To investigate the one-dimensional nonlinear consolidation characteristics of a double-layer foundation under multi-stage loading, a one-dimensional nonlinear consolidation equation for the double-layer foundation was established, and numerical solutions were obtained through the finite difference method. The accuracy of the proposed solution was validated by comparing it with existing analytical solutions and finite element analysis results. Based on these comparisons, the influence of nonlinear parameters, double-layer soil properties, and loading conditions on the consolidation behavior of the double-layer foundation was further examined. The results indicated that, under multi-stage linear loading conditions, an increase in the initial permeability coefficient ratio of the double-layer foundation resulted in a significant reduction in excess pore water pressure and an acceleration of consolidation. The compression index was found to predominantly affect the later stages of consolidation, with minimal impact on the early stages. The consolidation rate was observed to increase as the permeability coefficient ratio decreased. Despite notable differences in early consolidation behavior under varying loading conditions, the findings reveal that these discrepancies are alleviated in the later stages, ultimately resulting in no significant overall difference in the time required for the foundation to achieve complete consolidation.

The evaluation of thermo-hydro-mechanical (THM) coupling response of clayey soils has emerged as an imperative research focus within thermal-related geotechnical engineering. Clays will exhibit nonlinear physical and mechanical behavior when subjected to variations in effective stress and temperature. Additionally, temperature gradient within soils can induce additional pore water migration, thereby resulting in a significant thermo-osmosis effect. Indeed, thermal consolidation of clayey soils constitutes a complicated THM coupling issue, whereas the theoretical investigation into it currently remains insufficiently developed. In this context, a one-dimensional mathematical model for the nonlinear thermal consolidation of saturated clay is proposed, which comprehensively incorporates the crucial THM coupling characteristics under the combined effects of heating and mechanical loading. In current model, the interaction between nonlinear consolidation and heat transfer process is captured. Heat transfer within saturated clay is investigated by accounting for the conduction, advection, and thermomechanical dispersion. The resulting governing equations and numerical solutions are derived through assuming impeded drainage boundaries. Then, the reasonability of current model is validated by degradation and simulation analysis. Subsequently, an in-depth assessment is carried out to investigate the influence of crucial parameters on the nonlinear consolidation behavior. The results indicate that increasing the temperature can significantly promote the consolidation process of saturated clay, the dissipation rate of excess pore water pressure (EPWP) is accelerated by a maximum of approximately 15%. Moreover, the dissipation rate of EPWP also increases with the increment of pre-consolidation pressure, while the corresponding settlement decreases. Finally, the consolidation performance is remarkably impacted by thermo-osmosis and neglecting this process will generate a substantial departure from engineering practice.

The self-weight stress in multilayered soil varies with depth, and traditional consolidation research seldom takes into account the actual distribution of self-weight stress, resulting in inaccurate calculations of soil consolidation and settlement. This paper presents a semi-analytical solution for the one-dimensional nonlinear consolidation of multilayered soil, considering self-weight, time-dependent loading, and boundary time effect. The validity of the proposed solution is confirmed through comparison with existing analytical solutions and finite difference solution. Based on the proposed semi-analytical solution, this study investigates the influence of self-weight, interface parameter, soil properties, and nonlinear parameters on the consolidation characteristics of multilayered soil. The results indicate that factoring in the true distribution of self-weight leads to a faster dissipation rate of excess pore water pressure and larger settlement and settlement rate, compared to not considering self-weight. Both boundary drainage performance and soil nonlinearity have an impact on consolidation. If the boundary drainage capacity is inadequate, the influence of soil nonlinearity on consolidation diminishes.

The large-strain geometric assumptions and nonlinear compressibility and permeability have significant effects on the consolidation of soft soils with high compressibility. However, analytical solutions for large-strain nonlinear consolidation of soft soils with partially penetrating PVDs have been rarely reported in the literature. A double logarithmic model is adopted to describe the nonlinear compressibility and permeability of soft soils with high compressibility, and a large-strain consolidation model for soft soils with partially penetrating PVDs under the condition that the excess pore water pressure at the interface between the improved and unimproved layers is equal is established based on Gibson's large-strain consolidation theory. The analytical solution for the large-strain nonlinear consolidation model for soft soils with partially penetrating PVDs is obtained. The reliability of the analytical solution obtained in this study is verified by comparing it with the existing solutions under different conditions, and the maximum deviation between the two methods does not exceed 5 %. On this basis, consolidation behaviors of soft soils with partially penetrating PVDs under different conditions were analyzed by extensive calculations. Finally, the proposed analytical solution for the large strain consolidation model is applied to the settlement calculation of the Bachiem Highway Project, which further demonstrates the applicability of the consolidation model.

