Expansive clay soil is known to cause damage to pavements due to its volume fluctuations with changes in moisture content, a phenomenon observed globally in many countries. Implementing suitable stabilisation treatments is crucial for improving the mechanical and hydraulic properties of the expansive clay subgrade. While cement and lime have traditionally been widely used as soil stabilisers, there is a growing emphasis on sustainable engineering due to increased awareness of global warming. Seeking alternative green and sustainable materials for soil stabilisation is demanded now, and one such alternative is using ethylene-vinyl acetate (EVA) copolymer emulsion. However, the use of EVA copolymer emulsion for stabilising expansive clay has been relatively underexplored in existing studies. This study evaluates the feasibility of utilising EVA copolymer emulsion for stabilising expansive clay subgrade through comprehensive laboratory tests to assess the mechanical (compaction, unconfined compressive strength, California bearing ratio, resilient modulus, and direct shear), hydraulic (soil-water retention curve and swellshrinkage), and micro-chemical (thermogravimetric analyses and scanning electron microscopic) performance of the soil. The experimental results indicate that the inclusion of 1 % EVA copolymer emulsion into the expansive clay provided the highest mechanical properties, resulting in an increase in the unconfined compressive strength, soaked California bearing ratio, resilient modulus, and cohesion by 8.8 %, 177.8 %, 35.8 % and 19.4 %, respectively. Swell-shrinkage behaviour was also improved with the addition of EVA copolymer, with 1 % EVA copolymer presenting the lowest swell-shrinkage index of 3.19 %/pF (14 % decrease in shrink-swell potential compared to the untreated clay).

Clay soils are known to have a high swelling pressure with an increase in water content. This behavior is considered a serious hazard to structures built upon them. Various mechanical and chemical treatments have historically been used to stabilize the swelling behavior of clay soils. This work investigates the potential use of shredded plastic waste to reduce the swelling pressure and compressibility of clay soils. Two types of highly plastic clay (CH) soils were selected. Three different dimensions of plastic waste pieces were used, namely lengths of 0.5 cm, 1.0 cm, and 1.5 cm, with a width of 1 mm. A blend of plastic-cement waste with a ratio of 1:5 by weight was prepared. Different fractions of the plastic-cement waste blend with a 2 wt.% increment were added to the clay soil, which was then remolded in a consolidometer ring at 95% relative compaction and 3.0% below the optimum. The zero swell test, as per ASTM D4546, was conducted on the remolded soil samples after three curing periods: 1, 2, and 7 days. This method ensures the accurate evaluation of swell potential and stabilization efficiency over time. The experimental results showed that the addition of 6.0-8.0% of the blend significantly reduced the swelling pressure, demonstrating the mixture's effectiveness in soil stabilization. It also reduced the swell potential of the expansive clay soil and had a substantial effect on the reduction in its compressibility, especially with a higher aspect ratio. The compression index decreased, while the maximum past pressure increased with a higher plastic-cement ratio. The 7-day curing time is the optimum time to stabilize expansive clay soils with the plastic-cement waste mixture. This study provides strong evidence that plastic waste can enhance soil mechanical properties, making it a viable geotechnical solution.

Stabilizing problematic soils with new materials can reduce environmental problems and improve mechanical properties. This research uses the results of various tests, such as unconfined compressive strength (UCS), indirect tensile strength (ITS), ultrasonic pulse velocity (UPV), direct shear test, and standard Proctor compaction, to evaluate the effect of curing time and the nano aluminum oxide contents on the mechanical and shear characteristics of clay soil stabilized with cement and nano aluminum oxide. This research showed that the optimal content of replacing cement with nano aluminum oxide to stabilize clay soil is 0.9% by weight of cement. Adding the optimal content of nano aluminum oxide to cement-stabilized clay soil increased UCS and ITS by 28% and 51%, respectively. Also, the drained internal friction angle and cohesion increased by 17 and 25%, respectively. The results of UPV non-destructive testing can also be used to predict the mechanical characteristics of stabilized clay. By reducing cement consumption and enhancing soil stabilization, this research contributes to Sustainable Development Goals (SDGs) by promoting resource efficiency, lowering environmental impact, and supporting durable infrastructure development.

