Soil Volume Change Research Articles

The mechanical behavior of an expansive soil due to long-term seasonal rainfalls

Expansive soils, susceptible to be affected by the environmental conditions, expand when water is added and shrink when they dry out. This continuous change in soil volume is able to cause structures built on them to move unevenly and crack. To investigate the hydro-mechanical behavior of unsaturated expansive soils, many laboratory tests on these materials have been carried on and numerous models have also been proposed with a relatively large number of parameters. In this study, a simplified model based on Zarka method has been developed for unsaturated expansive soils. The direct determination of the steady solutions in Zarka analysis is able to replace classic step-by-step method and needs less model parameters. In this context, this paper presents a Zarka-based model to predict the volume change in unsaturated expansive soils under seasonal drought and rainfall cycles and the proposed model is implemented in the finite element code to simulate long-term behavior of a 2D structure consisting of expansive soils and subjected to successive drought and rainfall cycles. Finally, the numerical calculation defines the plastic strain field and the inelastic displacement field of the studied structure.

Effects of clay content on the volumetric behavior of loess under heating-cooling cycles

Although numerous studies have been carried out on investigating thermal volume changes in different soils, limited attention has been paid to loess. This study aims to investigate the effects of clay content on the deformation of loess under heating-cooling cycles. Three soils with different clay contents (i.e. SA: 7%; SB: 13%; SC: 35%) were prepared with loess collected in situ through the sedimentation method. The soil volume changes were measured under heating-cooling cycles by using a thermal invar oedometer. To interpret the experimental results, X-ray diffraction (XRD) and scanning electron microscope (SEM) tests were conducted to identify the composition and microstructure of tested soils, respectively. The results show that the plastic axial strains of SA, SB, and SC accumulate to a certain level with the increasing number of heating-cooling cycles. At the stable state, the plastic axial strain of SC is 264% and 52% larger than those of SA and SB, respectively. On the other hand, the linear thermal expansion coefficient of SC is 66% and 20% larger than those of SA and SB, respectively. As evidenced from the XRD test, the clay in loess mainly contains kaolinite, chlorite, and illite, while the composition of silt is dominated by quartz. The clay minerals are more sensitive to thermal fluctuations than quartz because of the electrical double layer. SC, whose clay content is deliberately enhanced, exhibits a larger plastic axial strain and linear thermal expansion coefficient than do SA and SB.

Effect of pore fluid and wet-dry cycles on structure and hydraulic conductivity of clay

Compacted clays in landfill applications are subjected to both physico-chemical changes and wet–dry cycles. Physico-chemical interactions occur at the microstructural level between the clay particles and chemical constituents such as brine solutions or leachates generated from landfill waste. Furthermore, the volumetric changes during wetting and drying also cause microstructural changes to compacted clays. The microstructural changes due to the physico-chemical interactions and wet–dry cycles are reflected at the macrostructural level and govern the macro-behaviour of compacted clays. Therefore, this paper brings out the combined effect of the interacting fluid and wet–dry cycles on volume change, microstructure and hydraulic conductivity of compacted clay soil. To achieve this, the compacted clay specimens were inundated with distilled water and sodium chloride (NaCl) solutions during wetting cycles. The experimental results showed that the ability of clay particles to swell at microstructural level and decrease the size of macropores in compacted clay was completely lost with 4 M sodium chloride solution and with increase in wet–dry cycles. Thus, the hydraulic conductivity of compacted clay specimen inundated with 4 M sodium chloride solution was unusually high at the end of the second and further wetting cycles even when subjected to higher effective confining pressures.

