Frozen soils exhibit unique mechanical behavior due to the coexistence of ice and unfrozen water, making experimental studies essential for engineering applications in cold regions. This review comprehensively examines laboratory investigations on frozen soils under static and dynamic loadings, including uniaxial and triaxial compression, creep, direct shear, and freeze-thaw (F-T) cycle tests. Key findings on stress-strain characteristics, failure mechanisms, and the effects of temperature and time are synthesized. Advancements in microstructural analysis techniques, such as computed tomography (CT), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and mercury intrusion porosimetry (MIP), are also summarized to elucidate the internal structural evolution of frozen soils. While significant progress has been made, further efforts are needed to better replicate complex environmental and loading conditions and to fully understand the interactions between multiple influencing factors. Future research should focus on developing novel experimental techniques, establishing standardized testing protocols, and creating a comprehensive database to enhance data accessibility and advance frozen soil research. This review provides critical insights into frozen soil mechanics and supports validating constitutive models and numerical simulations, aiding infrastructure design and construction in cold regions.

Erosion and seepage control is a prime concern for embankments, dams, and other hydraulic structures constructed with alluvial sandy soil due to its highly porous characteristics. Permeation grouting has been a popular solution for controlling seepage situations in such structures. In this study, unconfined compression tests and triaxial tests were performed to determine the strength properties of grouted alluvial sandy soil located in the Ganges-Brahmaputra-Meghna delta. A simple method was devised to prepare cylindrical grouted samples with water-cement ratios (W/C) of 2:1, 3:1, 4:1, and 5:1. Here, unconfined compressive strength test results revealed that the highest compressive strength of the grouted sandy soil samples was achieved at the 2:1 W/C ratio at all curing ages. Different failure patterns are observed for different W/C samples during unconfined compressive tests. Furthermore, triaxial tests were conducted on the grouted samples prepared at the 2:1 W/C ratio under consolidated undrained conditions. Dilation occurred during the volume change, and the pore pressure decreased with increasing confining stress. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy were conducted to discern the microstructural behavioral changes and the chemical characteristics of the grouted sandy samples, respectively. Here, SEM images revealed a reduction in porosity with decreasing W/C ratio and increasing curing age. Permeation grouting leads to a reduction in permeability without disturbing the soil microstructure. Therefore, permeation grouting is a very effective technique for improving the mechanical behavior of grouted alluvial sand.

Sandy soils are prone to engineering issues due to their high permeability and low cohesion in the natural environment. Therefore, eco-friendly reinforcement techniques are required for projects such as subgrade filling and soft soil foundation reinforcement to enhance their performance. This study proposes a synergistic reinforcement method that combines Enzyme-Induced Calcium Carbonate Precipitation with Glutinous rice slurry (G-EICP). The macroscopic mechanical properties and pore structure evolution of reinforced sand were systematically investigated through triaxial permeability tests, unconfined compressive strength (UCS) tests, and microstructural characterization based on Scanning Electron Microscope (SEM) and Micro- Computed Tomography (CT) tests. The results indicate that when the glutinous rice slurry volume ratio (VG) reaches 10%, the UCS of G-EICP-reinforced soil peaks at 449.2 kPa. The permeability coefficient decreases significantly with increasing relative density (Dr), VG, confining pressure (sigma 3), and seepage pressure (p). Microstructural analysis reveals that glutinous rice slurry may promote calcium carbonate crystal growth, potentially by providing nucleation sites, establishing a dual mechanism of skeleton enhancement and pore-throat clogging. The increased incorporation of glutinous rice slurry reduces the number of connected pores, lowers the coordination number, and elevates tortuosity, thereby inducing marked enhancements in both the strength and permeability of the treated soil compared to plain soil.

