Weathered residual soil of granite (WRSG) is the predominant type of excavated soil in southern China. This study explores the high-quality utilisation potential of WRSG by mixing it with a small amount of cement and preloading it within steel tubes to create preloaded-cement-soil filled steel tubular (PCSFST) columns. The research investigates the relaxation behaviour and axial compression performance of PCSFST columns through experiments, focusing on the influence of preloading indicator, cement content ratio, and water-to-solid rat io on their axial compression behaviour. The experimental results showed that an increase in the preloading indicator significantly enhanced the axial bearing capacity of the PCSFST column. Specifically, when the preloading indicator increased from 30 % to 90 %, the axial bearing capacity increased by 22.7 %. Although the increase from 6 % to 12 % in the cement content ratio significantly improved the unconfined compressive strength (UCS) of the cement-soil core, the corresponding reduction in the confining effect only resulted in a 3.2 % increase in the axial bearing capacity, indicating a limited benefit. A moderate increase in the water-to-solid ratio significantly boosted the UCS of the cement-soil core, which in turn, enhanced the axial bearing capacity of the PCSFST column. After the preloading load was released, the cement-soil core exhibited longitudinal rebound deformation, which significantly reduced the confining effect provided by the steel tube. Nevertheless, the contribution of the confining effect to the axial bearing capacity can reach as high as 37 %, partially compensating for the relatively low UCS of the cement-soil core. Finally, based on the experimental results, a formula was proposed to predict the axial bearing capacity of PCSFST columns, which demonstrated high prediction accuracy.

Global economic growth leads to massive plastic waste increase, posing severe environmental challenges worldwide. Addressing it demands innovative solutions like repurposing plastics for construction. Extensive engineering and environmental assessments can accelerate their adoption. This study explores the potential incorporation of plastic waste (in flake and pellet forms) into a cement-treated fine-grained soil through a comprehensive geotechnical experimental testing program and Life Cycle Assessment (LCA) study to assess their environmental sustainability. Experimental investigations were conducted on four distinct plastic types, namely polypropylene (PP), high-density polyethylene (HDPE), polylactic acid (PLA), and polyethylene terephthalate (PET), with varying weight percent inclusions of 2 %, 4 %, and 6 %. Results revealed a decreasing trend in maximum dry densities and strength (both unconfined compressive strength (UCS) and split tensile strength (STS)) with increasing plastic content. Sorptivity of soil generally increased with plastic inclusions, yet in the case of PET, for plastic content > 4 %, a notable drop in the rate of increase was observed. California bearing ratio (CBR) test results indicated a reduction in the CBR values by up to 18.33 % for 6 % plastic inclusions. LCA study findings favoured plastic flakes over pellets as a more sustainable material choice, exhibiting a lower environmental impact across all assessed indicators. This research findings offer insights into the potential utilization of plastic waste and promote sustainable geomaterial choices in road pavement construction.

Subgrade soil undergoes freezing in winter and thawing in summer in seasonal frost areas, which severely impacts the engineering performance of the subgrade soil. In order to enhance the frost resistance of subgrade while mitigating the environmental impact of incinerating industrial solid waste, rubber crumb was added to cementsoil in this study. The static triaxial and mercury intrusion porosimetry tests were conducted on freeze-thawed cement-soil and rubberized cement-soil. The effects of the number of freeze-thaw cycle and confining pressure on peak strength and initial elastic modulus were investigated. The pore size distribution, porosity, and fractal dimension under various numbers of freeze-thaw cycle were obtained based on the MIP test results. The damage parameter of the specimens was determined using the fractal dimension. A constitutive model with damage parameter of rubberized cement-soil was established. The results showed that the pore size distribution of the specimens deteriorated after the whole freeze-thaw cycles, with increases observed in macropore proportion, porosity, and damage parameters, while peak strength and fractal dimension decreased. The macropore proportion of cement-soil and rubberized cement-soil increased by 14.9% and 2.0%, respectively. The incorporation of rubber particles suppressed the development of pores and cracks and enhanced the frost resistance of the specimens. The damage parameter of rubberized cement-soil decreased by only 0.0186 by the end of 12 of freezethaw cycle. The established constitutive model was suitable for characterizing the stress-strain behavior of rubberized cement-soil. The findings facilitate the construction and design of subgrade engineering in seasonal frost areas, contributing to the development of sustainable, durable subgrade solutions and reducing the environmental impact of waste rubber tires.