Hydromechanical behaviour of overconsolidated unsaturated soil in undrained conditions

Hydromechanical behaviour of an unsaturated silt with various suctions and different overconsolidated ratios (OCRs) was investigated through a series of undrained triaxial tests (constant water contents, CW). All the samples were prepared from the slurry state. Different OCRs (= 1, 2, 4, and 8 in net stress) were achieved by unloading the samples to 400, 200, 100, and 50 kPa from an initial confining net pressure of 400 kPa. Then the samples were dried to various suctions (0, 100, 200, 300, and 400 kPa). Unsaturated samples with different OCRs were then sheared at CW conditions following the conventional triaxial compression (CTC) paths. Full hydromechanical responses including the changes in deviator stress, stress ratio, volumetric strain, suction, and degree of saturation with axial strain were monitored and are presented in this paper. Some key findings include (i) the critical state for unsaturated soils with different OCRs can be well defined by Bishop’s effective stress; (ii) the peak strength in Bishop’s effective stress increases with increase of OCR, but decreases with increase of suction in the undrained condition; and (iii) the volume change of unsaturated soils in undrained conditions is related to OCRs and the volume of pore air.

Influence of Soda Content on Desiccation Cracks in Clayey Soils

Alkaline clayey soil is considered to be a degraded soil, which causes serious issues in engineering and construction projects. The formation and development of desiccation cracks in alkaline clayey soils is a complex process affecting the strength, stability, and permeability of these soils. Therefore, to investigate how soda content can inhibit the development of desiccation cracks in alkaline clayey soils in Ulanhot, Inner Mongolia, China, free desiccation tests were performed to examine the cracks in alkaline clayey soil samples with different soda (Na2CO3) contents in the laboratory. During the cracking process, the changes in water content and the occurrence and evolution of cracks were recorded with a camera. Digital image processing was performed to analyze the structure characteristics of the surface cracks. The results indicated that the characteristics are influenced by the different soda contents. The soda inhibited the development of desiccation cracks in alkaline clayey soils. Three stages were found in the process of desiccation cracking in accordance with the rate of water loss: the residual, normal, and structural shrinkage stages. At <0.4 mol L−1 Na2CO3, the “three straight lines” model could be used to describe the volume shrinkage. However, at >0.4 mol L−1 Na2CO3, the structural shrinkage stage disappeared. Moreover, based on the general soil volume change equation and fractal theory, a model was formulated to quantitatively explain the relationship between the fractal dimension and the volume changes in the soil. The experimental results and equations are important for reducing subgrade deformation and slumps.Core Ideas Soda content can inhibit the development of desiccation cracks in clayey soils. There are three stages in the process of desiccation cracking in alkaline clayey soil. A model is formulated to explain the fractal dimension and the volume changes in the alkaline clayey soil. The structural shrinkage stage will disappear when Na2CO3 is >0.4 mol L−1.

An alternative approach to reduce algorithm-derived biases in monitoring soil organic carbon changes.

Quantifying soil organic carbon (SOC) changes is a fundamental issue in ecology and sustainable agriculture. However, the algorithm‐derived biases in comparing SOC status have not been fully addressed. Although the methods based on equivalent soil mass (ESM) and mineral‐matter mass (EMMM) reduced biases of the conventional methods based on equivalent soil volume (ESV), they face challenges in ensuring both data comparability and accuracy of SOC estimation due to unequal basis for comparison and using unconserved reference systems. We introduce the basal mineral‐matter reference systems (soils at time zero with natural porosity but no organic matter) and develop an approach based on equivalent mineral‐matter volume (EMMV). To show the temporal bias, SOC change rates were recalculated with the ESV method and modified methods that referenced to soils at time t1 (ESM, EMMM, and EMMV‐t1) or referenced to soils at time zero (EMMV‐t0) using two datasets with contrasting SOC status. To show the spatial bias, the ESV‐ and EMMV‐t0‐derived SOC stocks were compared using datasets from six sites across biomes. We found that, in the relatively C‐rich forests, SOC accumulation rates derived from the modified methods that referenced to t1 soils and from the EMMV‐t0 method were 5.7%–13.6% and 20.6% higher than that calculated by the ESV method, respectively. Nevertheless, in the C‐poor lands, no significant algorithmic biases of SOC estimation were observed. Finally, both the SOC stock discrepancies (ESV vs. EMMV‐t0) and the proportions of this unaccounted SOC were large and site‐dependent. These results suggest that although the modified methods that referenced to t1 soils could reduce the biases derived from soil volume changes, they may not properly quantify SOC changes due to using unconserved reference systems. The EMMV‐t0 method provides an approach to address the two problems and is potentially useful since it enables SOC comparability and integrating SOC datasets.

