Study on Variation Regularity of Adhesion Strength of Cohesive Soil Considering Pressure and Temperature Effects
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 investi-gate the variation regularity of adhesion strength of cohesive soil under different vertical pressures and interface tem-peratures,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 adhe-sion strength of the soil.The main factors affecting moisture tension are the number of contact water rings,tempera-ture,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.
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