输水隧洞穿越典型断面围岩结构安全分析

Structural Safety Analysis of Surrounding Rock of Water Conveyance Tunnel Crossing Typical Section

复杂地质条件是影响TBM输水隧洞结构安全的重要因素,以某引水工程中输水隧洞为研究对象,理论推导了渗流—应力全耦合作用的数学模型,针对TBM输水隧洞穿越断层和最大埋深段,建立三维有限元模型,计算分析围岩初始地应力场、渗流场,以及不同工况下围岩位移、塑性区和应力的分布规律,研究结果表明:初始地应力和孔隙水压力随着埋深的增加而增大,最大埋深处和断层处初始地应力分别达到1.342MPa、0.680MPa,孔隙水压力分别达到0.260MPa、0.200MPa;开挖过程中,断层和最大埋深段隧洞拱顶沉降量基本接近,相对差值仅为0.11%,而拱底抬升量差值较大,达到31.28%;断层处围岩塑性区主要出现在隧洞两侧,最大深度为2.920 m,最大埋深处围岩塑性区主要出现在隧洞拱顶,最大深度为8.627 mm;围岩最大压应力在断层和最大埋深段分别为7.987MPa、6.510MPa;内水压力作用,围岩位移和最大压应力相对于开挖阶段均有一定程度的降低。

Complex geological conditions are important factors affecting the structural safety of TBM water conveyance tunnels. Taking the water conveyance tunnel in a water diversion project as the research object, the mathematical model of the seepage-stress full coupling effect was theoretically derived. For the TBM water conveyance tunnel crossing the fault and the maximum buried depth section, a three-dimensional finite element model was established to calculate and analyze the initial in-situ stress field and seepage field of surrounding rock, as well as the distribution law of displacement, plastic zone and stress of surrounding rock under different working conditions. The results show that during the excavation process, the settlement of the arch crown of the fault and the tunnel with the maximum buried depth is basically close, and the relative difference is only 0.11%, while the difference of the uplift of the arch bottom is large, reaching 31.28%;The plastic zone of surrounding rock at the fault mainly appears on both sides of the tunnel, with a maximum depth of 2.920m, and the plastic zone of surrounding rock at the maximum buried depth mainly appears on the vault of the tunnel, with a maximum depth of 8.627mm. The maximum compressive stress of surrounding rock is 7.987 MPa and 6.510 MPa respectively in the fault and the maximum buried depth section. Under the action of internal water pressure, the displacement and maximum compressive stress of surrounding rock are reduced relative to the excavation stage.