermore, the strength with 3%, 4%, and 5% concentrations could regain limit values after sufficient recovery, which were calculated as 4.303 kPa, 8.255 kPa, and 14.884 kPa, respectively.
41
Brunori, F., M. C. Penzo e D. Torri. "Soil shear strength: Its measurement and soil detachability". CATENA 16, n. 1 (febbraio 1989): 59–71. http://dx.doi.org/10.1016/0341-8162(89)90004-0.
Testo completo
42
Morris, Peter H., J. Graham e David J. Williams. "Cracking in drying soils". Canadian Geotechnical Journal 29, n. 2 (1 aprile 1992): 263–77. http://dx.doi.org/10.1139/t92-030.
Testo completoAbstract (sommario):
Cracking in soils that are undergoing drying is controlled by soil suctions and by soil properties such as compression modulus, Poisson's ratio, shear strength, tensile strength, and specific surface energy. The paper reviews the occurrence and morphology of cracks in dry-climate regions of Australia and Canada. After reviewing the behaviour of unsaturated soils and the mechanics of cracking, solutions are developed based on (i) elasticity theory, (ii) the transition between tensile and shear failure, and (iii) linear elastic fracture mechanics. The solutions are compared and related to crack depths observed in the field. Key words : clay, cracks, crust, shear strength, soil suction, tensile strength, unsaturated soil, weathering.
43
Garga, Vinod K. "Effect of sample size on shear strength of basaltic residual soils". Canadian Geotechnical Journal 25, n. 3 (1 agosto 1988): 478–87. http://dx.doi.org/10.1139/t88-053.
Testo completoAbstract (sommario):
This paper first provides a brief review of the very limited data available on the size effect on strength of soils. Then it presents the results of an investigation of this effect on the drained strength of two residual soils derived from basalt. The dense basaltic soil, derived from weathering of columnar basalt, is fissured, whereas the vesicular basaltic soil, product of weathering of amygdaloidal basalt, is remarkably free of discontinuities. The results of tests on 500 mm square, 100 mm square, and 63.5 mm diameter direct shear tests, as well as on 36 mm diameter triaxial samples were obtained. The data clearly indicate the significant effect of fissures on the strength of dense basaltic soil, whereas the effect is absent in the vesicular soil. The reduction in strength with size in the former can be attributed almost totally to a loss of the cohesive component of shear strength. In the absence of tests on large-sized samples, a method is suggested to estimate the mass strength of such soils from results of tests on small-sized samples. Key words: fissures, residual soil, size effect, shear, strength, testing.
44
Ale, Temitayo Olamide, Olabode Olabanji Olofinyo, Oluremi Success Odebode e David Shola Esan. "EFFECT OF COMPACTION AT DIFFERENT ENERGY LEVELS ON THE GEOTECHNICAL PROPERTIES OF STABILIZED SOILS". Malaysian Journal of Geosciences 6, n. 1 (2022): 29–35. http://dx.doi.org/10.26480/mjg.01.2022.29.35.
Testo completoAbstract (sommario):
This study is aimed at evaluating the influence of compaction (at different energy levels) on the geotechnical properties of stabilized soils. To achieve this, four bulk soil samples (BDL1, BDL2 BDL3 & BDT) consisting of termite reworked soils and residual lateritic soils were collected at New Stadium Road, Awo hall, University of Ibadan, Nigeria at a depth of 2m for strength tests and at depths of 1m, 1.5m & 2m for index tests. Geotechnical analysis (index tests and strength tests) and geochemical analysis (X-ray Diffraction) were carried out on the sampled soils. The study revealed that the mineral constituents of the sampled soils are quartz, kaolinite and hematite; with the termite-reworked soil richer in kaolinite content than the quartz schist derived soil with about 125% increase. The values of index tests for both soils met the required Nigeria specification for good soil with termite reworked soil performing better. The values of specific gravity for both soils are close suggesting similar origin. AASHTO classification put termite-reworked soil within the range of A-2-7 (good rating) while most of the residual soil samples fall within A-7-5 to A-7-6 range (fair to poor rating). The stabilisation of residual lateritic soil using termite-reworked soil as stabiliser brought about increase in the values of maximum dry density, uncured unconfined compressive strength as well as the sun-cured unconfined compressive strength of the studied soil. The influence of stabilisation using termite-reworked soil was strongest at the highest level of compaction ((30%) of termite-reworked soil with the weight of residual soil). There also exist a fairly strong positive correlation between the amount of termite reworked soil and energy of compaction and between the uncured and sun-cured unconfined compressive strength was plotted against the number of blows for BDL1, BDL2 and BDL3 respectively. In sum, these stabilised soils are suitable for foundation and landfills materials.
45
Urbanek, Emilia, Rainer Horn e Alwin J. M. Smucker. "Tensile and erosive strength of soil macro-aggregates from soils under different management system". Journal of Hydrology and Hydromechanics 62, n. 4 (1 dicembre 2014): 324–33. http://dx.doi.org/10.2478/johh-2014-0034.
