非饱和土特性对朗肯土压力的影响

The Influence of Unsaturated Soil's Characteristics on Rankine Earth Pressure

为研究非饱和土物理力学性质,进行了粉质黏土的物性指标试验、饱和三轴试验和土-水特征曲线试验。基于Fredlund非饱和土抗剪强度准则和饱和土朗肯土压力理论,得到非饱和土土压力计算方法和公式。运用所得公式和试验成果分别研究基质吸力、地下水位和渗流状态对非饱和土土压力的影响,分析土压力变化规律。研究结果表明:基质吸力对总主动土压力、总被动土压力的作用相反,在基质吸力影响下,被动土压力变化幅度可达300 k N/m;考虑基质吸力作用时,地下水位变化对土压力影响明显增大;从蒸发到入渗状态,被动土压力下降幅度大于主动土压力增长幅度。

A series of experiments including physical properties tests, saturated triaxial tests and soil-water characteristic curve （SWCC） tests of silty clay are conducted to study the physieo-mechanical properties of unsatu- rated soil. The calculation method and formula for earth pressure of unsaturated soil are proposed on the basis of Fredlund＇ s shear strength criterion of unsaturated soil and Rankine theory of saturated soil. With the formula and test results, the influences of matrix suction, underground water level and seepage state on the earth pressure of un- saturated soil as well as the corresponding change rules of earth pressure are analyzed respectively. The research re- sults indicate ： the actions of matrix suction on the total active earth pressure and total passive earth pressure are op- posite and the amplitude of variation of the passive earth pressure can reach 300 kN/m under the effect of matrix suction; considering the action of matrix suction, the influence of the change of underground water on earth pres- sure increases obviously ; From evapotranspiration to seepage, the decrease amplitude of total passive earth pressure is greater than increasing range of total active earth pressure.