The Performance of Shear Strength and Volume Changes of Expansive Soils Utilizing Different Additives

Some clayey soils are generally classified as expansive soils which cause extensive damage to civil engineering structures due to change in its water content and the amount and type of clay size particles. Other important factors affecting the expansion behavior include the amount of non-expansive materials. This paper based on comparing two solutions to improve the soil parameters: the first solution to improve the soil with steel fiber and the second solution to improve the soil strength and volume changes with plastic waste material. Various tests conducted to study the effect of using different percentages of steel fiber and plastic waste material (4%, 8% and 12%) for each additives by dry weight of soil. The results presents that the steel fiber and plastic waste material significantly improved the soil strength and volume changes besides the physical properties of expansive clay soil which have susceptibility of swelling.

Soil anisotropic stress-strain prediction using Normalised Rotational Multiple Yield Surface Framework (NRMYSF) for compacted tropical residual sandy soils

Rotational Multiple Yield Surface Framework (RMYSF) is an anisotropic soil volume change model developed to integrate shear strength in characterising the soil volume change behaviour from the standpoint of the stress-strain response. The anisotropic soil volume change behaviour is described from the interaction between applied stress represented by the Mohr-Coulomb circle and shear strength in terms of curved-surface mobilized shear strength envelope. This research work is to enhance the current method of RMYSF using normalisation of axial strain to predict stress-strain behaviour. A series of triaxial tests has been conducted on Malaysian sedimentary sandy residual soil grade VI. The stress-strain curves and volume change behaviours were analysed using this enhanced method. Subsequently, the enhance method is apply to predict the soil stress strain respond and make comparison with the actual laboratory stress-strain curve. Essentially the normalised method of RMYSF has improved the accuracy of the prediction as presented in the paper.

Prediction of shrinkage behavior of soft soil using ramp loading consolidation theory

Soft soil is a highly saturated soil and its low shear strength undermines the reliability for construction. Hence, to reclaim soft soil for construction, more research is required to improve our understanding on the changes in soft soil properties with ongoing dewatering. Shrinkage behavior of soft soil is studied in this paper. Some of the previous studies focused on the simulation of soil volume change and matric suction change while neglecting the soft soil settlement during fully saturated stage of shrinkage. The aim of this research is to predict the settlement of soft soil at the stage where soil is fully saturated and moisture content is high. During this stage, suction of soil is assumed to be zero and the decreased pore water pressure induced by evaporation is taken as the main reason for settlement. With the soil shrinkage happening, the pore water pressure decreases due to water loss and effective stress increases, being the mechanical reason for soil settlement. To predict the settlement during fully saturated stage of soil shrinkage, the ramp loading consolidation theory is applied. The shrinkage test of saturated kaolin with initial moisture content of 150% has been conducted in laboratory and vertical settlement was recorded. Ramp loading consolidation simulation method is applied to soft soil settlement estimation and the prediction fits well with the experiment.

The influence of soil texture on the course of volume changes of soil

Volume changes of soil associated with soil moisture changes are caused by the presence of clay minerals from illite and montmorillonite groups. Clay minerals are found in the so-called clay soil component which can be quantified by laboratory analysis of the soil particle-size distribution. Consequently, the potential for volume changes in soil can be assessed from soil texture. In our study, 172 soil samples with different textures were used to measure dependencies between volume changes in soil and changes in soil moisture under laboratory conditions. The samples were collected from 11 sites in the Eastern Slovak Lowland. On the basis of the measurements, 10 mathematical models were created to compute the correlation between volume changes of soil and soil moisture content and texture. The highest accuracy was obtained with the model which assumes the content of particles < 0.002 mm. When comparing the clay particles < 0.001 mm (colloidal clay) with the particles < 0.002 mm (colloidal + physical clay) it was also found that the particles < 0.002 mm have a larger impact on the volume changes of soil than the particles < 0.001. The inclusion of particles > 0.002 mm (silt + sand) into the models resulted in either no or only negligible refinement of the soil volume change calculations.

