Influence Research Of Limestone Cave On The Construction Stability Of Single Track Railroad Tunnel

Karst disaster is often encountered in tunnel construction in mountain area. This geological phenomenon existence has creatted serious threaten to the tunnel construction and operation. Relied on the gold mountain tunnel of railway from YiChang to WanZhou, the paper summarized the domestic and foreign predecessor's research results, used the numerical experimentation method on the base of scene test, comprehensively researched the influence of karst caverns in different position and size to the single track railay tunnel construction, and proposed the design, construction and supports principles of traversing areas with karst caverns and the method system we should follow in construction. The primary content and conclusion including: (1) According to the survey, we analyzed and summarized the influence of karst caverns to the tunnel construction. We partitioned the influence from karst caverns to great span which caused collapses on the top and bottom of the tunnel and small span which caused displacement and stress change in structure of wall- rock supports. We proposed the wall security thickness formula to the destabilization on the top and bottom of the tunnel. (2) According to the analysis of collapses happened, we proposed two forms of tunnel rock destabilization. (3) According to the problem of structure design based on the inversion analysis of scene monitor, we illustrated the mechanics basic of displacement inversion analysis, proposed the concept of"displacement equivalent continuum elasticity-plastic body". (4) According to problems of small scale karst caverns, took the single track railroad tunnel as an example, we analyzed the influence to the stability of the tunnel. (5) We followed up the scene of construction, did scene position experiment, and researched the influence fom stress, the displacement of the wall-rock and internal force of the support structure, and confirmed the rationality of model analysis. (6) Combined with tunnel construction of railway from YiChang to WanZhou, we proposed the design, construction and supports principles of tunnel construction in karst areas on the base of numerical analysis, and the method system we should follow in construction. It provided the essential technical support and the theory guarantee to tunnel construction in karst areas.