隧道完整型岩盘渗透破坏失稳机制流固耦合模型试验研究

Liquid-solid Coupling Model Test to Investigate Seepage Failure Mechanism of Intact Confining Rocks of Tunnels

为研究深长隧道开挖过程中完整型岩盘在工程扰动和地下水渗流作用下发生渗透破坏的失稳机制,以在地形地质条件复杂的中西部地区修建的深长隧道-利万高速齐岳山隧道为工程背景,通过能够同时实现高水压加载和隧道开挖的渗流突水模型试验系统和配制的流固耦合相似材料,开展深长隧道完整型岩盘渗透破坏灾变演化规律的物理模型试验,研究了开挖扰动和防突岩盘厚度对其渗流特征的影响.研究结果表明:深长隧道完整型岩盘渗透破坏失稳突水本质是开挖扰动和地下水渗流耦合影响下突水通道逐渐形成、防突岩盘逐渐丧失阻水能力的结果;开挖扰动和防突岩盘厚度对围岩内水压力分布和涌水量具有显著的影响,围岩水压在承压水渗流作用下经历"稳定-增大-稳定"的过程;隧道开挖过程中,承载水压、涌水量与防突岩盘厚度分别表现出正、负线性关系,水力梯度及渗透系数均具有明显的分段特征,突变点前水力梯度和渗透系数基本稳定,突变点后水力梯度急剧减小而渗透系数快速增大;随着防突岩盘厚度的减小,岩盘的阻水性能逐渐降低,对外加水压的承压能力逐渐下降;突水灾害的发生虽具有很强的"突变"性,但突水通道的形成将经历一个较慢的渗透破坏过程.研究结果可为深长隧道突水灾变机理的研究提供参考.

In order to investigate the seepage failure mechanism of intact confining rocks of deep and long tunnels under the conditions of engineering activity and groundwater seepage,an experimental system for water-inrush simulation induced by high water pressure and excavation was developed.A similar material for liquid-solid coupling was compounded,based on the deep and long tunnel built in Midwest China where topographic and geologic conditions are very complex,i.e.,Qiyueshan Tunnel.Further study on the evolution of water inrush induced by seepage failure was done using the physical model tests,the influence of excavation and seepage on hydraulic characteristics was researched.The experimental results show that the water inrush induced by seepage failure results from the gradually formed of water-inrush channel and the gradually losing water resistant ability of the intact rock under the effects of excavation and groundwater seepage.The influence of the excavation and thickness of the intact rock on the water distribution and the groundwater inflow rate is significant.Water pressure within the surrounding rock could be almost firstly remaining constant,and then increasing,and finally remaining constant.A positive linear relationship between water pressure and the thickness of the intact rock,and a negative linear relationship between inflow rate and the thickness of the intact rock were found.Furthermore,the measured hydraulic gradient and the calculated hydraulic conductivity show phase characteristics:the hydraulic gradient and hydraulic conductivity would remain steady before the turning point,the hydraulic gradient drastically decreases and the hydraulic conductivity increases rapidly after the turning point.The water resistant ability of the intact rock will decrease along with the decrease of its thickness.Although the water-inrush disaster is a mutation disaster,the formation of water-inrush channel almost goes through a slow process.The results provide a valuable reference for the mechanism research of water inrush in deep and long tunnels.