Use of 3D finite element method for back study of a failed basement excavation in soft clay

摘要

In this paper, the three-dimensional finite element software, 3-D PLAXIS, is used to back studyrnpossible failure reason of a deep excavation project in soft clay. The building project is located in Taipei coveringrnan area of 200m by 200 m. General ground condition consists approximately 29m of soft with SPT-N of 1 to 5rnonly. The average elevation of the construction site is plus 4.4 m. It’s planned to excavate down to minus 9.5 m.rnIt is planned to leave a berm into 1(V) by 2.5 (H) slope along with installation of shotcrete and 70 cm of drilledrnshafts along the east side of the site. Two horizontal layers of H pile will then be installed when reaching thernsecond basement level. Slope failure occurs on the east side during excavation. Comparison between the 3DrnFEM analytical results and instrumentation measurement data showed asymmetric excavation and misjudgmentrnof the elevation of bedrock are the possible reasons to cause the failure of the excavation.