基于围岩变形主动控制理念的隧道支护时机虚拟支撑力法

Virtual Supporting Force Method for Tunnel Support Timing Based on the Concept of Active Deformation Control of Surrounding Rock

基于隧道纵向空间与时间效应构建求解隧道支护时机的虚拟支撑力法,并通过调整支护时机以达到主动调控围岩变形的目的。根据Drucker-Prager屈服准则,以围岩临空面单元的整体安全系数建立支护时机控制基准;利用掌子面掘进速率不变的假定,将隧道纵向空间问题转化为时间问题;基于围岩应力释放率和围岩整体位移完成系数与掌子面纵向推进的相互关系,提出求解支护体系(初期支护或超前支护)支护时机的力学模型及虚拟支撑力求解方法。依托成兰铁路茂县隧道,分别求解围岩级别不同、埋深不同、侧压力系数不同时支护体系的极限支护时机,对比有无超前支护2种情况下隧道变形的监测结果与求解方法得到的计算结果,验证该方法的有效性。结果表明:隧道Ⅲ级围岩拱顶和拱底的安全系数大于拱腰;围岩级别对支护时机的影响最大,其次为应力水平,最次为埋深;求解方法的计算结果与隧道实测结果间的绝对误差仅为1.3 cm,支护时机对围岩变形的主动控制效应显著。

Based on the longitudinal space and time effects of tunnels,a virtual supporting force method for solving the tunnel support timing was constructed to achieve the purpose of active deformation control of the surrounding rock by adjusting the support timing.According to the Drucker-Prager yield criterion,the support timing control standard was established using the overall safety factor of the free surface unit of surrounding rock,and the problem of longitudinal space of tunnel was transformed into that of time using the assumption of fixed tunneling rate of tunnel face.Based on the relationship between the stress release rate and the overall displacement completion coefficient of the surrounding rock and the longitudinal propulsion of the tunnel face,the mechanical model and the virtual supporting force method for solving the support timing of the support system(primary support or advanced support)were proposed.Relying on the Maoxian tunnel of ChengduLanzhou Railway,the maximum support timing of the support system with different surrounding rock levels,different buried depths and different lateral pressure coefficients was solved,respectively.Comparing the monitoring results of tunnel deformation with the calculation results obtained by the solution method with and without the advanced support,the effectiveness of the method was verified.The results show that the safety factors of the vault and the bottom are larger than those of the waist for the levelⅢsurrounding rock of the tunnel.The level of surrounding rock has the greatest influence on the support timing,followed by the stress level and the buried depth,respectively.The absolute error between the calculation results obtained by the solution method and the measured results of the tunnel is only 1.3 cm.The support timing has a significant effect on the active control of surrounding rock deformation.