Shear Strength Characteristic of Fissure Plane in Expansive Soil

Fissures generally exist in all of expansive soils. It always results in failure of expansive soil slope. Shear strength characteristics of fissure plane are studied and a new triaxial test method is recommended with typical expansive soil taken from Nanyang section of middle route of the South-to-North Water Transfer Project (SNWTP). The computed tomography technology is firstly introduced to shear strength test of fissure plane. The real failure stress of fissure plane is analyzed accurately through measurement of the fissure plane's real occurrence by CT scanning and shear strength parameters determined method is provided for triaxial test of fissure plane. The test results show that peak strength of fissure plane is much lower than that of bilateral expansive soil without fissures, and even smaller than residual strength of bilateral expansive soil without fissures. The reasons of these phenomena are that gray clay in fissures has higher water content, smectite content and particles orientation degree.