A Study Of Tunnel Stability Based On Rock Parameters Inversion

With the continuous development of China’s transportation construction, the number of highway tunnels is increasing, however,the stability of the tunnel has been become a major concern. In view of high complexity of the tunnel surrounding rock, it is difficult to obtain an accurate parameters of surrounding rock to evaluate tunnel stability directly,therefore it is necessary to take full advantage of monitoring measurement data acquired during tunnel construction which is used to calculate parameters.Under the guidance of this idea,the thesis uses Partridge Mountain Tunnel project which is part of Wenma Highway under construction as engineering basis.according to the site monitoring measurement data during tunnel construction,the geotechnical engineering finite difference software FLAC 3D is used to establish and calculate forward model,the inversion model is built and optimizated,the large computing software MATLAB is adopted to compute parameters of tunnel surrounding rock,the stability of the tunnel is analyzed according to the surrounding rock parameters obtained by inversion computing.the main contents of this research include the following aspects:(1) The regression analysis of measurement data and construction management of tunnelAccording to the actual situation of the project as well as the concept of NATM,the tunnel monitoring measurement program is formulated,the monitoring and measurement during construction is implemented, the site monitoring measurement data are collated,processed and regression analysised to analyze deformation of the surrounding rock,and information feedback and construction management mechanism of the Partridge Mountain tunnel is established.(2) Establishing and calculating of forward modelAccording to geological data, geological prospecting,geological forecasting and other related information of the partridge mountain tunnel,the range of surrounding rock physical and mechanical parameters are determined,the combination of physical and mechanical parameters of the surrounding rock are designed based on the orthogonal trial and uniform trial principle,the powerful geotechnical engineering software FLAC 3D is used to establish the three dimensional forward analysis model of tunnel,and calculate the vault settlement and horizontal convergence of corresponding position which used as training samples and test samples of BP neural network are calculated, on this basis, the major and minor roder of each parameter of surrounding rock that affects tunnel deformation is analyzed by matrix analysis method of orthogonal trial.(3) Establishion of inversion model and parameters calculationThe structure of the BP neural network is built and optimized further, the posterior sent method is used to determine its predictive ability,the suitable inversion calculation model for the physical and mechanical parameters of the tunnel surrounding rock is established,combined with the actual results of site monitoring and measurement during construction,as well as applicated to MATLAB,physical and mechanical parameters of the tunnel surrounding rock are computed. According to physical and mechanical parameters of the surrounding rock obtained by inversion calculation,the value of the vault settlement and horizontal convergence of the corresponding cross-section and the deviation between the measured value are calculated, thus scientificity and feasibility of inversion of the surrounding rock parameters is verified further.(4) The application of inversion results in tunnel constructionAccording to the surrounding rock physical and mechanical parameters obtained by inversion computing,three-dimensional calculation model of tunnel construction is built,strength reduction method is applied to calculate stability of tunnel surrounding rock, depth impact on the tunnel staility and security of lining structure, at the same time, measures to improve the tunnel stability are analyzed.