Silt soil is widely distributed in coastal, river, and lacustrine sedimentary zones, characterized by high water content, low bearing capacity, high compressibility, and low permeability, representing a typical bulk solid waste. Studies have shown that cement and ground granulated blast furnace slag (GGBFS) can significantly enhance the strength and durability of stabilized silt. However, potential variations due to groundwater fluctuations, long-term loading, or environmental erosion require further validation. This study comprehensively evaluates cement-slag composite stabilized silt as a sustainable subgrade material through integrated laboratory and field investigations. Laboratory tests analyzed unconfined compressive strength (UCS), seawater erosion resistance, and drying shrinkage characteristics. Field validation involved constructing a test with embedded sensors to monitor dynamic responses under 50% overloaded truck traffic (simulating 16-33 months of service) and environmental variations. Results indicate that slag incorporation markedly improved the material's anti-shrinkage performance and short-term erosion resistance. Under coupled heavy traffic loads and natural temperature-humidity fluctuations, the material exhibited standard-compliant dynamic responses, with no observed global damage to the pavement structure or surface fatigue damage under equivalent 16-33-month loading. The research confirms the long-term stability of cement-slag stabilized silt as a subgrade material under complex environmental conditions.

The Zhongning Grottoes, China, are one of the most important Tang Dynasty cultural sites on the Silk Road and contain numerous historical clay sculptures. Under the influence of human activities and natural weathering, the sculptures have experienced various types of damage, most significantly the extensive shedding of the outer fine clay layer, which plays a crucial role in maintaining the sculptures' overall structure. In this study, the mixture of soil, sand, and cotton fiber that was most suitable for restoring this layer was determined. The mechanical properties of fine clay layers with different sand and fiber contents were studied by shrinkage tests and soil beam bending tests. The main results were as follows: for a low sand content (0-45%), the tensile strength increased slightly with increasing fiber content. For a high sand content (>45%), the tensile strength decreased with increasing fiber content. The best effect was obtained for sand and fiber contents of 30-45% and 1-2%, respectively. The results provide a scientific basis for the restoration of clay sculptures in the Zhongning Grottoes.

The development pattern of shrinkage cracks in sandy clay under dry wet cycling conditions is relatively complex. This study employed indoor experiments and image analysis methods to explore the inhibition mechanism of jute fiber on drying shrinkage cracks in sandy clay under dry wet cycling conditions. The results demonstrated that the jute fiber effectively inhibits crack propagation through friction, overlap, and anchoring mechanisms. Notably, increasing the fiber content can considerably reduce soil crack rate and crack width and promote the micro crack formation. The water absorption capability of jute fiber helps to evenly distribute water in the soil, thereby slowing down the evaporation rate and limiting crack formation. For instance, the addition of 0.6 % jute fiber led to a decrease in its crack rate and average crack width by 15.4 % and 53.3 %, respectively, compared to pure clay. Furthermore, after 5 cycles of wet-dry cycles, the crack rate and average crack width of sandy clay with different dosages decreased by 65-80 % and 69-75 %, respectively. This study provides a theoretical basis and technical support for incorporating jute fiber in clay improvement, which is immensely significant for enhancing the durability and stability of clay in engineering applications.

Black cotton soil's notable swelling and shrinkage contribute to structural damage. This study examines the impact of nano rice husk ash (nRHA) variants on this soil: One synthesized in 60 h and another through 7 h combined dry-wet milling method. The primary objective is to assess the effects of nRHA treatment on the soil's index properties, engineering characteristics and swelling behavior. Laboratory tests including free swell index, Atterberg's limits, swelling potential, swelling pressure, unconfined compressive strength and consolidation tests were conducted on black cotton soil samples treated with both nRHA variants. Results indicated that the 7-h nRHA treatment led to lower plasticity and reduced swelling compared to the 60-h variant. Specifically, the 7-h treated soil showed decreased swelling pressure, compression index and rate of primary swelling, along with increased pre-consolidation pressure and unconfined compressive strength. The free swell index also decreased by 21% with the 7-h nRHA treatment. The superior performance of the 7-h milled nRHA is likely due to its higher calcium and reactive silica content, enhancing its stabilizing effect. This research highlights the 7-h nRHA as a more effective stabilizer for black cotton soil, offering a promising solution to mitigate its problematic volumetric behavior.

