考虑压力、温度效应的黏性土黏附强度变化规律研究

Study on Variation Regularity of Adhesion Strength of Cohesive Soil Considering Pressure and Temperature Effects

针对土压盾构在黏性地层中掘进时普遍会遇到刀盘结泥饼的问题,对现有的直剪试验装置进行改进,设计可控升温装置,开展不同竖向压力、界面温度下不同含水率黏性土的黏附强度变化规律研究,并基于水膜理论分析黏土的黏附机理。结果表明:黏土的黏附强度由水分张力决定,水分张力越大,则土的黏附强度越大;影响水分张力的因素主要为接触水环数量、温度、基质势。试样黏土的黏附强度随着含水率的增大表现为先增大后减小的变化规律,含水率约为25%时达到黏附强度峰值;界面温度对黏土黏附强度的影响取决于接触水环数量、温度、基质势变化趋势,当接触水环数量、温度削弱黏附强度的趋势大于基质势促强黏附强度的趋势,黏土黏附强度减小;当接触水环数量、温度削弱黏附强度的趋势小于基质势促强黏附强度的趋势,黏土黏附强度变大;随着竖向压力的增大,黏附强度呈线性增长趋势。

In response to the common problem of cutter head clogging in cohesive soil layers during shield tunnelling,improvements were made to existing direct shear test devices.A controllable heating device was designed to investigate the variation regularity of adhesion strength of cohesive soil under different vertical pressures and interface temperatures,and the adhesion mechanism of clay was analyzed based on the water film theory.The results show that the adhesion strength of clay is determined by moisture tension,with greater moisture tension leading to higher adhesion strength of the soil.The main factors affecting moisture tension are the number of contact water rings,temperature,and matrix potential.The adhesion strength of test soil samples increases first and then decreases with increasing water content,reaching a peak value at approximately 25%water content.The influence of interface temperature on the adhesion strength of clay depends on the trends of changes in the number of contact water rings,temperature,and matrix potential.When the trends of weakening adhesion strength due to the number of contact water rings and temperature are greater than the trend of promoting adhesion strength due to matrix potential,the adhesion strength of clay decreases;conversely,when the trends are opposite,the adhesion strength increases.With the increase of vertical pressure,the adhesion strength shows a linear growth trend.