Numerical simulation optimization analysis and field test for large deformation control of soft rock in Tabaiyi Tunnel

Taking Yunnan Tabaiyi Tunnel as the background of the research project, as the most complex tunnel in the whole line, its complexity is manifested as follows: the tunnel site area is a tectonic dissolution and erosion area, the geological condition is variable, crossing a number of faults and fracture zones, the local passage is water-rich, the rock weathering is serious, and the influence of tectonic stress is intense, etc. The original supporting action has resulted in large deformation of the initial support, deformation of the steel arch, and sudden mud and water surge. Under the original support, there were large deformation of the initial support, deformation of the steel arch frame, and sudden mud and water influx. The deformation and damage mechanism of the surrounding rock was studied by field investigation, rock structure analysis and numerical simulation. The surrounding rock is strongly—fully and moderately weathered metamorphic sandstone sandwiched with schist and slate mainly. Scanning electron microscopy observation of the rock body shows that the schist structure is obvious, the rock body structure is relatively loose, and the pores are more developed. The clay mineral content in the rocks is high, and the main components are illite and chlorite. The regional ground stress is mainly dominated by tectonic stress, and the groundwater in the tunnel site area is controlled by lithology, tectonics, topography and geomorphology, etc. The recharge of groundwater is closely related to rainfall, etc. The groundwater is mainly stored in the form of pore water of the loose accumulation layer, rock fissure water and karst water. Under the implementation of NPR anchor cable control system, the effect of large deformation management is remarkable, and the large deformation of surrounding rock is effectively controlled within 300 mm. In order to ensure the safety of the project and improve the construction efficiency, the optimization design of NPR anchor network and three-dimensional steel arch coupling support is carried out, and numerical simulation of several NPR anchor cable control systems is carried out using FLAC^3D and PFC^3D software to establish the NPR anchor network unit and double-layer three-dimensional steel arch with constant resistance to large deformation effect, and the deformation diagrams of the surrounding rock and the displacement diagrams of the support structure obtained from the simulation under the comparison and analysis of the various schemes are then carried out. Field test, the meter-level asymmetric deformation control results and numerical solutions for analysis and comparison, that the NPR anchor network and three-dimensional steel arch support system can solve the water-rich peripheral rock, mud, broken and local high-pressure water influx of engineering and technical problems, to get the NPR anchor cable as the core of the different support process of the coupled support parameters of the tunnel peripheral convergence under the deformation of the evolution of the law.