深埋高地应力水工隧洞地应力特征及岩爆脆性破坏深度预测研究

Research on In-Situ Stress Characteristics of Deep-Buried High-In-Situ Hydraulic Tunnel and Prediction of Rockburst Brittle Failure Depth

为解决高地应力情况下水工隧洞开挖时产生的岩爆问题,以新疆某高埋深水工隧洞为依托,并结合现场水压致裂法和钻孔套芯解除法测试获得的地应力数据。研究深埋引水隧洞区域地应力场分布规律,通过强度理论判断岩爆发生的可能性;在考虑高地应力与围岩开挖二次应力状态作用前提下,通过岩爆破坏区深度理论公式,结合现场数据计算出岩爆破坏深度。结果表明:1)隧洞处平均初始地应力应力基本在23 MPa左右,最大水平主应力为28.6 MPa,属于高地应力隧洞;2)三向主应力间的总体关系为σ_(H)(最大水平应力)>σ_(Z)(自重应力)>σ_(h)(最小水平应力),属于σ_(HZ)(走滑型)初始地应力场,以水平构造应力为主导;3)隧洞最大主应力与最小主应力之间差值较大,依据摩尔-库仑准则,表明该隧洞开挖的临空面会存在较大的剪应力,易引起隧洞发生岩爆;4)在隧洞开挖过程中,隧洞将会发生中—强等级的岩爆,发生岩爆脆性破坏最大深度为0.68 m。

In order to solve the rockburst problem caused by hydraulic tunnel excavation under the condition of high insitu stress,a deep-buried hydraulic tunnel in Xinjiang is taken as example,and the in-situ stress data from the tests are obtained combined the on-site hydraulic fracturing method and the drilling sleeve core removal method.First,the distribution laws of the in-situ stress field in the deep-buried hydraulic tunnel area are studied,and the possibility of rockburst occurence is judged through strength theory.Then,considering the effects of high in-situ stress and the secondary stress state of surrounding rock excavation,the damage depth of the rockburst is calculated through the theoretical formula of the depth of rockburst failure zone.The results show that:(1)The average initial in-situ stress at the tunnel is basically around 23 MPa,and the maximum horizontal principal stress is 28.6 MPa,which belongs to the high in-situ stress tunnel.(2)The overall relationship among the three-dimensional principal stresses isσ_(H)>σ_(Z)>σ_(h),which belongs to theσ_(HZ)-type initial in-situ stress field,and the horizontal tectonic stress is dominant.(3)The differential value between the maximum and the minimum principal stresses of the tunnel is large,and according to the Mohr-Coulomb criterion,it shows that the tunnel excavation will have a large shear stress on the free surface and easy to cause rockburst in tunnel.(4)During tunnel excavation,medium to strong rockburst will be occccrred in the tunnel,and the maximum depth of rockburst brittle failure is 0.68 m.