Improper anti-drainage treatment of weakly expansive soil subgrades can lead to significant post-construction deformation and uneven settlement, which severely affect the operational safety and service life of engineering projects. To comprehensively analyze the evolution of soil volume and strength under different hydraulic coupling paths during wetting-drying (W-D) cycles, a loaded W-D cycle testing device was developed. Soil volume was measured during the W-D cycles, and the shear strength and soil-water characteristic curves were analyzed after different cycles. The results indicate that during the W-D cycles, changes in soil volume and strength exhibited distinct stages with similar evolution characteristics. Under the investigated loading conditions, the soil demonstrated significant collapsibility during the wetting process, which gradually diminished as the number of cycles increased. Eventually, the W-D cycles caused the soil to reach an equilibrium state, where its swelling and shrinkage behavior became nearly elastic. At equilibrium state, there is a corresponding void ratio for any moisture content, which is the elastic void ratio (e0el). The e0el is irrespective of the number of cycles and initial dry density. Conversely, higher load and larger amplitude in W-D cycles tend to decrease the e0el. Furthermore, by correlating the unsaturated soil matric suction, secant modulus, and stress path, the volume evolution mechanism of the soil was analyzed based on the soil effective stress theory and pore evolution. The results of this study can serve as a crucial reference point for revealing the deformation mechanism of weakly expansive soil subgrades and selecting appropriate road settlement control methods.

Expansive soils have significant characteristics of expansion by water absorption, contraction by water loss. Under the freeze-thaw (F-T) cycles, the engineering diseases are more significant, and the serious geotechnical engineering incidents are induced extremely easily. The aim is to investigate the mechanical response characteristics of geogrid-reinforced expansive soils (GRES) under F-T cycles. Based on a series of large-scale temperature-controlled triaxial tests, influencing factors were considered, such as the number of F-T cycles, the geogrid layers, and the confining pressure. The results showed that: (1) Friction between the expansive soil and geogrid and the geogrid's embedded locking effect indirectly provided additional pressure, limited shear deformation. With the increase in reinforced layers, the stress-strain curve changed from a strain-softening to a strain-hardening type. (2) Elastic modulus, cohesion, and friction angle decreased significantly with increasing number of F-T cycles, whereas dynamic equilibrium was reached after six F-T cycles. (3) The three-layer reinforced specimens showed the best performance of F-T resistance, compared to the plain soil, the elastic modulus reduction amount decreases from 35.7% to 18.3%, cohesion from 24.5% to 14.3%, and friction angle from 7.6% to 4.5%. (4) A modified Duncan-Zhang model with the confining pressure, the F-T cycles, and the geogrid layers was proposed; the predicted values agreed with the measured values by more than 90%, which can be used as a prediction formula for the stress-strain characteristics of GRES under freeze-thaw cycling conditions. The research results can provide important theoretical support for the practical engineering design of GRES in cold regions.

Expansive soils, when wetted, exert swell pressure on the structures built over them, often leading to damage. To quantify this additional pressure, researchers have often measured the vertical and lateral swell pressure. However, when expansive soils surround the structures in all directions, measuring the all-round swell pressure becomes more appropriate. In this context, an Isotropic - Pressure Monitoring Device (I-PMD) was employed in the present study for the measurement of all-round swell pressure for the soils C1, C2, C3, and C4 by wetting them from different initial states at constant volume conditions and was observed to be in the range of 20 kPa to 850 kPa. Also, comparative studies have been performed to comprehend the significance of all-round swell pressure measurement over conventional methods. Additionally, a relationship was proposed to predict the all-round swell pressure of the soil based on its vertical swell pressure measured by conventional methods.

Expansive soils are susceptible to cracking due to significant moisture fluctuations, which can potentially lead to structural instability. Although geogrid reinforcement is widely used to control soil swelling and shrinkage, its effects on cracking behavior are not fully understood. This study investigates the influence of geogrid reinforcement on the cracking behavior of expansive soils by comparing soil samples reinforced with two layers of geogrid to unreinforced samples under evaporation conditions. Crack development was monitored using high- resolution imaging and fluorescence tracing to measure crack depth and calculate surface crack ratio. Additionally, moisture content distribution and evaporation rates were assessed. The results show that geogrid reinforcement reduced the total crack ratio by 1.34% and decreased average crack depth by 43.5%, leading to a more uniform crack distribution with smaller openings. Both internal and external cracks facilitated moisture exchange between the soil and atmosphere. The frictional and interlocking effects at the soil-geogrid interface effectively inhibited cracking and reduced moisture migration. The uniaxial geogrid also induced anisotropy crack restraint, with environmental exposure and geogrid orientation playing critical roles in crack control. Overall, these findings demonstrate the effectiveness of geogrids in enhancing the stability of expansive soils and limiting atmospheric influence through crack suppression.

The thermal stabilization of expansive soils has emerged as a promising and sustainable alternative to conventional chemical stabilization methods, addressing the long-standing challenges associated with soil swelling and shrinkage. This review critically evaluates the mechanisms, applications, and advancements in thermal stabilization techniques, with a particular focus on both traditional approaches (e.g., kiln heating) and emerging innovations such as microwave heating. This study synthesizes recent research findings to assess how thermal treatment modifies the mineralogical, physical, and mechanical properties of expansive soils, reducing their plasticity and improving their strength characteristics. Comparative analysis highlights the advantages, limitations, and sustainability implications of different thermal methods, considering factors such as energy efficiency, scalability, and environmental impact. While thermal stabilization offers a viable alternative to chemical treatments, key challenges remain regarding cost, field implementation, and long-term performance validation. The integration of thermal treatment with complementary techniques, such as lime stabilization, is explored as a means to enhance soil stability while minimizing environmental impact. By addressing critical research gaps and providing a comprehensive perspective on the future potential of thermal stabilization, this review contributes valuable insights for researchers and engineers seeking innovative and sustainable solutions for managing expansive soils.

