Change In Soil Behavior Research Articles

Mechanical behaviour of saline soil under triaxial compression

Soluble salts in soil cause changes in soil behaviour, the extent of which varies depending on salinity levels. Salt-induced soil deformation leads to various engineering problems. Na2SO4 is among the most widespread and influential salts. This study focuses on Na2SO4 and investigates its effects on soil strength via a series of triaxial tests performed in the laboratory. The study examines different levels of salt and moisture content. Additionally, the study investigated the soil mechanism through its meso and micro structure. The research indicates that the impact of salinity on soil strength is modulated by moisture content. In situations where moisture content is low, salinity markedly affects the soil strength; however, as moisture content increases, the impact of salinity on soil strength decreases. Salinity alters the shape, size and orientation of soil particles, resulting in modifications to the interparticle and charge forces. This ultimately leads to changes in the soil strength parameters.

Reuse of water treatment plant sludge mixed with lateritic soil in geotechnical works

This work investigates the possibility of reusing water treatment sludge (WTS) at as-collected water content mixed with lateritic soil in geotechnical works to avoid waste disposal and reduce the exploitation of natural soils. Three mixtures with different proportions of soil to WTS (5:1, 4:1, 3:1) were prepared. Leaching and solubilization tests were conducted for environmental characterization of the WTS. Particle size distribution, consistency limits and specific gravity of solids of the soil and the three mixtures were determined for geotechnical characterization. Compaction, permeability and triaxial compression tests were carried out to investigate the geotechnical behaviour of the materials. The sludge was classified as non-hazardous and non-inert by Brazilian standards. The addition of sludge to the soil did not significantly change its granulometry but led to a reduction in the specific gravity of solids and an increase in the plasticity index. In the compaction tests, the maximum dry unit weight decreased, and the optimum moisture content increased with WTS addition. The hydraulic conductivity of the mixtures was between 10 and 100 times that of the soil. In triaxial compressive tests, there was an increase in strain and a reduction in strength during shear, as well as an increase in the friction angle (between 1º and 4º) and reduction in cohesion (between 9 kPa and 16 kPa). Despite causing changes in soil behaviour, the addition of sludge does not preclude the use of the resulting mixtures in geotechnical works, since the parameters remain as established in the literature and technical. However, a case-by-case analysis must be carried out before using the mixtures.

The Impact of Land Use Change on Perform (Soil-Water) System in Middle Part of Mesopotamian Plain

In spite of hydrology and geology disciplines` are relatively well known in Iraqi management strategy, unlike soil and its distribution system. Thus, describing strong indicator for evaluating water pathways, minerals, and materials in different soils is necessary to reduce the associated risks. However, the aim of this research is identified the change in soil behavior by observation, and interpretation the facts for effective indication mode. This mode is evaluated some features and properties in (soil- water) horizons from a focus on land use change in (e.g built up and rural) areas compared with riparian sites in middle region of Iraq. The evaluation is included field sampling by using `Drill auger` instrument and laboratory tests for analysis. The results areinterpreted as onset of soil impairment indices under changing in human activities, agricultural practices, climate change and effect of water movement. The elements are considerably bound with silt and clay particles which ultimately minimize leaching ability to lower layers in each horizon. The free access of water and air allows rapid oxidation of elements and caused materials corrosion and the output of leaches which can contaminate ground water and surface water. Besides, some elements are negatively correlated with concentrations of calcium carbonate. The content of sulfur compound in assorted land uses is uneven and increased with increase water content or agitating time. Also, the sulfur oxidation even if small proportion in fill material lead to the output of polluted drainage water and attack construction material when structural backfill and for bulk fill. Thus, its significant to consider these features for ameliorative engineering behavior.

Shear strength behaviour of sand-bentonite mixtures with pumice additivite under high temperature

Depending on increase in the number and type of energy geostructures, studies on the change in soil behavior against heat increase becomes more important. The engineering properties such as permeability, volume deformation of surrounding soils around energy structures mustn’t alter in the presence of heat and thermal cycles. Pumice is a material used in many fields especially for thermal insulation. For that reason, pumice can be used for increasing the resistance of soils in the presence of heat. In this study, the shear strength behavior of sand-bentonite mixtures was investigated with pumice additive under high temperature. In the experiments, 10% and 20% pumice were added to 10% and 20% sand-bentonite mixtures and compaction, direct shear tests were conducted. The direct shear tests were performed both room temperature and under 80°C. The results have shown that the pumice additive increased the shear strength of sand-bentonite mixtures under high temperature when compared the test results under room temperature.

