考虑局部流阻的稀疏裂隙岩体隧道非达西流涌水预测模型

People's life and wealth in tunnels are threatened by large scale and nonlinear water inflow, which often happens through faults and wide tension fissures as they are the main seepage channels of fractured rocks. Aiming at overcoming the disadvantage of mainly using linear Darcy's law and disregarding the local water head loss in fracture network seepage and tunnel inflow predication research, this program uses natural quartz sandstone to construct a physical model for modelling fracture network seepage, and then discuss the real motion state and its transition law, on the basis of identifying the non-Darcy flow hydraulic parameters of each fracture by fitting them using Forchheimer equation. By means of introducing theories for calculating the local water head loss of cross fracture into network head loss distribution analysis, a seepage model will be built for fracture network flow calculation based on Kirchhoff law, and then a non-Darcy tunnel inflow predication model should be derived from it by setting the outlet flow of fractures as a goal with comprehensively validated by physically modelling and numerically modelling. This project is expected to reveal the actual seepage state and its transition rule in fractures, and provide a new method for predicting water inflow into tunnels in sparsely fractured rocks. It is valuable for theoretical research and engineering application, on safety guarantee of tunnel construction and operation as well as protection for the living and ecological environment in tunnel areas.

断层、宽张裂隙等是裂隙岩体的主要渗流通道，被隧道揭穿后常发生大规模非线性涌水，威胁洞内生命及财产安全。针对裂隙网络渗流和隧道涌水预测主要采用线性达西定律且不考虑局部流阻等不足，本项目采用天然石英砂岩构建裂隙网络渗流的物理模型，运用Forchheimer方程计算单裂隙非达西流水力参数，探析水流运动状态及其沿程演变规律；引入交叉水流局部水头损失计算理论，研究裂隙网络流阻分布，基于Kirchhoff定律建立裂隙网络渗流模型；以裂隙出口流量为求解目标，推导裂隙被隧道切穿后的涌水预测模型，采用物理模拟和数值模拟进行综合验证。通过本项目研究，可望揭示裂隙真实渗流状态及其演变规律，为稀疏裂隙岩体隧道涌水预测提供新思路，研究成果对保障隧道施工和运营安全，保护隧道地区人居和生态环境，具有重要理论价值和实践意义。

断裂破碎带及宽张裂隙处涌水具有高速、高压和高致灾的特点，严重威胁隧道施工和运营安全。针对常规隧道涌水预测方法因未考虑裂隙中水流状态和忽略裂隙交叉处局部损失进而导致预测结果失真的问题，本项目采用天然大理石岩块构建单裂隙、交叉裂隙和网络裂隙渗流的物理模型，研究了裂隙中的渗流规律、局部流阻和非达西流涌水预测模型。项目取得的主要研究成果如下：1）岩体裂隙中的渗流可以用Forchheimer方程描述，该方程的参数a、b均可表达为隙宽e的幂函数；2）以压力梯度-流量曲线的斜率突变点作为达西-非达西流转变的临界点，在试验中验证可行；3）裂隙交叉引起的局部流阻与交叉角度θ和渗流速度v有关，可用正弦函数或logistic函数表达；4）基于物理试验和Kirchhoff定律，计算得出网络裂隙中局部流阻占总水头损失的6.1%～23.2%，不容忽视；5）由于裂隙网络的复杂性，其涌水预测模型会因裂隙网络构成、隙宽、水头和局部交叉角度等不同而不同，不考虑裂隙宽度变化的情况下，裂隙网络非达西流涌水预测可采用通用模型Q=f(a,b,H,θ)表达。上述研究成果为正确认识裂隙中的渗流状态及渗流规律、快速计算交叉处的局部流阻和准确预测稀疏裂隙岩体隧道非达西流涌水奠定了重要的理论基础，对保障隧道施工和运营安全具有现实意义。