Research On Waterburst Prediction And Treatment Measures In Micang Mountain Tunnels

With the continuous expansional scale of highway construction, China has built a number of long tunnels, extra-long tunnels and tunnel groups. As the underground building, construction of a tunnel project often sufferred gushing water and other geological disasters and huge hazards which were seriously affected the construction safety and tunnel operations.This paper takes the Micang mountain highway tunnel in Bazhong-Shanxi highway as the research object. Through the surveys and studies on the engineering geological conditions and hydrogeological conditions in Micangshan tunnel, identified the supply, runoff and discharge conditions and groundwater type. Then synthetically selected the evaluating indicator, and established the gushing water hazard prediction and evaluation system for Micangshan tunnel. According to the tunnel gushing water prediction by traditional theory and numerical simulation method, revealed the propose for the integrated advanced geological prediction and rational efficient measures for preventing gushing water disasters. Through the research acquire the following results and knowledge:(1)According to the preliminary Micang engineering geological, hydrogeological conditions and the analysis of factors affecting the geological environment and Gushing water, and using fuzzy math chromatographic analysis, select lithology conditions, topography and landforms conditions, geological structure, tunnel length and depth and karst status as the criterion level, amd divided it into a number of program levels. By quantifying and valuing the selected index, established the Gushing water hazard prediction and evaluation systems for Micangshan tunnel.(2)The evaluation results from the Gushing water hazard prediction and evaluation systems for Micangshan tunnel are as follows:An extremely dangerous zone(V), 3 high-risk zones(IV), 6 danger zones(III), 8 low-risk zones(II), and no low-risk area. The total length of Micangshan tunnel is 13392 m, which the high risk zone(V) is 1640m(occupying 12.2%), the high-risk zone(IV)is 726m(occupying 5.4%), the danger zone(III) is 1056m(occupying 7.9%), the low risk zone(II) is 9970m(occupying 74.4%). Studies have shown that risk level of gushing water in Mingmi Cangshan tunnel concentrated in the extra-high danger zone, high danger zone and mid-danger zone.(3)Through the deep analysis of the geological conditions and characteristics of groundwater cycle in Micangshan tunnel, calculated the Gushing Water in Micangshan tunnel by the traditional theory of rainfall infiltration method, groundwater dynamics method, and Visual modflow numerical simulation. The calculation results show that: the gushing water calculated by rainfall infiltration water inflow calculation method is significantly smaller than other methods, the calculation results from groundwater dynamics Inflow Dupuit theoretical formula method is slightly smaller, the inflow results calculated by using the Goodman tunnel water empirical formula is relatively close to the largest inflow results by the numerical computation. According to the risk prediction and evaluation of the Micangshan tunnel, the maximum inflow was 100901 ~ 104513.976 m3/d in K41+440~K43+080 in extremely dangerous zone(V), while the others were K41+260~K41 + 440 and K43+080~K43+ 360 in the high-risk zones(IV).(4)Summarize and analyze the advantages and disadvantages as well as the response characteristics of various advanced methods for prediction of adverse geological disasters. According to the complex geological conditions and different risk evaluation results in Micang mountain tunnel, Though the advanced forecasting methods such as geological analysis, TSP method, ground penetrating radar and advanced drilling method to prevent the occurrence of water inrush disaster. And initially established the geological prediction technology system for the Micangshan tunnel project and provide a more complete integrated forecasting model for the comprehensive tunnel advanced geological prediction.(5)Through the study of the tunnel control measures and Gushing water hazard characteristics of the Micangshan Tunnel, formulate the principle to prevent the Water Gushing:the principle of combining sealing and emissions, the principle of combining tunneling and geological forecast, the principles of integrated governance in local conditions, timing of governance, tracking and monitoring, the principles of dynamic control of information technology.(6)According to the risk analysis of the Micangshan tunnel Gushing water and water inflow forecast, take measures to different Gushing water-related disasters, dredging and backfilling take full pre-grouting deep section, deep tunnel surrounding pre-grouting.