Effects of specimen preparation method on the volume change of clay under cyclic thermal loads

Previous investigations of the volume change of soil with different fabric patterns have been mostly carried out at a constant temperature. To investigate the influence of the specimen preparation method on the volume change of saturated clay under cyclic thermal loads, reconstituted, intact and recompacted specimens were tested. Thermal axial strains of these specimens in a normally consolidated state were measured using a temperature-controlled invar oedometer apparatus. The soil fabric of each specimen was evaluated using a scanning electron microscope (SEM) and a mercury intrusion porosimeter (MIP). All specimens showed continuous contraction as the number of thermal cycles increased, albeit at a decreasing rate. After five heating and cooling cycles with temperatures ranging from 15 to 70°C, the accumulated plastic axial strain of the reconstituted specimen was 38% and 68% larger than those of the intact and recompacted specimens, respectively. The SEM visualisations and MIP measurements demonstrate that these observed differences can likely be attributed to different distributions of clay particles in the soil specimens (with a 28% clay content). In the intact and recompacted specimens, most of the clay particles formed silt-size aggregates. In the reconstituted specimen, the clay particles filled the spaces between silt particles and the soil fabric was homogeneous overall.

Variation of Suction during Wetting of Unsaturated Collapsible Gypseous Soils

Gypseous soils represent as essential soils that exhibit unsaturated behavior that differs completely than their behavior during soaking. Their strength, stiffness, and compressibility are dependent on the degree of saturation.The soil used in this research is disturbed natural gypseous soil having three different percentages of gypsum; 55, 30 and 18%. Nine model tests were conducted to investigate the variation of suction, settlement and total vertical stress with time, also, to study the effect of wetting on the volume change of unsaturated gypseous soil. The soil container used with inner dimensions of (length 700× width 700× height 600 mm). A square footing with (100 mm) sides was used. Models in loose, medium and dense soils were prepared. Watermark monitor data logger model 900M was used, with automatic data collection device that measures soil suction in kPa. The saturation process involved the complete saturation until the suction sensors readings approach to zero. The saturation process was established by allowing the water to infiltrate through the soil in upward-direction with a steady flow and head of 2 m.For all soil models, the time needed to reach the zero suction (saturation state) increased with the increase of the initial dry density. The initial value of suction for all soils increased with decreasing of the initial water content. The drop in the readings of suction may be due to the effect of gypsum content on the adsorption of water that leads to the saturation of the sensors surrounding area. Â

Numerical Modeling of Water Flow in Expansive Soils with Simplified Description of Soil Deformation

Abstract In this paper we describe a numerical model of transient water flow in unsaturated expansive soils and the resulting soil volume change. The unsaturated flow equation is solved in a 2D domain using a finite-volume method and an explicit time discretization scheme. Strains in the soil mass are calculated by two simplified approaches, assuming that the strain state is either 1D (in the vertical direction only) or 2D with equal strains in horizontal and vertical directions. The model is applied to two cases described in the literature, in which the strains were computed from the solution of the stress equilibrium equation. It is shown that the simplified methods give results which are reasonably close to the more complex approach based on the equilibrium equations. The proposed model can be used to predict time-varying soil shrinkage and swelling caused by natural and anthropogenic factors.