Hydrothermal solidification offers an effective, sustainable method for stabilizing clay soil, addressing environmental concerns while improving geotechnical properties. Facilitating pozzolanic reactions between lime and clay under controlled temperature and pressure significantly enhances compressive strength and soil durability. This process promotes calcium silicate hydrate (C-S-H) formation, reduces industrial waste, and supports lime reuse, making it an energy-efficient soil improvement approach. This study investigates the impact of lime addition (0-20%) and various chemical and physical parameters on clay soil compressive strength. Key chemical components include SiO2 (20.1-76.9%), Al2O3 (7.6-34.8%), Fe2O3 (0.6-32.9%), CaO (0.1-43.5%), MgO (0-9.56%), Na2O (0.01-2.8%), and K2O (0.1-3.9%). Physical properties such as density, plasticity index (6-34.5%), and liquid limit (24-65.2%) were analyzed alongside process parameters like heating temperature (60-1000 degrees C), curing time (0-120 days), and curing temperature (20-41 degrees C). Using a dataset of 152 samples divided into training and testing groups, the statistical analysis focused on the leaching coefficient (Lc) and silica-sesquioxide ratio (Kr). Lc emerged as the most significant factor, achieving an R2 of 0.89 and an RMSE of 1.13 MPa. This study found that the compressive strength of lime-treated clay soils varied from 0.02 MPa to 11.9 MPa, influenced by lime concentration, chemical composition, and processing factors. Increased lime additions, particularly when combined with hydrothermal treatment, led to significant strength enhancements owing to improved pozzolanic activity. The plasticity index (PI) markedly diminished with lime stabilization, enhancing workability and mitigating volumetric variations. The density of treated soils rose from 0.8 g/cm3 to 2.1 g/cm3, signifying improved particle compaction and less porosity. The mechanical enhancements indicate that hydrothermal solidification efficiently converts expanding clay into a robust and stable material appropriate for geotechnical applications. Increased Lc improved compressive strength through enhanced pozzolanic activity and density, while higher Kr values, indicating lower CaO availability, yielded limited strength gains. Lc consistently outperformed Kr and other chemical compositions in enhancing clay soil compressive strength.

In this research, the mud diapirism phenomenon in the Membrillal sector in Cartagena is characterized to analyze its spatiotemporal evolution. The goal is to geomorphologically, geotechnically, and geologically characterize the area to zone regions with the greatest susceptibility to geological hazards and provide an updated diagnosis of the phenomenon. This study is conducted due to the risks that mud diapirism poses to infrastructure and the safety of local communities. Understanding the behavior of these structures is essential for designing effective mitigation measures and optimizing urban planning in areas affected by this phenomenon. The methodology used includes collecting secondary data and implementing geophysical, geotechnical, and laboratory tests. Among the techniques employed are the Standard Penetration Test (SPT), the excavation of test pits, and electrical resistivity tomography, which revealed mud deposits at different depths. Laboratory studies also evaluated the physical and mechanical properties of the soil, such as Atterberg limits, grain size distribution, moisture content, and expansion tests, in addition to physic-chemical analyses. Among the most relevant findings is the presence of four active mud vents and four mud ears, representing an increase compared to the previous study that only recorded three mud vents. The tests revealed mud deposits at 1.30 m and 10 m depths, consistent with the geotechnical results. Laboratory tests revealed highly plastic soils, with Liquid Limits (LL) ranging from 44% to 93% and Plastic Limits (PL) ranging from 14% to 46%. Soil classification showed various low- and high-plasticity clays (CL and CH) and silty clays (MH), presenting challenges for structural stability and foundation design. Additionally, natural moisture content varied between 15.8% and 89%, and specific gravity ranged from 1.72 to 2.75, reflecting significant differences in water retention and soil density. It is concluded that diapirism has increased in the region, with constant monitoring recommended, and the Territorial Planning Plan (POT) has been updated to include regulations that mitigate the risks associated with urban development in affected areas.

