Research On Back-analysis Of The Rock Parameters And Load Distribution Ratio In The Process Of Tunnel Construction

With the great development of economy, the construction of highway and railway has been greatly expanded. In this process, the tunnel construction is necessary. However, massive construction of tunnel project, kinds of problems existed in the design and construction have been gradually exposed.The determina--tion of rock parameters and load distribution ratio are two of the most important, these tow problems largely influence the quality of supporting structure's design and construction, so it is urgency to solve these two problems to design a more reasonable supporting structure.This paper based on the construction of the jiu-ling highway tunnel, work on the back-analysis of rock elastic modulus and the load distribution ratio, the main work and characteristics are below:1. Against the difference between tunnel project problems and the general engineering problems, elaborated the necessity of displacement back-analysis in tunnel project, and introduce the basic principles of rock elastic modulus, initial stress back-analysis.2. An improved weighted least squares method is proposed to solve the ill-posed problems in displacement back-analysis, which has been vertified. A software to determine the value of rock elastic modulus and initial stress is produced under the basic principles of displacement back-analysis and the knowledge of weighted least squares method, then this software is used in the actual project to calculate nine -ling tunnel elastic modulus of rock and initial stress.3. This paper introduces the concept of rock stress release in the process of tunnel excavation, and studies on the influence of rock stress release caused by rock physical parameters and the application timing of supporting structure through numerical analysis. Also, it derives stress release value after each exvavation with the combination of elasticity theory and makes some suggestions in the construction of the tunnel.4. The value of load on tunnel rock , first lining and second lining in three different situations are calculated with the formula of rock stress release rate, and finally we get the formula used to calculate the load distribution rate in three different situations.5. Through the comparative analysis of the actual project monitoring data and three-dimensional numerical simulation, we sum up the force characteristics of the tunnel lining in construction, and verify the conclusions of the problems of load release raised in this paper.