In engineering practice, properly characterizing the spatial distribution of soil liquefaction potential and induced surface settlement is essential for seismic hazard assessment and mitigation. However, geotechnical site investigations (e.g., cone penetration test (CPT)) usually provide limited and sparse data with high accuracy. Geophysical surveys provide abundant two-dimensional (2D) data, yet their accuracy is lower than that of geotechnical investigations. Moreover, correlating geotechnical and geophysical data can effectively reduce site investigation costs. This study proposes a data-driven adaptive fusion sampling strategy that automatically develops an assessment model of the spatial distribution of soil liquefaction potential from spatially sparse geotechnical data, performs monitoring of liquefaction-induced settlement, and integrates spatiotemporally unconstrained geophysical data to update the model systematically and quantitatively. The proposed strategy is illustrated using real data, and the results indicate that the proposed strategy overcomes the difficulty of generating high-resolution spatial distributions of liquefaction potential from sparse geotechnical data, enables more accurate judgment of settlement variations in local areas, and is an effective tool for site liquefaction hazard analysis.
The undrained shear strength of clay is an important index for the calculation of the bearing capacity of the foundation soil, the calculation of the soil pressure of the foundation pit, and the analysis of the slope stability. Therefore, the purpose of this paper is to conduct a comprehensive study of the combined use of machine learning with clay theoretical equations to estimate it. Under the Bayesian framework, the CatBoost algorithm (CatBoost–Bayesian) based on Bayesian optimization algorithm was developed to obtain the feature importance level of soil parameters affecting the undrained shear strength of clay, so as to adaptively couple the theoretical equation of undrained shear strength of K0 consolidated clay, which was derived from the modified Cambridge model. Then, the theoretical equation of undrained shear strength of the isotropically consolidated clay was established from the critical state of the clay parameters. Finally, it was illustrated and verified using the experimental samples of Finnish clay. The results indicate that the theoretical equation established by the overconsolidation ratio and effective overburden pressure parameters can well estimate the undrained shear strength of isotropically consolidated clays, and the parameter uncertainty can be considered explicitly and rigorously.
The phyllite-weathered soil is a regional speciality. It is essential to study the changes in shear strength of phyllite-weathered soil under dry-wet cycles to understand the changes in mechanical properties of phyllite-weathered soil in the process of dry-wet climate and to manage the slope of phyllite-weathered soil. This paper simulated 12 dry-wet cycles on the specimens of remodelled phyllite-weathered soil. Direct shear and SEM tests were conducted on the specimens in the 0th, 3rd, 6th, 9th, and 12th drying paths. The effects of moisture content and the number of dry-wet cycles on the shear strength of phyllite-weathered soil were analysed macroscopically and microscopically. The following conclusions were obtained: (1) The cohesion of the weathered soil of phyllite will be reduced by increasing the number of cycles, and the more the number of dry-wet cycles, the more pronounced the reduction; the internal friction angle of the weathered soil of phyllite will be reduced by increasing the number of cycles, but the pattern of the decrease in the internal friction angle is not obvious. (2) The increase in the number of dry-wet cycles will increase the stiffness and brittleness of the phyllite-weathered soil specimen, and it will change from the weak hardening type of plastic damage to the solid softening type of brittle damage after a certain number of cycles. (3) The SEM test found that phyllite-weathered soil particles in Longsheng, Guilin are large, and most of the particles are in face-to-face and angle-to-face contact, which is easy to form a hollow structure, and the dry density value of the soil in the natural state is small. At the same time, the soil is reddish-brown in colour because of the leaching of Fe2 O3. The shear strength index of the cemented phyllite-weathered soil with Fe2 O3 is more significant than that of phyllite-weathered soil in other areas. The soil has a good shear strength index and a small dry density.
To understand the performance of ecological pervious concrete prepared with mixed sandstone/limestone aggregates, limestone and sandstone were used as two aggregates. The sandstone-to-limestone volume ratio was calculated in 0 : 1, 0.25 : 0.75, 0.5 : 0.5, 0.75 : 0.25, and 1 : 0 in coarse aggregate to prepare ecological pervious concrete specimens. The compressive test, water permeability test, cooling test, evaporation test, alkaline test, and scanning electron microscope (SEM) tests were carried out with qualified compressive strength as the indicator to determine the optimum sandstone-to-limestone volume ratio for the ecological pervious concrete. The results show that the water permeability, cooling property, and evaporation property of the ecological pervious concrete increase with the sandstone content. When the sandstone-to-limestone volume ratio is less than 0.32 : 0.68 (the substitution rate of sandstone for limestone in ecological pervious concrete is 32%), the strength of ecological pervious concrete meets the requirements of 5 MPa and achieves the best permeability coefficient of 9 mm/s. This realizes the full use of net water storage and cooling capacity of the ecological pervious concrete and makes the ecological pervious concrete meet the construction requirement of slope protection in sponge cities in the south.
To explore the effect and applicability of contour reverse slope terraces in water and soil conservation of karstic red clay soil area in northern Guangxi, rainfall simulation experiments were conducted on bare red clay soil slopes laid with contour reverse slope terraces to find the erosion pattern in response to different rainfall intensities (15, 30, and 50 mm/h) and bedrock porosities (1%, 3%, and 5%). The results showed that contour reverse slope terraces can change the spatial distribution of surface runoff, divert surface runoff to the underground, and increase underground sediment yielding. It is found that contour reverse slope terraces can effectively reduce surface soil erosion though it still remains dominant erosion for red clay terraced farmland, with surface runoff reduced by 71%, 52%, and 46% and surface sediment loss reduced by 70%, 65%, and 63%, respectively, when the rainfall intensity is set at 15 mm/h, 30 mm/h, and 50 mm/h. It is concluded that contour reverse slope terraces can help reduce water and soil erosion of red clay terraced farmland in northern Guangxi.
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