Modeling of the swelling–shrinkage behavior of expansive clays during wetting–drying cycles

This paper presents a constitutive model for simulating the swelling–shrinkage volume change of expansive soils during wetting–drying cycles. Based on the concept of the critical swelling–shrinkage state proposed by Zhao et al. [21], the elastic swelling–shrinkage deformation, plastic swelling/shrinkage deformation, and accumulative deformation during wetting–drying cycles were analyzed. Influences of the initial dry density and stress applied on the yield suction were discussed. The suction decreasing yield surface (SD) and suction increasing yield surface (SI) were defined. The variations of SD and SI yield surfaces were proposed. Calibration was performed with results of the cyclic wetting–drying tests conducted. The proposed model was validated by simulating cyclic wetting–drying tests conducted on compacted GaoMiaoZi (GMZ) bentonite. Good agreements were obtained between the simulation results and the experimental ones. Using the proposed model, influences of dry density and stress applied on the swelling–shrinkage deformation and accumulative deformation of expansive soil were well described.

Volume change and microstructure of calcareous soils contaminated with sulfuric acid

Acid contamination of soils is a common problem within fertilizer and petrochemical industries. Soil properties could be altered due to acid contamination, especially the volume change within the vicinity of the contaminated soils. There are huge petrochemical and fertilizer industries in the industrial areas that produce or utilize different acids. Further, most of the soils used for road bases and under pavement and walkways are calcareous in nature. These carbonate soils are susceptible to large volume change when attacked by acids. This research aims to study the volume and microstructural changes using two calcareous soils, i.e. non-plastic and plastic marls, due to interaction with sulfuric acid at three different concentrations. The soil samples were prepared in high-density polyethylene (HDPE) molds that were placed in large containers and instrumented with linear variable differential transformer (LVDT) to measure the volume change. The morphology and composition analyses were studied utilizing scanning electron microscopy and X-ray diffraction. Results of this investigation indicate that the volume change and acid concentration were proportional except in the case with the non-plastic marl at high acid concentration. This was ascribed to the severe reaction of sulfuric acid with the carbonate minerals resulting in blocking the paths for further infiltration of the acid into the whole soil.

In-Situ High Resolution Dynamic X-ray Microtomographic Imaging of Olive Oil Removal in Kitchen Sponges by Squeezing and Rinsing.

Recent advances in high resolution X-ray tomography (μCT) technology have enabled in-situ dynamic μCT imaging (4D-μCT) of time-dependent processes inside 3D structures, non-destructively and non-invasively. This paper illustrates the application of 4D-μCT for visualizing the removal of fatty liquids from kitchen sponges made of polyurethane after rinsing (absorption), squeezing (desorption) and cleaning (adding detergents). For the first time, time-dependent imaging of this type of system was established with sufficiently large contrast gradient between water (with/without detergent) and olive oil (model fat) by the application of suitable fat-sensitive X-ray contrast agents. Thus, contrasted olive oil filled sponges were rinsed and squeezed in a unique laboratory loading device with a fluid flow channel designed to fit inside a rotating gantry-based X-ray μCT system. Results suggest the use of brominated vegetable oil as a preferred contrast agent over magnetite powder for enhancing the attenuation coefficient of olive oil in a multi fluid filled kitchen sponge. The contrast agent (brominated vegetable oil) and olive oil were mixed and subsequently added on to the sponge. There was no disintegration seen in the mixture of contrast agent and olive oil during the cleaning process by detergents. The application of contrast agents also helped in accurately tracking the movement and volume changes of soils in compressed open cell structures. With the in house-built cleaning device, it was quantified that almost 99% of cleaning was possible for contrasted olive oil (brominated vegetable oil with olive oil) dispersed in the sponge. This novel approach allowed for realistic mimicking of the cleaning process and provided closer evaluation of the effectiveness of cleaning by detergents to minimize bacterial growth.

