To address the engineering problems of road subsidence and subgrade instability in aeolian soil under traffic loads, the aeolian soil was improved with rubber particles and cement. Uniaxial compression tests and Digital speckle correlation method (DSCM) were conducted on rubber particles-cement improved soil (RP-CIS) with different mixing ratios using the WDW-100 universal testing machine. The microcrack and force chain evolution in samples were analysed using PFC2D. The results showed that: (1) The incorporation of rubber particles and cement enhanced the strength of the samples. When the rubber particles content was 1% and the cement content was 5%, the uniaxial compressive strength of the RP-CIS reached its maximum. Based on the experimental results, a power function model was established to predict the uniaxial compressive strength of RP-CIS; (2) The deformation of the samples remains stable during the compaction stage, with cracks gradually developing and penetrating, eventually entering the shear failure stage; (3) The crack and failure modes simulated by PFC2D are consistent with the DSCM test. The development of microcracks and the contact force between particles during the loading are described from a microscopic perspective. The research findings provide scientific support for subgrade soil improvement and disaster prevention in subgrade engineering.

Most gravel roads leading to rural areas in Ghana have soft spot sections as a result of weak lateritic subgrade layers. This study presents a laboratory investigation on a typical weak lateritic subgrade soil reinforced with non-woven fibers. The objective was to investigate the strength characteristic of the soil reinforced with non-woven fibers. The California Bearing Ratio and Unconfined Compressive Strength tests were conducted by placing the fibers in single layer and also in multiple layers. The results showed an improved strength of the soil from a CBR value of 7%. The CBR recorded maximum values of 30% and 21% for coconut and palm fibers inclusion at a placement depth of H/5 from the compacted surface. Multiple fiber layer application at depths of H/5 & 2 h/5 yielded CBR values of 38% and 31% for coconut and palm fibers respectively. The Giroud and Noiray design method and the Indian Road Congress design method recorded reduction in the thickness of pavement of 56% to 63% for coconut fiber inclusion and 45% to 55% for palm fiber inclusion. Two-way statistical analysis of variance (ANOVA) showed significant effect of depth of fiber placement and fiber type on the geotechnical characteristics considered. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic),CBR(sic)(sic)7%(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)H/5(sic)(sic)(sic)(sic)(sic)(sic),CBR(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)30%(sic)21%. (sic)H/5(sic)2H/5(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)CBR(sic)(sic)(sic)(sic)38%(sic)31%. Giroud&Noiray(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)56%(sic)63%,(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)45%(sic)55%. (sic)(sic)(sic)(sic)(sic)(sic)(ANOVA)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

This study systematically investigated the pore structure response of kaolin and illite/smectite mixed-layer rich clay in a reconstituted state to one-dimensional (1D) compression by first performing oedometer tests on saturated clay slurries, followed by characterising their pore structure using multi-scale characterisation techniques, with the primary objective of advancing the current understanding of the microstructural mechanisms underlying the macroscopic deformation of such clays. Under 1D loading, the volume reduction observed at the macro level essentially represented the macroscopic manifestation of changes in inter-aggregate porosity at the pore scale. It was the inter-particle pores that were compressed, despite the interlayer pores remaining stable. Two distinct pore collapse mechanisms were identified: kaolin exhibited a progressive collapse of particular larger pore population in an ordered manner, whereas illite/smectite mixed-layer rich clay demonstrated overall compression of inter-aggregate pores. Accordingly, mathematical relationships between the porosity and compressibility parameters for these two soils were proposed, with the two exhibiting opposite trends arising from their distinct microstructural features. Approaching from the unique perspective of pore structure, quantitative analysis of pore orientation and morphology on the vertical and horizontal planes demonstrated some progressively increasing anisotropy during compression. These findings provide important insights into porescale mechanisms governing clay compression behaviour and enrich the limited microporosity database in soil mechanics.

Sulfate saline soil is considered as an inferior subgrade construction material that is highly susceptible to damage from salt heaving and dissolution. Polyurethane/water glass (PU/WG) is an efficient grouting material widely used in underground engineering; however, its application in saline soil reinforcement has not yet been reported. In this study, PU/WG was used to solidify sulfate-saline soils. The influence of the dry density, curing agent ratio, and salt content on the strength was evaluated. The mechanical properties of the solidified soil were determined by conducting uniaxial compression strength tests, and crack development was detected using acoustic emission technology. The reinforcing mechanism was revealed by scanning electron microscopy tests and mercury intrusion porosimetry. The results indicated that the peak stress, peak strain, and ultimate strain increased with increasing dry density and PU/WG content, whereas they decreased with increasing salt content. The relationship between the peak stress, density, and PU/WG can be described using linear functions. The relationship between the peak stress and salt content can be described by a second-order polynomial function. The larger the dry density and the higher the PU/WG content, the steeper the stress-strain curves and the lower the ductility. Further, the higher the salt content, the higher the ductility. Soil with a higher dry density, more PU/WG, and less salt content exhibited higher brittleness. Thus, PU/WG can fill in the original disorganized and large pores, thereby increasing the complexity of the internal pore structure via organic-inorganic gel reactions.

The strength, deformation, and hydraulic properties of geomaterials, which constitute embankments, vary with fine fraction content. Therefore, numerous research studies have been conducted regarding the effects of fine fraction content on the engineering properties of geomaterials. Howe ver, there have only been a few studies in which the effects of fine fraction content on the soil skeletal structure have been quantitatively evaluated and related to compaction and mechanical properties. In this study, mechanical tests were conducted on geomaterials with various fine fraction contents to evaluate their compaction and mechanical properties focusing on the soil skeletal structure and void distribution. Furthermore, an internal structural analysis of specimens using X-ray computed tomography (CT) images was conducted to interpret the results of mechanical tests. As a result, it was discovered that the uniaxial compressive strength increased with fine fraction content, and the maximum uniaxial compressive strength was observed at a low water content, not at the optimum water content. Additionally, the obtained CT images revealed that large voids, which could ser ve as weak points for maintaining strength, decreased in volume, and small voids were evenly distributed within the specimens, resulting in a more stable soil skeletal structure.

