The Trial Research On Basic Mechanical Properties Of Expansive Soils In Hefei

Expansive soil is mainly composed of Montmorillonite and Illite, it has expansive structure,multiple flaw,swelling and shrinkage characteristic,swelling and softening after absorbing water,shrinking and splitting after losing water and swelling and shrinkage during the alternate wet and dry seasons engineering properties. Expansive soil is widely distributed around the world, From lake sediments to the shale, they are likely to be expansive soil. Many countries, such as South Africa, China, Myanmar, the United States, Canada, UK, India, Australia and so on in the international academic conference reported that they encountered problems of expansive soil. The expansive soil has been found in more than 20 provinces in China, Anhui province is one of the provinces where the expansive soil most widely distributed.The expansive soil can be found in Hefei, Huainan, Luan and Huaibei. The buildings, railways, highways, airport and water conservations which constructed on it will be destroy cause it's swell-shrink characteristic.This resulted in one thousand million dollars to the national economic loss.In this paper, the expansive soil in Hefei has been used as the research object,for the current focus of the study of expansive soil, through extensive laboratory reaserch and field testing to carry out the swelling-shrinkage characteristics and creep characteristics of expansive soils.The research results are as follows.1. Analysis the distribution,depth,macro and micro characteristics of Expansive soil,comprehensive study the swelling and shrinkage characteristic,effect factors and regional distribution of expansive soil,shows the relationship between swelling and shrinkage characteristic and buried depth.2. Base on a lot of indoor soil tests, through doped lime test, showes the relationship between the swelling force and primary moisture , the swelling rate and primary moisture , the swelling force and lime content, the swelling rate and lime content, the biggest dry density and lime content, the optimum moisture and lime content, and also study on approach to identification and classification of expansive soil.3. By research a large number of domestic and international information, summed up the development of constitutive relations for unsaturated expansive soil, analysis the problems of unsaturated expansive soil constitutive computational model. 4. Through a mass uniaxial compression test and creep of the typical unsaturated expansive clays in Hefei, get the clay's basic behavior of compressive strength and different pre-stress conditions of compressive strength in different regions.5. Based on the results of uniaxial compression creep tests of expansive soil in Hefei area, in-depth analysis the creep properties of the unsaturated expansive soil; Based on the existing soil creep model,proposed the unsaturated expansive soil constitutive model in Hefei area.