Overall Instability Failure Mechanism and Monitoring Strategy Research of the Shallow Tunnel under Unsymmetrical Pressure during Operation Period

Aiming at the safety of tunnel operation, based on investigation and statistical analysis a large number operating diseases, comprehensively considering interaction between surrounding rock structure, this paper establishes failure criteria for rocks lining materials by using numerical limit theoretical methods, analyzes overall stability instability mechanism shallow under unsymmetrical pressure during operation period strength reduction method in light tunnel, proposes reasonable monitoring strategy, also constructs index system. The research results show that structure is affected bias due to asymmetry terrain. probability disease asymmetric terrain conditions significantly higher than general has experienced three development stages from shear instability, including mass fracture sliding, structural damage, which can be divided into eight processes. During key indicators surface deformation are subsidence slope top horizontal displacement itself, followed uplift bottom slope. Meanwhile, close attention should paid stress states sliding direction perpendicular demonstrates principal compressive more sensitive tensile listed as early warning stress.