粗粒土静止侧压力系数试验

Experimental study of at-rest lateral pressure coefficient of coarse-grained soil

对某土石坝地基覆盖层2种级配的砂卵砾石料进行大型单向压缩试验,试验中,土压力盒基于标定方法提供的参数得到试样内的水平应力和垂直应力,进而计算其静止侧压力系数K_0。研究水标法和砂标法对粗粒土的适用程度,探讨K_0试验结果的可靠性;分别对2种级配土料进行中三轴CD试验,测定土料的有效内摩擦角,然后依据相关经验公式计算K_0,验证经验公式的有效性。结果表明:砂标法对于粗粒土来说是一种较可靠的标定方法;在竖向应力足够大时,K_0试验误差可以忽略不计,所测定的K_0接近实际值;Federico基于Terzaghi的已激发有效摩擦角概念而推导出的有效内摩擦角与静止侧压力系数之间的关系式较适合粗粒土。

A large-scale uniaxial compression test was conducted for two types of graded sand-grained materials from the overburden of a dam. The horizontal stress and vertical stress of sand- grained materials were measured using soil pressure boxes with parameters obtained from a calibration method,and then the at-rest lateral pressure coefficient（ K_0） was calculated. By studying the applicability of the hydraulic and sand calibration methods,the reliability of the experimental results of K_0 was analyzed. The results show that the sand calibration method is a reliable calibration method for coarse-grained soil. When the vertical stress is large enough,the experimental error of K_0 can be ignored,and the value of K_0 is close to the actual value. The triaxial CD test was conducted for two types of graded sand- grained materials to measure the effective angle of internal friction,and then K_0 was calculated through the relevant empirical formula and compared with the test value to obtain an empirical formula that is suitable for coarse-grained soil. The results show that the relationship expression between the at-rest lateral pressure coefficient and the effective angle of internal friction,which was proposed by Federico and was based on the concept of a mobilized effective angle of internal friction proposed by Terzaghi,is appropriate for coarse-grained soil.