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Study on the Safety Factor of Tunnel Proximity Pile

Author: XuHao
Tutor: WangCheng
School: Chongqing Jiaotong University
Course: Bridge and Tunnel Engineering
Keywords: Tunnel Safety factor Finite Element Strength Reduction The displacement the release coefficient Tunnel Proximity pile foundation
CLC: U451
Type: Master's thesis
Year: 2010
Downloads: 66
Quote: 0
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Abstract

Geotechnical Engineering three main research object slope foundation with the tunnel, the first two can be carried out geotechnical stability analysis, only tunnel surrounding rock has no real sense of stability analysis, but also in the experience of the design phase, This has greatly affected the level design of the tunnel project. Tunnel Proximity pile foundation stability problems do not have a better method of analysis, has not put forward a suitable index for judging in the design process is the basis of the experience of the pile tunnel distance control principles. In this thesis, a more detailed study of subtraction in the tunnel Proximity pile foundation stability analysis and design as well as tunnel displacement release coefficient for FEM strength. Work and innovation of the main points are as follows: by studying the rock mass strength pile loads pile and tunnel distance, pile depth of various factors on the stability of the tunnel under the pile foundation loads, calculations show that pile foundation the tunnel impact critical distance from the tunnel side walls about 1 times the hole diameter. When the pile and the tunnel when the distance is less than the critical distance pile foundation, load changes have a greater impact on tunnel safety factor, load increases double the the safety coefficient decreases by about 1/4. Tunnel surrounding rock rock mass strength rock safety factor greater impact rock strength of this article is to reduce from sandstone to mudstone wall rock safety factor is reduced by 1/4. ② With advancing tunnel face for the release of surrounding rock displacement coefficient affect the greater the rock mass strength parameters (cohesion and angle of internal friction) and the initial stress state (Poisson's ratio), the deformation modulus of Wai rock displacement release coefficient has little effect, affect the amount of about 1%. The maximum amount of influence is the Poisson's ratio of the side walls, reaching more than 20%, but a relatively small impact on the vault and the bottom; strength parameters of the univariate analysis, when it reaches a certain magnitude to continue increased release of surrounding rock deformation and displacement ratio will approach a constant value. Surrounding the displacement of release is mainly concentrated in the monitoring section Diameter range of 0.5 times, accounting for 70% to 80% of the total displacement, displacement emission cent of the total displacement, especially when the tunnel face by monitoring sectional 0.5 times Diameter 50% to 60%. ③ When surrounding rock release coefficient greater than 60%, the same release coefficient with decreasing rock strength, the pile loads tunnel security coefficient decreases rapidly when Ⅴ grade wall rock, tunnel safety factor of less than 1, not suitable to be built on the lower strength of the surrounding rock pile foundation. The higher strength rock safety factor, there is a large safety reserves.

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