Given the frequent occurrence of expansive soil slope failures during rainy season, in situ borehole shear tests were conducted to investigate how loading-added modes and rainfall conditions affect the shear strength parameters of expansive soils. The results obtained were used to analyze an actual engineering project under various construction practices and depths of rainfall infiltration, with the goal of elucidating the mechanisms behind expansive soil landslides. The test results indicate that rainfall infiltration leads to a significant reduction in cohesive force, while the internal friction angle decreases slightly. Cohesive force increases linearly with greater preload pressures, whereas the internal friction angle decreases linearly as preload pressure increases. Numerical simulations revealed that rainfall-induced sliding occurs at shallow depths along a broken-line sliding surface. For unprotected expansive soil cut slopes, the safety factor experiences a sharp decline as the depth of rainfall infiltration increases. Timely support measures significantly enhance slope stability; however, the supporting load can mitigate the softening effect only up to a certain extent. Additionally, two methodologies for selecting preload pressures in practical engineering applications have been proposed.

Virtual reality technology can provide the public with an immersive sense of participation, promote the public's cognition and evaluation of urban design, and has application value in the field of public participation in urban design. However, there are still some problems in the application of VR in public participation in urban design, such as the weak theoretical basis, which limits its application and promotion. The purpose of this study is to supplement the research on the theoretical basis and application methods of VR application in the field of public participation in urban design, try to build a method with theoretical basis, which can meet the two-way balance of public participation, and guide the effective application of VR in the field of public participation in urban design. VR can support the public to recognize the meso and micro scale content of urban design, and has the advantages of cognition, evaluation and mobilization of participation enthusiasm. This paper summarizes the rules of VR application in public participation in urban design, and verifies some application rules through public participation experiments.

Expansive soils are prone to strength degradation after rainfall, yet conventional slope stability analyses often rely on laboratory-derived shear strength parameters that may overestimate in-situ conditions. This study evaluates and compares the shear strength of expansive soils using the borehole shear test (BST), laboratory direct shear test (DST), and consolidated undrained test (CUT) under natural and flooding conditions. Results show that shear stress- shear displacement (or axial strain) curves generally exhibit weak hardening characteristics. Significant reductions in cohesive strength occur after flooding. The cohesive force obtained by DST and BST decreases by 18.2 kPa and 13.1 kPa after flooding respectively, while the internal friction angle decreases slightly within 3°. Laboratory tests consistently yield higher strength parameters than BST, while flooding BST values closely align with those measured on actual slip surfaces. Numerical modeling of an unstable cut slope confirms that using flooding BST parameters produces more realistic safety factors. The findings highlight the importance of incorporating in-situ testing under representative moisture conditions for reliable slope stability design in expansive soils.

The interaction between salt solutions and expansive soils is critical for engineering in chemically aggressive environments. However, the effect of iodide salts on pore water distribution in expansive soils remains poorly understood. This study investigated the transverse relaxation time (T₂) characteristics of pore water in expansive soils under varying KI concentrations (0–20%), moisture content (8.7–26.0%), and dry density (1.26–1.79 g/cm³) using nuclear magnetic resonance (NMR). All T₂ curves exhibited a single peak. Increasing moisture content from 8.7% to 26.0% resulted in increases of approximately 63% in T₂ at peak and 408–439% in peak area. Increasing KI concentration decreased both T₂ at peak by up to 33.3% and peak area by up to 44.0% within the tested range, attributed to diffuse double-layer compression and signal loss. Increasing moisture content broadened the T₂ distribution and linearly increased T₂ at peak and peak area, indicating water gradually occupied larger pore spaces as moisture content rose. T₂ at peak was independent of dry density, while the peak area showed a linear relationship with dry density, consistent with mass balance. The observed systematic linear relationships among T₂ at peak, peak area, and the three experimental variables suggest that NMR is a promising tool for the quantitative assessment of salt solution effects on pore water in expansive soils. These findings provide a theoretical basis for evaluating salt-affected expansive soils in coastal and arid regions.