Abstract: In order to study the influence of shallow-buried and excessive-large diameter shielded tunnel excavation in the saturated sand layer underneath of a large footprint building, a numerical finite element model was established by using commercial software MIDAS GTS. The settlement and deformation of above building without protective measures were numerically evaluated. From the numerical results, the proposed protective measures included tunnel excavation control as the primary measured and aided by the secondary grouting. The deformations of the building with and without protective measures were compared with the monitoring data. The results show that: 1. Without protective measures, the maximum settlement at the crest of the tunnel was about 18.2mm, and the maximum differential settlement of the adjacent columns of the inner frame was 6.45mm. After the completion of the tunnel, the maximum settlement of the soil mass above the tunnel was 28.2mm, and the settlement of the inner frame column has exceeded the warning value. (2) The maximum differential settlement of pillar foundation was about 2mm by the numerical prediction after the primary excavation control and supplementary grouting reinforcement measures applied in the tunnel. (3) Based on the analysis of onsite monitoring data, the monitored differential settlement of the maximum pillar foundation was about 0.8mm after the twocell tunnel passing through. The predicted data from the numerical simulation and the monitored data were consistent and the of control indices for the construction safety control met the requirements.

Key words: excessive large diameter, slurry-water balance, super shallow embedment, building protection, large volume