Numerical Analysis Of Influence Of Karst Caves On Stability Of Tunnels Surrounding Rock Mass

Around the world, karst region distributes most widely in China, and with the fast development of national economy, more and more underground engineerings are constructed in karst region, therefore the stabiliyt of karst tunnel has been a pressing problem in the course of engineering construction. To accomplish the construction, we must figure out the techniques for dealing with the effect of karst to engineering and the geologic hazard caused by construction. At present, little research has been done on tunnels in karst caves region, and the applied method focus on numerical analysis including distinct element method, boundary element method and finite element method, etc. However, it is a challenging job for such numerical analysis to obtain the process of destroying. For tunnel construction, we are interested largely in the possible destroying form of the opening, which is unsolvable by common numerical method. Spot testing or experiment is money-consuming on one hand, and the obtained data usually deviate from practical situation or unapplicable on the other hand.To accurately evaluate the stability of karst tunnel, this paper makes two dimensional Elastic finite element numerical analysis on the destroying condition of surrounding rock using the RFPA software developed by Center for Rockburst and Induced Seismisity Research of Northeastern University.1. Safety factor is introduced into the stability analysis for tunnel surrounding rock to obtain the safety factor of caves with different size, distance and position. Throught analysis, it is clear that compared with size and distance, the distribution of caves has larger effect on safety factor. With respect to different form of distribution, when comparing the effect to the stability of surrounding rock, the largest one is side cave, then is bottom cave, the smallest is top cave.2. The research shows us the dynamic destroying process of tunnel surrounding rock, the results prove that the destroying domino effect area is mainly conentrated on the area...