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).

Lime-activated ground granulated blast furnace slag (GGBS) is usually used to treat gypseous soils. However, sulphate-bearing soils often contain other sulphates, e.g., sodium sulphate (Na2SO4), potassium sulphate (K2SO4) and magnesium sulphate (MgSO4). Therefore, in this study, lime-GGBS was used as a curing agent for stabilising four sulphate-bearing soils, which were named as Na-soil, K-soil, Mg-soil, and Ca-soil. Unconfined compressive strength (UCS), swelling, X-ray diffraction, scanning electron microscopy and inductively coupled plasma spectroscopy tests, were conducted to explore the macro- and micro-properties of the lime-GGBS-stabilised soils. The results showed that at 5000 ppm sulphate, stabilised Mg-soil had the lowest swelling and highest UCS. At 20,000 ppm sulphate, stabilised Ca-soil had the lowest swelling, while stabilised Na-soil had the highest UCS. Generally, increasing sulphate concentration decreased swelling for Ca-soil but increased for other three soils, and decreased UCS for Mg-soil but increased for other three soils. This was because less ettringite was generated in the stabilised Ca-soil and the formation of magnesium silicate hydrate (MSH) in the stabilised Mg-soil. Therefore, the sulphate type had a significant impact on the swelling and strength properties of lime-GGBS-stabilised sulphate-bearing soil. It is essential to identify the sulphate type before stabilising the soil on-site.

As the increasing demand for deep mineral resource extraction and the construction of deep vertical shafts by the artificial ground freezing method, the stability and safety of shaft that traverse thick alluvial depend significantly on their interaction with the surrounding deep frozen soil medium. Such interaction is directly conditioned by the mechanical properties of the deep frozen soil. To precisely capture these in-situ mechanical properties, the mechanical parameters tests using remodeled frozen specimens cannot ignore the disparities in consolidation history, stress environment and formation conditions between the deep and shallow soils. This study performs a series of long-term high-pressure K0 consolidation (where K0 represents the static earth pressure coefficient, describing the ratio of horizontal to vertical stress under zero lateral strain conditions), freezing under sustained load and unloading triaxial shear tests utilizing remodeled deep clay. This study presents the response of unloading strength and damage properties under varying consolidation stresses, durations, and freezing temperatures. The unloading strength increases sharply and then stabilizes with consolidation time. The unloading strength shows an approximate linear positive correlation with the consolidation stress, while a negative correlation with the freezing temperature. The strengthening rate of the unloading strength due to freezing temperature tends to decrease with increasing consolidation time. Additionally, an improved damage constitutive model was proposed and validated by incorporating the initial K0 stress state and a Weibull-based assumption for damage elements. Based on the back propagation (BP) neural network, a prediction method for the stress-strain curve was offered according to the consolidation stress level, initial stress state, and temperature. These results can provide references for improving the mechanical testing methods of deep frozen clay and revealing differences in mechanical properties between deep and shallow soils.

There has been a growing interest in controlled low strength material CLSM due to its engineering features, such as self-leveling and early strength development, as well as it potential for utilizing industrial waste. Still, the dynamic properties on CLSM are rarely studied. This study evaluates the feasibility of red mud as a partial aggregate replacement in foamed-lightweight CLSM, incorporating high-carbon fly ash and preformed foam. We varied both the red mud contents RMc and foam volume ratio FVR within the mixtures and examined their impact on unconfined compressive strength and dynamic properties including shear modulus G and damping ratio D. The results reveal that the red mud enhances foam stability, leading to more uniform pore structures and increased porosity, which reduces bulk densities. Despite higher porosity, red mud serves as a strong alkaline activator, enhancing geopolymer reactions of high-carbon fly ash and thereby increasing both compressive strength and initial shear modulus G0. Interestingly, increasing FVR had minimal impact on the D, while higher RMcnotably increased D, highlighting its distinct role in energy dissipation. The red mud-incorporated foamed CLSM exhibits strain-dependent normalized shear modulus G/G0 comparable to that of gravel, while its D is 40-100 % higher than gravel or gravelly soil at shear strain of 1.10-5, which corresponds to typical traffic-induced vibration levels. Moreover, theoretical volumetric-gravimetric relationships are introduced to account for the combined effects of FVR and RMcon CLSM behavior. These findings demonstrate that the red mud included foamed CLSM can be utilized as advanced structural backfill material capable of effectively mitigating the vibrations induced by traffic, low-amplitude seismic events, and mechanical sources.

