Analysis And Control Teehnology Research On The Stability Of The Tunnel Face

Along with the rapid development of traffic, underground engineering projects have evidently increased, and followed that long-large, deep-buried and unsymmetrical pressure tunnels are emerged in large numbers. It's inevitable that along the tunnel we'll encounter different ground conditions, and tunnels across different geological grounds will face a variety of geological disasters. These will not only cause the difficulty of tunneling, the damage of construction equipment, but also the delay of the construction period, increasing the project cost, and the danger to life. Given the current situation, it's important and urgent to analyze and control the stability of the face.The thesis, based on the projects of the Dujia mountain tunnel of Guanggan high way, has applied the mathematical theory of fuzzy and numerical calculation method. Taking the test in situ into account, the stability of the face is researched from the qualitative and quantitative aspects. The following are the results:1,Give a conclusion of the unstable situation of the face from eight aspects, including the instability type, the instability extent etc. Analyze the instability mechanism from the tunnel stress characteristics after the excavation and the rock deformation. Finally, propose the project definition of face instability, taking account of the typical example of the instability of the Dujia mountain tunnel.2,The extent of the instability is graded according to the instability mechanism, the stress ratio of the surrounding rock, the practical instability of the face in situ, and the range of the surrounding rock's classification. It's considered that the range of the instability is graded into five grades. Then, according to the mathematical theory of fuzzy, a dynamic assessment system for the face's stability is established with C/C++ language on account of the five factors and the thirty four evaluation indicators. After that, applying the system to the Dujia mountain tunnel for a dynamic evaluation, the result is consistent with the practice. In the end, assess 100 cross-sections with the system, and the success rate is 92%.3,Analyze the support types of the face in terms of four aspects, including the deformation character of the tunnel where the face is arrived, the deformation of the surrounding rock etc. Besides, in terms of the practical situation of the Dujia mountain tunnel, measure the extruded and convergence deformations, and then conclude the extruded and convergence characteristic curve. What's more, choose three tunneling methods and analyze them with Three-dimensional numerical simulation. The first method is one without any advanced support. The second is small pipe grouting and performed core-soil in front of the face. The third is reinforcing the core-soil with forepoling fiber bolt and performed core-soil; other conditions remaining same. Then analyze the stress and strain of the surrounding rock after excavation. It's verified that advanced core rock can be seen as the important basis for the long-term and short-term deformations. Meanwhile, it's tested that the deformation of the advanced core rock can be controlled through reinforcing the advanced core rock by increasing its strength, so as to control the tunnel's deformation and the long-term and short-term load. It's confirmed that the support method is scientific and feasible. It can be concluded that Dujia mountain tunnel should be reinforced by class fiber composites to ensure the tunnel's stability.