Numerical analysis of reducing tunneling effect on viaduct piles foundation by jet grouted wall

Purpose. The target of this study is divided into two parts. The first part is concerned with capability of numerical model to simulate the tunneling process. The second part is related to studying the interaction mechanism between the tunnel, protection technique, and soil. This study themes are investigated by analyzing different protection technique configuration, considering different stiffness of the grouted wall, and applying different interface coefficient between the wall and the soil. Methods. The method used in this study to check the accuracy of the proposed numerical model is 4-D ABAQUS program. The typical excavation of a tunnel is simulated step by step with an assumed rate of tunnel advancement (0.5 to 1.5 m/hr). The soil material utilized in this model is elastic perfectly plastic (the Mohr-Coulomb criterion), while elastic material is modeled as solid element (S4R) adopted for lining, grouting, filling gaps, shielding, constructing piles, and jet grouted wall. Findings. Results showed that the closer jet grouting to the tunnel with embedded length of 1.5 times tunnel diameter, the better effect on reducing the lateral deformation and bending moment generated on piles. Otherwise, increasing wall thickness more than double grouted column diameter would not affect its shielding efficiency. Furthermore, either increasing or decreasing friction coefficient even if rough between the grouted wall and soil had no effect on the pile behavior. Additionally, applying Mohr-Coulomb criteria for grouted wall with high stiffness allowed realistic response of the pile group. Originality. Capability of the proposed model is verified by back analysis of Changsha Subway Line 1 project, where the shield tunnel would be constructed near existing pile groups of L off-ramp of the Xinzhong Road viaduct.