In response to the environmental challenges posed by conventional expansive soil stabilization methods, this study investigates the low-carbon potential of industrial by-products-cement kiln dust (CKD) and calcium carbide slag (CCS)-as sustainable stabilizers. A comprehensive series of laboratory tests, including compaction tests, free swelling rate measurements, unconfined compressive strength (UCS) evaluations, and scanning electron microscopy (SEM) analyses, were conducted on expansive soil samples treated with varying dosages in both single and binary formulations. The results indicate that the binary system significantly outperforms individual stabilizers; for example, a formulation containing 10% CKD and 9% CCS achieved a maximum dry density of 1.64 g/cm3, reduced the free swelling rate to 22.7% at 28 days, and reached a UCS of 371.3 kPa. SEM analysis further revealed that the enhanced performance is due to the synergistic formation of hydration products-namely calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H)-which effectively fill interparticle voids and reinforce soil structure. These findings demonstrate that the dual mechanism, combining rapid early-stage hydration from CCS with sustained long-term strength development from CKD, offers a cost-effective and environmentally sustainable alternative to traditional stabilizers for expansive soils.

Due to the local geology, expansive soils with weak geotechnical properties pose significant challenges to civil engineering projects. Enhancing soil strength and reducing plasticity are essential for supporting diverse construction endeavors. Given the abundance of lime and natural pozzolana in Algeria, this study investigates their influence on the geotechnical characteristics of clayey soils. The research examines the lime and natural pozzolana impact expansive clay soil's consistency, mechanical properties, classification, and microstructural and mineralogical composition. Soil samples are treated with lime and natural pozzolana at varying percentages (0% to 6% and 0% to 20%, respectively) and cured for 1 and 28 days to assess the effect of curing time. Results demonstrate that incorporating natural pozzolana significantly enhances the properties of lime-treated expansive soil, resulting in improved soil fabric and increased cementitious material production compared to lime alone. X-ray diffraction and microscopic analysis revealed the formation of new pozzolanic products (C-A-S-H) alongside existing C-S-H and C-A-H phases in lime-natural pozzolana-treated soil. The study effectively enhances clay soil's workability and geotechnical properties by combining lime and natural pozzolana, offering promising insights for soil improvement in civil engineering projects.

This study investigates the long-term effects of landfill leachate contamination on soil hydraulic conductivity and shear strength parameters over a 12-month period, addressing the current lack of comprehensive long-term experimental data in this field. Laboratory permeability tests and direct shear tests were performed on sandy clayey silt samples contaminated with leachate at concentrations ranging from 5% to 25%. Microstructural and mineralogical analyses were conducted using SEM and XRD to identify the mechanisms behind observed changes. The results identify a critical threshold at 15% contamination where soil behavior transitions from granular to cohesive characteristics, marked by significant changes in both hydraulic and mechanical properties. Hydraulic conductivity increases at low contamination levels but decreases significantly at higher levels, while friction angle shows an immediate reduction from 36.5 degrees to 31-31.5 degrees and cohesion exhibits a three-phase evolution pattern, reaching peak increases of 151.5% at 15% contamination. The hydraulic conductivity changes are controlled by contamination level rather than exposure time, maintaining stable values throughout the testing period, whereas shear strength parameters demonstrate more complex temporal evolution patterns. These findings provide essential parameters for landfill design and stability assessment, demonstrating how leachate concentration affects long-term soil behavior through mineral formation and structural modification.

This study investigates the mechanical enhancement of sandy soils through cement stabilization modified with Consoil, targeting improved pavement substructure performance. Unconfined compressive strength (UCS) tests were conducted on samples with varying cement contents (3%, 6%, 9%), Consoil dosages (0%, 5%, 10%, 15%, 20% by cement weight), and curing periods (3, 7, 28, 90 days). Field Emission Scanning Electron Microscopy and X-Ray Diffraction analyses complemented mechanical testing to understand strengthening mechanisms. Results demonstrated that 15% Consoil consistently optimized strength development across all cement contents, with 9% cement and 15% Consoil achieving peak 90-day UCS of 17.74 MPa, representing a 67% increase over control samples. Microstructural analysis revealed progressive matrix refinement with increasing Consoil content, while XRD indicated enhanced pozzolanic activity through calcium hydroxide consumption. The study introduces Consoil as an effective stabilization additive, establishing optimal dosage rates and demonstrating significant strength improvements through synergistic cement-Consoil interactions. The findings provide new insights into strength enhancement mechanisms in Consoil-modified cement-stabilized soils, offering practical guidelines for designing high-performance pavement substructures. The research contributes to sustainable construction practices by optimizing cement usage through Consoil incorporation.

