【作者】 罗鹏；

【导师】 刘建；

【作者基本信息】 西南交通大学 ， 环境工程（专业学位）， 2019， 硕士

【摘要】 断裂破碎带及宽张裂隙处涌水具有速度快和水量大等特点,严重威胁隧道施工安全。常见隧道涌水预测方法主要基于达西定律且忽略裂隙交叉处的局部损失,存在不能恰当描述裂隙型涌水通道内水流高速运动规律和绝对水头压力估计过大等问题,结果是涌水预测值与实测值相差巨大。针对裂隙型隧道高速涌水预测结果失真的问题,基于自然基金项目(41602241),本文首先构建了单裂隙、交叉裂隙的物理模型,研究了裂隙内水流运动规律和裂隙交叉处局部水头损失的表达式;在此基础上,进一步构建裂隙网络的物理模型,研究裂隙网络流阻的表达与分布。基于前述研究成果,最后建立了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,为准确预测裂隙型隧道涌水奠定了理论基础。选用长度70cm、厚度1.8cm的天然大理石岩块构建隙宽为1.17mm的单裂隙渗流试验模型,试验结果表明:裂隙中水流呈非达西流状态(Re=19856.45~35633.80);相较达西线性方程,Forchheimer方程由于同时具有粘性项和惯性项,能更好地描述裂隙中水流的运动规律。选用长度70cm、厚度1.8cm的天然大理石岩块构建30°、60°和90°的交叉裂隙渗流试验模型。基于单裂隙渗流规律研究成果和测压点之间的水头损失和流量测试值,获取整条裂隙段的水文参数,再根据总水头损失与沿程水头损失和局部水头损失之间的关系,计算裂隙交叉处的局部水头损失。结果表明:随着交叉角度的增大,裂隙交叉处的局部流阻也随之增大;裂隙交叉处的局部损失系数可表达为ζ=0.3392(sinθ)+1.0638;局部流阻在整个流阻中占比例约4.8%~11.5%,若被忽略,其引起的误差是显而易见的。选用长度80cm、宽度70cm、厚度1.8cm的天然大理石岩块构建了包含2个进口、2个出口、8段平直裂隙、4个交叉节点(均为90°交叉)的裂隙网络试验模型。试验结果表明:当裂隙网络承受相同压力差的情况下,1#和2#进、3#和4#出的流量最大,1#进、3#出的流量最小;网络流阻与流量有关,可表达为R_w=f(Q,a,b,θ);局部流阻在整个网络裂隙流阻中占比例约6.1%~23.2%,且该比例随出口数量的增加亦将大幅度增加,其影响不容忽视。基于前述研究成果,建立了不同裂隙分布时,考虑局部流阻的隧道非达西流涌水预测模型:Q=f(H,a,b,l,θ),为准确预测隧道涌水奠定了理论基础。应用该模型的关键是,获取裂隙分布及裂隙露头的水文参数。更多还原

【Abstract】 The gushing water at the fracture zone and the wide fracture zone are characterized by high speed and large water volume,which seriously threaten the safety of tunnel construction.The common tunnel water inrush prediction method is mainly based on Darcy’s law and ignores the local loss at the intersection of cracks.There are problems such as the high-speed motion law of the water flow and the excessive estimation of the absolute head pressure in the fracture-type water channel.The result is a huge difference between the predicted value of the water inrush and the measured value.Aiming at the problem of distortion of high-pressure water surge prediction results in fractured tunnels,based on the natural fund project(41602241),this paper firstly constructed a physical model of single-fracture and cross-fracture,studied the law of water flow in cracks and the expression of the local head loss at the intersection of the crack.On this basis,the physical model of the fracture network is further constructed to study the expression and distribution of the flow resistance of the fracture network.Based on the above research results,the non-Darcy flow water prediction model of sparsely fractured rock mass tunnel considering local flow resistance is established,which lays a theoretical foundation for accurately predicting the water inrush of fractured tunnel.A natural marble block with a length of 70cm and a thickness of 1.8cm was used to construct a single-fracture seepage test model with a gap width of 1.17mm.The test results show that the water flow in the fracture is non-Darcy flow state(Re=19856.45~35633.80);Compared with the Darcy linear equation,the Fochheimer equation can better describe the motion law of water flow in the fracture due to both the viscous term and the inertial term.A natural marble block with a length of 70 cm and a thickness of 1.8 cm was used to construct cross-fracture seepage test model of 30°,60°and 90°.Based on the research results of the single-fracture seepage law and the head loss between the pressure-measuring points and flow test values,the hydrological parameters of the entire fracture segment are obtained,then calculate the local head loss at the intersection of the cracks based on the relationship between the total head loss and the head loss and local head loss along the path.The results show that with the increase of the intersection angle,the local flow resistance at the intersection of the fracture increases;The local loss coefficient at the intersection of the fracture can be expressed asζ=0.3392(sinθ)+1.0638;The local flow resistance accounts for about 4.8%to 11.5%of the total flow resistance,If it is ignored,the error caused by it is obvious.A fracture network test model consisting of two inlets,two outlets,eight sections of straight cracks,and four intersections(all 90°intersections)was constructed using natural marble blocks of length 80cm,width 70cm and thickness 1.8cm.The test results show that when the fracture network is subjected to the same pressure difference,the flow rates of 1#and 2#,3#and 4#are the largest,and the flow of 1#and 3#is the smallest;the network flow resistance is related to the flow.It can be expressed as R_w=f(Q,a,b,θ).The local flow resistance accounts for about 6.1%to 23.2%of the total network flow resistance,and the ratio will increase greatly with the increase of the number of exports,and its impact cannot be ignored.Based on the above research results,the tunnel non-Darcy flow water prediction model considering local flow resistance is established when different fracture distributions are established:Q=f(H,a,b,l,θ),which lays a theoretical foundation for accurately predicting tunnel water inrush..The key to applying this model is to obtain the fracture distribution and the hydrological parameters of the fracture outcrop.更多还原