Abstract: A deep excavation project was in the highly sensitive soil layer area in Xichang, which is about 12m deep. Excessive lateral deformations in the supporting system were observed three meters after the excavation. Evaluations are performed on the adjacent environments and deformations, poor geological conditions, precipitations and the space effect of the deep excavation are the potential main factors of these serious deformations. Throughout the back analysis, the shear strength parameter of the soil mass after the excavation deformation hazard was only 1/3 of that presented in the geotechnical investigation report. According to the load test of the ground anchor, the standard value of axial pull-out force per meter within the bond length was about 28.27kN. A third-party expert panel discussion based on these results suggested that mitigation methods of “ground anchor with expanded angle jet grouting” and “corner supporting” be used to control the deformations. These measures mitigated deformation effectively and the safety and smooth construction of the project were ensured.

Key words: Deep Excavation, High Sensitivity Soil, Excavation Deformation, Diagonal Braces, Deep Excavation Supporting Reinforcement