Sandy red clay, abundant in clay minerals, exhibits a marked sensitivity to variations in water content. Several of its properties are highly prone to deterioration due to wet-dry cycling, potentially leading to slope instability. To investigate the multi-scale deterioration patterns and the underlying chain mechanism of sandy red clay subjected to wet-dry cycles, this study conducted systematic tests on remolded sandy red clay specimens through 0 to 5 wet-dry cycles, with the number of cycles (N) as the variable. The study's results indicated the following, under wet-dry cycling: (1) Regarding the expansion and shrinking properties, the absolute expansion rate (delta a) progressively increased, whereas the absolute shrinkage rate (eta a) gradually decreased. Concurrently, the relative expansion rate (delta r) and relative shrinkage rate (eta r) gradually declined. (2) At the microscale, wet-dry cycles induced significant changes in the microstructure, characterized by increased particle rounding, disrupted stacked aggregates, altered inter-particle contacts, enlarged and interconnected pores, increased number of pores, and a reduction in clay mineral content. (3) At the mesoscale, cracks initiated and propagated. The evolution of cracks undergoes stages of initiation stage, propagation stage, and stable stage, and with the crack rate increasing to 2.0% after five cycles. (4) At the macroscale, the shear strength exhibited a continuous decline. After five cycles, cohesion decreased by as much as 49.6%, whereas the internal friction angle only decreased by 4.3%. This indicates that the loss of cohesion was the primary factor contributing to the strength deterioration. (5) A 19.4% decrease in the slope factor of safety (Fv) occurred after five cycles. This reduction was primarily attributed to the decrease in material cohesion and the upward shift in the potential sliding surface. Under the influence of wet-dry cycles, slope failures typically transitioned from overall or deep sliding to localized or shallow sliding.

Volume expansion can occur in overconsolidated clay during shear loading and heating. However, the volume expansion mechanisms driving these two phenomena are different from each other, and it is important to propose a model that can be adopted to describe these two volume expansion phenomena. A new model is proposed to describe the two aforementioned volume expansion phenomena. Specifically, the following three innovative points are made: (1) The thermal-mechanical coupling yield surface is proposed in the p-q-T space, and the overconsolidation stress R can be used to reflect the loss effect of overconsolidation degree during the heating process. The modified unified hardening parameter is used to reflect the shear shrinkage of normal consolidated clay and the shear dilatancy of overconsolidated clay. (2) The nonassociative flow law is used to express the direction of plastic strain increment. The phase transformation stress ratio is expressed as an exponential function of the overconsolidated stress ratio, which can be used to reflect three typical volume deformation modes of overconsolidated clay: full shrinkage deformation, dilatancy deformation after contraction, and full dilatancy deformation. (3) A rotational hardening rule that reflects the anisotropic properties of initial partial consolidation of clay is introduced so that the proposed model can be adapted to reflect the increase of soil stiffness caused by K0 consolidation, as well as the hysteresis loop phenomenon for deviatoric strain and stress relationship curve caused by cyclic loading. The comparison results between prediction and test data show that the proposed new thermal-mechanical coupling model can be easily and conveniently applied to describe the deformation and failure behavior of overconsolidated clay relevant to thermal effects.

Thermal backfill is an integrated part of underground electrical cable infrastructures systems, ground heat source pumps and radioactive waste repositories, as it minimizes resistance to heat transfer away from these systems. The heat transfer capacity and current carrying capability of underground electrical cables are significantly affected by thermal conductivity of backfill material and the surrounding soil media. Therefore, this research paper compares the thermal conductivity and shrinkage results of compacted (low to high densities) fly ash- and sand-bentonite mixtures with bentonite contents of 30%, 50%, 60%, 80% and 100%. The thermal conductivity of mixtures increased from 1.05 Wm-1K-1 to 1.20 Wm-1K-1 with the addition of fly ash content from 20 to 70% by weight in bentonite. The thermal conductivity bentonite-sand mixture was also found to be increased from 1.21 Wm-1K-1 to 1.83 Wm-1K-1 with increasing sand content. Additional to this, the bentonite-sand and bentonite-fly ash-based backfill materials surrounding heat-sensitive structures experience shrinkage and desiccation cracking due to thermal drying. Therefore, the desiccation volumetric shrinkage tests of bentonite-sand and bentonite-fly ash mixtures were conducted and found that the presence of sand or fly ash reduces shrinkage strain. Based on the experimental results, this study suggests a sustainable utilization of fly ash up to 50%-70% as an effective thermal backfill material in electrical cable infrastructure systems. Thus, the application of fly ash as a construction material reduces environmental impact and cost, aligning with the goals of sustainable development.

