岩石单裂隙渗流粗糙起伏角修正公式研究

发布时间：2018-04-15 07:30

本文选题：渗流 + 粗糙角　；参考：《清华大学》2014年博士论文

【摘要】：岩石裂隙渗流问题的研究具有重要科学意义和工程实用价值。而天然裂隙的粗糙起伏对渗流特性的影响往往不能忽略。本文针对目前粗糙裂隙渗流研究中的一些不足之处,提出了基于粗糙角修正的裂隙渗流公式。运用数值模拟方法和前人的渗流试验进行了对比和验证。最后将公式应用于裂隙岩体渗流模型中,修正了粗糙度对渗流的影响。研究的主要内容如下。分析了10条典型JRC轮廓曲线上的各种粗糙参数,提出了使用有效起伏角即粗糙角α作为研究粗糙裂隙水力特性的核心参数。运用基于Navier-Stokes方程的Fluent软件模拟了锯齿状与JRC典型轮廓两种裂隙的二维渗流场。分析了300多个不同粗糙度、开度、压力梯度的计算工况后,发现在Re10的层流状态下,二维粗糙裂隙的流量系数与粗糙角关系为C=cos4α;而在过渡流态Re10时,流量系数与α、偏转角β、Re都有关。运用局部立方定律也同样推导出了层流渗流公式。基于裂隙微元体与局部立方定律推导出了能描述具有三维粗糙面的裂隙层流渗流的公式,它能够同时考虑裂隙面两个方向上粗糙角对渗流的影响,并反映了粗糙角对渗流的各向异性作用。根据粗糙角与其它粗糙参数的关系,得到了包含各种粗糙变量的渗流公式,扩展了公式的应用范围。建立了100多个形态各异的三维粗糙裂隙数值模型,包括三角锯齿、正弦曲线、JRC轮廓和分形随机四种形状。将数值模拟结果与立方定律、二维裂隙剖面推导的单向粗糙角修正的渗流公式、及三维裂隙推导的二向粗糙角修正的渗流公式的计算值进行对比。发现基于二向粗糙角修正的渗流公式与数值模拟结果最为一致,平均误差只有0.79%,反映了公式的准确性。利用耿克勤的裂隙渗流试验数据进行了公式的验证。在裂隙张拉渗流试验中,公式预测了人工与天然两种粗糙裂隙的渗流量与开度的关系。在裂隙的压密渗流试验中,实验结果分别验证了本文的渗流公式、裂隙变形理论、及推导出的粗糙裂隙渗流-应力耦合关系式,表明公式在渗流应力耦合问题中同样适用。最后将粗糙角修正的渗流公式应用在裂隙交叉流计算分析、裂隙岩体渗流模型数值计算、及裂隙岩体渗流应力耦合模型数值计算中。发现考虑了裂隙粗糙度的计算结果都有明显的变化,因此不能忽略裂隙粗糙度的影响。此外,各应用例子表明粗糙裂隙渗流公式具有广泛的实用性。
[Abstract]:The study of rock fracture seepage is of great scientific significance and practical engineering value.However, the influence of the roughness of natural fractures on seepage characteristics can not be ignored.In this paper, a new formula of fracture seepage based on rough angle correction is put forward in view of some shortcomings in the research of rough fracture seepage at present.The numerical simulation method is compared with the previous seepage test.Finally, the formula is applied to the seepage model of fractured rock mass, and the influence of roughness on seepage is corrected.The main contents of the study are as follows.Various rough parameters on 10 typical JRC contour curves are analyzed, and the effective relief angle (伪) is proposed as the core parameter to study the hydraulic characteristics of rough fractures.Using Fluent software based on Navier-Stokes equation, the two dimensional seepage fields of sawtooth and JRC typical contours are simulated.After analyzing more than 300 calculation conditions of different roughness, opening and pressure gradient, it is found that under laminar flow state of Re10, the relationship between flow coefficient and rough angle of two-dimensional rough fracture is C=cos4 伪, while in transitional flow state Re10, the relation between flow coefficient and roughness angle is C=cos4 伪.The flow coefficient is related to 伪 and deflection angle 尾 -re.The formula of laminar flow is also derived by using the local cubic law.Based on the crack microelement and local cubic law, a formula for describing the laminar flow of a fracture with three dimensional rough surface is derived, which can simultaneously consider the influence of the rough angle on the seepage in both directions of the fracture surface.It also reflects the anisotropic effect of rough angle on seepage.According to the relationship between rough angle and other rough parameters, the seepage formula containing various rough variables is obtained, and the application range of the formula is extended.More than 100 3D rough fracture numerical models with different shapes are established, including triangular sawtooth, sine curve JRC profile and fractal random shape.The numerical simulation results are compared with the calculated values of the cubic law, the unidirectional rough angle modified seepage formula derived from the two-dimensional fracture profile and the two-dimensional rough angle modified seepage formula derived from the three-dimensional fracture.It is found that the seepage formula based on the two-direction rough angle correction is the most consistent with the numerical simulation results, and the average error is only 0.79, which reflects the accuracy of the formula.The formula is verified by Geng Keqin's fracture seepage test data.In the fracture tensile seepage test, the formula predicts the relationship between the seepage flow and the opening of artificial and natural rough fissures.In the compression seepage test of fractures, the experimental results verify the seepage formula, the theory of fracture deformation and the coupling relationship between seepage and stress of rough fractures, respectively. It shows that the formula is also applicable to the seepage stress coupling problem.Finally, the seepage formula modified by rough angle is applied to the calculation and analysis of fracture cross flow, the numerical calculation of seepage model of fractured rock mass, and the numerical calculation of seepage stress coupling model of fractured rock mass.It is found that the calculation results of fracture roughness have obvious changes, so the influence of fracture roughness can not be ignored.In addition, the application examples show that the rough fracture seepage formula has wide practicability.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV223

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