Backfill mining is a lucrative method for extracting coal buried under buildings, and water bodies, which can substantially increase the resource usage efficiency by mitigating the strata movement and surface subsidence. Its effectiveness depends on the mechanical properties of granular backfill materials. A permeability test was performed on gangue and fly ash samples under different stress levels using an original seepage test system. The variation patterns of the broken rock's internal pressure and permeability were determined. The test results indicate the weakening of the seepage effect on granular materials and a gradual reduction of washed away fly ash. The permeability values fall into the range of 3.2 x 10(-15) similar to 3.2 x 10(-13)m(-2), and non-Darcy factor is between 3.2 x 10(10) and 3.2 x 10(12) m(-1). This phenomenon was more pronounced in samples with smaller particle sizes. As the axial stress increased, the backfill material showed a decline in permeability and an increase in the non-Darcy flow coefficient. As the content of fly ash increased, the mass loss grew sharply, which occurred mainly at the early seepage stage. The results are considered instrumental in the characterization of water and sand inrush.

This experimental study is to find a solution to reduce the amount of waste and at the same time improve the geotechnical properties of fine soils. Compaction, odometer, direct shear tests, and unconfined compression tests were carried out on a clay with a very high degree of plasticity mixed with 0%, 10%, 20%, 30%, and 40% of recycled concrete aggregates (RCA). The addition of concrete aggregates to the clayey soil shows an increase in the maximum dry density and a reduction in the optimum water content. The odometer tests results showed that the increase in the recycled material content leads to a decrease in the compression index, swelling index and creep index. On the other hand, the pre-consolidation stress, the odometric modulus, the consolidation coefficient and the permeability coefficient increase with increasing RCA content. According to the direct shear test, the higher RCA content provided an improvement in shear strength which is accompanied by an increase in the dilatant character. For different curing times and for a content of 10% recycled concrete aggregate, the unconfined compressive strength increased compared to the untreated soil.

Building structures on clayey soil presents unique challenges to geotechnical engineers due to the inherent variability in clayey soil consistency. Understanding engineering properties of clayey soils is essential for accurate geotechnical design and the prevention of potential issues such as settlement and instability. The current study provides crucial insights for geotechnical assessments and engineering solutions in the area, highlighting key soil properties that affect the classification of clayey consistency. Advanced machine learning (ML) models were employed to predict the in situ clay consistency, a vital parameter for evaluating the deformation resistance of clayey soils under structures. The ML predictions are based on nine features representing the physical and mechanical properties of the clay, which are easily determined through laboratory and field evaluations. A dataset comprising 173 samples is compiled, which extracted from Nile Delta in Egypt, incorporating data on the basic properties of the soils to train and test several ML classification algorithms. The classification models, including logistic regression, k-nearest neighbors, support vector machine, random forest, and gradient boosting classifiers, are evaluated using metrics such as accuracy, sensitivity, specificity, and F1-score. The results demonstrate that the gradient boosting classifier model exhibits the highest accuracy in predicting clay class, achieving 97% and 86% accuracy for the training and testing datasets, respectively. These findings offer a valuable framework for efficiently and cost-effectively classifying clays, assisting geotechnical engineers in making informed decisions about foundation design and construction on clayey soils. Additionally, the study establishes equations to predict the undrained shear strength of clayey soil based on its basic properties, providing a practical and accurate method for estimating soil strength characteristics. These contributions enhance the understanding and management of clayey soil behavior in geotechnical engineering, offering essential guidance for foundation design and construction projects in clayey soil regions.

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.

Infrastructure construction on coastal areas such as ports, bridges and airports require ground improvements when marine soils contain soft ground which includes fine grains in general. Fine-grained soils consist of clastic or non-clastic grains. Based on the mineralogy of soils, compressibility of soils shows different behavior. Fine-grained clay mineral soils show plastic and time-dependent deformation due to consolidation during constructions while silty soils without clay minerals show low compressibility. However, biogenic soils such as diatomaceous earth are more compressible than other silty fine-grained soils. Although fine-grained soils with clastic minerals and biogenic minerals are classified as silt, the behavior of clastic soils are less compressible compared to biogenic soils which have inner pores. We conducted one-dimensional consolidation experiments to investigate compressibility of diatomaceous earth and non-plastic mineral fines such as silica silt. The coefficient of consolidation, and volumetric compressibility are estimated, and show that the trends of diatomaceous earth properties are different from other silty soil properties based on the consolidation tests. We found that particle breakage plays a crucial role in compressibility of diatomaceous soils. While the compressibility of diatomaceous soils is similar to clastic soils at low stress, the differences in compressional behavior between two soils are distinct at high stress. The diatomaceous earth shows time-dependent compressibility due to creep or secondary compression by particle breakage process. Thus, settlement analysis should include the impact of morphology and mineralogy of fine-grained soils.

Industrial wastes cause damage to the environment and pose a threat to public health. The utilization of industrial wastes is inevitable if a circular economy needs to be achieved. Cement kiln dust (CKD) is a potential engineering material that can be used in many civil engineering works. The volume change behavior of a CKD is reported here. One-dimensional swelling and compression tests were carried out on CKD specimens to derive the compressibility parameters and coefficient of permeability. A cyclic wet-freeze-thaw-dry test was carried out to study the volume change of the material upon exposure to various seasonal climatic processes under a low surcharge pressure. The experimental results show that CKD can exhibit swelling under light loads. The correlations between plasticity properties and compressibility parameters that are applicable to fine-grained soils were found to overestimate the parameters of the CKD. The magnitudes of frost heave and thaw settlement were found to be significant, with an uprising type of movement accompanied by strain accumulation when the material was taken through several wet-freeze-thaw-dry cycles.

