Study On Feet-lock Bolt Supporting Effect For Tunnels In Soft Surrounding Rock

At present, the Feet-lock bolt (tube) is increasingly used in soft rock tunnel construction, it can control the sinking of the tunnel primary support effectively, the maintenance of the stability of tunnel structure plays a role in reuse. However, in the tunnel design and construction, the specifications, direction, length, volume and other support parameters of the feet-lock bolt (tube) is still groping in the experience of the stage. The supporting effect and mechanism of the feet-lock bolt (tube) hadn't researched and concluded systematically.In this paper, based on the system research of the feet-lock bolt (tube) mechanism, using the finite element analysis software MIDAS/GTS to numerically simulate and compute the feet-lock bolt (tube)support effect in soft rock tunnel, considering the effect of rock deformation around tunnel caused by the feet-lock bolt (tube) on different angles, different length and different quantity, through the analysis between various influent factors and the tunnel crown settlement, clearance and bolt axial force, the results show that, with the angle increases between Feet-lock bolt and horizontal, dome subsidence decreases, clearance convergence volume increases, and the vault settlement, clearance convergence gradually reduced with foot anchors length increases.Through the soft rock at all levels, the number of foot anchors of different support effects of tunnel were analyzed to optimize is given in gradeâ…£rock tunnel should adopt the single-row foot anchors; in V grade rock tunnel should adopt the double foot anchors; inâ…¥level of suitable rock tunnel in three rows of lock pin anchor tube.In addition, through the comparative analysis of the feet-lock bolt (tube) at the tunnel test section between on-site monitoring data and finite element simulation results on the tunnel of BaoJiashan, MingYazi and TianHengshan, to verify the use of feet-lock bolt (tube) can effectively improve the overall security and stability of the tunnel structure.In this paper, a variety of the feet-lock bolt (tube) best parameters can be designed as a reference for similar projects, the calculation methods provides a better reference for the engineering design, it has important significance for the current construction of the tunnel project.