非饱和土的抗剪强度与含水率关系的试验研究

Testing study of relationship between water content and shear strength of unsaturated soils

研究非饱和土的抗剪强度及其随含水率的变化规律,对工程实践具有重要意义。在总结前人试验研究成果的基础上,以欠固结的第三系粉砂土为研究对象,对原状土和两种控制含水率方法的重塑土进行直剪试验,并与前人研究进行对比。研究结果表明,随着含水率的增加,土的抗剪强度降低,含水率对抗剪强度的影响主要是降低了土的黏聚力,对内摩擦角的影响较小。含水率与黏聚力之间的关系可以由两个直线段描述,第2直线段的斜率要大于第1直线段,当含水率增加到一定值时,土的黏聚力急剧下降。通过控制干密度,添加不同质量的水来改变土样含水率的重塑土方法,不仅改变了土样的含水率,还改变了土的压实度和颗粒结构,因此,土的抗剪强度的变化是含水率和压实度共同影响的结果,在分析试验结果时应该引起重视。

It＇s important to study the relationship between water content and shear strength of unsaturated soils for engineering practice.On the basis of concluding the previous tests results,direct shear tests of undisturbed soil and remolded soils of which the water contents are controlled by two different ways are conducted,choosing the unconsolidated silt of Tertiary as a study object.The results show that the shear strengths of soils decrease with increasing the water content.The main influence of increasing water content on shear strength is decreasing the cohesion;and the influence on the internal friction angle of soils is little.The relationship between cohesion and water content of unsaturated soils can be described by two lines and the slope of the second line is greater than the first line which imply that when water content reaches some value,the cohesion of soils decline fast.The way to change the water content of remodeled soils by controlling the dry density of soils and adding different mass of water,has not only changed the water content of soils,but also the compaction and structure of soils.So the change of shear strength is influenced by both water content and compaction of soils;and it should be paid close attention when analyzing the test results.