Carbonate sand, widely distributed in coastal regions, presents challenge due to its high stress-dependent and time-dependent (creep) compressibility. While soil stabilization techniques have traditionally focused on enhancing the strength of carbonate sand, the evaluation on the compressibility performance of cemented carbonate sand remains a critical aspect for most envisaged practical applications. In light of recent developments in self-healing approaches for soil stabilization, this study investigated the potential of calcium alginate/Tung oil capsules to mitigate compressibility in carbonate sand. The encapsulated Tung oil serves as a healing agent, gradually releasing within the sand matrix when subjected to void ratio changes during compaction, hardening and bonding sand grains after a 30-day drying. Long-term stepwise one-dimensional compression tests were conducted on both clean sand and sand-capsule composite with different initial relative density and particle size. The overall and stress-dependent compressibility was reduced for fine sand-capsule composite, while capsules had adverse effect on the compressibility of medium and coarse sand-capsule composite. Capsules could not reduce the creep but increase the elastic response of all sand-capsule composites. The Tung oil bonding could reduce the compressibility by preventing particle breakage of sand during loading. The stabilization mechanism of capsules in carbonate sand with different particle size was further investigated through thermal analysis, CT scan and microscopic analysis, revealing that the compressibility mitigation by capsules depended on the amount of Tung oil release from capsule, which was controlled by the pore structure of sand-capsule composite.

The presence of heavy metal in soil poses major threats to the environment and integrity of structures. Rapid industrialization further increases the rate of contamination of heavy metal in soil. The presence of heavy metal contaminants in soil changes the geotechnical properties of soil, which will affect the structure atop the contaminated sites. Changes in mechanical properties of soil could alter the compressibility behaviour of soil. The purpose of this research is to determine the compressibility behaviour of zinc contaminated residual soil with different concentration levels of zinc. A total of thirty samples including a control sample were prepared with ZnSO4.7H20 concentrations of 0 mg/L, 500 mg/L, 1000 mg/L, and 2000 mg/L with curing period of 0 days, 7days, and 28 days. The samples were tested for One-Dimensional Consolidation Oedometer test, pH test, and Electric Conductivity test. The results show a decrease in compression index value, void ratio, and coefficient of consolidation as the concentration of zinc increases. Compression index value decrease to the lowest value of 0.143 under 2000mg/L concentration at 28 days curing period. Void ratio achieves the highest value with 500 mg/L concentration at 7 days curing period while the control sample shows the lowest void ratio value. As for coefficient of consolidation, the highest value is achieved for sample with 500 mg/L at 7 days curing period where the control sample shows the lowest value. The pH value of soil declines to acidic value from 5.82 to 3.84 under concentration of 2000 mg/L at 28 days curing period while electric conductivity increases from 156 us/cm to 2990 us/cm at 0 days curing period.

Population growth has resulted in industrialization, massive construction, and significant mining to supply the population's ever-increasing needs. The study deals with waste material utilization for soil properties enhancement, reducing construction costs and benefiting the environment. Bottom ash, one such effluent released from thermal power plants, was used in percentages 0, 20, 50, 70, and 100% by weight. Laboratory tests were conducted, including the sand replacement method, unconfined compression test, and shear test, to study the enhanced mechanical properties of the soil, adding bottom ash to it. Initially, the property of backfill material is enhanced and further it is used behind the wall along with the geofoam placed strategically to significantly reduce lateral stresses exerted on the retaining wall further optimizing the overall structural efficiency. Geofoam of three different densities, 11 kg/m3 (11EPS), 16 kg/m3 (16EPS), and 34 kg/m3 (34EPS), has been tested to understand how the compressive strength and corresponding modulus values change with the unit weight and strain rate. It was observed that with an elevating density of geofoam, unit weight, compressive strength, shear strength, and shear strength parameters increased, whereas water absorption capacity decreased. The results of this study can be used as a reference for the quality control of geofoam. The effective use of geofoam placed behind a stiff retaining wall in reducing lateral stresses brought on by a combination of backfill material and loading conditions was evaluated using a finite element model. The results obtained through the numerical investigations were validated with the differential element method developed. Results obtained through numerical and calculated models were in good accord with a percentage error of less than 20%. The impact of geofoam density, relative thickness, and friction angle of backfill on the efficiency of geofoam in reducing lateral stresses was then investigated using a parametric analysis. Earth pressure reduction obtained for different backfill types and lower density geofoam (11 EPS) of thickness 10 cm was between 23.27 and 62.72% obtained numerically. The highest earth pressure reduction, i.e., 64.17%, was obtained for 11EPS geofoam of thickness 15 cm laid behind the bottom-ash-backfilled retaining wall. Parametric charts prepared with the obtained results can help determine the required thickness of geofoam for any desired earth pressure reduction efficiency.

Lime stabilization has long been identified as an effective method for reducing the swelling potential of expansive soils. Despite numerous studies evaluating the volumetric behaviour of lime-stabilized expansive soils, the influence of stress history variations on deformation characteristics of these soils has not been adequately explored. This study specifically evaluates the impact of stress history conditions on compressibility characteristics of lime-stabilized expansive soils, with special attention to the rebound index at different loading stages. In this regard, one-dimensional consolidation-swell tests were conducted on samples containing different lime percentages (3% to 12%) under various stress history conditions. To include different stress history conditions, overconsolidation ratio (OCR), seating pressure, and loading step were varied during the induction of stress history in the samples. Results showed that OCR and seating pressure significantly influenced both the rebound (increased up to 118%) and compression indices (decreased up to 53%), while the loading step had a negligible impact on the compressibility properties of stabilized soils. Additionally, when comparing the relative importance of investigated parameters, it was revealed that, OCR had the highest influence on the rebound index (up to 118.0% increase), while the compression index was most significantly affected by lime percentage (up to 61.4% decrease).