Assessment of SSI interaction effects for deep diaphragm walls and adjacent buildings considering spatial variability of parameters, post-peak behavior and concrete cracking

Abstract

Recent research works into the design and response evaluation of deep diaphragm walls and induced settlements to adjacent buildings demonstrated that the nonlinear behavior of surrounding soil, cracking effects affecting the structural members’ flexural rigidity and spatial variability of soil parameters are a prerequisite for a rigorous analysis of serviceability performance. However, as a result of the complexity of the mechanisms developed in the case of deep multi-propped retaining structures, most of the proposed Soil Structure Interaction (SSI) design methodologies are biased towards geotechnical or structural behavior by adequately capturing the nonlinearities of the one field and considering a rather simplified behavior of the other. With the aim to bridge the gap between the above design methodologies, a fully coupled analysis of a multi-propped diaphragm wall of an underground station with a supporting grout slab at the excavation bottom has been carried out. Further to the nonlinear behavior of the soil, the spatial variability of the grout treated zone strength and stiffness together with the post-peak behavior have been considered. In addition, the concrete cracking effects, associated with substantial decrease of structural members’ stiffness, have been taken into account. Comparative simplified empirical approaches disregarding cracking effects by adopting constant diaphragm wall flexural rigidity instead, have been carried out as well. Interesting conclusions were drawn relating the results of the above simplified approaches and the Serviceability Limit State (SLS) analyses with regard to the response of the diaphragm wall, the bending moment distribution along the wall and the displacement field in the surrounding soil and adjacent buildings.