Soft soil subgrades often present significant geotechnical challenges under cyclic loading conditions associated with major infrastructure developments. Moreover, there has been a growing interest in employing various recycled tire derivatives in civil engineering projects in recent years. To address these challenges sustainably, this study investigates the performance of granular piles incorporating recycled tire chips as a partial replacement for conventional aggregates. The objective is to evaluate the cyclic behavior of these tire chip-aggregate mixtures and determining the optimum mix for enhancing soft soil performance. A series of laboratory-scale, stress-controlled cyclic loading tests were conducted on granular piles encased with combi-grid under end-bearing conditions. The granular piles were constructed using five volumetric proportions of (tire chips: aggregates) (%) of 0:100, 25:75, 50:50, 75:25, and 100:0. The tests were performed with a cyclic loading amplitude (qcy) of 85 kPa and a frequency (fcy) of 1 Hz. Key performance indicators such as normalized cyclic induced settlement (Sc/Dp), normalized excess pore water pressure in soil bed (Pexc/Su), and pile-soil stress distribution in terms of stress concentration ratio (n) were analyzed to assess the effectiveness of the different mixtures. Results indicate that the ordinary granular pile (OGP) with (25 % tire chips + 75 % aggregates) offers an optimal balance between performance and sustainability. This mixture reduced cyclic-induced settlement by 86.7 % compared to the OGP with (0 % TC + 100 % AG), with only marginal losses in performance (12.3 % increase in settlement and 2.8 % reduction in stress transfer efficiency). Additionally, the use of combi-grid encasement significantly improved the overall performance of all granular pile configurations, enhancing stress concentration and reducing both settlement and excess pore water pressure. These findings demonstrate the viability of using recycled tire chips as a sustainable alternative in granular piles, offering both environmental and engineering benefits for soft soil improvement under cyclic loading.

Horizontal frost heave disasters frequently occur in cold-region engineering projects, making it essential to understand water migration mechanisms along horizontal directions during freezing processes. Using a selfdeveloped one-dimensional visualization horizontal freezing apparatus, unidirectional horizontal freezing tests were conducted on soft clay under varying temperature gradients, and the development process of the cryostructures was continuously observed. The results indicate that the thermal-hydraulic processes, including temperature evolution, water content variation, pore-water pressure dynamics, and soil pressure changes, demonstrate similarities to vertical freezing patterns, with temperature gradients primarily influencing the magnitude of parameter variations. Under the influence of gravity, the freezing front forms an angle with the freezing direction, attributed to differential freezing rates within soil strata. Post-freezing analysis showed dualdirectional water redistribution (horizontal and vertical), with horizontal migration dominating. Maximum water content was observed 1-3 cm from the freezing front. Distinct cryostructures formed in frozen zones were identified as products of tensile stresses generated by low-temperature suction and crystallization forces. The study highlights the coupling of water transfer, thermal changes, mechanical stresses, and structural evolution during freezing and suggests that water migration and cryostructure formation are interrelated processes. This research provides robust experimental evidence for advancing the theoretical framework of horizontal water migration mechanisms in frozen soil systems.

Deep soil mixing (DSM) is a widely used ground improvement method to enhance the properties of soft soils by blending them with cementitious materials to reduce settlement and form a load-bearing column within the soil. However, using cement as a binding material significantly contributes to global warming and climatic change. Moreover, there is a need to understand the dynamic behavior of the DSM-stabilized soil under traffic loading conditions. In order to address both of the difficulties, a set of 1-g physical model tests have been conducted to examine the behavior of a single geopolymer-stabilized soil column (GPSC) as a DSM column in soft soil ground treatment under static and cyclic loading. Static loading model tests were performed on the end-bearing (l/h = 1) GPSC stabilized ground with Ar of 9 %, 16 %, 25 %, and 36 % and floating GPSC stabilized ground with l/h ratio of 0.35, 0.5, and 0.75 to understand the load settlement behavior of the model ground. Under cyclic loading, the effect of Ar in end-bearing conditions and cyclic loading amplitude with different CSR was performed. Earth pressure cells were used to measure the stress distribution in the GPSC and the surrounding soil in terms of stress concentration ratio, and pore pressure transducers were used to monitor the excess pore water pressure dissipated in the surrounding soil of the GPSC during static and cyclic loading. The experimental results show that the bearing improvement ratio was 2.28, 3.74, 7.67, and 9.24 for Ar of 9 %, 16 %, 25 %, and 36 %, respectively, and was 1.49, 1.82, and 2.82 for l/h ratios of 0.35, 0.5, and 0.75 respectively. Also, the settlement induced due to cyclic loading was high under the same static and cyclic stress for all the area replacement ratios. Furthermore, the impact of cyclic loading is reduced with an increase in the area replacement ratio. Excess pore water pressure generated from static and cyclic loads was effectively decreased by installing GPSC.

