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岩体裂隙网络二维非线性渗流特性与模型
Two-Dimensional Nonlinear Flow in Rock Fracture Networks:Characteristics and Modeling
【作者】 刘杰;
【导师】 王者超;
【作者基本信息】 山东大学 , 岩土工程, 2019, 硕士
【摘要】 对于岩石工程中常见的裂隙岩体,其内部发育的裂隙网络是水及其他流体流动的主要通道。地下水封石油洞库是利用地下水渗流实现其功能的典型岩石工程,渗流场分析要求高,裂隙渗流特性研究对洞库性能评价有着非常重要和直接的作用,同时对于水利水电、核废料地下处置、岩土环境保护等重大工程都具有重要意义。而且对于复杂岩体裂隙网络在较高水力梯度作用下,常用的裂隙线性渗流理论在很多工程实践中已经难以适用,裂隙网络的非线性渗流问题也成为岩石力学和水文地质等领域的研究重点之一。本文主要针对岩体裂隙网络,将裂隙网络划分为单裂隙和交叉裂隙进行研究,采用室内试验、理论分析和数值模拟相结合的研究方法,综合分析了岩体单裂隙和交叉裂隙的非线性渗流特性,提出了交叉裂隙非线性渗流计算模型,并开展了裂隙网络非线性渗流计算应用和验证。主要成果如下:(1)研究了粗糙度对单裂隙渗流的影响,建立了考虑粗糙度的单裂隙渗流模型。定制了裂隙渗流试验仪器,运用3D打印技术制作了9个粗糙单裂隙模型,开展了大范围雷诺数条件下不同粗糙度单裂隙的渗流试验。对单裂隙线性渗流模型进行了推导分析,从理论方面解释了线性渗流模型的适用条件。分析对比了不同参数的粗糙单裂隙非线性渗流特性,得到了粗糙度与非达西系数β、临界雷诺数Rec的关系式,以及单裂隙中非达西效应因子E、沿程损失系数λ的变化特性。(2)提出了交叉裂隙非线性渗流计算模型。以交叉裂隙为研究对象,综合考虑交叉裂隙的交叉角度、开度、粗糙度等特征因素的影响,提出并验证了交叉裂隙的非线性渗流计算模型,为交叉裂隙非线性渗流研究提供了可通用的理论方法。模型形式统一,结构简单,便于总结对比不同交叉裂隙工况的渗流特性。进一步研究了交叉裂隙非线性渗流的临界雷诺数和微观流动结构的变化。(3)建立了交叉裂隙非线性渗流模型参数与交叉裂隙影响因素的关系表达式。设置了不同特征的交叉裂隙工况进行模型,对比分析了交叉裂隙计算模型中非线性参数的变化,得到了非线性参数关于交叉裂隙特征因素的表达式,并通过组合工况进行了验证。(4)开展了离散裂隙网络二维非线性渗流计算应用和验证。根据对单裂隙渗流特性和交叉裂隙非线性渗流计算模型的研究,应用离散裂隙网络非线性渗流计算方法,对裂隙网络渗流计算和地下储油库水封性评价案例进行了分析,并通过与数值模拟等不同方法的对比,验证了裂隙网络非线性渗流计算方法的可行性、准确性。表明在裂隙网络渗流计算中应考虑交叉裂隙的影响和裂隙网络渗流的非线性特性。
【Abstract】 For fractured rock masses commonly found in rock engineering,the internally developed fracture network is the main channel for water and other fluid flows.The underground water-sealed oil storage is a typical rock engineering that uses groundwater flow to realize its function.The analysis accuracy of flow field is demanded to be high.The study of fluid flow characteristics has a very important and direct effect on the performance evaluation of the storage.At the same time,it is of great significance for water conservancy and hydropower,underground disposal of nuclear waste,geotechnical environmental protection and other major projects.Also,the commonly used linear fracture flow theory is difficult to apply in complex rock mass fracture networks under high hydraulic gradients for many engineering practices.The nonlinear flow of the fracture network has become one of the key research topics in the fields of rock mechanics and hydrogeology.In this paper,the rock fracture network is divided into single fractures and intersecting fractures.The non-linear characteristics of fraracture flow are comprehensively analyzed by means of laboratory experiment,theoretical analysis and numerical simulation.In this paper,a non-linear flow calculation model of intersecting fracture is proposed,and the nonlinear flow calculation method of fracture network is applied and verified.The major results of this study are summarized below:(1)The influence of roughness on single fracture flow was studied,and a single fracture flow model considering roughness was established.The fracture flow test instrument was customized,and 9 rough single fracture models were fabricated by 3D printing technology.The flow experiments of different rough single fractuers under large Reynolds number conditions were carried out.The linear flow model of single fracture was deduced and analyzed,and the applicable conditions of the linear seepage model were explained theoretically.The nonlinear characteristics of rough single fracture flow with different geometrical parameters were analyzed and compared,and the relations between non-Darcy coefficient P,critical Reynolds number Rec and roughness,and the variation characteristics of non-Darcy effect factor E and friction factor λ were obtained.(2)A non-linear flow calculation model for intersecting fracture was proposed.Taking the influence range of intersecting fractuer as the research object,considering the intersecting-angle,aperture and roughness of intersection,a non-linear flow calculation model of typical intersecting fractuers was proposed and verified by numerical simulation,which provided a general theoretical method for the study of non-linear flow characteristics of intersecting fractures.The model was unified in form and simple in structure,which was convenient for summarizing and comparing the flow characteristics of different intersecting fracture cases.The characteristics of critical Reynolds number and microscopic flow structure of intersecting fracture non-linear flow were further studied.(3)The parametric expressions of non-linear flow calculation model for intersecting fracture were obtained.The intersecting fracture cases with different characteristics were set,and the variation of nonlinear parameters in calculation model was compared and analyzed.The parametric expressions of non-linear flow calculation model with respect to the intersecting fracture characteristics were obtained and verified by combined cases.(4)The nonlinear flow calculation method for two-dimensional discrete fracture network was applied and verified.Based on the study of flow characteristics of single fracture and nonlinear flow calculation model of intersecting fracture,the nonlinear flow calculation method of discrete fracture network was applied to analyze the flow calculation of fracture network and a case study on containment properties of underground oil storage.The feasibility and accuracy of the nonlinear flow calculation method for fracture network were verified by comparison with different methods such as numerical simulation.It was shown that the influence of intersecting fracture and the nonlinear characteristics of fracture network flow should be considered in the flow analysis of fracture network.
【Key words】 rock fracture flow; single fracture; intersecting fracture; nonlinear flow model; flow of fracture network;