Abstract: Design of vertical hole supporting structure in foundation should be based on its active earth pressure. So it is often necessary to calculate the active earth pressure on the hole wall after excavation of vertical holes. The foundation containing vertical hole is a typical axisymmetric problem, the traditional Rankine or Coulomb solution which is based on plane strain assumption is inapplicable, the existing methods for axisymmetric active earth pressure often presume the ratio of earth pressure and the major principal stress (tangential stress coefficient ?) is constant, such as Harr-Von Karman hypothesis and other similar methods, this assumption is not rigorous in theory and the calculated results have large enough error. In this paper, the slip line field equations for axisymmetric problem are established, the method of maximizing the active earth pressure and the iterative method are used to solve the circumferential compressive stress coefficient the ?, the effects of soil parameters and vertical hole geometry parameters on ? are analyzed, then the accurate value of active earth pressure can be determined. This method is more rigorous in theory and the result is more reasonable compared to that under plane strain assumption condition.

Key words: axisymmetric vertical hole, active earth pressure, slip line, tangential stress coefficient