The Study Of Consolidation Tests On Hefei Unsaturated And Cohesive Soils

The properties of unsaturated soil are very complicated and our projects encounter unsaturated soil so frequently. Our study on the unsaturated soils is at elementary stage. The unsaturated soils in Hefei are the typical unsaturated soil in our country. It is the foundation of the projects which have been built and is going to be the foundation of the buildings which are going to be constructed, and the compressibility of the foundation is very important for the projects. But at present, But at present, our achievements on Hefei unsaturated soils are rare, so we are wanting in the compressibility of Hefei unsaturated soil. Then this paper has researched the characteristics of the typical unsaturated and cohesive soil in Hefei area. Firstly,1-D consolidation tests are conducted on the remade samples with saturability level60%,80%,90%; moisture content15%,20%,25%; depths5m,10m,20m; respectively. Secondly, the same experiments are conducted on the remade samples of depths20m with saturability and moisture content equal to the samples above, but under different consolidation load, different pre-consolidation load, different ratio of load increment, different interval of load increase and different constant suction. At last, we have analyzed and summarized the results of the tests above, and obtained the ultimate conclusions below:(1) The cohesive soil has a greater internal friction angle when it’s in low water content. This would cause the sudden failure of internal friction in the soil particles and can lead a leap settlement under a appropriate load, The internal friction angle will be lubricated and then decreased when its water content rise, so the settlement would decrease and the viscidity of the sample would be enhanced.(2) The primary consolidation course of the unsaturated and cohesive soils from Hefei can be divided into two stages:one would drain the air rapidly, the other one would drain the air and water simultaneously in a less rapid and constant speed. And both the two stages can be fitted preferably on settlement curve.(3) The compressibility of the unsaturated and cohesive soils from Hefei is changeable and complex, which is bound up with the soil depth, saturability (moisture content), load, pre-consolidation load, ratio of load increment, interval of load increase and suction, and so on.(4) This article has summarized the value of Ca/Cc obtained by all the tests conducted, and the statistics show that there is only a part of the samples’results (5/33) are in accordance with the conclusion obtained by Mesri and Godlewski, and the saturability of those samples is either80%or90%. But the results of the samples with saturability60%are smaller than Mesri and Godlewski’s, the results from the tests which controlled suck are larger than their’s.