The time-dependent behaviour of soft and clayey soils treated with Deep Cement Mixing (DCM) columns is important for analyzing the long-term performance of civil engineering infrastructures. Previous studies on DCMinstalled composite soil (CS) have primarily focused on examining the soil strength and stiffness characteristics. The limited focus on the time-dependent settlement and stress-strain distribution of CS underscores the need for a more comprehensive understanding of this complex phenomenon. In this study, a lab-scale physical ground model is designed and developed to investigate the time-dependent settlement profile of the composite Montmorillonitic Clay soil (MMC). The settlement behaviour of the ground model is assessed using Creep Hypothesis B and the results are further validated with the Power Law Model. Additionally, a FEM-based numerical simulation is performed to examine the time-dependent settlement and the stress distribution between the column and surrounding clay soil at different depths. The results from the physical model test show that the time-dependent parameter of the ground model (i.e., DCM column installed in MMC) is proportionate to the loading rate until the failure of the DCM column is reached. However, the time-dependent parameter was found to be decreased by 59.04 % in the post-failure phase of the DCM column. This reduction indicates that the DCM column was the primary load-bearing component before its failure. The numerical study shows that the pore water pressure dissipation in the clay soil and DCM column interface was similar at various depths. The top and bottom sections of the DCM column possess higher stress levels, which demonstrates its susceptibility for failure in the DCM column.

The occurrence of settlements induced by soil liquefaction will exert a substantial influence on buildings situated in earthquake-prone regions. Previous studies integrated the viscous-damping force into the governing equation to characterize building settlements and considered the apparent viscosity as an important parameter. The existing equation can be utilized to predict the settlement magnitude in the final stage as well as its evolution. However, due to the insufficient description of apparent viscosity, it is commonly regarded as a constant during the process of evaluating settlement. When adopting this mechanism, the evolution of building settlement often proves inadequate in fully capturing actual conditions. The aim of this study is to propose a prediction model for estimating liquefaction-induced settlement of shallow-founded buildings, which is formulated by an analytically differential equation. The proposed model incorporates the time-dependent viscosity of liquefied soil and introduces the concept of a soil column submerged in liquefied soil during seismic shaking. The evolution of settlement and the final settlement magnitude induced by soil liquefaction is evaluated through the analytical estimation, and these findings are subsequently compared with the results obtained from centrifuge experiments and numerical simulations. Furthermore, the proposed model is employed to investigate the correlation between building settlement and the geometric characteristics of shallow foundations. The proposed methodology shows considerable promise as an intermediate tool for assessing building settlement, offering practical simplicity in real scenarios.

Non-Darcy seepage can more accurately quantify the bearing capacity of jacked piles during the bearing and reconsolidation processes. This paper is divided into three parts. Firstly, it theoretically analyzes the pore water pressure distribution in the soil around the pile through differential treatment of the equation. Secondly, it simulates the pile sinking process and the reconsolidation process of the soil around the pile after sinking by ABAQUS, and then a parameter analysis is conducted. Finally, a time analysis of the pile bearing capacity is conducted. The results show that the dissipation rate of excess pore water pressure (EPWP) and the consolidation rate of the pile side will be underestimated at the initial stage of consolidation if the influence of non-Darcy seepage is ignored, while the opposite is true in the later stage. The strength and effective stress of the soil are greatly improved in the early stage of consolidation, and the bearing capacity of the static pressure pile is also significantly enhanced. In the later stage of consolidation, as the excess pore pressure of the soil around the pile slowly dissipates, the bearing capacity of the static pressure pile also increases steadily. This paper studies the dissipation of EPWP to make the design of pile foundation bearing capacity more rational and to improve the economic benefits.