In engineering projects involving expansive clay, its mechanical and chemical properties are enhanced through soil stabilization using various admixtures such as fly ash, lime, and cement. Considering the admixture's limitation in recent years, the employment of waste materials in stabilizing such soils is highly encouraged. This study investigates the efficacy of digestate ash as a soil stabilizer under diverse temperature conditions (100 degrees C to 800 degrees C) through an unconfined compressive strength test at an optimal stabilizer content. The Atterberg's limits and compressive strength test were performed on the clay with and without additives at room temperature through various curing times (0 and 28 days). The digestate ash was used at 0 to 25% (by dry clay weight) as an additive along with the initial consumption of lime as an activator at 4.5% (by dry soil weight). The maximum unconfined compressive strength value of 336 kPa was observed when using 15% digestate ash obtained at 560 degrees C for a curing period of 28-days. The significant alteration in mineralogical and chemical composition was identified when the DA-modified clay underwent X-ray diffraction and fourier transform infrared examinations. This research facilitates better understanding of digestate ash-based soil stabilization in different thermal conditions, aiding sustainable soil improvement in civil engineering and environmental remediation.

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.

The presence of expansive clay causes roads to undergo damage such as wavy, cracked, and even potholes. This type of soil shows that the soil is prone to swelling and shrinking. A base soil handling method against the effects of swelling and shrinking is chemical soil stabilization such as mixing the soil with lime, cement or additional materials. In this study, the stabilization method used was the fly ash and bottom ash geopolymerization reaction. Fly ash and bottom ash is an effective alternative to replace cement. Fly ash and bottom ash with addition of alkali activators of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) can serve as a binder similar to cement. This study aimed to improve the physical property and mechanical property tests of the soil such as bearing capacity and swelling potential as a requirement for subgrade. All physical property test results revealed that using fly ash-bottom ash geopolymer paste can improve qualities such as specific gravity, Atterberg limit, and grain size to improve expansive clay soil. Likewise, the mechanical property test results showed that the subgrade stabilized with fly ash-bottom ash geopolymer can increase its strength to surpass the requirements for road subgrades.

The construction sector has undergone significant reforms towards increased sustainability in recent decades. Therefore, there has been a great interest in developing alternative binders for stabilising expansive clay subgrades and improving their mechanical properties while mitigating their swelling and shrinking behaviour. One such alternative binder is vinyl acetate-ethylene (VAE) polymers. However, there are only a few studies on utilising polymers, especially VAE polymers, for clay stabilisation. Specifically, there is a lack of research on using VAE polymer-stabilised clays for road subgrade purposes. This study aims to address this knowledge gap by evaluating the potential of using a VAE solid powder polymer to stabilise expansive clay subgrade through a comprehensive series of mechanical tests as well as physicochemical and microstructural analyses. The results of the experiments provide evidence that the introduction of the polymer considerably improved the mechanical strength and swell and shrinkage behaviour of the expansive clay.

Expansive soils, prone to significant volume changes with moisture fluctuations, challenge engineering infrastructure due to their swelling and shrinking. Traditional stabilization methods, including mechanical and chemical treatments, often have high material and environmental costs. This study explores fibrous by-products of flax processing, a sustainable alternative, for reinforcing expansive clay soil. Derived from the Linum usitatissimum plant, flax fibers offer favorable mechanical properties and environmental benefits. The research evaluates the impact of flax tow (FT) reinforcement on enhancing soil strength and reducing cracking. The results reveal that incorporating up to 0.6% randomly distributed FTs, consisting of technical flax fibers and shives, significantly improves soil properties. The unconfined compressive strength (UCS) increased by 29%, with 0.6% FT content, reaching 525 kPa, compared to unreinforced soil and further flax tow additions, which led to a decrease in UCS. This reduction is attributed to diminished soil-fiber interactions and increased fiber clustering. Additionally, flax tows effectively reduce soil cracking. The crack length density (CLD) decreased by 6% with 0.4% FTs, and higher concentrations led to increased cracking. The crack index factor (CIF) decreased by 71% with 0.4% flax tows but increased with higher FT concentrations. Flax tows enhance soil strength and reduce cracking while maintaining economic and environmental efficiency, offering a viable solution for stabilizing expansive clays in geotechnical applications.