Abstract: The numerical analysis method is adopted to study the vertical deformation mechanism of the retaining wall caused by unloading. A hypothetical model which considers the interaction between wall and soil, is established in the finite difference software. The ideal elastoplastic model is adopted to simulation the characteristics of contact property between soil and diaphragm wall. The vertical displacement of soil, the relative displacement of soil and wall and the distribution of friction under the 3 kinds of soil parameters are compared and analyzed. The results show that the vertical displacement of the wall can be divided into two parts the soil rebounded one and relatively sliding between subsoil and wall tips. The displacement of soil is mainly affected by unloading effect which is determined by soil parameter. The settlement of the wall decreases with the increase of soil cohesion. The uplift of the wall increases with the increase of friction angle. The relative sliding of wall tips and soil is governed by the frictional forces on two sides of the wall. With the increase of contact property, the frictional force increases and will lead to larger vertical displacements.

Key words: excavation, diaphragm wall, vertical displacement, soil-structure interaction