Abstract：The purpose of this paper is to find the distribution laws of the shear force between vertical shaft and surface soil，and to lay a foundation for mechanical model of shaft in soil. The formation and characters of elastic shear force and plastic shear force are analyzed. The problems existed in the past research are discussed. The Mohr-Coulomb¢s strength theory，the stress state theory as well as the shear displacement method in soil mechanics are applied to research the variation laws of two kinds of shear forces with soil depth. The calculation formulas of two kinds of shear forces are obtained. The result will play an important part in the analysis of the stress distribution laws and the stress variation laws in dangerous point in shaft and in the research of the forecast theory of shaft rupture. The research result has reference to the study of the shear force between pile stake and soil.
