A novel thermo-hydro-mechanical-chemical (THMC) coupling model grounded in thermodynamic dissipation theory was established to unravel the intricate behavior of unsaturated sulfate-saline soils during cooling crystallization. The model quantifies energy transfer and dissipation during crystallization and introduces a method to calculate the amount of sulfate crystallization. It intricately captures the interdependencies between crystallization, pore water pressure, crystallization pressure and volumetric expansion, while also accounting for the dynamic feedback of latent heat from phase transitions on heat conduction. The reliability of the model was validated through experimental data. Numerical simulations explored the effects of cooling paths, thermal conductivity, initial salt content and initial porosity on the crystallization behavior and mechanical properties. The model provides theoretical support for optimizing the engineering design and facility maintenance of sulfatesaline soils.

Bridges with shallow foundations are highly susceptible to flood scouring due to their limited embedment depth and small contact area between the soil and foundation. This can lead to foundation voids, posing a serious threat to bridge safety. To prevent and mitigate scouring risks, this paper investigates the riverbed scouring characteristics of shallow foundation bridges under different hydrological conditions.The study found that under high water levels and flow velocities, scour depth significantly increased.Under extreme hydrological conditions, a horseshoe vortex forms at the base of the front end of the bridge pier, causing scour pits on both sides of the upstream face of the foundation, which is the main cause of foundation voids that first appear at 2580 s with a maximum scour depth of -2.51 m and a void area of 0.5%, continuing to increase over time.Based on simulated scouring data, this study proposes a method for converting boundary conditions from a scouring model to a mechanical model. This method utilizes point cloud reverse engineering technology to generate a riverbed surface from the three-dimensional coordinate matrix of the boundary and import it into the structural analysis field. Hydraulic effects are calculated using a CFD model and transferred to the structural domain through fluid-structure interaction technology, achieving multi-physical field coupling among water flow, soil, and structure. This method addresses the current limitations in simulating complex scouring forms in bridge flood damage research, providing reliable technical support for subsequent studies on the damage behavior of shallow foundation bridges under flood scouring conditions.

Study region: The source area of the Yangtze River, a typical catchment in the cryosphere on the Tibet Plateau, was used to develop and validate a distributed hydrothermal coupling model. Study focus: Climate change has caused significant changes in hydrological processes in the cryosphere, and related research has become hot topic. The source area of the Yangtze River (SAYR) is a key catchment for studies of hydrological processes in the cryosphere, which contains widespread glacier, snow, and permafrost. However, the current hydrological modeling of the SAYR rarely depicts the process of glacier/snow and permafrost runoff from the perspective of coupled water and heat transfer, resulting in distortion of simulations of hydrological processes. Therefore, we developed a distributed hydrothermal coupling model, namely WEP-SAYR, based on the WEP-L (Water and energy transfer process in large river basins) model by introducing modules for glacier and snow melt and permafrost freezing and thawing. New hydrological insights for the region: In the WEP-SAYR model, the soil hydrothermal transfer equations were improved, and a freezing point equation for permafrost was introduced. In addition, the glacier and snow meltwater processes were described using the temperature index model. Compared to previously applied models, the WEP-SAYR portrays in more detail glacier/ snow melting, dynamic changes in permafrost water and heat coupling, and runoff dynamics, with physically meaningful and easily accessible model parameters. The model can describe the soil temperature and moisture changes in soil layers at different depths from 0 to 140 cm. Moreover, the model has a good accuracy in simulating the daily/monthly runoff and evaporation. The Nash-Sutcliffe efficiency exceeded 0.75, and the relative error was controlled within +/- 20 %. The results showed that the WEP-SAYR model balances the efficiency of hydrological simulation in large scale catchments and the accurate portrayal of the cryosphere elements, which provides a reference for hydrological analysis of other catchments in the cryosphere.

Ground deformation induced by frost heave is a matter of concern in cold region engineering construction since it affects surrounding structures. Frost heave, which is related to the heat-water-stress interaction, is a complicated process. In this study, a heat-water-stress coupling model was established for saturated frozen soil under different stress levels to quantify the water redistribution, heat transfer, frost heave, and water intake. An empirical formula for the soil permeability considering the confining and deviator pressures was employed as an indispensable hydraulic equation in the coupling model. The Drucker-Prager yield criterion matched with the Mohr-Coulomb criterion was employed in the force equilibrium equation to investigate the deformation due to the deviator and confining pressures. The anisotropic frost heave during unidirectional freezing was further considered in the coupling model by introducing an anisotropic coefficient. Subsequently, based on the above coupling relationship, a mathematical module in COMSOL Multiphysics was applied to calculate the governing equation numerically. Finally, the proposed model was validated through an existing frost heave experiment conducted under various temperature gradients and stress levels. The results of the freezing front, water redistribution, water intake, and frost heave ratio predicted using the proposed model were found to be consistent with the experimental results.