To investigate the coupled time effects of root reinforcement and wet-dry deterioration in herbaceous plant-loess composites, as well as their microscopic mechanisms, this study focused on alfalfa root-loess composites at different growth stages cultivated under controlled conditions. The research included measuring root morphological parameters, conducting wet-dry cycling tests, and performing triaxial compression tests and microscopic analyses (CT scanning and nuclear magnetic resonance) on both bare loess and root-loess composites under various wet-dry cycling conditions. By obtaining shear strength parameters and microstructural indices, the study analyzed the temporal evolution of the shear strength and microstructural characteristics of root-loess composites under wet-dry cycling. The findings indicated that the alfalfa root-loess composite effective cohesion was significantly higher than that of the plain soil in the same growth stage. The alfalfa root-loess composite effective cohesion increased during the growth stage in the same dry-wet cycles. The alfalfa root-loess composite effective cohesion in the same growth stage was negatively correlated with the number of dry-wet cycles. The fatigue damage of the soil's microstructure (pore coarsening, cement hydrolysis, and crack development) increased continuously with the number of dry-wet cycles. However, due to the difference in mechanical properties between roots and the soil, the root-soil composite prevented the deterioration of the soil matrix strength by the dry-wet cycles. As the herbaceous plants grow, the time effect observed in the shear strength of the root-soil composite under the action of dry-wet cycles is the result of the interaction and dynamic coordination between the soil-stabilizing function of the herbaceous plant roots and the deterioration caused by drywet cycles.

This research explores the stabilization of clay soil through the application of geopolymer binder derived from silicomanganese slag (SiMnS) and activated by sodium hydroxide (NaOH). This research aims to evaluate the effects of key parameters, including the percentage of slag, the activator-to-stabilizer ratio, and curing conditions (time and temperature), on the mechanical properties of the stabilized soil. Unconfined compressive strength (UCS) tests were conducted to assess improvements in soil strength, while scanning electron microscopy (SEM) was employed to analyze the microstructural changes and stabilization mechanisms. The results demonstrated that clay soil stabilized with SiMnS-based geopolymers exhibited significant strength enhancement. Specifically, the sample stabilized with 20% SiMnS and an activator-to-slag ratio of 1.6, cured at room temperature for 90 days, achieved a UCS of 27.03 kg & frasl;cm2. The uniaxial strength was found to be positively correlated with the SiMnS content, activator ratio, curing time, and temperature. Additionally, the strain at failure remained below 1.5% for all samples, indicating a marked improvement in soil stiffness. SEM analysis revealed that geopolymerization led to the formation of a dense matrix, enhancing soil particle bonding and overall durability. These results emphasize the potential of SiMnS-based geopolymers as a sustainable and effective soil stabilizer for geotechnical applications.

The foundation soil below the structure usually bears the combined action of initial static and cyclic shear loading. This experimental investigation focused on the cyclic properties of saturated soft clay in the initial static shear stress state. A range of constant volume cyclic simple shear tests were performed on Shanghai soft clay at different initial static shear stress ratios (SSR) and cyclic shear stress ratios (CSR). The cyclic behavior of soft clay with SSR was compared with that without SSR. An empirical model for predicting cyclic strength of soft clay under various SSR and CSR combinations was proposed and validated. Research results indicated that an increase of shear loading level, including SSR and CSR, results in a larger magnitude of shear strain. The response of pore water pressure is simultaneously dominated by the amplitude and the duration of shear loading. The maximum pore water pressure induced by smaller loading over a long duration may be greater than that under larger loading over a short duration. The initial static shear stress does not necessarily have a negative impact on cyclic strength. At least, compared to cases without SSR, the low-level SSR can improve the deformation resistance of soft clay under the cyclic loading. For the higher SSR level, the cyclic strength decreases with the increase of SSR.

