Prediction of the Field Response of Soil-Support Systems in Deep Excavations

The task of predicting the performance of deep excavations is challenging due to the existence of many influencing factors. Strength and deformation parameters of soil, type, stiffness of the support system, and sequence of excavation and installation of support elements are very important factors in studying the performance of deep excavations. Performance of deep excavation support systems is related to both stability and deformation. Ground deformation around the excavations can damage surrounding buildings, streets and utilities. Therefore understanding the factors affecting the performance of deep excavations and the ability to predict the behavior of the support system and the associated ground deformations is an important issue for geotechnical engineers. In this paper, two case studies with well documented data of field measurements are analyzed numerically. The analyses are performed using the finite element program “PLAXIS-2D”. Two material soil models are implemented in the analyses: the hardening soil model and Mohr Coulomb model. In both analyzed case studies, good agreement between the field measured displacements and the calculated displacement using the hardening soil model is obtained. Results of analysis showed also that the hardening soil model is superior to Mohr Coulomb model in predicting the displacements in both case studies. After calibrating the numerical model, a parametric study is performed to investigate the effect of anchor-pretension-force on the resulting deformation for case study (A) and the effect of strut stiffness on the resulting deformation for case study (B). Results of these analyses showed that both factors have important effects on the resulting excavation-support-system deformation.