Splayed Bifurcation Tunnel Stability Analysis And Its Security Control

Branched tunnel is a novel tunnel form with special structure. It is made up of four parts. One end is a big-arch section for four-lane; the other end is two separated tunnels; the middle includes double-arch section and small spacing section. Now branched tunnel is one of the best ways to build tunnels due to its many advantages such as high flexibility to mountain chain of precipitous topography and complex geological condition, less occupation of space and low total cost. However, the construction and research of branched tunnel are still at the preliminarily stage, especially devoid of systematic and comprehensive research, which led to lack of guideline for design and construction in engineering practice.Based on the Baziling branched tunnel of Hurongxi highway which is being constructed, this thesis involves the means of field monitoring and numerical simulation, focuses on the construction method, blast vibration and thickness of mid-rock, brings forward feasible technical measures to guarantee the long-term stability of this project. The research achievement can render service for design and construction of branched tunnels.In this thesis, the methods and contents of field monitoring, layout and locations of monitoring items are detailedly expatiated. The rock mass deformation including deep displacement, circumjacent convergence and vault settlement, primary support force and final lining force are analyzed according to the monitoring data. This work will bring two aspects of merit. For one thing, as construction monitoring, it can guarantee the safety of Baziling branched tunnel and provide helpful reference to check the rationality of design. For another, it can give other branched tunnels that are being constructed or will be constructed beneficial advices owing to the receipt of rules from this project.In the next place, the blast vibration numerical simulation of big-arch section, double-arch section and small spacing section is carried out with FLAC^3D. The distribution laws of stress, displacement and velocity field based on different quantity of explosive and different blast position are obtained. In virtue of peak particle velocity criteria, the maximal single-stage initiating explosive under different classifications of rock mass and different excavation methods is proposed...