Experimental Research On Shear Strength Parameters Of Active Soil During Excavation

Excavation engineering is a very important project in civil engineering. The prime problem that needed to be solved is its safety and economy. In design of retaining structure, the reliability of the computing results relies mainly on the proper selection of shear strength parameters (c and ). So it is exigent to devise a set of experiments according to the actual stress path of soil to determine its shear strength parameters.In this paper, some present experimental methods of shear strength parameters are briefly described and the shortcomings of them are pointed out. Then in order to obtain the right shear strength parameters for design of deep pit excavation, the author did a lot of normal tri-axial CU experiments and tri-axial CU tests that can simulate the actual process of excavation using soil sample of different depth. The pore pressure, relationship of stress and strain, and the shear strength parameters obtained by unloading tests are different from those obtained by loading tri-axial tests. Later the difference is analyzed in the respect of stress path and microstructure. At last, by use of a practical project the author compared and analyzed the two sets of shear strength parameters obtained by two different stress paths.The conclusion is that it is more similar to practical soil pressure distribution if shear strength parameters are used which are obtained by the experiments that can simulate the actual process of active soil during excavation. So it is more reasonable to use shear strength parameters obtained by tri-axial experiments that can simulate the process of excavation in design of retaining structure.