Swelling soils are increasingly recognized as a critical issue in geotechnical engineering, as their presence can lead to substantial damage to built structures. When structures are built on such soils and free swelling is prevented, stresses can develop that may lead to significant damage to the structure. Soil stabilization through the use of additive materials has garnered considerable attention as an effective method for mitigating this problem. The objective of this study was to stabilize the clay soil (CH) with high swelling potential by using sea shell, lime and zeolite additives in two stages. In the initial phase, consistency limits were tested by mixing high plasticity clay soil mixed with 8-10-12-14-16% sea shell 0-3-5-6-8% lime (one of the most used soil stabilizer) and 0-5-10-15-20% zeolite by weight. The three mixtures and the two best percentages determined for each mixture were then combined. Upon completing these steps, five experimental sets were prepared by combining the percentages that yielded the best results. Compaction test, percent swelling test and swelling pressure tests were performed with these datas. According to the test results, adding 14% sea shell, 6% lime and 5% zeolite by weight (SS14L6Z5) gave the smallest swelling value as 1,07% and highes swelling pressure as 23 kPa. This study concludes that the combined use of these additives led to a substantial 96% increase in swelling pressure, along with a marked reduction in swelling potential.

In this study, the effects of vertical strain and hydration time on the mechanical behavior and microstructure of expansive soils are examined, addressing the challenges they pose to engineering structures due to moisture-induced swelling pressure and deformation. Conducting hygroscopic expansion tests on soils with varying initial dry densities, the study explores the relationship between swelling pressure and vertical strain. Additionally, the effect of different hydration times on these properties is assessed. Using mercury intrusion porosimetry, the soil specimens are dissected into top and bottom layers to observe microstructural changes over varying hydration periods. The results indicate a decline in swelling pressure and expansion rate with increased strain; at 1% strain, there is a 54% decrease in vertical swelling pressure and a 41% reduction in lateral pressure. Expansion rate attenuation is more significant, with an 83% decrease in vertical and 92% in lateral rates. The research concludes that the hydration process under limited strain consists of two stages: the initial strain stage, with pronounced top layer expansion, and a subsequent constant-volume stage, where the top layer undergoes compression and the bottom layer expands significantly.

Rigid pavements built on an expansive subgrade often sustain damage due to differential movement caused by variations in the subgrade moisture content and the resulting swelling pressure. This study aims to introduce an approach based on swelling pressure for analyzing the deformation of rigid pavements. The analysis takes into consideration the effect of soil matric suction on the modulus of subgrade reaction and potential swelling pressure. The numerical analysis was carried out using the pasternak foundation model, wherein the pavement was idealized as an Euler-Bernoulli beam, the pasternak shear layer represented the granular sub-base supporting the pavement, and the expansive soil was modelled using winkler springs. To demonstrate the practical applicability of the proposed model, a case study is presented for an Indian site and the outcomes are presented. The parametric study clearly illustrates that the modulus of subgrade reaction of expansive soil is the most sensitive and significant parameter for improving the flexural response of the pavement. A flowchart outlining the evaluation procedure is included to provide a visual representation of the analysis process.

In pipeline engineering in expansive soil areas, swelling pressure is frequently determined by laboratory tests as an essential design parameter. During the processes of filling and rolling, lateral residual stress exists in the soil, which significantly influences the swelling pressure. In this study, a series of expansion and residual stress tests is conducted on compacted expansive soil s with different initial dry densities and moisture contents. The variation rules of the swelling pressure for different specimen preparation methods are compared. The effects of the initial conditions on the lateral residual stress are analyzed. The range of initial conditions for the influence of lateral residual stress on swelling pressure is investigated. In addition, based on the Mercury Intrusion Porosimetry (MIP), the change rule of the soil microstructure under different initial conditions is obtained. A microcosmic mechanism for the lateral residual stress acting on the vertical swelling pressure is proposed. The results demonstrate that the lateral residual stress increases with increasing dry density and decreases with increasing moisture content. Based on the variation range of the initial specimen condition, the influence of the lateral residual stress on the swelling pressure can be distinguished using slash (omega 0=112.5 rho 0-157.75\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\omega }_{0}\text{=}112.5{\rho }_{0}-157.75$$\end{document}). When the lateral residual stress exceeds the range of approximately 130-170 kPa, the swelling pressure is influenced, and the greater the lateral residual stress, the greater the effect.

