| The water inrush scourge was a very serious problem for karst existing in most areas of our country. Longer,bigger and deeper tunnels would be built with the railway running faster and faster. Karst water inrush scourge might come forth when the tunnel was excavated, if the tunnel was built in these areas, where existed plentiful water, high pressure of water, karst cave and faultage, and which could lead to the loss and pollution of groundwater.In this paper, the basic law of tunnel hazard was summarized. The water inrush mechanism of tunnel karst was analyzed by fracture mechanics and catastrophe theory, and the safe thickness of rock wall, which to prevent the water inrush, was educed respectively from fracture failure and instability theory. The grout pervasion mechanism was inferred based on viscosity varying characteristics with time and laboratory simulation test, which could be used to control the grout pervasion areas. The prevention measures, which included"avoiding, bypass, block water up, drainage and reinforce", was discussed in combination with engineering construction. This paper mainly included the following aspects:(1) The karst water inrush was summarized in combination with the tunnel construction, which included the law, scourge characteristics, prevention methods and treatment measures of karst water inrush.(2) The rock strengthσ1 was affected by some factors that included the fissure direction,fissure length,confine pressureσ3 and fissure water pressure, when it suffered from pressure shear stress states or tensile shear stress states respectively. The rock wall to prevent the water inrush was simplified plane strain fixed end beam, and its stress states was answered by simplified model. The critical states of fissure rupture was analyzed when it suffered from different stress states, which included pressure shear stress or tensile shear stress respectively, and the safe thickness of the rock between karst and tunnel was determined by the fissured fracture critical state of karst water inrush.(3) Based on catastrophe theory, two aspects were analyzed, one was instability mechanism of the rock between karst and tunnel, the other was the parameter variation that influenced on the rock instability, then the safe thickness of the rock could be anwsered. (4) The karst inrush disaster results were analyzed firstly, then the risk of water inrush disasters was studied by reliability theory to meet with the errors and local of drilling hole and other geological prediction methods. By comparing with different risk criteria, which of karst water inrush was established, and data management system was developed by use of VISUAL BASIC 6.0, which could be used to manage the data information, determine the disaster risk.(5) Firstly, mixing nano perfusion agents with portland cement together, and adding different water cement ratio to test its mobility that was compared with portland cement's mobility, which gave the water cement ratio recommendatory values of mixing nano perfusion agents with portland cement together. Secondly, based on the same grout mobility, grout shrinkage was tested and compared between mixing nano perfusion agents with portland cement together and portland cement, and gave the recommendatory values, which blended nano perfusion agents with portland cement. Sand was used to simulate the seepage of grout filling, and the used to simulate the grouting effect of rock cranny.(6) In order to overcome the inflow of fissure and drilling hole, having carried out a experiment to test the two liquid grout gel time of cement and water glass that added nano perfusion agent, and test the gel time of different cement ratio and water glass, and test the gel time of different baume degrees when the ratio of cement and water glass was 1:1, and analyzed the change law of gel time.(7) Based on the viscosity varying characteristics with time, a pervasion model of sand or fissure grouting was established, and some affection factors to pervasion areas, which included pervasion coefficient of different sand, fissure length, grouting pressure, grouting drill hole diameter, gel time, were analyzed. The reasonable grouting parameter, which included material, grouting pressure, drilling hole diameter and pervasion areas, could be adopted to prevent the grout diffusing to more areas when grouting in the rock between tunnel karst cave.(8) According to the mechanism of karst water inrush, the application technology about water buck and grouting of karst water inrush scourge with engineering congstruction.
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