Experimental study of strength characteristics of cement-soil under plane strain condition

In order to study the mechanical property of cement-soil,the plane strain tests and consolidated drained triaxial(CD) tests are carried out.Characteristics and strength properties of stress-strain curve of cement-soil are discussed.The results show that the stress-strain curve has softening behavior;the softening degree is related to confining pressure and it is obvious under the condition of plane strain state;the strength failure envelopes of both CD test and plane strain test are linear and the Mohr-Coulomb criterion can be applied here;the residual strengths of both CD test and plane strain test increase linearly along with the increase of confining pressure.Moreover,the residual strength of plane strain test is greater than that of CD test;the ratio of residual strength to peak strength increases with the increase of confining pressure and the increasing rate slows down.Under the condition of plane strain,the failure strength is 1.4 to 1.6 times of the CD test result.According to the microstructure and conservation of energy principle,the softening causes of cement-soil are analyzed.The gel material such as cement hydrate is the major factor.The softening characteristic is intensified because of the effect of intermediate principal stress.