基于桩-土界面直剪试验的黏性土超孔隙水压力变化规律研究

Study on the variation of direct shearing test of pile-soil interface on excess pore water pressure in clayey soil

利用大型恒刚度直剪仪在不同的界面粗糙度和剪切速率试验条件下,施加法向应力25、50、100、150kPa,基于黏性土中桩-土界面直剪试验研究了桩-土界面超孔隙水压力变化规律.研究结果表明:剪切前超孔隙水压力受法向应力的影响,法向应力越大,超孔隙水压力越大;桩-土界面剪切过程随着法向应力的增大,超孔隙水压力逐渐增大,在高法向应力下超孔隙水压力增幅减小;界面粗糙度和剪切速率对桩-土界面剪切过程超孔隙水压力产生交互影响,在不同应力水平下界面粗糙度和剪切速率对超孔隙水压力也有不同的影响效果,高法向应力水平下随界面粗糙度和剪切速率增大超孔隙水压力增幅小于10%,低法向应力水平下增幅可达30%.因此不可以忽略界面粗糙度和剪切速率对桩-土界面剪切过程超孔隙水压力的影响.

A large-scale constant stiffness direct shearing test apparatus capable of applying normal stress 25,50,100,150 kPa, is designed and developed to study the variation of di-rect shearing test of pile-soil interface on excess pore water pressure in clayey soil under dif-ferent roughness and shearing rates. It is shown that excess pore water pressure is influenced by normal stress before shearing, higher normal stresses offer higher excess pore water pres-sure. The excess pore water pressure decreases with increasing the normal stresses during the process of shearing. The increase amplitude of excess pore water pressure decreases un-der higher normal stresses. The excess pore water pressure of pile-soil interface is influenced by both roughness and shearing rate in the process of shearing. The interface roughness and shearing rate offers different influencing effect on excess pore water pressure under different normal stresses. The increase amplitude of excess pore water pressure decreases less than 10% under higher normal stresses, the largest increase up to 30 % under lower normal stres-ses , with the increasing roughness and shear rate. So the roughness and shearing rate should be considered in the analysis of excess pore water pressure of pile-soil interface in the process of shearing.