Hydro -thermal coupling is the essence of the freeze -thaw process, and theoretical studies of this coupled process have been hot topics in the field of frozen soil. Darcy's law of unsaturated soil water flow, heat conduction theory, and relative saturation and solid -liquid ratio are based on this paper. According to the principle that the cumulative curve of particle gradation of canal foundation soil is similar to soil -water properties. A soil -water characteristic curve is derived using the cumulative particle gradation curve. VG model is then used to fit soil -water characteristic curves to obtain the canal foundation soil's hydraulic characteristic parameters, and the established hydro -thermal coupling model is modified to reflect canal foundation soil hydro -thermal evolution more objectively. A closed system one-way freezing test method is used to verify the feasibility of the proposed method in this part. The results show that the optimal parameters of the VG model of the subsoil are a = 0.06, n = 1.2, and m = 0.17, and the temperature and water fields obtained from the simulation are in good agreement with the measured data, showing the utility of the hydro -thermal coupling model in predicting hydraulic parameters. Analysis of the multi -field interaction mechanism and dynamic coupling process of the canal foundation soil during freezing and thawing. This has great importance for preventing freezing damage in canals and protecting agricultural safety.

The extended duration of mulching in Xinjiang cotton fields leads to a significant decline in the tensile strength of plastic film. When recycling is in operation, the soil and the spring teeth of the machinery used can easily cause secondary damage and fracture the residual film. Establishing appropriate working parameters for recycling is essential to enhance the overall quality of collection efforts. By analyzing the motion process of a chain-tooth residual film pickup device, we identified key working parameters that significantly impact the efficiency of recycling. Employing the finite element method (FEM) and a coupled algorithm incorporating smooth particle hydrodynamics (SPH), we developed a coupled finite element model representing the interaction among spring teeth, soil, and residual film. Through simulation and analysis of the process of inserting the spring teeth into the soil to collect film, we derived the governing rules for residual film stress and deformation changes. Utilizing forward speed, rotational angular velocity, and angle of entry into the soil of the spring teeth as test factors and selecting the residual film stress and the residual film deformation as test indices, we conducted a multi-factor simulation test. We established a mathematical model correlating test factors with test indices, and the influence of each factor on the test index was analyzed. Subsequently, we optimized the working parameters of the spring teeth. The results indicated that the optimal working parameters are forward speed of 1111.11 mm/s, rotational angular velocity of 25 rad/s, and angle of entry into the soil of 30 degrees. At these values, the average peak stress of residual film was 4.51 MPa and the height of residual film pickup was 84.48 mm. To validate the optimized the spring teeth impact on performance, field experiments were conducted with recovery rate and winding rate as test indices. The results demonstrated a 92.1% recovery rate and a 1.1% winding rate under the optimal combination of working parameters. The finite element model presented in this paper serves as a reference for designing and analyzing key components of residual film recycling machines.

A rotor vibration potato-soil separation device (RVPSD) is proposed in view of poor potato-soil separation and higher potato damage rate. Separation efficiency between potatoes and soil and the potato damage rate are selected as evaluation indicators, and a coupling simulation model of potato-soil separation based on Discrete Element Method (DEM) and Multibody Dynamics (MBD) is built up according to structure and working principle of the separation device. The optimal combination of working parameters of the RVPSD is obtained via simulation experiment. The results show that the optimal working parameters of vibration point position, conveying speed of potato-soil separation elevating chain, rotor amplitude and rotor vibration frequency are 646.5 mm, 1.08 m/s, 26.7 mm and 5.9 Hz respectively. The field validation experiment is carried out based on the optimal combination parameters. The results show that the potato-soil separation efficiency and potato damage rate of the RVPSD are 97.8 % and 1.16 % respectively, the field experiment results are basically consistent with the simulation results, which proves the correctness of the simulation model. It can provide theoretical reference for rotor vibration potato-soil separation process simulation and device parameter optimization.

Prestress loss of anchor cables can cause a change in the internal force for the support structure of a foundation pit or slope, which may cause engineering accidents. The coupling effect between an anchor cable and the creep of rock and soil is the main factor that leads to the loss of prestress of the anchor cables. However, the traditional Hooke-Kelvin (H-K) viscoelastic model could not accurately predict the long-term loss of prestress. To solve this problem, based on the H-K viscoelastic model, a new H-3K viscoelastic model was proposed, consisting of two generalized Kelvin bodies connected in parallel, and its creep equation and relaxation equation were also derived. Focusing on slope engineering in Longnan City, Gansu Province, China, the prestress of anchor cables calculated by the proposed model were compared with the monitoring data. The result that the H-K creep coupling model is more accurate in predicting prestress loss of anchor cables in the initial stage, but from a long-term perspective, the H-3K creep coupling model provided a more accurate prediction. By connecting more generalized Kelvin bodies in parallel, stress shared by the elastic body can be reduced and stress loss due to anchor cable relaxation can be approximately compensated for to make the prediction results closer to the monitored values. However, when there are more than three Kelvin bodies in parallel, the model prediction results will change only slightly. Therefore, the H-3K creep coupling model is sufficient for practical engineering.