Physicochemical and consolidation properties of compacted lateritic soil treated with cement

The consolidation of a fine-grained lateritic soil, treated with compound Portland cement (CEMII/BM 32.5N) up to 9% by weight of the dry soil and prepared at three different molding water contents (ωDRY, OMC, and ωWET), was investigated by means of a one-dimensional consolidation test. The physicochemical and microstructural properties of the compacted lateritic soil-cement mixture were investigated using Raman spectroscopy, polarized light microscopy (PLM), scanning electron microscopy (SEM), and pH measurement. The results show that cement admixtures resulted in the formation of tobermorite, afwillite, ettringite, portlandite, and calcite. However, tobermorite and afwilite, which are calcium silicate hydrates (CSH) whose mechanisms of formation are the pozzolanic and alkali silica reactions, appear from 6% added cement. The fixing point of the pH (12.4) is also obtained from 6% added cement. It is the threshold value at which the material begins to develop an adequate mechanical performance. In general, as the content of cement in the soil is increased, the yield stress increases from 1 to 3 times in comparison to untreated soil. For effective vertical stresses smaller than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is 2–7 times faster than that for specimens not treated with cement, while for effective vertical stresses higher than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is about 0.5–1.5 times faster than that for specimens not treated with cement. Permeability and secondary compression are reduced 1–9 times and 2–11 times that of the untreated samples, respectively. These changes are attributed to the creation of chemical bonds and aggregation that accompany the addition of cement. The results also show that it would be desirable for soil samples to be prepared at the dry side of optimum (ωDRY) when the optimum moisture content (OMC) is not reached at the site. These results indicate that significant and desirable changes in soil behavior can be achieved when the soil is admixed with CEM II/BM 32.5N cement, thus providing the possibility of using the tested lateritic soil in road construction.

Surprising Soil Behaviour: Is It Really!!!

Several instances of unexpected soil behavior, which either conventional or advanced forms of soil mechanics could not be explained are termed as ‘Surprising’. Several cases of unexpected behavior, more particularly heave in fine grained soils are due to contamination of foundation soil. An attempt is also made to understand and explain the mechanism of heave based on extensive laboratory and field studies on contamination of soils with strong acid and alkali solutions. Also the heave in lime stabilized soil in the presence of sulphate after long periods of interaction has been relooked with recent work. The mechanism and characteristics of occurrence of this type of heave in both swelling and non-swelling soils, which is different from conventional swell in expansive soil, is not understood. Conventional remedial approaches to control the heave would fail. Particular attention is paid to draw a special testing plan and analyzing the results from more fundamental principles. It was brought out that changes in the mineralogy of the soil which occur over geological ages (rock cycle) are triggered and occur in relatively shorter period due to interaction with strong acid or alkaline solutions. The associated changes in soil behaviour are explained based on mineralogical alterations, fabric and physic-chemical environment. Very often, more than formation of swelling minerals formed, the free energy released by mineral transformations controls the induced heave in soils. Some of these considerations are also important to overcome the problems in natural soils and initiate appropriate remedial measures.

Dynamic response of liquefiable sand improved by microbial-induced calcite precipitation

Microbial-induced calcite precipitation (MICP), a novel bio-mediated ground improvement method, was explored to mitigate liquefaction-prone soils. Geotechnical centrifuge tests were used to evaluate cementation integrity and the response of MICP cemented sands to dynamic loading. The cementation integrity testing reveals a change in behaviour from ‘soil like' to ‘rock like', with an increase in treatment level. Results from dynamic testing demonstrate a clear increase in resistance to liquefaction of MICP-treated sands compared to untreated loose sand. The MICP sands were treated to varying levels of cementation (light, moderate and heavy cementation levels) and assessed using non-destructive shear wave velocity measurements. The centrifuge models were all subjected to ground motions consisting of sine waves with increasing amplitudes. Accelerations, pore pressures and settlements were measured in the soil during shaking, and the changes in soil behaviour and post-shaking shear wave velocity for soils prepared to different cementation levels are discussed. Increased resistance to liquefaction was demonstrated with a decrease in excess pore pressure ratios in the MICP-treated models, as well as in reduced post-shaking settlements; however, surface accelerations were amplified at heavy levels of cementation. A tradeoff between improving liquefaction resistance and minimising undesirable higher surface accelerations needs to be considered when designing the soil improvement level.

Permeation of compacted clay with organic fluids

Penetration of organic liquids through the soil causes contamination and considerable changes in the geotechnical properties of soils. In general, these changes are attributed to variations in the dielectric constant and chemistry of the pore fluids, which result in several changes in soil behaviour. For this reason, it is necessary to investigate the geotechnical properties of contaminated soils for engineering and environmental purposes. In the present study, an extensive laboratory investigation programme was carried out on a clayey soil to examine the effect of different percentages of pore fluids on sedimentation time, plasticity and shear strength of the soil obtained from Famagusta, North Cyprus. Contaminated specimens were prepared with different percentages of 0, 20, 40 and 60% ethylene glycol by volume of distilled water. Index tests were performed in order to investigate the sedimentation time and the plasticity changes in the contaminated soils. Finally, unconfined compression tests were carried out on the contaminated samples to evaluate the shear strength parameter of the soil. The results showed a decrease in sedimentation time and plasticity, and it was also shown that the unconfined compressive strength of the contaminated soils decreases with increasing percentage of ethylene glycol.

