Finite Element Modelling of Staged Construction of Anchored Diaphragm Walls

The design of anchored diaphragm walls assumes a trapezoidal earth pressure distribution for the determination of shear forces and bending moments in the wall. However, it was recommended based on reduced-scale model tests performed in a very dense soil stratum. In the case of a loose stratum, the shear strength might get mobilized, influencing the wall rotations and displacements. Consequently, it can lead to an alteration in the earth pressure distribution acting on the diaphragm wall. Therefore, a 2D FE model is developed in OpenSees software to understand the behaviour of an anchored diaphragm wall with loose foundation soil. In order to understand the development of forces for loose underlying soil, the staged construction procedure of anchored diaphragm walls is modelled precisely. It includes excavation of soil, placement and pre-stressing of anchors successively, one after another. The FE model is validated with the results from a reduced scale test on the anchored diaphragm wall. The magnitude of maximum normalized earth pressure for the loose soil stratum is almost half of the values observed for the denser stratum. The passive resistance mobilized below the excavation level is also lower in that case. The soil conditions should, therefore, be considered while adopting a suitable earth pressure distribution for analysing or designing the anchored diaphragm wall.