| Tunnel construction in Karst area is a difficult problem, which puzzled engineering circle. And, lots of disasters happen during shallow tunnel construction in Karst development area for many factors such as Karst, undergroundwater and shallow geological structure, etc. Due to complexity of shallow and Karst tunnel geological complexion, there is lack of the effective research results about shallow and Karst disaster research at present, and the research status lags behind the requirement of tunnel construction development seriously. Shallow and Karst section of Yuwushan Tunnel on highway from Suining to Chongqing is 450m long, where Karst is developed, underground is riched, and the surrounding rock is badly impacted by geological comformation, so its geological complexion is very complicated. In tunnel construction,there happened three times collapses (including one erath's surface collapse), four times mud breakout and six times water bursting, and many times of the phenomena of sunken hole, earth splitting and water losing in paddy field and so on on the earth's surface.This paper was sponsored by key project of China National Science and Nature Fund"the stability and reliabiity of tunnel and underground space structure(50334060)"and"Research on monitoring measurement of YunWushan tunnel in Chongqing to SuiNing highway". Aimming at the complexion of Karst geological disasters occurred in Yunwushan Tunnel shallow and Karst section construction, this paper analyzed the mechanism of Karst geological disaster in shallow and Karst section, researched the measure of disaster forecast and prevention in shallow and Karst section, analysed the reason and disposal process of the super erath's surface collapse. And after all, the following results were concluded:①Combine the geological disaster complexion in shallow and Karst section, this paper analysed the mechanism of Karst geological disaster in shallow and Karst section, the result shew that Karst hole, water, geological conformation and engineering factor were the main factors.②The geological disaster in shallow and karst section not only shew the characteristic of Karst tunnel and shallow tunnel, but also had characteristic of strong outburst, big incidence and fast evolutive speed.③Brung forward that Advanced geology prediction, advance support and monitoring measurement, three aspects assembled a system of Karst geological disaster forecast and prevention. Get across to the information of advanced geology prediction, fetched up the lack of geological reconnaissance, decided measure of advance support. The result of monitoring measurement modified the design of advance support and initial support. Therefore, three measure were form to a relationship and constantly modified circular system.④The analysis of the super erath's surface collapse occurred and developed course shew that this collapse arosed by the factor of geological conformation, mud breakout and water etc. The main reason of leading the collapse scale extended was earth's river water swarmed into sinking section.⑤The collapse disposal project was in reason, which proved by the same result of numerical value simulation and monitoring measurement. The result shew biggish load bear place of concrete lining constructon was at left and right spandrel, vault took the second place, the less place was the arch below. The reason of biggish value of arch apex subsidence was not set up the middle support and temporary invert in every step of excavation.⑥The result of numerical value simulation analysis shew that there was not appeared yield area above the vault after sinking area had filled back, which was also approved by the result of monitoring measurement. It was obvious that the load bear of support structure was ameliorated availably by support pipe reinforced and encrypted.
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