Testo completoAbstract (sommario):
Abstract Reduced soil tillage practices are claimed to improve soil health, fertility and productivity through improved soil structure and higher soil organic matter contents. This study compares soil structure stability of soil aggregates under three different tillage practices: conventional, reduced and no tillage. The erosive strength of soil aggregates has been determined using the abrasion technique with the soil aggregate erosion chambers (SAE). During abrasion soil aggregates have been separated into the exterior, transitional and interior regions. The forces needed to remove the material from the aggregate were calculated as erosive strength and compared with the tensile strength of the aggregates derived from crushing tests. The relationship between aggregate strength and other soil properties such as organic carbon and hydrophobic groups’ content has also been identified. The results show that erosive and tensile strength of soil aggregates is very low in topsoil under conventional and reduced tillage comparing with the subsoil horizons. Negative correlation was found between the content of organic carbon, hydrophobic compounds and erosive aggregate strength which suggests that the stabilising effect of soils organic carbon may be lost with drying. The positive relationship between the tensile strength and erosive strength for aggregates of 8-5 mm size suggests that the total strength of these aggregates is controlled by the sum of strength of all concentric layers
46
COOTE, D. R., C. A. MALCOLM-McGOVERN, G. J. WALL, W. T. DICKINSON e R. P. RUDRA. "SEASONAL VARIATION OF ERODIBILITY INDICES BASED ON SHEAR STRENGTH AND AGGREGATE STABILITY IN SOME ONTARIO SOILS". Canadian Journal of Soil Science 68, n. 2 (1 maggio 1988): 405–16. http://dx.doi.org/10.4141/cjss88-037.
Testo completoAbstract (sommario):
Soil-erodibility indices were investigated in two regions of Ontario to evaluate their seasonal variation and differences between soil types. Shear strength and water-stable aggregates >0.5 mm were strongly negatively correlated with gravimetric soil water content for a Guelph sandy loam soil in southwestern Ontario. Similar variation of shear strength was estimated in three other southwestern Ontario surface soils as a result of seasonal changes in moisture content. Shear strength and aggregate stability increased as four eastern Ontario soils, ranging in texture from loamy sand to clay, dried and warmed following spring thaw. Laboratory incubation at constant temperature and water content showed that shear strength increased in two fine-textured soils with increasing degree days but changed very little in two coarse-textured soils. At the point-of-thaw in the field, all of the eastern Ontario soils exhibited very high values of the indices 1/shear strength and 1/aggregate stability, averaging approximately 15 times those of early July. During spring fallow and seed-bed to 10% canopy periods, the mean values of these indices were 3.7 and 1.4 times, respectively, those in early July. For winter-thaw conditions in the three southwestern Ontario soils, the index 1/shear strength averaged 17 times greater than in the summer. Spring values of this index averaged approximately twice those of summer. Results suggest that Ontario soils are much more susceptible to erosion under thaw and spring conditions than later during the growing season. Soil water content and soil warming may affect the re-establishment of resistance to erosion in soils rendered erodible by freezing, thawing, and saturation. Key words: Erodibility, shear strength, aggregate stability
47
Vennik, Kersti, Thomas Keller, Peeter Kukk, Kadri Krebstein e Endla Reintam. "Soil rut depth prediction based on soil strength measurements on typical Estonian soils". Biosystems Engineering 163 (novembre 2017): 78–86. http://dx.doi.org/10.1016/j.biosystemseng.2017.08.016.
Testo completo
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Peth, Stephan, Rainer Horn, Orsolya Fazekas e Brian G Richards. "Heavy soil loading its consequence for soil structure, strength, deformation of arable soils". Journal of Plant Nutrition and Soil Science 169, n. 6 (dicembre 2006): 775–83. http://dx.doi.org/10.1002/jpln.200620112.
Testo completo
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Samatha Chowdary, P., K. Siva Prasada Rao e G. Sanijya. "Strength enhancement studies on expansive soil by utilization of unburnt agricultural waste". IOP Conference Series: Earth and Environmental Science 982, n. 1 (1 marzo 2022): 012054. http://dx.doi.org/10.1088/1755-1315/982/1/012054.
Testo completoAbstract (sommario):
Abstract In order to determine stability and to support any structure underlying soil bearing strength is necessary. Of all the soils available in India black cotton soils rich in montmorillonite is one of the most problematic and expansive soils as they are every dangerous for construction because of its swelling and shrinkage properties. Such types of soils can be stabilized using locally available waste materials either agricultural or industrial. The waste materials can be used to improve the bearing strength of the soil and decrease in cost of construction. This paper focuses on improvement of strength and stability of lime treated expansive soil by using rice husk ash as additive. Compaction, Unconfined strength test, and California bearing ratio tests were performed on soil by adding lime in increments of 2 to 12% and then optimum lime was determined. To the optimum lime soil mix rice husk ash an agricultural waste was added in increments of 2 to 12 % and optimum RHA was determined.
50
Sianturi, Novdin Manoktong, Mohd Khairul Amri Kamarudin, Dermina Roni Santika Damanik, Virgo Erlando Purba e Deardo Samuel Saragih. "The Mechanical Behavior of Soft Soil Stabilized with Lime and Volcanic Ash". MEDIA KOMUNIKASI TEKNIK SIPIL 28, n. 1 (29 luglio 2022): 118–27. http://dx.doi.org/10.14710/mkts.v28i1.41963.
Testo completoAbstract (sommario):
The properties of soft clay can be seen from the compressive strength value through the unconfined compressive strength (UCS) test. Soft soil was less well used as the subgrade for construction. The aim is to determine the increase in the unconfined compressive strength and bearing capacity of the foundation due to the addition of lime and volcanic ash on soft soil. Soft soil has undrained shear strength < 25 kPa based on the unconfined compressive strength test. The unconfined compressive strength test has been conducted on the soil-lime mixture and soil-volcanic ash mixture of 3-12% respectively to the weight of dry soil. The highest unconfined compressive strength values were found in soils with 6% of lime and 9% of volcanic ash. The bearing capacity of the foundation on soil stabilized with 6% lime increased 13.7 times, while the bearing capacity of the foundation on the soil with the addition of 9% volcanic ash increased the ultimate bearing capacity of 8.7 times the bearing capacity of the foundation on soft soil. The bearing capacity of the foundation on lime stabilized soil is higher than the bearing capacity of the foundation on volcanic ash stabilized soil.