Finite element analysis of deep excavation: A case study

Abstract

World population increases day by day. In order to meet this increasing population’s basic needs such as sheltering, transportation and social activities, necessity for underground structures gradually increase. As a result, deep excavations become more important each passing day while excavations deepen. In order to design the optimum system which ensures the safety of environment, roads, structures and the excavation, the excavation properties should be modelled so that it reflects the actual geometry and boundary conditions. The ground parameters, which have crucial effect on the solution, should also be determined precisely. In this study, a deep excavation with a depth of 33.0 m performed on over-consolidated Ankara Clay is investigated. The excavation system was designed to be consisted of double-row of piles supported by multilevel anchors. Inclinometer and load cell installations on the shoring elements have been made for the inspection of the pile wall displacements and anchor forces. Back analysis is made in order to obtain the ideal ground parameters which give the measured displacements and anchor forces. This analysis is conducted by a series of Plaxis analysis in which ground parameters are changed iteratively in order to find their values that give the measured displacements and forces. For these Plaxis analyses, three different models namely; Hardening Soil, HS small and Mohr Coulomb are used and ground parameters are determined. Finally, ground parameters obtained by back analysis for different soil models and the parameters determined from field tests are compared and a correlation is proposed to simulate the behavior of over consolidated Ankara clay.