Research On Surrounding Rock Deformation Control Technology Of Tunnel Crossing Fault Fracture Zone

With the rapid development of transportation in China’s central and western regions,the construction of tunnels in geologically complex areas has become a problem that must be faced in highway construction.Under the strong tectonic movement,there are a large number of fractured rock masses in the central and western regions,and when tunnels pass through fractured rock masses,engineering accidents such as large deformation of surrounding rock and failure of support structures are prone to occur.In order to prevent engineering accidents,the acquisition method of fractured surrounding rock is studied,and on the basis of accurately obtaining parameters,the deformation control technology of fractured surrounding rock tunnels is proposed.The main research contents of this paper are as follows:1)Based on the Hoek-Brown strength criterion,the geological strength index and disturbance factor were determined as highly sensitive parameters by analyzing parameter sensitivity.Improved rock mass block size index,Barton rock mass classification system,and underground excavation surrounding rock classification method were introduced to quantitatively grade the structural characteristics of rock mass.The structural surface conditions and joint feature coefficients were introduced to quantitatively grade the structural surfaces of rock mass,forming an improved geological strength index quantitative grading system.Based on rebound tests of disturbed rock and rock mass,a semi-quantitative calculation method for the disturbance factor of rock mass was established.2)The physical and mechanical parameters of amphibole pyroxenite were obtained through indoor rock physical and mechanical tests.By combining the results of field investigation and testing with those of indoor experiments,the required parameters for evaluating the geological strength index and disturbance factor of the surrounding rock at different sections of the faulted fractured zone of the Fengshuliang Tunnel were obtained.The geological strength index and disturbance factor of the faulted fractured rock mass were quantified,and the corresponding physical and mechanical parameters of the rock mass were obtained based on the Hoek-Brown strength criterion.The parameters were then transformed equivalently into the shear strength index of the rock mass under the Mohr-Coulomb strength criterion.3)Comparison and analysis of commonly used construction methods for fractured surrounding rock of faults were carried out,and the surrounding rock of grade III to V were subdivided into sub-grades.The improved geological strength index quantification system was combined with sub-grades of surrounding rock to provide suitable construction methods for different sub-grades of surrounding rock.4)Based on the improved quantification system,the physical and mechanical parameters of the rock masses at different sections of the fractured faulted surrounding rock and the recommended support schemes based on the sub-classification of the rock masses were obtained.A numerical model was established to simulate the construction stage on-site,and the rationality of the optimized support scheme was demonstrated through on-site testing.The numerical simulation results were basically consistent with the monitoring and measurement results of the on-site test section.The physical and mechanical parameters of the rock masses at different sections obtained by the optimized scheme were relatively accurate,and the sub-classification of the surrounding rock in the fractured faulted zone was reasonable.The recommended support schemes for different sub-classified rock masses could effectively control the deformation of the surrounding rock.