The ground spring method used for calculation the stress and deformation of the earth-retaining wall for braced excavation must express the load and resistance on the ground of the excavated side while simulating them in accordance with the actual ground condition, in addition to expressing the earth pressure on the back side. To express the load and resistance of the excavated side it is necessary to enter the earth pressure at equilibrium, the horizontal subgrade reaction coefficient, and the passive earth pressure. The earth pressure at equilibrium and horizontal subgrade reaction coefficient are used to express the load and resistance when the ground of the excavated side is in elastic state while the passive earth pressure is used when the above described soil is in plastic state.
This paper studies the earth pressure at equilibrium and horizontal subgrade reaction coefficient while using the elastic finite element method. The calculation equation, which includes factors with substantial influence, are proposed on the basis of the above study. Then, through comparison of the proposed equation with existing studies and with mesured value it was confirmed that the proposed equation are practically applicable.