由于海底隧道隧道施工方法和支护体系的复杂性,仅采用某一个稳定性指标对围岩及支护结构的安全性进行正确判定具有一定的困难。依据围岩及支护结构的力学特性,首次提出周边位移、变形速率、变形加速度3参数定量指标和支护结构裂缝状态、地下水状态2参数定性指标5参数安全判定指标;依据隧道位移管理基准,将围岩及支护结构变形过程分为不稳定、险情、异常和正常4个危险等级;依据实测位移累计值U和位移控制基准U0以及围岩变形时间t,确定围岩及支护结构不同危险等级下的容许变形速率;最后通过定量和定性综合分析,确定大断面海底隧道5参数施工阶段安全判定基准,为正确判定围岩-支护结构的稳定性和有效预防坍方事故的发生,提拱了判定依据。本基准已在厦门东通道(翔安)海底隧道获得有效的实施。
Because of the complexity of construction methods and support system of subsea tunnels,it is difficult to judge the surrounding rock and support safety only by using one stability index.Five determinant indexes about the surrounding rock and support safety are put forward based on their mechanical characteristics,including three quantitative indexes of surrounding deformation,deformation rate and deformation acceleration and two qualitative indexes of groundwater state and support state of tunnels.The hazard zones are classified based on the displacement control criteria as follows: unstable state,dangerous state,abnormal state and normal state.The allowable deformation rate of surrounding rock and support is determined for different hazard grades based on the total deformation U,displacement control criteria U0 and deformation time of surrounding rock and support t.Finally,the determinant criterion for safety of large cross-section subsea tunnel during construction is put forward by analyzing qualitative and quantitative indexes.It is instructive for judging the safety of surrounding rock and support and for forecasting the collapse of tunnels.This criterion has been implemented in Xiamen East Passage subsea tunnel.