Theoretical and experimental study of initial cracking mechanism of an expansive soil due to moisture-change  

作　　者：吴珺华 袁俊平 吴宏伟 

机构地区：[1]Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University [2]Geotechnical Research Institute,Hohai University [3]College of Civil Engineering and Architecture,Nanchang Hangkong University [4]Department of Civil Engineering,Hong Kong University of Science and Technology,Kowloon

出　　处：《Journal of Central South University》2012年第5期1437-1446,共10页中南大学学报（英文版）

基　　金：Project(2006BAB04A10) supported by the National Science and Technology Pillar Program during the 11th Five Year Plan of China;Project(51008117) supported by the National Natural Science Foundation of China

摘　　要：Swelling and shrinkage due to moisture-change is one of the characteristics of the expansive soil,which is similar to the behavior of most materials under thermal effect,If the deformation is restricted,stress in expansive soil is caused by the swell-shrinking.The stress is defined as "moisture-change stress" and is adopted to analyze swell-shrinkage deformation based on the elasticity mechanics theory.The state when the total stress becomes equal to the soil tensile strength is considered as the cracking criterion as moisture-change increases.Then,the initial cracking mechanism due to evaporation is revealed as follows:Different rates of moisture loss at different depths result in greater shrinkage deformation on the surface while there is smaller shrinkage deformation at the underlayer in expansive soil;cracks will grow when the nonuniform shrinkage deformation increases to a certain degree.A theoretical model is established,which may be used to calculate the stress caused by moisture-change.The depth of initial cracks growing is predicted by the proposed model in expansive soil,A series of laboratory tests are carried out by exposing expansive soil samples with different moisture-changes.The process of crack propagation is investigated by resistivity method.The test results show good consistency with the predicted results by the proposed theoretical model.Swelling and shrinkage due to moisture-change is one of the characteristics of the expansive soil, which is similar to the behavior of most materials under thermal effect. If the deformation is restricted, stress in expansive soil is caused by the swell-shrinking. The stress is defined as ＂moisture-change stress＂ and is adopted to analyze swell-shrinkage deformation based on the elasticity mechanics theory. The state when the total stress becomes equal to the soil tensile strength is considered as the cracking criterion as moisture-change increases. Then, the initial cracking mechanism due to evaporation is revealed as follows： Different rates of moisture loss at different depths result in greater shrinkage deformation on the surface while there is smaller shrinkage deformation at the underlayer in expansive soil; cracks will grow when the nonuniform shrinkage deformation increases to a certain degree. A theoretical model is established, which may be used to calculate the stress caused by moisture-change. The depth of initial cracks growing is predicted by the proposed model in expansive soil. A series of laboratory tests are carried out by exposing expansive soil samples with different moisture-changes. The process of crack propagation is investigated by resistivity method. The test results show good consistency with the predicted results by the proposed theoretical model.

关 键 词：expansive soil swell-shrinking deformation moisture-change CRACK RESISTIVITY 

分 类 号：TU443[建筑科学—岩土工程] S781[建筑科学—土工工程]