Soil-water characteristics curves (SWCC) have proved useful in estimating parameters used in modeling unsaturated geotechnical properties of soils including permeability and strength. Either saturation, gravimetric, and instantaneous and initial volumetric water content designation can be used to develop SWCCs. Studies have shown that any of the designations will give good estimates for soils that do not undergo volume change with suction change whereas, for soils that undergo substantial volume change, only saturation and instantaneous volumetric water content designation obtained by incorporating shrinkage curves can give correct estimates. Transition oil sands tailings have fines content that cannot be categorized as sandy or fine materials, and research on volume change with suction change in these materials is limited. In this study, HyProps, Tempe cells, and a chilled-mirror water potential meter were used to measure suction and corresponding water contents for samples that were prepared by mixing coarse sand and Fluid Tailing by ratios that mimic transition zone tailings. Shrinkage tests were also performed to observe the extent of volume change with suction increase. Air Entry Values (AEV) estimated from SWCCs based on gravimetric water content were found to be lower than those estimated from saturation-based SWCCs due to substantial volume changes in these materials with suction increase. The use of saturation water content designation is recommended in estimating AEV for transitional oil sands tailings. This is useful information in predicting the long term unsaturated geotechnical behavior of these materials for environmental management and safety purposes.

Soil shrinkage during the drying process (water stress) is one of the main issues in expansive soils of paddy fields. It occurs due to decrease in soil water content, resulting in changes in soil volume and the geometry of pores, leading to the formation of cracks and higher water loss. The aim of this study was to assess the shrinkage characteristic curve and pore size of paddy soils to determine the shrinkage -swelling behavior in Guilan province, Iran. 120 soil samples were collected from the study area. Pore size was determined using soil moisture retention curve (SMRC). It was established by plotting the soil water content (theta) versus the corresponding matric suction (h), and the shrinkage curve by plotting the void ratio (e) against the moisture ratio (upsilon). The suction-pore relationships were also determined. Furthermore, the geometric factors indicating the change in vertical (subsidence) and horizontal (crack) volume of the soils were determined and varied from 1.23 to 2.53, indicating that the vertical change in soil volume is predominant. The zero, residual and proportional shrinkage phases accounted for less than 2 %, 8-38 %, and 61-91 % of the total soil volume change, respectively. The shrinkage capacity of the soils ranged from 0.52 to 1.37. Cation exchange capacity and clay content were identified as the most important factors affecting soil shrinkage properties. In general, the studied paddy soils have great potential for swelling- shrinkage and cracking during the drying process due to the large percentage of expandable clays and the medium to fine pores. The resultant cracks negatively affect crop yield by damaging plant roots and increasing water losses through the soil profiles.

Expansive soils are known to be hazardous materials for infrastructure due to their high shrinking or swelling potential. Understanding the shrinking factors of expansive soils such as montmorillonite (MMT) is essential for predicting their mechanical properties. The interactions between the components of Na-MMT clays, e.g., MMT layer-layer (LL), layer-cation (LC), layer-water (LW) and water-cation (WC), are responsible for its shrinking behavior. In this study, molecular dynamics simulation and grand canonical Monte Carlo simulations are used to investigate the interaction energy evolution in the layered structure of Na-MMT for the shrinkage mechanisms analysis of clay. The results of simulation indicate that the magnitude of the interaction energy contributed by the interlayer cations dehydration is the driving force of the interlayer shrinkage. Furthermore, in the hydrated state, with one water layer, two water layers and three water layers, the attractive interactions between WC and LW, maintain the stability of the clay layers. However, at the dry state, the interaction energy between layers and cations appears to be the most essential component in holding the stacked layers together, which provides structural stability to the clay sheets. Finally, the study reveals that intermolecular interactions contribute to the mechanical properties of clays such as cohesive and elastic properties.