Evaluating the possibility of shield jamming in squeezing grounds
Excavation of long and deep tunnels by shielded TBMs is a safe, fast, and efficient method of tunneling that mitigates many risks related to ground conditions. However, TBM applications in difficult conditions such as squeezing ground may lead to problems such as shield jamming. For successful tunneling in such conditions, it is essential to study the pertinent ground and operational factors and their impact on ground behavior and possibility of shield entrapment to mitigate the related risks. In this study, the controlling parameters that impact the risks of tunneling by shielded TBMs in squeezing ground are examined. A parametric study was performed by using a full 3D numerical simulation to quantify the influence of various factors on machine entrapment. The results of this study shows the role of ground conditions and in-situ stresses, as well as machine components on convergence and shield pressures. Sensitivity analysis of most important parameters and their impacts on entrapment risks and preliminary results are discussed in this paper.