The soilbags reinforcement has been widely used for soft soil foundation improvement due to its high compressive strength and deformation modulus considering the time limit of many projects and the characteristics of the reclaimed soil. However, despite the strength and deformation properties of soilbags reinforcement, the drainage characteristics of soilbags reinforcement is a crucial factor that creates a large challenge to foundation improvement for soft soil. Thus, this study developed a four-staged surcharge preloading on soilbags-reinforced soft soil foundation and focused on its drainage consolidation effectiveness. The contrasting laboratory tests were performed in four identical experimental boxes with clayey soil from the Nanjing, China. Four-staged preloading were applied on the soilbags-reinforced testing model, respectively, the data of the settlement and water discharge during the test are monitored, and after the tests, the water content and shear strength at different positions are measured. And three contrasting tests considering the possible drainage channels of soilbags reinforcement were also conducted. The results show that the consolidation effect is achieved with the soilbags reinforcement in terms of the settlement, pore water pressure, water content and shear strength after consolidation.

This study investigates the influence of unsymmetrical surcharge on the piles of a bridge located in a coastal soft soil area, aiming to elucidate the deformation characteristics of the piles. The impact of some key parameters, including soft soil properties and unsymmetrical surcharge, on pile deformations is evaluated through 3D finite element numerical analysis and parameter sensitivity analysis. The results show that unsymmetrical surcharge significantly influences the displacement of both the piles and the surrounding soil, with both being affected by the soil arching effect. The parameter sensitivity analysis reveals that Poisson's ratio of the soft soil, and the stiffness of the piles have minimal impact on horizontal displacement. In contrast, the elastic modulus, cohesion, and internal friction angle of the soft soil, as well as the height and slope of the unsymmetrical surcharge, have significant effects on the piles. When the unsymmetrical surcharge is applied parallel or perpendicular to the bridge, the parallel surcharge has a relatively minor impact on the pile. The horizontal displacement of the pile follows an exponential relationship with L/B, D/h, and B/d. A functional relationship can be established between these parameters to predict the pile's horizontal displacement.

This study developed all-solid-waste-based curing agents using industrial solid wastes-ground granulated blastfurnace slag (GGBS), carbide slag (CS), and sulfate solid wastes (electrolytic manganese residue (EMR), desulfurized-gypsum (DG), and phosphogypsum (PG))-to stabilize engineering sediment waste (ESW). Based on the simplex centroid design, three ternary curing agents (GGBS-EMR-CS (GEC), GGBS-DG-CS (GDC), and GGBSPG-CS (GPC)) were prepared. The optimal ratios for GEC, GDC, and GPC are 60:12:28, 70:27:3, and 70:21:9, respectively. Compared to ordinary Portland cement (OPC), the unconfined compressive strength (UCS) of ESW stabilized with these curing agents increased by 78 %, 178 %, and 98 %, respectively. Sulfate components synergistically activates GGBS and CS, promoting needle-like ettringite (AFt) formation, which fills pores and enhances strength. Meanwhile, COQ emissions and costs were reduced up to 99 % and 73 %, respectively. This study developed all-solid-waste-based curing agents with excellent mechanical performance, low costs, and near net-zero emissions, which provided a sustainable solution for ESW stabilization.