Full-scale testing of lateral pressures in expansive clay under various saturation conditions is crucial to better understand the behavior of these soils and predict potential damage to structures. However, due to their complexity and cost, only a few full-scale physical testing studies on expansive soils have been reported in the literature. This study aims to provide new insight into the evolution of lateral swelling pressure in expansive soils under infiltration via full-scale physical testing. For this purpose, a heavily instrumented 3-m high masonry wall backfilled with an expansive clay was built and subjected to infiltration. The backfill was compacted in 95% of standard Proctor at a moisture content near optimal to simulate field conditions. The degree of saturation, pore-water pressure, temperature, suction, and lateral and vertical pressures were monitored at different locations during the test. Results showed that the development of lateral pressure is rapid during initial saturation and levels out as the clay approaches saturation levels. This finding highlights the importance of monitoring lateral pressure over time to accurately predict its behavior. The study also found that lateral pressure develops prior to vertical pressure, depending on the area and restraint. The lack of vertical pressure observed during the test is attributed to the continued displacement of the concrete block wall and settlement of the clay with increased area and wet weight of the soil. This finding is important for backfill against basement walls, retaining walls, and foundation units, where the mass of the expansive soil is limited, and effective stress is limited to one dimension.

This paper presents a comprehensive design study conducted in Saudi Arabia, focusing on the performance evaluation of an inverted T foundation system in a building constructed on expansive soils. The study aimed to investigate the causes of damage and evaluate the performance of a proposed inverted T foundation. A single story market building in a semi-arid region with expansive soil was constructed utilizing a 40 cm-thick mat foundation as a precautionary measure against soil swelling. However, the building experienced instability and damage shortly after completion. This study explored the replacement of the existing mat foundation with an inverted T foundation. The research involved assessing the ability of the inverted T foundation to withstand swelling pressures and its impact on the structural members of the building. Design guidelines and tools were developed to support the design and analysis of the inverted T foundation. Economic feasibility was also evaluated. The study compared the effects of swelling pressure on two types of foundations: a mat foundation and a rigid strip foundation. The results showed that the inverted T foundation demonstrated less upward movement and was found more effective in mitigating the detrimental effects of soil expansion compared to the mat foundation. Design guidelines and tools, including schedules, and charts were developed to support the design and analysis of the inverted T foundation. The findings have significant implications for the design and construction of buildings on expansive soils, offering insights into the effectiveness of the inverted T foundation as an alternative solution. The research contributes to the knowledge of foundation design on expansive soils in general and provides practical guidance for engineers and practitioners in similar geological contexts.

The swelling soils, also known as expansive soils, increase in volume due to an increase in moisture content. The settlement of expansive soils could be the main reason for considerable damage to roads, highways, structures, irrigation channel covers, and the protective shell of tunnels that use bentonite for wall stability. Therefore, it is important to determine the amount of swelling pressure in expansive soils. This research uses two laboratory swelling test methods with constant volume (CVS) and ASTM-4546-96 standard, the swelling pressure of lime-stabilized bentonite soil has been estimated. Based on the key findings of this study, the swelling pressure values of pure bentonite samples tested using the ASTM-4546-96 method, compared to the constant volume swelling test, show an approximately 170% increase.