Energy pile groups transmit geothermal energy and have attracted widespread attention as one of new building energy-saving technologies. Accurately predicting the time-dependent behaviors of energy pile groups is a challenge, given the complex thermal and mechanical interactions between piles, surrounding soils and the pile cap. This study presents a semi-analytical solution for analyzing energy pile groups within heat exchangers. Utilizing the transformed differential quadrature method, a flexible coefficient matrix for the saturated surrounding soils is acquired, which accounts for both consolidation and heat transfer. The piles are segmented, and the discrete solving equations considering thermal stresses and expansion are formulated. To accurately reflect the interactions among piles-to-piles, piles-to-soils and piles-to-pile cap, the coupled matrix equations are constructed with involving both the displacement coordination and the force equilibrium at the pile-soil interface as well as the pile cap. The validity of the proposed solution is confirmed through comparisons with results from onsite tests and simulations using COMSOL. Pivotal parameters including temperature variations, pile spacing, and the relative stiffness are discussed through examples. Compared with traditional simulation and field test, the proposed solution enables fast and accurate prediction of displacement and load distribution across pile groups, facilitating the safety evaluation of heat exchangers.

Marine soft clays are known for their poor engineering properties, which, when subjected to prolonged static and dynamic loading, can lead to excessive settlement of offshore pile foundations and subsequent structural instability, resulting in frequent engineering failures. This study examines the bearing and deformation behavior of jacked piles in these clay deposits under both static and cyclic loading conditions using a custom-designed model testing apparatus. Emphasizing the time-dependent load-carrying capacity and accumulated cyclic settlement of piles, the research uses artificially structured clay to more accurately simulate stratum conditions than traditional severely disturbed natural clays. Model pile testing was carried out to analyze the effects of soil structure and cyclic loading patterns on the long-term response of jacked piles. Key factors investigated include initial soil structure, pile jacking-induced destruction, soil reconsolidation post-installation, disturbed clay's thixotropic effects, and cyclic loading's impact during service. Results show that increasing the cement content within the clays from 0 % to 4 % nearly doubled pile penetration resistance, led to a more significant accumulation of excess pore water pressure (EPWP), and accelerated its dissipation rate. Additionally, the ultimate load-carrying capacity of jacked piles also doubled. Higher cement content slowed pile head settlement rates and reduced stable cumulative settlement values, requiring more cycles to reach instability. Under high-amplitude, low-frequency cyclic loads, hysteresis loops of the model piles became more pronounced and rapid. This study enhances understanding of the long-term cyclic behavior of jacked piles in soft soils, providing valuable insights for designing offshore piles.

Subway station structures near coast are at risk of corrosion caused by chloride, resulting in material and structural component deterioration over time and impacting overall performance during earthquakes. This study proposes a numerical framework for the time-dependent seismic fragility analysis of subway station structures, considering chloride-induced corrosion, based on the IDA method. This study utilizes finite element simulations of typical subway station structures in Qingdao, Shandong, China, focusing on nonlinear dynamic interactions between soil and structure, as well as the impact of chloride-induced corrosion on aging effects. The time- dependent damage states within subway station structures are determined through a nonlinear static pushover analysis. Subsequently, the IDA method is employed to generate time-dependent seismic fragility curves and surfaces specific to subway station structures. The numerical results indicate that the impact of chloride-induced corrosion on the subway station structure cannot be ignored. In the corrosion environment, the seismic performance assessment of subway station structures must take into account time-dependent damage states resulting from the degradation of material properties and the reduction in seismic capacity. The probability of a subway station structure exceeding various damage states monotonically increases during its service life. The subway station structure primarily suffers minor to moderate damage under the ground motion with a return period of 2450 or 10000 years, as it reaches its design service life.

The anchor is commonly applied to enhance the seismic stability of a slope. Presently, the seismic permanent displacement of slope is widely estimated with a constant yield acceleration based on Newmark sliding block method, which is not a realistic scenario. Besides, the soil slope is mostly inhomogeneous and anisotropic, where a circular slip surface is not quite suitable for slope stability analysis. To overcome the shortcomings of estimation method of earthquake-induced displacement, a point-to-point strategy is applied to generate the instant discrete failure mechanism of inhomogeneous and anisotropic anchored slope to determine the time-dependent yield acceleration by limit analysis. The recursive formulas of slope and anchor parameters versus seismic displacement at tiny time interval are established to predict the dynamic behavior of slope. The seismic displacement at tiny time interval is estimated by Newmark sliding block method, and the total earthquakeinduced displacement is subsequently determined. The anchor axial force increases significantly during seismic excitation, which causes a time-dependent characteristic of yield acceleration. Moreover, the effect of inhomogeneity and anisotropy is investigated. The slope becomes more vulnerable to earthquake while the inhomogeneity of unit weight is considered. An increment in inhomogeneous factor or a decrement in anisotropic factor of friction angle or cohesion causes the stability of anchored slope to increase.

