CT-triaxial shear tests on the meso-structure evolution and strength of unsaturated loess Q_3 during unloading confining pressure

By the computerized tomography(CT),a series of unloading confining pressure tests were done on the condition of suction control to test the inside structural evolution of unsaturated loess Q3.The tests have proved that the relation between stress and strain of unsaturated loess Q3 becomes hardening as hyperbola,that is,the breakage of the specimen is plastic;the yielding stress of the specimen can be educed easily from the CT data and enforced deviator stress during the tests to see clearly the accretion of yielding stress with the increase of suction and confining pressure;compared with the test result of immovable confining pressure and accreting deviator stress,the strength parameter of unsaturated loess Q3 with unloading confining pressure CT-triaxial shear tests is lower on account of the different stress path.The equation of the unsaturated loess Q3 structural evolution has been set up by the definition of structure parameter.