Abstract The section of soft surrounding rock around the Yanmenguan tunnel, which exhibits a straight align? ment, has large overburdens and tectonic stresses, which is extremely challenging for deformation control during tunnel construction. Considering the characteristics of the squeezing surrounding rock around the Yanmenguan tunnel,a study was conducted with respect to measures for excavation deformation control. The Finite Differential Method (FLAC3D) was used to determine the rational length of the reserved core soil of the arced pilot tunnel during threebench seven- step construction, and the length of the system anchor bolt was optimized based on the scope and shape of the plastic zone of the tunnel surrounding rock. Furthermore, a study on the mechanical effect of the double-layer support and the construction time of the inner support was carried out: it concludes that it is best for construction of the inner support to take place at the same time as that of the inverted arch of the outer support. Comprehensive deformation control techniques, which include a 3~4 m long core soil, advanced support, an optimized system anchor bolt, a feet-locked anchor bolt and double-layer support (H175+I22a), are proposed based on numerical simulation and engineering practice that consider the squeezing surrounding rock around the Yanmenguan tunnel.
Abstract：
The section of soft surrounding rock around the Yanmenguan tunnel, which exhibits a straight align? ment, has large overburdens and tectonic stresses, which is extremely challenging for deformation control during tunnel construction. Considering the characteristics of the squeezing surrounding rock around the Yanmenguan tunnel,a study was conducted with respect to measures for excavation deformation control. The Finite Differential Method (FLAC3D) was used to determine the rational length of the reserved core soil of the arced pilot tunnel during threebench seven- step construction, and the length of the system anchor bolt was optimized based on the scope and shape of the plastic zone of the tunnel surrounding rock. Furthermore, a study on the mechanical effect of the double-layer support and the construction time of the inner support was carried out: it concludes that it is best for construction of the inner support to take place at the same time as that of the inverted arch of the outer support. Comprehensive deformation control techniques, which include a 3~4 m long core soil, advanced support, an optimized system anchor bolt, a feet-locked anchor bolt and double-layer support (H175+I22a), are proposed based on numerical simulation and engineering practice that consider the squeezing surrounding rock around the Yanmenguan tunnel.
2017, Vol. 54 