Stabilization Effectiveness of Treatment with T-Shaped Deep-Mixing Column for Low-Volume Roads

Deep-soil mixing using column elements is a widely used technology for improving soft soil properties for low-volume roads in China. The deep-mixing method has some limitations, because a high-treatment area over the entire column length makes this method expensive and impractical. On the basis of a stabilization mechanism and factors that affect column construction quality, a T-shaped bidirectional soil–cement deep-mixing column has been successfully developed and proved to be effective and economical. As part of quality control of field improvement of these columns, seismic piezocone penetration tests (SCPTUs) were used. The tests can provide near-continuous measurements of tip resistance, sleeve friction, and pore pressure induced during the penetration. This paper discusses field SCPTUs that were performed in the untreated soils and the interpile soils between the T-shaped bidirectional soil–cement deep-mixing columns at the Huzhou lacustrine clay site in China. Soil properties estimated from the SCPTU data both before and after improvement methods were compared to assess the effectiveness of soil improvement. These results indicate that the use of SCPTUs will improve understanding of the changes in soil behavior achieved by this novel deep-soil mixing method for low-volume roads.

Ground Densification Due to Sand Compaction Piles

ABSTRACT The geotechnical properties of granular soils can be improved using compaction piles. However, the compaction effect and the extent of the densification are not yet clear. Well controlled in situ tests are necessary to investigate this problem. Further insight about the densification process can also be gained by performing numerical analysis using a constitutive model that takes into account the effect of density and confining pressure on the behavior of soils. This paper presents numerical analyses in which a recently proposed model, named subloading tij, is used to simulate these effects. The construction process of sand compaction piles involves two stages: the metal casing driving and the sand pile compaction. The process is simulated sequentially and the relative influence of each stage is quantified for different initial ground density conditions. The extent and effectiveness of the densification are also quantified. The results of these predictions are qualitatively compared with the results of field tests carried out before and after the execution of compaction piles in an artificial loose sand deposit. There is good overall agreement between the numerical predictions and the test results, showing that a combination of these two investigation approaches is a way forward to better understanding the densification process. However, this can only be achieved if the constitutive model can properly account for the change in soil behavior with densification.

Subject index of volume 93

The consolidation of a fine-grained lateritic soil, treated with compound Portland cement (CEMII/BM 32.5 N) up to 9% by weight of the dry soil and prepared at three different molding water contents (ωDRY, OMC, and ωWET), was investigated by means of a one-dimensional consolidation test. The physicochemical and microstructural properties of the compacted lateritic soil-cement mixture were investigated using Raman spectroscopy, polarized light microscopy (PLM), scanning electron microscopy (SEM), and pH measurement. The results show that cement admixtures resulted in the formation of tobermorite, afwillite, ettringite, portlandite, and calcite. However, tobermorite and afwilite, which are calcium silicate hydrates (CSH) whose mechanisms of formation are the pozzolanic and alkali silica reactions, appear from 6% added cement. The fixing point of the pH (12.4) is also obtained from 6% added cement. It is the threshold value at which the material begins to develop an adequate mechanical performance. In general, as the content of cement in the soil is increased, the yield stress increases from 1 to 3 times in comparison to untreated soil. For effective vertical stresses smaller than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is 2–7 times faster than that for specimens not treated with cement, while for effective vertical stresses higher than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is about 0.5–1.5 times faster than that for specimens not treated with cement. Permeability and secondary compression are reduced 1–9 times and 2–11 times that of the untreated samples, respectively. These changes are attributed to the creation of chemical bonds and aggregation that accompany the addition of cement. The results also show that it would be desirable for soil samples to be prepared at the dry side of optimum (ωDRY) when the optimum moisture content (OMC) is not reached at the site. These results indicate that significant and desirable changes in soil behavior can be achieved when the soil is admixed with CEM II/BM 32.5 N cement, thus providing the possibility of using the tested lateritic soil in road construction.

GEOTECHNICAL ASPECTS OF SUBSIDENCE RELATED TO THE FOUNDATION DESIGN OF EKOFISK PLATFORMS.