In the construction of cold region engineering and artificial freezing engineering, soil-rock mixture (SRM) is a frequently encountered geomaterial. Understanding the mechanical properties of frozen SRM is crucial for ensuring construction safety. In this paper, frozen SRM is considered as a multiphase material consisting of a soil matrix and rock. By employing a single-variable approach, the relationship between UCS and rock content was revealed, and the effects of rock content on the stress-strain curve shape and failure mode were analyzed. The test results indicate that rock content significantly influences the stress-strain curve and failure mode of SRM. The specimen preparation with different rock content is unified using a given relative compactness. The uniaxial compressive strength (UCS) of the frozen specimens increases firstly and then decreases as rock content increases, which is unaffected by temperature or rock size. The classic quadratic polynomial is suggested to describe the variation rule. The failure modes of specimens with low, medium and high rock content correspond to shear failure, bulge failure and splitting failures, respectively, which transmits from shear failure to splitting failure as the rock content increases.

Understanding the temperature-dependent behavior of sands is essential for geotechnical engineering applications, especially in environments with long-term temperature variations. This study investigates the effects of temperature (T) on the shear strength and creep deformation (Delta epsilon CP) of KMUTT and Hostun sands through a series of consolidated drained triaxial compression (CDTC) tests. Monotonic loading (ML) and sustained loading (SL) schemes were applied to evaluate shear strength and creep behavior under various stress levels (SL) and temperatures. The temperature effect parameter (Af) was introduced to quantify the reduction in shear strength at elevated T relative to a reference temperature (T0 = 30 degrees C). Experimental results show that shear strength decreases as temperature increases, with Hostun sand being more temperature-sensitive than KMUTT sand. Under SL, significant Delta epsilon CP was observed, increasing with both SL and T, while resumption of shearing after SL did not affect peak shear strength. A hyperbolic empirical equation was developed to predict Delta epsilon CP for a given creep duration (Delta tCP), SL, and T, incorporating temperature effects via Af. The model was validated with experimental results and showed strong predictive capability, especially during the primary creep stage. However, discrepancies appeared at high SL, where secondary creep effects became more pronounced. The proposed model offers a practical framework for predicting long-term creep deformation in sands under temperature variations, enhancing geotechnical design in thermally influenced environments.

Earthen construction is one of the earliest and most ubiquitous forms of building. Compressed stabilized earth blocks (CSEBs) combine compressed components including inorganic soil, water, and a stabilizer such as Portland cement, and can achieve greater strength than other earthen construction methods. Typically, site-specific soil comprises the bulk material in CSEB construction, which minimizes the quantity of construction materials that need to be provided from off-site and motivates this type of building material for remote locations. However, onsite manufacturing and innate soil variability increase the variability of CSEB mechanical properties compared to more standardized building materials. This study characterizes the effects of varying mix compositions and initial compressions on the density, compressive strength, and variability of compressed stabilized earth cylinders (CSECs) created from sandy soil. CSEC samples comprising nine mix compositions and four levels of initial compression provide data for the (i) statistical evaluation of strength, density, and variability and (ii) development of predictive equations for density and compressive strength, with R2 values of 0.90 and 0.89, respectively.

Microbial-induced calcite precipitation (MICP) is an eco-friendly soil stabilization technology widely applied to the solidification of aeolian sand. To further enhance the effectiveness of MICP in cementing aeolian sand, this study introduced wheat straw powder (WSP) as a reinforcing material and conducted experimental research on WSP-enhanced microbial cemented aeolian sand. By combining macroscopic physical and mechanical tests with discrete element method (DEM) simulations, this study systematically investigated the mechanisms by which WSP enhances microbial cementation and the mesoscopic failure characteristics of the material. The results indicated that adding WSP significantly increased the calcium carbonate content, resulting in uniform calcite deposition and encapsulation of sand particles. This enhancement increased the compressive strength and deformation resistance of the cemented sand columns, with a notable increase in strain at failure. DEM simulations further revealed that as the calcium carbonate content increased, macroscopic cracks within the sand columns evolved from single to multiple pathways, eventually penetrating the entire sand column along the loading direction. The internal bonding failure process could be divided into compaction, expansion, and rapid growth stages. Additionally, the uniformity of particle bonding in WSP-reinforced sand columns significantly impacted their macroscopic mechanical behavior, with uneven interparticle bonding likely inducing microcrack accumulation, leading to severe fracture patterns. These findings provide valuable insights for optimizing microbial cementation techniques for aeolian sand.

We propose a test procedure to quantify the response of dry sand to cyclic compressional loading under constrained conditions. The test procedure is designed to represent the response of sand layers to upward propagating P-waves during an earthquake event. Such P-waves are prominent within the vertical component of earthquake ground-motions, which is often ignored or simplified in common practice of seismic hazard analysis, despite its potential damaging effects. In the proposed method, the lateral deformation is restrained within a triaxial device, through variations of the cell pressure, thus maintaining pure compression while allowing moderate to large axial strains. Both dry and saturated samples are tested, and the compressive stiffness is computed from the full stress-strain loops. We show that as long as drained conditions are maintained and volume changes are allowed - the response of a saturated sample to slow cyclic loading is representative of the response of dry sand to seismic loading, despite the differences in saturation and in strain rates. Finally, we compare the proposed method to cyclic loading within a rigid cell and discuss the differences and limitations that the new proposed method overcomes.