Study On Strength Of Surrounding Rock For Exceptionally Large Scale Underground Railway Station

This paper is based on the engineering of Badaling underground station of the new Jing Zhang Inter-city rail. Read some relevant information and have a basic understanding about the current situation of large-span underground engineering and rock classification based on fuzzy mathematics, and then do the following work according to the pre-survey and experimental data k and get some research results:1. According to the experimental data and survey material, study the surrounding rock level again by fuzzy mathematics based on the RMR classification. According to the evaluation results known that the surrounding rock of the Badaling underground station can be considered the three on the weak side or four on the strong side, select the three level to design if consider the economic benefits, select the four level to design if consider the construction safety.2. Fit the different strength criterion based on the conventional triaxial test data of the Bdaling granite. According to the fitting results, it is recommended that the strength criterion of Drucker-Prager can be used in engineering.3. Study the impact of plastic zone by span of underground engineering through qualitative style. The results show that the second principal stress and geological conditions have a certain impact on the plastic zone.4. Study the rock pressure on the supporting structure by different span and different computing theory. Through the calculation results of the rock pressure, the Platt’s theory rely on a higher on coefficient of rock solid and the results of calculations are unsafe; the results of the calculations of the rock pressure by Terzaghi’s theory and Bieniawski’s theory rock pressure are maximum and are not fit to deeply engineering; the results of the calculations by Highway tunnel design specifications are in the middle and have some average effect, so it can be used as a reference design.5. Study the impact of rock strength by section shape and flat rate depending on the analytic hierarchy process. From the results get the order of the weight of the different sections:D₃（Oval）> D₄（Round）> D₂（horseshoe）> D₁（rectangular）, the shape of oval is the best.6. Study the surrounding rock stress state through changing the flat rate of the oval-shaped section from0.5to0.9and get the optimal flat rate by the results of the calculations. Through the numerical simulation results and combined with practical experience of large span underground works in the past, the flat rate of the large and depth span underground engineering should be controlled in the range of0.6to0.8. Chose the flat rate of0.70for the design and construction to the Badaling underground stations.7.Study the change of the surrounding rock stress of different construction steps and propose a suggestion of excavation、construction and support. According to the calculation results of the numerical simulation, the dome will become unstable and the degree of stress concentration of the arch waist will become higher and the arch bottom will muster with the conduct of the construction, so the monitoring and measurement should be strengthened, and the timely deal with supporting measures to when the discovery of signs of instability.