Zhao Rongfei, Liu Xincheng, Li Qi, Jin Dan, Gao Wei
College of Water Conservancy, Shenyang Agricultural University, Shenyang, 110866, Liaoning, China.
College of Engineering, Shenyang Agricultural University, Shenyang, 110866, Liaoning, China.
Sci Rep. 2024 Aug 22;14(1):19478. doi: 10.1038/s41598-024-68935-1.
The freezing and thawing cycle is one of the primary causes of damage and instability to buildings in seasonal frost regions. During this process, the mechanical properties of soil are affected, leading to settlement, cracking, or deformation of infrastructure. Mitigating or reducing the occurrence of building frost damage in seasonal frost regions has become an important subject of study. Freeze-thaw (F-T) action will influence the distribution of moisture inside the reinforced soil and change the strength of thawing soil, which is closely related to the main influencing factors, such as initial moisture content, compaction degree, reinforced spacing, number of freeze-thaw cycles (FTC), freezing temperature, and effective vertical stress. Cohesion is an important index to determine the shear strength of clay, which is important to analyze the change in cohesion after F-T. Meanwhile, cohesion is closely related to soil moisture content. This study conducted orthogonal experiments on these primary influencing factors (6 factors at 5 levels) through FTC tests, triaxial tests, and moisture content tests to determine the undrained cohesion and moisture content of the clay after FTC, thereby establishing the influence of reinforcement on soil strength under freeze-thaw conditions. Based on the experimental results, SPSS software was used to fit the regression equations of undrained cohesion and moisture content expressed by the main influencing factors at different heights of the clay. Optimization options for the main influencing factors were obtained with Matlab software when the highest undrained cohesion values 6.8, 10.6, 8.9 kPa and lowest moisture content values 24.0%, 24.3%, 26.2% appeared in upper, middle and lower parts of the testing clay structure respectively, in conditions of - 15 °C freezing temperature and 5 times FTC. And determined the optimal combinations of moisture content, reinforcement spacing, compaction density, and vertical load at different heights. Decreasing reinforced spacing in silty clay was beneficial for liquid underwater seepage after F-T. The redistribution of internal moisture in the soil sample strengthened its undrained cohesion, thereby increasing the soil's shear strength. Comparing reinforcement conditions at different locations, it was found that when there were 3 layers of reinforcement with a spacing of 150 mm between them, this spacing was optimal. It played a significant role in improving the soil's shear strength and enhancing its bearing capacity. For reinforced clay itself, the order of the main factors influencing the undrained cohesion of soil after F-T, from high to low, was initial moisture content, reinforced spacing, and compaction degree.
冻融循环是季节性冻土地区建筑物损坏和不稳定的主要原因之一。在此过程中，土壤的力学性能受到影响，导致基础设施沉降、开裂或变形。减轻或减少季节性冻土地区建筑物冻害的发生已成为一个重要的研究课题。冻融（F-T）作用会影响加筋土内部水分的分布，并改变融化后土的强度，这与初始含水量、压实度、加筋间距、冻融循环次数（FTC）、冻结温度和有效垂直应力等主要影响因素密切相关。黏聚力是确定黏土抗剪强度的一个重要指标，分析冻融后黏聚力的变化很重要。同时，黏聚力与土壤含水量密切相关。本研究通过冻融循环试验、三轴试验和含水量试验，对这些主要影响因素（6个因素，5个水平）进行正交试验，以确定冻融循环后黏土的不排水黏聚力和含水量，从而确定冻融条件下加筋对土壤强度的影响。基于试验结果，利用SPSS软件拟合黏土不同高度处主要影响因素表示的不排水黏聚力和含水量的回归方程。当在-15℃冻结温度和5次冻融循环条件下，试验黏土结构上部、中部和下部分别出现最高不排水黏聚力值6.8、10.6、8.9kPa和最低含水量值24.0%、24.3%、26.2%时，用Matlab软件得到主要影响因素的优化方案。并确定了不同高度处含水量、加筋间距、压实密度和垂直荷载的最优组合。在粉质黏土中减小加筋间距有利于冻融后液体的水下渗流。土样内部水分的重新分布增强了其不排水黏聚力，从而提高了土的抗剪强度。比较不同位置的加筋条件，发现当有3层加筋且层间距为150mm时，该间距为最优。它在提高土的抗剪强度和增强其承载能力方面发挥了重要作用。对于加筋黏土本身，冻融后影响土不排水黏聚力的主要因素从高到低依次为初始含水量、加筋间距和压实度。