This study focuses on enhancing structural strength in flood-prone regions by utilizing industrial waste under varying temperature conditions. Industrial waste's increasing usage and its environmental implications require deeper comprehension. The escalating adoption of industrial waste as an alternative construction material underscores this shift. The research employs fly ash (F), ground-granulated blast-furnace slag (G), and lime (L) to augment geotechnical properties and bolster the flood resistance of stabilized soil. Various clay, lime, GGBS, and 2% fly ash mixtures are tested under optimal moisture and maximum dry density conditions. The curing spans 1, 7, 14, 28, 56, and 90 days at ambient temperature and 3 degrees C. Subsequent unconfined compressive strength (UCS), durability, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and field emission scanning electron microscopy (FE-SEM) analyses are conducted. Results highlight a 257% UCS increase at 14 days' curing for the 8% GGBS + 6% Lime + 2% Fly ash mixture at ambient temperature, while the mix of 6% GGBS + 8% Lime + 2% Fly ash records a 686% UCS enhancement after 90 days' curing at 3 degrees C. Lime concentration affects the plasticity index and maximum dry unit weight (MDU). Upon water immersion, durability testing indicates an 11-17% strength reduction for lime, GGBS, and fly ash samples. The microstructural evaluation identifies hydration products like calcium aluminate silicate-hydrate and calcium silicate hydrate. According to the findings, using industrial waste can be a promising solution to pavement sustainability, especially after the flood, and it can reduce related costs and decrease CO2 emissions.

Sugarcane bagasse ash is a kind of agricultural waste with a large quantity and good volcanic ash reactivity, it is necessary to find a way to reasonably utilize it to prevent environmental pollution caused by long-term accumulation. In this paper, the effect of sugarcane bagasse ash on the short-term mechanical properties of coastal cement soil were studied, and unconfined compressive tests and triaxial shear tests were carried out. The sugarcane bagasse ash content was set to 0 %, 1 %, 2 %, 3 %, 4 % and 5 %, respectively, the cement content was set to 5 %, and the curing age was set at 7d. The test results show that sugarcane bagasse ash can effectively improve the unconfined compressive strength and triaxial shear strength of cement soil, exhibiting a trend of increasing first and then decreasing with the increase of its content. When the sugarcane bagasse ash content is 1 %, the unconfined compressive strength reaches the maximum value of 2040 kPa, which is 56 % and 8 % higher than that of cement soil with 5 % and 7 % cement content, respectively. Compared with cement soil with 5 % cement content, the triaxial shear strength increases by 12 %similar to 17 %, the internal friction angle phi and cohesion c increases by 3 %similar to 8 % and 2 %similar to 11 %, respectively. The SEM test results show that the addition of bagasse ash can promote the hydration of cement to produce hydrated calcium silicate and other hydration products, fill the internal pores of the sample, and make the microstructure of the modified cement soil tend to be dense. The research results provide a reference for the application of sugarcane bagasse ash modified cement soil in practical engineering.

Graphene oxide (GO) has been shown to improve the static mechanical properties of cement soils. However, the dynamic mechanical properties of GO-modified cement soils are rarely investigated. Therefore, in this study, the effects of different confining pressures, GO contents, and curing ages on the small-strain dynamic shear modulus (G) and damping ratio (D) of GO-modified coastal cement soil (GOCS) are investigated via resonant column tests. The results show that the G of GOCS increases with the confining pressure, GO content, and curing age, whereas D decreases. Moreover, the GOCS indicate the highest stiffness improvement when 0.05 % GO is used as a modifier. The variation patterns of the maximum dynamic shear modulus and maximum damping ratio with the increase in the confining pressure, GO content, and curing age of the GOCS are consistent with the measured results. Microstructural analysis shows that the incorporation of GO can promote the early cement hydration of GOCS and increase its internal calcium-silicate-hydrate gel as well as its crystal types and numbers. The filling and bridging effects of GO not only enhance the stiffness of GOCS, thus increasing its G value, but also effectively reduce the energy consumption of the vibration wave in the sample, thus reducing its D value. The results of this study can provide important references and guidance for the design and construction of coastal soft-soil roadbed projects.