Comparison of Soil–Water Characteristic Curves from Conventional Testing and Combination of Small-Scale Centrifuge and Dew Point Methods

Soil–water characteristic curve (SWCC) is an important unsaturated soil property relating the water content of a soil to soil suction and it is conventionally measured using Tempe cell, pressure plate and salt solution methods. However, these tests are tedious and time consuming. The SWCC measurements using fast and efficient methods are required for engineering designs such as excavation, slope protection, retaining wall and landfill cover designs. This paper describes the testing procedures and apparatuses associated with rapid measurements of a complete SWCC of a residual soil as obtained from combined measurements using a small-scale centrifuge and dew point methods. The SWCC test results obtained using these alternative methods were compared with the SWCC data from Tempe cell, pressure plate and salt solution methods. Shrinkage tests were carried out in this study to incorporate the volume change of soil into SWCC. The experimental data from all SWCC tests were evaluated using first order analysis with 95% confidence interval for determination of upper and lower bounds of SWCC. The analysis results showed that the SWCC data obtained from tests using small-scale centrifuge and dew point methods were in good agreement with those obtained from Tempe cell, pressure plate and salt solution methods. This indicates that the combination of small-scale centrifuge and dew point methods can be used to generate a complete curve of SWCC for the residual soil. In addition, the time required to perform SWCC tests using the alternative methods is shorter than the SWCC tests using the conventional methods.

Utilization of waste marble to enhance volume change and strength characteristics of sand-stabilized expansive soil

In this paper, marble waste is evaluated as a secondary material to be utilized as potential stabilizer to improve the volume change and strength characteristics of sand-amended expansive soil, proposed as a possible landfill, pavement or sub-base material in a semi-arid climate. An experimental program was conducted on sand-expansive soil enhanced with marble waste, abundantly found as a by-product of construction industry, obtained from two different sources with different gradations, denoted as marble powder (MP) and marble dust (MD). One-dimensional swell, volumetric shrinkage, consolidation, unconfined compressive and flexural strength tests were conducted on expansive soil–sand mixtures with 5, 10 and 20% waste marble inclusions over curing periods of 7, 28 and 90 days. Test results showed that 10% marble powder and 5% marble dust by dry mass were the optimum amounts for mitigating the swell–shrink potential and compression index as well as yielding the highest unconfined compressive and flexural strength values. Moreover, the rate of reduction in swell potential versus the flexural strength over the curing periods studied is highest in 10% MP- and 5% MD-included specimens, the latter being more insensitive to this change. The soil mixtures displayed brittle behavior after marble addition, hence its utilization as a secondary additive to sand-amended expansive soil is recommended for soils exposed to lower flexural loads such as light traffic.

Stochastic modeling of volume changes in expansive soils

Stochastic analysis procedure was developed to predict the probability and range of volume changes in expansive soils. The plastic limit is an appropriate datum for estimating volume changes in the absence of continuous water content data. Results indicated that the soil usually exhibits swelling (30 mm) due to the prevalent dry conditions. The volume changes ranged between − 44 and + 104 mm for the investigated soil. Similarly, the likelihood to have − 30, + 30, and + 60 mm volume change was 5, 50, and 20%, respectively.

Strategies on Reuse of Clayey Expansive Soils as Embankment Material in Urban Development Areas: A Case Study in New Urbanized Zones

Volume changes in clayey expansive soils may result in the settlement or heave of structures, making such materials inappropriate in the design of soil structures. Lime and its derivatives provide an increase in the plastic limit of clay, and have gained considerable attention in soil stabilization techniques. In this regard, optimum lime addition combined with an innovative construction procedure provides new possibilities for the construction of roads in urban areas. In this study, the first straightforward strategy for the ionic immobilization of lime between clay laminar structures, based on a component self-assembly process, is presented. The method is applied to an area with expansive clays in the city of Madrid (Spain). The clayey soils were characterized by DRX, SEM, particle size distribution, swelling tests, and bearing capacity analyses. This strategy reduces the need for the transportation of discarded materials to landfill and the acquisition of new resources. In addition, the proposed methodology allows for a reduction in the environmental impact associated with urban development in expanding urban areas.