深埋硬岩隧洞系统砂浆锚杆的加固机制与加固效果模拟方法

系统布置的砂浆锚杆是深埋硬岩隧洞主要支护结构,锚杆与围岩组成锚杆–围岩复合结构体,使围岩的力学特性得到改善。基于岩体的莫尔–库仑(M-C)屈服准则,推导锚杆–围岩复合结构体满足M-C准则的应力条件。结合岩体劣化本构模型,提出确定锚杆–围岩复合结构体力学参数的方法。锚杆与弹性围岩和屈服围岩组成的锚杆–围岩复合结构体的力学参数确定方法不同,锚杆与屈服围岩组成的锚杆–围岩复合结构体的力学参数与围岩当前状态的等效塑性应变有关。基于此提出一种模拟隧洞开挖支护过程中系统普通砂浆锚杆加固效果的数值方法。该方法能较好地模拟锚杆支护时机对围岩稳定性的影响。最后运用该方法对锦屏II级水电站2#引水隧洞围岩稳定性进行分析,为隧洞的施工和支护设计提供参考依据。

REINFORCING MECHANISM AND SIMULATING METHOD FOR REINFORCING EFFECTS OF SYSTEMICALLY GROUTED BOLTS IN DEEP-BURIED HARD ROCK TUNNELS

Systematically grouted bolts,as the main support structure of deep-buried hard rock tunnels,compose the bolt-rock composite structure with surrounding rocks,which reinforces the mechanical property of surrounding rocks.Based on the Mohr-Coulomb(M-C) criterion,the stress condition and the strength of the composite structure meeting the M-C criterion were derived under high-stress conditions.Combining with the rock mass deterioration model(RDM) of brittle rock,an approach to determine the mechanical parameters of the composite structure was presented.The difference of mechanical parameters between two different composite structures of bolt-elastic surrounding rock and bolt-yielding surrounding rock was taken into account.In this approach,the mechanical parameters of the bolt-yielding surrounding rock composite structure were associated with present equivalent plastic strain of surrounding rocks.A numerical method,which could model the reinforcing effect of normally grouted bolts laid out systematically during excavating and supporting stages,was proposed.It is identified that this method has an advantage over other methods in modeling the effect of supporting time on surrounding rock stability.Finally,the method was applied to evaluate the stability of surrounding rocks,and related references were provided for design and construction of the diversion tunnel #2 of Jinping II hydropower station.