In semi-arid areas, light buildings, highways, and pavements are frequently damaged by the subsurface swelling or shrinkage of expansive soils during both wetting and drying cycles. The goal of this research is to explore the X-ray diffraction of natural clay with bentonite additives in order to determine the amount of expanding minerals in the clay based on changes in the diffractometer profile and diffraction intensity. Mineralogical studies are crucial for determining the geotechnical behavior of these soils. Five semi-arid areas were chosen to explore the key minerals that influence geotechnical behavior. The various geological backgrounds were reflected in differing expansivities, and X-ray diffraction revealed considerable mineralogy differences between the five zones under consideration. Non-sharp peaks rose above background intensities in zones containing smectite clay minerals. Significant expanding minerals produced distinct peaks in the clays. Adding 10, 20, 30, and 40% commercial bentonite changed the peak size and area beneath the peak. Overlapping intensities in clay minerals can affect the intensity of peaks in lower 2 theta ranges. This was discovered to influence the method of quantification and can be improved by the usage of heating or glycolation processes. The diffraction profile for each examined area is supplied, along with an identification of expansion minerals. The methodology is provided for estimating clay minerals in areas with similar geological origins. Qatif clays were discovered to be the most expansive with estimated expanded mineral concentrations ranging from 23.9 to 34.7%. The remaining four clays had mineral concentrations ranging from 4.4 to 20%. Two proposed semi-quantitative methods are investigated. The peak intensity method produced better results than the area under the peak method.

The paper explores challenges arising from the existence of expansive clay soils, renowned for causing structural damage and exhibiting detrimental environmental effects. Implementing a novel approach, this study introduces the use of fly ash (Class F) and shredded face masks (FMs) to enhance soil properties. Fly ash (FA), known for its pozzolanic properties, is combined with shredded waste FMs to reinforce the soil. Remolded specimens underwent comprehensive laboratory testing, including Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), Swell Test, Consolidation Test, and Triaxial Test. The optimal blend identified as 0.9% FMs + 20% FA achieves an optimal equilibrium of strength, stability, and reduction in swelling. The UCS exhibited an increase with the addition of FA, and this improvement was further enhanced with the inclusion of 0.9% FMs, surpassing the specified subgrade CBR values. The percentage of swell exhibited a notable decrease from 5.9% to 1.8% with the incorporation of FA + FMs. This sustainable approach aims to conserve valuable resources and mitigate challenges associated with waste disposal along with the economic benefits to contribute to achieve UN SDGs 2030.

To address environmental concerns related to cement-stabilized expansive soil and the safety risks of caustic-activated blast furnace slag, this study explores the use of lime-activated blast furnace slag as an alternative stabilizer in northern Hebei, China. The effects of slag dosage, curing time, and osmotic pressure on the expansion, osmotic properties, and strength of the improved soil were evaluated through free expansion rate, permeability coefficient, and unconfined compressive strength tests. Results show that adding slag-lime significantly reduces soil expansion. As slag content increases, the free expansion rate decreases exponentially. During the curing period of 3-7 days, expansion declines and stabilizes between 7-14 days. Similarly, the permeability coefficient permeability coefficient decreases with higher slag content, following a quadratic trend. Under osmotic pressures of 0.1-0.2 MPa, the permeability coefficient permeability coefficient increases but stabilizes between 0.2-0.4 MPa.Furthermore, slag-lime significantly enhances unconfined compressive strength, which increases linearly with slag content. The stress-strain curve follows a logistic function in the rising stage and a rational fractional equation in the descending stage.This study demonstrates that lime-activated blast furnace slag is a sustainable and effective alternative for stabilizing expansive soils while reducing dependence on cement.

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.

Expansive soils can cause large-scale damage to the infrastructure. Soil stabilization with Portland cement and lime has been widely utilized as a solution to this problem. However, these stabilizers are non-renewable and energy-intensive. Alkali-activated binders are alternatives with lower carbon dioxide emissions. This research evaluated an expansive soil stabilization with an alkali-activated binder produced from sugarcane bagasse ash (SCBA), hydrated eggshell lime (HEL) and sodium hydroxide (NaOH). Free-swelling tests alongside a statistical analysis evaluated the influence of dry unit weight (12.5 and 14.5 kN/m(3)), binder (4 and 10%) and moisture content (19.7 and 24.7%) and curing time (0 and 7 days) on the stabilized mixtures. A four factors factorial design with duplicates and central points was outlined. To better understand the NaOH and SCBA influence over the soil expansion additional tests were performed. In general, an increase on the studied factors reduced swelling, especially binder content. However, the alkali-activated cement presented no clear correlation between higher density and higher expansion. Swell reduced from 13.8% (12.5 kN/m(3) and 19.7% moisture) and 8.8% (12.5 kN/m(3) and 24.7% moisture) to 2.5% and 0%, respectively, after 7 days and 10% binder addition for the alkaline cement. For Portland cement, swell reduced from 13.8% (10.2 kN/m(3) and 22.5% moisture) and 12.5% (10.2 kN/m(3) and 27.5% moisture) to 1.8% and 1%, respectively, after 7 days and 4% binder addition. Samples containing NaOH expanded less than samples molded with only water. Finally, the alternative binder might be a viable option to replace Portland cement for expansion control.