Observed Ground Pressures and Internal Forces of the Shanghai Yangtze River Tunnel

Estimating soil pressure acting on the tunnel lining accurately is critical to study the mechanical behavior of shield tunnels. The evaluation of internal forces can also contribute to the understanding of the mechanical behavior of segmental lining. This paper presents observed ground pressures and internal forces of the Shanghai Yangtze River Tunnel, which is a large cross-section tunnel with an outer diameter of 15.0 m. The observed ground pressures of the tunnel show obvious sinusoidal fluctuations with the water level of the Yangtze River. The observed ground pressures are closer to the values given by Terzaghi's formula. This means that soil arch still exists although the buried depths are only about 1.5D (D represents the diameter of the tunnel). The observed bending moments are generally greater than theoretical ones, and measured hoop forces are approximately twice as much as theoretical results. This indicates that internal forces calculated by conventional models could only reveal the stress related to the ground load. Observed internal forces could be greater than calculated internal forces because assembling stress is not included.