宽级配砾质土快速三轴固结排水剪试验影响因素研究

On influencing factors of quick consolidated-drained triaxial tests of widely-graded gravelly soils

宽级配砾质土是由砾石料和黏土料按一定比例混合而成,其具有压缩性低、抗剪强度大等特点,目前常作为土石坝心墙料或路基填料而得到广泛应用。由于宽级配砾质土渗透系数较小,在常规三轴固结排水剪(CD)试验中固结排水较慢,导致其试验周期很长。为了提高固结排水的效率,可采用一种在试样中心加圆柱形砂芯的快速三轴CD试验方法。基于快速三轴CD试验,通过变化不同砂芯类别、不同砂芯直径、不同掺砾量等各因素,全面研究了各因素对宽级配砾质土快速三轴CD试验的影响。研究结果表明,快速三轴CD试验方法能够有效加快试样排水固结,从而加快整个试验进程;砂芯类别、砂芯直径、掺砾量等因素均对试验固结排水速度和剪切过程应力应变产生不同程度影响;砂芯直径越小,其试验成果与无砂芯试样越接近。

Widely-graded gravelly soil is composed of gravelly and clayey material in a certain proportion. It has the characteristics of low compressibility and high shear strength. At present, it is widely used as the core material for embankment dams and subgrade filling. Due to the low permeability of well-graded gravelly soil, the consolidation process is slow in conventional consolidateddrained(CD) triaxial tests, resulting in a long test period. In order to improve the efficiency of consolidation process, a quick triaxial CD test method with cylindrical sand core in the center of specimen is proposed in this paper. A comprehensive study on the influence of various factors on the quick triaxial CD test of well-graded gravelly soils is performed by changing types of sand cores, diameters of core sand cylinder and gravel contents. Results show that the proposed quick triaxial CD test method can effectively accelerate the consolidation process of the specimen, thus speeding up the whole test. Various factors including type of sand core, diameter of core sand cylinderand gravel content show different levels of influence on the speed of consolidation process and the stress-strain curve in the subsequent shearing stage. The smaller the diameter of the sand core is, the closer the test results are to those of specimens without sand cores.