Keywords PHILLIPS PETROLEUM, IMPERIAL COLLEGE, FUGRO FOUNDATIONS, DESIGN, PLATFORMS, EKOFISK, SUBSIDENCE, GEOTECHNICS, STEEL, PILED, JACKETS, FINITE ELEMENTS, ANALYSIS, CRUST, MEASUREMENT, MOVEMENT, PROGRESSIVE, EFFECT, IN SITU, BEHAVIOUR, SOILS, SEABED, STRENGTH, STRESS, STRAIN, MODELS, STRATIGRAPHY, PILES, CAPACITY, STRUCTURES, INTERACTION EKOFISK, NORTH SEA... Show All

Indigenous Knowledge and Classification of Soils in the Andes of Southern Peru

AbstractIndigenous cultures throughout the world have substantial, systematic knowledge of soils gained during many generations of land use; however, little of this knowledge has been scientifically documented. Recent literature indicates that knowledge among traditional cultures could add to scientific understanding of soils and be useful in international agricultural development. This study investigated indigenous soil knowledge in the Colca Valley, Peru, where terrace agriculture has been practiced for at least 15 centuries. Previous research suggested enhanced tilth and fertility of ancient agricultural soils, measured by criteria such as thickened A horizons, lower bulk density, and greater levels of organic C, N, and P relative to nearby uncultivated Mollisols. Long‐term soil conservation is partly attributed to traditional management practices such as terracing, a form of conservation tillage, fertilization, and irrigation. To test the hypothesis that a body of knowledge underlies traditional soil management practices, interdisciplinary studies were conducted, involving linguistic evaluation of soil terms, anthropological field interviews, soil and geomorphic mapping, and basic morphological and laboratory characterization of soils identified by farmers. Anthropological research revealed a hierarchical soil classification system, with up to four categorical levels and about 50 soil and earth material names, that emphasizes soil texture and other properties important in agricultural management. Soil analyses indicated a fairly close correspondence between indigenous texture classes and those used in U.S. soil classification. Local farmers recognize several soil features and horizons such as duripans, soil variation with depth, distribution of soils on the landscape, and changes in soil behavior under different conditions.

Treatment of Oil-Contaminated Soils for Identification and Classification

Abstract An experimental investigation was performed to evaluate the effects of oil contamination on soils and to establish a methodology to identify and classify contaminated soils. Identification and classification tests were performed before treatment, cleaning, stabilization, or disposal of contaminated soils. There are no standards for identification and classification of contaminated soils. Fine-grained, oil-contaminated soils are often identified and classified as granular soils with large particle sizes and may result in selection of improper treatment techniques. In this study, four uncontaminated soils were first identified and classified; then, all four soils were mixed with 3% motor oil. The oil-contaminated soils were first tested for identification and classification and then treated by (1) heating in ovens at various temperatures (low-temperature desorption), (2) adding solvents (solvent extraction), and (3) adding surfactants (treatment with surfactants). The processed soils were then reidentified and reclassified. Test results showed that treatment with a surfactant produced near-virgin soils for all four soil types. The solvent extraction was adequate only for the silty sand and the silty clay. The low-temperature thermal treatment was inadequate for all four soils. To further confirm the above test results, the low-plastic clay was mixed with 6% motor oil and the above test program repeated. This soil with a higher degree of contamination produced the same results. To provide an explanation for the change in soil behavior due to oil contamination, low-plastic soil was mixed with oil up to 70% by weight and Atterberg limit tests performed. It was concluded that fine-grained soils when contaminated with oil behave as granular soils with particle aggregation. Since soils in this study were artificially contaminated, one should exert caution when applying the results of this study to soils in contact with oil for many years.

The Behavior at the Shrinkage Limit of Clay Undergoing Drying

Abstract In this paper, possible links between the shrinkage limit and distinct changes in other properties of a clay soil undergoing drying are discussed. These properties include the volumetric air content of the soil, the heat of wetting, the tensile strength, the total suction, and the thermal resistivity of the soil. The distinct changes are of interest in themselves, and possible explanations for them are briefly discussed. For soil under extremely dry conditions, more importance should perhaps be attached to using the shrinkage limit as an index to changes in soil behavior, and this topic warrants further research.

Marine geotechnology—state of the art

Abstract The state of the art in marine geotechnology can best be defined with reference to what is known about soils on land. Differences between these two states of knowledge are the significant problems for the marine environment. Among the major problems addressed in this paper are (a) Sampling of soils, which involves much more serious disturbance than is considered acceptable on land. Disturbance results from several uniquely marine factors including total stress release and drilling mud overpressure, (b) Underconsolidation, or excess in situ pore pressure, caused by rapid rates of sedimentation, gas, leaks from an artesian pressure source, or cyclic loading. (c) Gas in sediments, which can cause an increase in the in situ pore pressure, hinders subsurface investigation, and is a major cause of sample disturbance. (d) The difficulty and necessity of in situ measurements. (e) The predominance of dynamic loading effects which can cause significant changes in soil behavior. A major difference between geotechnical engineering on land and in marine areas is the use of effective stress methods. Significant improvement in geotechnical engineering offshore can be achieved through the increased use of effective stress methods. Illustrations of these improvements are presented in this paper with particular reference to the problems of submarine slope stability.