Response of building to shallow tunnel excavation in different types of soil

This research investigates the tunneling induced building responses in different types of soil via finite element (FE) method. Different simulation techniques, namely contraction factor method and stress reduction method, are applied in FE-model to simulate the volume loss during the excavation process. A wide range of soils, including limestone, dense/loose sand, stiff/soft clay and silt, are taken into account in this study. The considered building responses include the surface settlement profile, position of inflection point, deflection ratio in sagging/hogging zone, horizontal compressive/tensile strain, etc. The relationship between these building responses and soil/building properties is investigated. Local sensitivity analysis is further applied to distinguish the relative importance of soil stiffness and strength in determining the deflection ratio of the building settlement profile. The results show that soil properties play a significant role in determining the building responses. Generally, soil with larger initial elastic modulus results in higher deflection ratios and horizontal strains of the building. Furthermore, in order to provide a guideline for practical tunneling design, an upper bound design curve of modification factor to greenfield deflection ratio or horizontal strain for different types of building is derived in both sagging and hogging zones.