A Study On Deformation Law Of Highway Tunnel Mizhi NO.1 Excavated In Loess

In order to study the deformation law of highway tunnel Mizhi 1, this paper adopts total station to take an on-site monitoring and measurement of rown settlement and clearance convergence in the tunnel, and did finite element analysis on the loess tunnel construction process by software (MIDAS/GTS). Main research contents and results are:(1). The surrounding rock deformation increased sharply in the beginning of tunnel excavation, in the phase from tunnel excavation to sidewall construction, the crown settlement value reached to 273.4mm, and the clearance convergence value reached to 268.4mm, the deformation value in this stage was over 84% in the total deformation value. So, the inverted arch construction effective decreased the deformation. The deformation accords with the law of logarithmic function.(2). The result of crown settlement measurement shows that the deformation value was 37.4% in left and 33.3% in right in the total deformation value before the core soil excavation. The result of clearance convergence measurement shows that the deformation value was 27.0% in left and 14.7% in right in the total deformation value before the core soil excavation. So, the deformation in this stage is big, but, traditional measurement example for surveyor's level and convergence of equipment will miss this part of deformation due to the effect of the core soil. So, it is suggested to widely adopt the total station to measure the rock surrounding deformation in highway tunnel.(3). The primary support structure adopted a straight wall in tunnel, and in construction, the left adopt the closed primary support structure but not the right, besides, including the unsymmetrical load phenomenon, so, in the left tunnel, measuring the final deformation value and the final deformation ratio were biggish, clearance convergence was bigger than crown settlement of left individual section but of right all of three sections, but, average value of the left crown settlement and clearance convergence was 2.5 times of the right, and there are two biggish longitudinal cracks on tunnel. So, it is suggested that the lining struction employs curved sidewall with inverted arch, and the primary support structure is closed in timely in construction.(4). The deformation gradually lead to stable when the distance between monitoring section with the excavating section is out of 3 times tunnel hole diameter, and now, the secondary lining should be timely constructed.(5). The result of on-site monitoring and measurement and simulation analysis of finite element was basically same, the deformation in left was bigger than in right. So, the closed primary support structure has a significant influence on limiting rock deformation.This study gives an effective guidance of the construction of Mizhi 1 highway tunnels, and can provide a reference for future similar projects.