The unified hardening model for clays and sands (CSUH) can adequately represent the stress-strain characteristics of various soil types. However, being an incremental elastoplastic constitutive model, the CSUH model requires extensive iterative computations during parameter identification, resulting in significant computational time. To improve computational efficiency, this study derives the elastoplastic compliance matrix and stress-strain incremental relationships under different stress paths, eliminating the repeated solving of equations typically required during iterative processes. Furthermore, a dynamic step size iterative method is proposed based on the changing slope characteristics of the stress-strain curves. This method divides the total axial strain into two segments: in the initial segment (approximately the first 30% of total strain), where the curve slope is steep, smaller step sizes with arithmetic progression distribution are employed, while in the latter segment (approximately the remaining 70%), characterized by a gentle curve slope, larger and uniformly distributed step sizes are adopted. Comparative analyses between the proposed dynamic step size method and the traditional constant-step iterative method demonstrate that, under the premise of ensuring calculation accuracy, the dynamic step size method significantly reduces the iteration steps from 3000 to 50, thus decreasing the computational time by approximately 47 times. Finally, the proposed method is applied to parameter identification of Fujinomori clay, calcareous sand, and Changhe dam rockfill materials using the CSUH model. The predictions closely match experimental results, confirming the CSUH model's capability in accurately describing the mechanical behaviors of different soils under various stress paths. The dynamic step size iterative approach developed in this study also provides valuable insights for enhancing computational efficiency and parameter identification of other elastoplastic constitutive models.

Given the crossing-obstacle problems of wheeled vehicle on soft beaches, the changing rules with driving speeds of the crossing-obstacle ability of wheeled vehicle, soil moisture content, and soil type on soft beach ground were innovatively studied in this paper, with the hook traction force taken as the evaluating index. It showed that the RMS values of wheeled vehicle hook traction force, which was 9484N at 5 km/h and 8859N at 20 km/h, decreased with the increase in driving speed when the wheeled vehicle crossed the horizontal ditch. It collected soft beach ground soil samples and tested the parameters of mechanical properties. By considering specific structural parameters of the wheeled vehicle, this paper constructed the simulating model of the crossing obstacle ability of wheeled vehicle on the soft beach, analyzed the differences between the simulation and test result through full-scale vehicle tests. It discussed the influential factors of the crossing obstacle ability of wheeled vehicle on soft beach ground, indicated that the crossing obstacle ability of wheeled vehicle on soft beach increased with the increase of equipment's driving speed and soil moisture content. This paper creatively proposed a method to evaluate the equipment's off-road trafficability based on the combination of soil in-situ collection, soil tank test, dynamic simulation and experimental verification, and proposed the influencing factors and changing rules of equipment's off-road trafficability on soft beach ground, which laid a theoretical foundation for the research on the off-road trafficability of wheeled vehicle.

After landing in the Utopia Planitia, Tianwen-1 formed the deepest landing crater on Mars, approximately 40 cm deep, exposing precious information about the mechanical properties of Martian soil. We established numerical models for the plume-surface interaction (PSI) and the crater formation based on Computational Fluid Dynamics (CFD) methods and the erosion model modified from Roberts' Theory. Comparative studies of cases were conducted with different nozzle heights and soil mechanical properties. The increase in cohesion and internal friction angle leads to a decrease in erosion rate and maximum crater depth, with the cohesion having a greater impact. The influence of the nozzle height is not clear, as it interacts with the position of the Shock Diamond to jointly control the erosion process. Furthermore, we categorized the evolution of landing craters into the dispersive and the concentrated erosion modes based on the morphological characteristics. Finally, we estimated the upper limits of the Martian soil's mechanical properties near Tianwen-1 landing site, with the cohesion ranging from 2612 to 2042 Pa and internal friction angle from 25 degrees to 41 degrees. (c) 2024 Published by Elsevier B.V. on behalf of China University of Mining & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Riverbank instability in the seasonally frozen zone is primarily caused by freeze-thaw erosion. Using the triaxial freeze-thaw test on the bank of Shisifenzi Bend in the Yellow River of Inner Mongolia, we investigated the changes in the mechanical properties of the soil at different freezing temperatures and freeze-thaw times, and analyzed the bank's stability before and after freezing based on the finite element strength reduction method. The results showed that the elastic modulus, cohesion, internal friction angle and shear strength of the soil tended to decrease with the increase in the number of freeze-thaw cycles and the decrease in freezing temperature. After 10 freezing cycles at - 5 degrees C, -10 degrees C, -15 degrees C and -20 degrees C, the modulus of elasticity of soil decreased by 40.84 similar to 68.70%, the cohesion decreased by 41.96 similar to 56.66%, the shear strength decreased by 41.92 similar to 57.32%, respectively. Moreover, the stability safety coefficient of bank slope decreased by 18.58% after freeze-thaw, indicating that the freeze-thaw effect will significantly reduce the stability of bank slope, and the bank slope is more likely to be destabilized and damaged after freeze-thaw.

In-situ leaching (ISL) has gained prominence as a non-destructive method for rare earth element (REE) extraction, particularly in regions like China. However, concerns over the environmental impact and soil stability due to ISL activities have surfaced following a landslide incident. This article distills the essence of a comprehensive research endeavor that delves into the effects of ammonium sulfate ISL leaching, employing concentrations of 0.05M, 0.1M, and 0.5M, on soil mechanical properties. The study encompasses physicochemical, physical, and mechanical tests, unveiling substantial alterations in shear strength, cohesion, angle of internal friction, zeta potential, liquid limit, plastic limit, and plasticity index following leaching. XRF and XRD analyses reveal the presence of REEs and distinctive mineral phases in the soil samples. Overall, ISL induces a weakening of the soil, raising concerns about potential slope failures and emphasizing the need for a deeper understanding of ISL's impact on soil properties in the context of REE mining.