The behavior of soft soils distributed in coastal areas usually exhibits obvious time-dependent behavior after loading. To reasonably describe the stress-strain relationship of soft soils, this paper establishes a viscoelastic-viscoplastic small-strain constitutive model based on the component model and the hardening soil model with small-strain stiffness (HSS model). First, the Perzyna's viscoplastic flow rule and the modified Hardin-Drnevich model are introduced to derive a one-dimensional incremental Nishihara constitutive equation. Next, the flexibility coefficient matrix is utilized to extend the one-dimensional model to three-dimensional conditions. Then, by combining the HSS elastoplastic theory with the component model, the viscoelastic-viscoplastic small-strain constitutive model is subsequently established. To implement the proposed model for numerical analysis, the corresponding UMAT subroutine is developed using Fortran. After comparing the results of numerical simulations with those of existing literature, the reliability of the constitutive model and the program written in this paper is verified. Finally, numerical examples are designed to further analyze the effects of small-strain parameters and viscoelastic-viscoplastic parameters on the time-dependent behavior of soft soils.

The time-dependent deformation behavior of silty mudstone brings pronounced difficulties for the construction and maintenance of slope engineering, which has attracted much attention. This study examines the creep characteristics of silty mudstone through multistaged loading tests and studies the creep-induced microstructural evolution using Scanning Electron Microscopy (SEM). To mitigate the variability caused by natural defects in the rock, similar material specimens were prepared to substitute silty mudstone for experiments. The results demonstrate that creep strain escalates stepwise with stress level, with the magnitude of each increment being contingent upon the applied confining pressure (sigma 3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\sigma _{3}$\end{document}). The strain rate undergoes three phases including attenuation, stabilization, and acceleration. Cumulative strain correlates positively with sigma 3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\sigma _{3}$\end{document}, while the initial creep rate declines before slightly increasing. Creep failure predominantly manifests in a shear pattern, with sigma 3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\sigma _{3}$\end{document} controlling the development of fractures in terms of their length, number, and angle. SEM analysis reveals that increased sigma 3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\sigma _{3}$\end{document} facilitates the expansion of transgranular cracks, displaying a coupled ductile-brittle fracture mode. Furthermore, sigma 3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\sigma _{3}$\end{document} variably affects the micropore morphology (pore size, area, roughness, and regularity), with the differences in pore structures under various sigma 3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\sigma _{3}$\end{document} being distinguished by the fractal dimension. Also, the fractal dimension is positively correlated with porosity, which can be quantitatively characterized using a nonlinear logarithmic function. The interaction between particles and cement, coupled with the development of cracks and pores, is identified as the primary mechanism of structural failure during the creep process.

Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load. Due to the complexity of biological structures, the underlying micro-behaviors involving time-dependent deformation are poorly understood. For this, an abnormal phenomenon was observed where the axial and lateral creep deformations were mutually independent by a series of triaxial tests under constant stress and strain rate conditions. The significantly large lateral creep deformation implies that the creep process cannot be described in continuum mechanics regime. Herein, it is hypothesized that sliding mechanism of crystal cleavages dominates the lateral creep deformation in coral reef limestone. Then, approaches of polarizing microscope (PM) and scanning electronic microscope (SEM) are utilized to validate the hypothesis. It shows that the sliding behavior of crystal cleavages combats with conventional creep micro-mechanisms at certain condition. The former is sensitive to time and strain rate, and is merely activated in the creep regime. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).