To comprehensively consider the impacts of stratification, residual pore water pressure, soil nonlinearity, and boundary permeability on consolidation settlement of soft soil foundations for accurate prediction, a continuous drainage boundary condition is proposed in this study that reflects the residual pore pressure under multistage loading, and a nonlinear elastic constitutive model based on the double logarithmic model is adopted to account for the nonlinear consolidation behaviour of soils. A UMAT subroutine is developed based on the proposed boundary condition and nonlinear elastic constitutive model. Subsequently, the developed subroutine is compared with the built-in linear elastic soil constitutive model in ABAQUS and engineering examples. The application of continuous drainage boundaries in stratified foundations is analysed, as well as the influence of factors such as the loading rate and soil nonlinearity on consolidation settlement. The results indicate that, compared to the built-in model, the subroutine developed in this study can be employed to more accurately calculate the nonlinear consolidation of multilayered foundations under multistage loading. By adjusting the loading rate parameter alpha k, consolidation under different loading conditions can be predicted. Additionally, the proposed boundary condition simplifies the calculations for soft soil foundations with sand layers, providing a novel computational approach for the design of construction loading schemes and long-term settlement predictions in soft soil foundations.

A simplified solution for coupled creep and nonlinear consolidation of soils has been presented based on the disturbed state concept (DSC). The nonlinearity of the problem due to the change of the material properties and thicknesses of the soil layer, and creep was considered in the proposed solution. The state of the soil before primary consolidation was considered as initially relatively intact, and after primary consolidation during the pure creep phase was considered as finally fully adjusted state. The state of the soil during the coupled creep and consolidation process was related to its relatively intact and fully adjusted states using two consolidation and creep state functions that have been derived based on the numerical solution of the problem. Using the consolidation state function, the solutions of Terzaghi's theory of consolidation in two initial and end of the primary consolidation states were interpolated to achieve the solution of the nonlinear primary consolidation phase. The creep state function was used to implement the effect of the creep deformation during and after the primary consolidation in the settlement calculations. The result of the proposed method was verified by the results of the numerical and approximate methods along with laboratory data in the literature.

Temperature changes affect the nonlinear consolidation process in soils, and there is limited associated theoretical research. In this study, the governing equations for nonlinear consolidation and thermal conduction are developed, and a mathematical model for one-dimensional nonlinear thermal consolidation in saturated clay under the impeded drainage boundary is established, where the temperature-dependent compressibility and permeability are considered. Meanwhile, the finite-difference solutions for nonlinear consolidation and the analytical solutions for thermal conduction are obtained, respectively. Furthermore, the proposed model's reasonableness is verified by comparison with other theoretical models. Based on this, the impact of several factors on nonlinear thermal consolidation behaviors is investigated. With a rise in temperature increment (Delta T), the dissipation rate of excess pore water pressure (EPWP) accelerates in the later consolidation stage, and the final settlement becomes larger. In addition, the EPWP dissipation rate grows remarkably with an increasing impeded drainage boundary parameter (mu). In particular, the impeded drainage boundary can be degraded into a drainage boundary when the value of mu becomes large (e.g., mu = 100 m-1). Increasing preconsolidation pressure (pcR) results in a reduction in settlement, and the maximum values of EPWP decline with a rising linear loading time (tc). Overall, this study contributes to the accurate prediction of the nonlinear consolidation process taking the thermal effect into account. This study might provide a basis for the analysis of soil consolidation features in geotechnical projects that involve thermal effects, which have been growing in number in recent decades. For instance, an approach that combines thermal treatment with surcharge preloading has started to be employed for soft soil reinforcement. When this method is used in practical engineering projects, the changes in EPWP and settlement can be predicted based on the model developed in this study. In addition, this study reveals that increasing the temperature by 60 degrees C can lead to an increase in the final settlement of saturated clay by approximately 25%, compared with ambient temperature treatment. Besides, compacted clay, which typically serves as a bottom engineering barrier, might be subject to consolidation deformation due to varied temperatures and external loading. The model presented could contribute to properly predicting the porosity change in compacted clay under this scenario.

The implementation of composite piles has emerged as an appealing technology for reinforcing soft ground through fulfilling the requisite bearing capacity and facilitating consolidation. Nonetheless, previous investigations into the consolidation behavior of composite pile-improved ground have neglected the nonlinearity of soil compression and permeability. In this context, the logarithm models of e-lgcr and e-lgk are introduced to establish an analytical model for the nonlinear consolidation of composite ground with composite piles. Based on equal strain assumption and annular equivalent method, detailed solutions under four special loading schemes are then obtained. Additionally, a comprehensive analysis is conducted to assess the influence of various parameters on the nonlinear consolidation behavior of composite ground, and the feasibility of current model is verified by degenerations. The results show that ignoring the nonlinearity will lead to an overestimation of consolidation rate when the soil's compression indices exceed the permeability indices. Moreover, the consolidation rate of composite ground is inversely proportional to cru/cr ' s0 and Cc/Ckh(v), while demonstrating a direct proportionality to Ksp, Ksg, and kg/kv0. However, cru/cr ' s0 mainly influences excess pore water pressure at the upper layer, and the influence of Cc/Ckv on the consolidation rate is limited and can even be ignored in comparison to Cc/Ckh. Finally, the proposed model is successfully applied to an engineering project in situ, where the obtained results exhibit a noteworthy agreement with the measured data.