基于离散-连续耦合的岩溶隧道防突岩体安全厚度预测OA北大核心CSTPCD

In order to effectively prevent disasters of sudden water inrush during karst tunnel construction,the recent typical cases of sudden water inrush in Chinese karst tunnels are first investigated,and the formation mechanism and influencing factors of sudden water inrush in tunnels are summarized.Secondly,a discrete-continuous coupling model is established and the method of multiple regression theory is adopted to define criteria for determining the failure of anti-outburst rock mass,categorize the failure modes of anti-outburst rock mass in karst tunnels and propose the crack development law.Then,considering factors affecting the minimum safe thickness of anti-outburst rock mass,prediction formulas for the minimum safe thickness of anti-outburst rock mass are established respectively for three scenarios:the karst cave is located above,below and on the side of the tunnel.Finally,the approach is validated through the Deqing Tunnel Project.The results show that the failure modes of anti-outburst rock mass mainly include bending failure,overall shear failure,and composite failure;and its failure process,based on crack development speed,can be divided into three stages:initial stage,rapid development stage,and gentle development stage.Key factors,in descending order of significance,include water pressure in the solution cavity,surrounding rock bonding parameters,solution cavity span,solution cavity height-to-span ratio and tunnel burial depth in turn.Minimum safe thicknesses for anti-outburst rock masses in the three construction sections of the Deqing Tunnel are calculated as 2.964,5.263 and 0.961 m,respectively.The accurate assessment of sudden water inrush validates the prediction formulas for the minimum safe thickness of anti-outburst rock mass,which can be used to predict and evaluate the risk of sudden water inrush in karst tunnels.