砾粒掺入对黏土断裂韧度的影响

以探究土体断裂韧度特性为目的,采用改进后的标准三点弯曲试验,消除了自重对试验结果的影响,在掺入不同含量和不同粒径大小的砾粒的情况下,制备相同含水率、干密度和初始裂缝的试样,测试其断裂韧度的变化以及观察裂缝扩展规律.结果表明:当掺入砂砾含量在0%~20%的时候,断裂韧度随着砂砾含量的增高而逐渐降低;当掺入砂砾的粒径在2~40mm的时候,在相同砂砾含量情况下,其断裂韧度随着掺入粒径的增加而增加;当掺入砂砾的粒径在0.75~2mm的时候,在相同砂砾含量情况下,其粒径大小对断裂韧度值没有明显影响;掺入颗粒的粒径大小会影响裂缝的扩展方向和发育数量,与掺入粗砾的试样相比较,掺入细砂的试样在裂缝区域更易于出现细小的网状裂纹,而掺入粗砾试样中的裂缝在扩展过程中更容易出现弯折现象.

The Influence of Gravel Mixed to Fracture Toughness of Clay

In order to explore the fracture toughness characteristic of soil,based on the improved standard three-point bending tests,affect of geostatic stress to the test results had been removed.Mixing soil with gravel of different content and different particle size to produce specimens which has the same moisture content,dry density and the initial crack,to study the variety of fracture toughness and propagation rules of crack.The result shows that while gravel content is between 0% and20%,the fracture toughness decreases as the gravel content increases.When particle size is between 2mm and 40 mm,with the same gravel content,fracture toughness decreases at a lower rate as the gravel particle size increases.When particle size is between 0.75 mm and 2mm,the partical size of gravel had no significant effect on the fracture toughness.The result also proved that the particle size had impact on the directions and number of crack.Compared with coarse particle,specimens with fine particle will had more tiny reticulate crack at crack region.Specimens with coarse particle had bending phenomenon more easier in the developing process of crack.