An integrated determination method of optimal supporting time against TBM jamming

TBM (Tunnel Boring Machine) jamming and support failure occur frequently with inappropriate supporting time, particularly when TBM crosses adverse geology. Given this, an integrated determination method of optimal supporting time against TBM jamming was proposed. In this paper, the causes and failure mechanism of large deformation in the tunnel were revealed through X-ray diffraction (XRD) measurement of the rocks. The frictional resistance of TBM shield and the stress of support under different supporting time and measures were investigated by numerical simulation. It was shown that early installation of the support will lead to excessive load on the support, resulting in support failure. Contrarily, delayed installation of the support will lead to excessive tunnel deformation, inducing TBM shield jamming. The optimal supporting time was determined by comprehensively analyzing the critical deformation of TBM jamming and ultimate stress of support. The deformation of surrounding rock in the range of 31.6 mm similar to 39.9 mm was the optimal support time in this study. Installation support with an optimal supporting time can ensure the safety of TBM and support simultaneously. The range of optimal supporting time decreases continuously with the weakening of support parameters. Specifically, the support measures (bolt + steel arch, shotcrete + bolt) cannot simultaneously ensure the safety of the TBM and support. The research results can effectively guide the prevention of jamming and support design in TBM tunnels.