A comprehensive series of tests, including dynamic triaxial, monotonic triaxial and unconfined compressive strength (UCS) tests, were carried out on reconstituted landfill waste material buried for over twenty years in a closed landfill site in Sydney, Australia. Waste materials collected from the landfill site were treated with varying percentages of cement, and both treated and untreated specimens were investigated to evaluate the influence of cement treatment. The study examined the dynamic properties of cement-treated landfill waste, including cumulative plastic deformation, resilient modulus, and damping ratio, and also analysed the impact of cyclic loading on post-cyclic shear strength in comparison to pre-cyclic shear strength. The UCS tests and monotonic triaxial tests demonstrated that untreated specimens subjected to monotonic loading exhibited a progressive increase in strength with rising axial strain, whereas cement-treated specimens reached a peak strength before experiencing a decline. During cyclic loading, with the inclusion of cement, a significant reduction in cumulative plastic deformation and damping ratio was observed, and this reduction was further enhanced with increasing cement content. Conversely, the resilient modulus showed substantial improvement with the addition of cement, and this enhancement was further amplified with increasing cement content. The formation of cementation bonds between particles curtails particle movement within the landfill waste material matrix and prevents interparticle sliding during cyclic loading, leading to lower plastic strains and damping ratio while increasing resilient modulus. Post-cyclic monotonic testing revealed that cyclic loading caused the partial breakage of the cementation bonds, resulting in reduced shear strength. This reduction was higher on samples treated with lower cement content. Overall, the findings of the research offer crucial insights into the possibility of cement-treated landfill waste as a railway subgrade, laying the groundwork for informed design decisions in developing transport infrastructure over closed landfill sites while using landfill waste materials available on site.

A set of direct shear tests on the soil-geotextile interface (SGI) were conducted using a temperature-controlled constant normal stiffness (CNS) direct shear apparatus. This was done in order to evaluate the effects of normal stiffness, initial normal stress, soil water content, and temperature on SGI shear behavior and microdeformation patterns. The observations indicate that all shear stress-shear displacement curves demonstrate strain-hardening characteristics, with SGI cohesion and friction angle increasing at higher normal stiffness and lower temperatures. At freezing conditions, water content significantly affects the interface friction angle, while this effect is minimal at positive temperatures. Normal stress increases with higher water content, lower temperatures, and higher normal stiffness. Shear stress initially rises with normal stress before decreases, with a more pronounced rise under sub-zero conditions. Normal stress shrinkage shows a positive correlation with normal stiffness. Micro-deformation analysis of soil particles at the interface indicates significant strain localization within the shear band, which is less pronounced under sub-zero temperatures compared to positive temperatures. These patterns of normal displacement vary across analysis points within the shear band, with the macroscopic normal displacement reflecting a cumulative effect of these microscopic variations.

The large coal production and consumption has caused environmental problems worldwide as a source of energy production with irreparable effects on soil, water, and the ecosystem. In addition, producing coal waste in coal washing plants and burying it intensifies the issue in nature. Due to the rising generation of coal waste from various sources, this study utilized several forms of coal waste obtained from a coal-washing plant in the production of both structural concrete (with a water-cement ratio of 0.54) and non-structural concrete (with a water-cement ratio of 0.7). The impact of coal waste on compressive strength (CS) was examined at curing ages of 7, 28, and 56 days. Various percentages of coal waste were substituted for both cement and sand. A superplasticizer was incorporated into the concrete mixtures to enhance the workability and achieve the desired slump and strength levels. According to the compressive strength findings, the ideal replacement level of sand with jig coal waste was 30 %. For 56-day-old specimens, the optimal substitution rates for cement with jig coal waste powder, flotation coal waste, and coal waste ash were found to be 10 %, 10 %, and 20 %, respectively. Notably, adding 10 % coal waste powder and coal waste ash increased compressive strength by 22 %, 23 %, and 44 % at 56 days.