This research is the result of work on implementing a closed-loop economy in geotechnics, which aligns with the broader concept of a circular economy in construction by promoting the use of waste materials and reducing environmental impact. The research presented in the article focuses on the use of fluidized bed furnace bottom ashes, a by-product of coal combustion in fluidized bed boilers, in the production of cement-soil jet grouting slabs. Samples were analyzed for their structural and mechanical properties to assess their suitability for geotechnical applications. The mixtures were distinguished between those using CEM I and those using CEM II. Mixes based on two types of cements had an additional division based on the amount of additives: reference mix, 5% ash, 15% ash, and 10% ash + 5% microsilica. The conducted experiments aim to determine the physico-mechanical parameters of the new mixtures, highlighting the potential of these materials in mining and geotechnical technologies. The research took into account the impact of time over a period of two years for mortars and 28 days for cement-soil. The authors' studies included determining the compressive strength, bending strength, and imaging using computed tomography. Computed tomography allowed imaging of the internal structure and porosity analysis. Employing CEM II as the primary binding material slows early strength gain, but adding microsilica significantly enhances strength, compaction, and durability. Despite improved properties, CT imaging revealed increased cracking in mixtures with CEM II, indicating reduced water tightness and highlighting areas for further study.

Cement-soil mortar is a composite material that provides an efficient and cost-effective solution for a wide range of construction applications. This study analyzes the mechanical properties of cement-soil mortar through experimental investigation and explores the application and parameter calibration of the Concrete Damage Plasticity (CDP) model in the finite element simulation of cement-soil mortar. Additionally, an innovative Initial Defect Generation (IDG) method is proposed to enhance the accuracy in simulation of failure mode. The research findings provide a simulation framework that balances simplicity and accuracy for cement-soil mortar. Uniaxial compressive tests are first conducted on cement-soil mortar specimens with water contents ranging from 40 % to 70 %, and cement-to-soil proportions from 30 % to 300 %. Based on the experimental results, the regression relationships correlating unconfined compressive strength (UCS) with elastic modulus, peak strain and stress-strain curves are established. Then, the simplified equations for calculating CDP model parameters from the UCS of cement-soil mortar are further proposed following damage mechanics. A parameter table summarizing the calculation methods for all relevant CDP parameters is provided to streamline the model calibration process. Simulations incorporating the simplified calibration method and IDG method successfully replicated the stress-strain responses and failure modes observed in uniaxial compressive strength tests of cement-soil specimens with varied strength. The results demonstrate the reliability and broad applicability of this simulation framework in predicting the mechanical performance of cement-soil mortar.

Cement-soil mixed piles reinforcement is considered to be an effective way to improve the bearing capacity of the monopile foundation for offshore wind turbine in soft clay. In this study, a numerical model is developed to study the behaviors of the pile in cement-soil mixed piles reinforced soil. Factors influencing the reinforcement efficiency of cement-soil mixed piles method, including the reinforcement width, reinforcement depth, and the layout configuration, are investigated. Considering the improvement in both bearing capacity and deformation characteristics, a configuration with inner and outer rings and connecting walls with a replacement ratio of 66.15% is thought to be the optimum reinforcement configuration, while the structure stability and scour protection are also benefited. A method called the equivalent pile diameter method is proposed for the design of cement-soil mixed piles. Equations based on single parameter and multi-parameters for the design of the cementsoil mixed piles reinforcement are presented. This study and the proposed method are aimed at simplifying and facilitating the design of the pile foundation in offshore soft clay.

This paper reports numerical simulation and field test research on the horizontal static and cyclic loading performance of a single pile reinforced by cement-soil. 3D numerical models of soil-cement soil-concrete pile with various reinforcement sizes were established in ABAQUS. By comparing the effects of different cement-soil reinforcement widths and depths on bearing capacity and bending moments, a reinforcement width of 3 times of the pile diameter and a reinforcement depth of 1/4 of embedded depth are the optimal design parameters. On this basis, unidirectional and bidirectional cyclic loading tests were conducted on reinforced and unreinforced piles with a length of 40 m and a diameter of 1.6 m, respectively. The test results indicate that the critical horizontal load of reinforced pile increased by 40%, and the peak bending moment decreased by approximately 14.5% compared to unreinforced pile. This enhancement is attributed to the cement-soil around the pile, which increases the soil resistance and limits the horizontal displacement of the pile head. The cyclic hysteresis curve of reinforced piles is fuller than that of unreinforced piles, exhibiting a larger hysteresis area and a 74.5% increase in the initial stiffness of the pile head. Additionally, the cement-soil surrounding the pile mitigates the effects of cyclic weakening and plastic accumulation under cyclic loading.