制样方法对非饱和压实黄土强度变化影响的试验研究

Experimental Research on the Effect of the Sample Preparation Methodson the Strength Change of the Unsaturated Compacted Loess

摘要:

为研究不同制样方法对非饱和压实黄土抗剪强度指标的影响规律，进行不同干密度压实土在预湿及加湿两种制样方法下的剪切试验研究。结果表明：预湿制样试验中，存在一个临界含水率影响着试验黄土的黏聚力、摩擦角，当试样的含水率低于临界含水率时，抗剪强度随含水率增加而提高，而当含水率高于临界含水率时，抗剪强度随含水率的增加而降低；抗剪强度指标总体随试样干密度的增大而增大。加湿制样试验中，随着试样含水率的增加，黏聚力连续降低，摩擦角随含水率的增加先提高后降低，对比预湿试样而言，含水率对摩擦角的折减程度降低。可以看出制样方法对非饱和压实黄土黏聚力的影响特征比较突出，当含水率低于临界含水率时加湿试样的黏聚力比预湿试样大，而当含水率高于临界含水率时预湿试样的黏聚力较高，认为加湿试样存在类似"木桶效应"，而预湿试样则与试样整体水平有关。研究结果对于进一步加深非饱和黄土抗剪强度指标的适用性研究具有一定参考价值。

Abstract:

The shear tests of compacted loess with different dry densities were conducted using two different sample preparation methods (pre-humidification and humidification) to study their influence on the shear strength index of the unsaturated compacted loess. The results of this study exhibit the presence of critical moisture content that affects the cohesion and friction angle of the loess in the pre-wetting sample preparation test. When the moisture content of the sample was lower than the critical moisture content, the shear strength increased with increasing moisture content; however, when the moisture content of the sample was higher than the critical moisture content, the shear strength decreased with increasing moisture content. Further, the shear strength index generally increased with the increasing dry density of the sample. During the wetting sample preparation test, the cohesion continuously decreased with increasing moisture content, and the friction angle initially increased and subsequently decreased with increasing moisture content. When compared with the pre-wetting sample, the reduction degree of the moisture content to the friction angle decreased. It can be observed that the sample preparation method significantly influences the cohesion of the unsaturated compacted loess. When the moisture content of the sample was lower than the critical moisture content, the cohesion of the wetting sample was larger than that of the pre-wetting sample; however, when the moisture content of the sample is higher than the critical moisture content, the cohesion of the pre-wetting sample is larger. It can be considered that the wetting sample exhibits a similar "barrel effect"; the pre-wetting sample is related to the overall level of the sample. The research results exhibit a certain reference value for further applicability of the shear strength index of the unsaturated loess.