PurposeThis paper aims to develop a probabilistic framework which combines uncoupled cofferdam stability analysis, random forest and Monte Carlo simulation for cofferdam reliability analysis.Design/methodology/approachThe finite element method and limit equilibrium method are used to calculate the seepage field and stability of cofferdam, respectively. Sufficient training and validating random samples are generated to obtain a random forest surrogate model with acceptable accuracy. The calibrated random forest model combined with MCS is used to conduct cofferdam reliability analysis. The proposed methodology is illustrated using a typical cofferdam model.FindingsThe numerical simulation results demonstrate that a larger pore water pressure leads to a lower stability of the cofferdam and vice versa. The increase in the slope angle significantly reduces the stability of cofferdam on the corresponding side, while the stability of cofferdam on the other side is mainly affected by the internal pore water pressure. The increase in the width and height of the reverse pressure platform significantly enhances the stability of cofferdam, and the changes in the angle of the reverse pressure platform affect the stability of cofferdam to some extent. The probability of failure (Pf) of cofferdam increases gradually with increasing vertical and horizontal scales of fluctuation, coefficient of variation, and cross-correlation coefficient when the degradation degree of soil properties is low. It is worth noting that the effect of vertical and horizontal scales of fluctuation, coefficient of variation, and cross-correlation coefficient on the Pf of cofferdam changes significantly when degradation coefficient decreases to a critical value.Practical implicationsA geotechnical engineer could use the proposed method to perform cofferdam reliability analysis.Originality/valueThe reliability of cofferdam can be efficiently and accurately studied using the proposed framework.

This paper presents an efficient two-and-a-half dimensional (2.5D) numerical approach for analysing the long-term settlement of a tunnel-soft soil system under cyclic train loading. Soil deformations from train loads are divided into shear deformation under undrained conditions and volumetric deformation from excess pore water pressure (EPWP) dissipation. A 2.5D numerical model was employed to provide the dynamic stress state owing to the moving train load and the soil static stress state by the gravity effect for the determination of their accumulations. Then, an incremental computation approach combined with the initial strain approach in the framework of the 2.5D model was developed to compute the long-term deformation of the tunnel-soft soil system, considering the influence of the soil hardening due to EPWP dissipation. This approach helps to determine the distribution of the progressive settlement, transverse and longitudinal deformations in the tunnel-soil system, overcoming traditional limitations. A comparison of settlements computed using this approach with measured settlements of a shield tunnel in soft soil shows good agreement, indicating the effectiveness of the proposed approach in analysing train-induced progressive deformation of the tunnel-soil system.

During tunnel excavation in a soft soil stratum, a transparent model test can present the whole failure process, and a similar transparent material with stable physical and mechanical properties is essential for obtaining valid experimental results. Therefore, a new type of similar transparent material was developed in which fused quartz sand served as the coarse aggregate, nanoscale hydrophobic fumed silica powder acted as the binder, and a mixture of n-dodecane and 15# white oil was used as the pore fluid. The key parameters of the developed similar transparent material, including unit weight, internal friction angle, cohesion, and compression modulus, were evaluated. Furthermore, the consistency between the similar transparent material and natural soft soil was verified in three aspects, namely, physical properties, compressive strength characteristics, and shear properties. Finally, appropriate adjustment measures were proposed based on the results of the analysis of variance (ANOVA) and the analysis of range (ANOR) to meet the similarity requirements of parameters under different engineering conditions.

The high water content of soft soil leads to complex sedimentation, consolidation, and permeability characteristics, posing challenges to engineering design and construction. Although existing research has made progress in the field of consolidation and settlement characteristics, discussions on the low stress stage are still insufficient, and there is a lack of appropriate mathematical models to describe it. At the same time, the correlation and differences between the degree of consolidation used for settlement calculation and the degree of consolidation used for pore water pressure calculation have not been fully clarified. This study improves the measurement method for permeability coefficients and optimizes consolidation equipment, conducting research on the permeability and consolidation characteristics of soft soil with high water content. The research results show that soft soil with high water content exhibits significant consolidation settlement under low stress, and the incremental settlement decreases with the increase of consolidation stress. The void ratio and compression coefficient undergo drastic changes during consolidation, with a difference of 2 to 4 orders of magnitude, especially significant during the low-pressure stage. This study indicates the existence of a critical stress of about 4 kPa and proposes a segmented method to describe the consolidation and permeability characteristics of soft soil with high water content, establishing an e-lg sigma-lgk relationship model, which can effectively reflect the consolidation behavior of super-high water content soft soil. At the same time, the study also finds that in practical engineering applications, the degree of consolidation used for settlement calculation and the degree of consolidation used for pore water pressure calculation should be considered comprehensively to more accurately predict the consolidation process and guide construction.