ABSTRACT
Twin 6.4 m TBMs are to be launched from a shaft parallel to a railway corridor. The twin tunnels descend at shallow depth (3.0 m to 15.6 m) for approximately 430 m. As the tunnels are launched at shallow depth in soft soil and one of them must descend to pass beneath the railway, a solution is required to ensure tunnelling induced settlements will be controlled and be less than the strict acceptable limits.
A 120 m long 3D FE model was developed to evaluate settlement impacts of TBM tunnelling under the railway and to assess the effectiveness of proposed Ground Improvement for controlling settlements. The study included sensitivity analysis of face pressures, soil type, and tunnelling depth. This paper summarizes the solutions investigated and the approach used for developing a suitable solution. Discussion concludes with insights from the 3D modeling and preferred settlement mitigation methods applicable to similar projects.