In the high-level radioactive waste (HLW) deep geological repository, bentonite is compacted uniaxially, and then arranged vertically in engineered barriers. The assembly scheme induces the initial anisotropy, and with hydration, it develops more evidently under chemical conditions. To investigate the anisotropic swelling of compacted Gaomiaozi (GMZ) bentonite and the further response to saline effects, a series of constant-volume swelling pressure tests were performed. Results showed that dry density enhanced the bentonite swelling and raised the final anisotropy, whereas saline inhibited the bentonite swelling but still promoted the final anisotropy. The final anisotropy coefficient (ratio of radial to axial pressure) obeyed the Boltzmann sigmoid attenuation function, decreasing with concentration and dry density, converging to a minimum value of 0.76. The staged evolution of anisotropy coefficient was discovered, that saline inhibited the rise of the anisotropy coefficient (Delta delta) in the isotropic process greater than the valley (delta(1)) in the anisotropic process, leading to the final anisotropy increasing. The isotropic stage amplified the impact of soil structure rearrangement on the macro-swelling pressure values. Thus, a new method for predicting swelling pressures of compacted bentonite was proposed, by expanding the equations of Gouy-Chapman theory with a dissipative wedge term. An evolutionary function was constructed, revealing the correlation between the occurrence time and the pressure value due to the structure rearrangement and the former crystalline swelling. Accordingly, a design reference for dry density was given, based on the chemical conditions around the pre-site in Beishan, China. The anisotropy promoted by saline would cause a greater drop of radial pressure, making the previous threshold on axial swelling fail. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Because of the inherent rheological property of transparent gel, laponite has been proposed for soil densification to withstand seismic events. Since the swelling behaviors of laponite could affect the soil-nanoparticle structure, one of the most important research topics is the swelling capacity of nanoparticles, particularly laponite. Hence, the objective of this study is to investigate the swelling properties of fresh laponite and sand treated with different contents of laponite. The swelling characteristics of compacted laponite hydrogel were investigated using a one-dimensional consolidation test setup. Results showed that the swelling strain of compacted laponite increased with time and as the concentration of laponite increased in specimens. The initial swelling of fresh laponite took around 4 weeks to attain equilibrium, while in the reswelling tests, laponite reached equilibrium within 60 h. The reswelling strain of laponite was higher than the initial swelling of fresh laponite, with a distinct reswelling behavior compared to other clay minerals. This swelling strain of laponite was found to be consistent with other clay minerals in which the swelling strain is caused by interlayer and double-layer forces. Scanning Electron Microscope images revealed that the structures of swollen laponite are continuous sheet-like irregular structures with pore size. Moreover, the swelling strain of the sand-laponite mixture with 3% laponite reached equilibrium after 40 h, whereas the swelling strain of sand-laponite with 5% laponite specimen did not reach equilibrium even after 50 h. In this study, the water retention ratio and changes in laponite hydrogel characteristics due to repeated drying and wetting processes were also investigated. In addition, the swelling pressure of compacted laponite hydrogel was also estimated, which varied in a range of 5.6-8.6 kPa throughout the experiment.

Expansive clays present serious issues in a variety of engineering applications, including roadways, light buildings, and infrastructure, because of their notable volume changes with varying moisture content. Tough weather conditions can lead to drying and shrinking, which alters expansive clays' hydro-mechanical properties and results in cracking. The hydro-mechanical behavior of Al-Ghatt expansive clay and the impact of wetting and drying cycles on the formation of surface cracks are addressed in this investigation. For four cycles of wetting and drying and three vertical stress levels, i.e., 50 kPa, 100 kPa, and 200 kPa, were investigated. The sizes and patterns of cracks were observed and classified. A simplified classification based on main track and secondary branch tracks is introduced. The vertical strain measure at each cycle, which showed swell and shrinkage, was plotted. The hydromechanical behavior of the clay, which corresponds to three levels of overburden stress as indicated by its swell potential and hydraulic conductivity was observed. It was found that at low overburden stresses of 50 kPa, the shrinkage is high and drops with increasing the number of cycles. Al-Ghatt clay's tendency to crack is significantly reduced or eliminated by the 200 kPa overburden pressure. The results of this work can be used to calculate the depth of a foundation and the amount of partial soil replacement that is needed.