Accurately predicting stress-strain characteristics is crucial to ensuring the regulated capacity and controlled deformation of the tubes during and after construction. However, research on the shear strength of geotextile tubes under surcharge loading, especially after dewatering, is insufficient. This study proposes an analytical model with a Stress-State Boundary (SSB) and Yield Function to comprehensively describe the stress-strain behavior of Load-Bearing Geotextile Tubes (LGTs). The SSB is designed to predict the initial state of stress in the infill soil prior to load application, while the Yield Function is formulated to express the shear stress path experienced by the LGT before fabric failure. The model considers various factors that affect LGT behavior, including diverse soil mechanical parameters, nonlinear fabric stiffness, initial tension due to self-weight and principal stress axes rotation. Results show that a decrease in Poisson's ratio corresponds to an increase in failure stress. Moreover, it was demonstrated that the axial failure strain can be influenced by the geotextile linear or nonlinear behavior. Notably, the study highlights that tube height and inclination angle significantly affect the geotextile's confining effect. Beyond theoretical contributions, the analytical model serves as a valuable tool for optimizing geotextile tube design and execution, contributing to project success and longevity through enhanced structural stability.

A series of direct shear tests under constant normal loading conditions were carried out on specimens of bolted sandstone single-joint treated with different numbers of dry-wet cycles. The experimental results show that the peak shear strength and shear stiffness of bolted sandstone joints were significantly reduced after 12 dry-wet cycles. The decrease in the shear strength of rough joints is more significant than that of flat joints. Due to the decrease in the strength of the surrounding rock, the deformation characteristics of the bolts are significantly affected by the number of dry-wet cycles performed. With an increase in the number of dry-wet cycles, the plastic hinge length of the bolt gradually increases, resulting in an increase in the corresponding shear displacement when the bolt breaks. Compared with the tensile-shear failure mode of the bolts in flat joints, the tensile-bending failure mode arises for bolts in rough joints. A shear curve model describing the whole process of bolted rock joints is established based on the deterioration of rock mechanical parameters caused by dry-wet cycles. The model proposed considers the change in the friction angle of the joint surface with the shear displacement, which is applied to the derivation of the model by introducing the dynamic evolutionary friction angle parameter. The reasonably good agreement between a predicted curve and the corresponding experimental curve indicates that this method can effectively predict the shear strength of a bolted rock joint involving rough joint under dry-wet cycling conditions. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting 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/).

In practical scenarios, tunnels may unavoidably cross active fault zones, leading to potentially severe damage by active fault displacement during earthquakes. Previous studies have failed to clearly establish an analytical method that considers both compressive and frictional behavior between tunnels and the soil that surrounds them, hindering the understanding of the tunnel -soil interaction. To address this, a finite element model (FEM) has been developed in this study to investigate the compressive and frictional characteristics of the tunnel -soil interaction of a reverse active fault -crossing tunnel. The model identifies six distinct zones of tunnel -soil interaction, namely, two active zones, two passive zones, and two separation zones. Building on these findings, the active fault -tunnel system was divided into three equivalent sub -systems, and an analytical method was established by creating and then combining equations for each sub -system. By applying the Pasternak Elastic Foundation Beam theory and Elastic theory, an analytical method is introduced that can simultaneously consider the distributed non-linear compressive interactive stress and non-linear frictional interactive stress. The results of the analytical method were validated with the FE results under three series of geological conditions. Through a quantitative examination of the similarity ratio and length of influence, the analytical results were seen to effectively reflect the characteristics of the soil -tunnel interaction and exhibit a good agreement with the FE results. It is concluded that the analytical model will serve as a computational reference for the design of reverse active fault -crossing tunnels.

To date, few models are available in the literature to consider the creep behavior of geosynthetics when predicting the lateral deformation (delta) of geosynthetics-reinforced soil (GRS) retaining walls. In this study, a general hyperbolic creep model was first introduced to describe the long-term deformation of geosynthetics, which is a function of elapsed time and two empirical parameters a and b. The conventional creep tests with three different tensile loads (P-r) were conducted on two uniaxial geogrids to determine their creep behavior, as well as the a-P-r and b-P-r relationships. The test results show that increasing P-r accelerates the development of creep deformation for both geogrids. Meanwhile, a and b respectively show exponential and negatively linear relationships with P-r, which were confirmed by abundant experimental data available in other studies. Based on the above creep model and relationships, an accurate and reliable analytical model was then proposed for predicting the time-dependent delta of GRS walls with modular block facing, which was further validated using a relevant numerical investigation from the previous literature. Performance evaluation and comparison of the proposed model with six available prediction models were performed. Then a parametric study was carried out to evaluate the effects of wall height, vertical spacing of geogrids, unit weight and internal friction angle of backfills, and factor of safety against pullout on delta at the end of construction and 5 years afterwards. The findings show that the creep effect not only promotes delta but also raises the elevation of the maximum delta along the wall height. Finally, the limitations and application prospects of the proposed model were discussed and analyzed.

The degradation of near-surface permafrost under ongoing climate change on the Qinghai-Tibet Plateau (QTP) is of growing concern due to its impacts on geomorphological and ecological processes, as well as human activities. There is an increased need for an in-depth understanding of the evolution of permafrost temperature (Ttop) and active-layer thickness (ALT) at a fine scale on the QTP under climate change. This study evaluated the permafrost thermal development over the QTP for the period 1980-2100 at a 1 km(2) scale using a physically analytical model accounting for both climatic and local environmental factors based on multi-source data. The model results were validated against thermal borehole measurements and baseline maps. The modeled current (2001-2018) permafrost area (Ttop <= 0 degrees C) covers 1.42 x 106 km(2) (ca. 56.1% of the QTP land area), 10.1% of which thawed over the historical period 1981-2000. To assess how the ground thermal regime could develop in the future, we utilized the multi-model ensemble mean of downscaled outputs from eight climate models under three Shared Socio-economic Pathways (i.e., SSP126, 245, and 585) in CMIP6 to force the permafrost model. Model results suggest that the current (2001-2018) permafrost extent is likely to dramatically contract in the future period (2021-2100), as indicated by consistent Ttop warming and ALT increasing due to climate changing. About 26.9%, 59.9%, 80.1% of the current permafrost is likely to disappear by the end of the 21st century under SSP126, SSP245, and SSP585 scenarios, respectively. The simulation results may further provide new opportunities to assess the future impacts of climate warming on environments and engineering development over the QTP.

A physically based one-dimensional sharp-interface model of active layer evolution and permafrost thaw is presented. This computationally efficient, semianalytical, nonequilibrium solution to soil freeze-thaw problems in partially saturated media is proposed as a component of hydrological models to describe seasonal ground ice, active layer evolution, and changes in permafrost temperature and extent. The model is developed and validated against the analytical Stefan solution and a finite volume coupled heat and mass transfer model of freeze-thaw in unsaturated porous media. Unlike analytic models, the interface model provides a nonequilibrium solution to the heat equation while permitting a wide range of temporally variable boundary conditions and supporting the simulation of multiple interfaces between frozen and unfrozen soils. The model is implemented for use in discontinuous permafrost peatlands where soil properties are highly dependent on soil ice content and infiltration capacity is high. It is demonstrated that the model is suitable for the representation of variably saturated active layer and permafrost evolution in cases both with and without a talik.