摘要
等效水力隙宽和水力梯度是影响岩体裂隙网络渗流特性的重要因素。制作裂隙网络试验模型,建立高精度渗流试验系统;求解纳维-斯托克斯方程,模拟流体在裂隙网络内的流动状态,研究等效水力隙宽和水力梯度对非线性渗流特性的影响。结果表明,当水力梯度较小时,等效渗透系数保持恒定的常数,流体流动属于达西流动区域,流量与压力具有线性关系,可采用立方定律计算流体流动;当水力梯度较大时,等效渗透系数随着水力梯度的增加而急剧减少,流体流动进入强惯性效应流动区域,流量与压力具有强烈的非线性关系,可采用Forchheimer方程计算流体流动。随着等效水力隙宽的增加,区别线性和非线性流动区域的临界水力梯度呈幂函数关系递减。当水力梯度小于临界水力梯度时,控制方程可选立方定律;当水力梯度大于临界水力梯度时,控制方程可选Forchheimer方程,其参数A和B可根据经验公式计算得到。其研究结果可为临界水力梯度的确定及流体流动控制方程的选取提供借鉴意义。
Equivalent hydraulic aperture and hydraulic gradient are two important factors that significantly affect the permeability of rock mass fracture networks. A test model of fracture network is made and a high accuracy seepage testing system is established. The Navier-Stokes equations are solved to simulate the flow state of the fluid in the fracture network; and the influences of equivalent hydraulic aperture and hydraulic gradient on nonlinear seepage characteristics are studied. The results show that when the hydraulic gradient is smaller, the equivalent permeability holds constants, indicating that fluid flow is in the Darcy＇s flow region; the flow and the pressure have linear relationship and the cubic law can be selected as the governing equation of fluid flow. In contrast, when the hydraulic gradient is higher, the equivalent permeability decreases dramatically with the increment of hydraulic gradient, and fluid flow is in the strong inertia region; the flow and pressure have a strong nonlinear relationship, which can be calculated by the Forchheimer equation. As the equivalent fracture aperture increases, the critical hydraulic gradient, which is utilized to characterize the onset of nonlinear flow in fractures, will decrease following a power law function. When the hydraulic gradient is smaller than the critical hydraulic gradient, the cubic law is selected as governing equation; when the hydraulic gradient is greater than the critical hydraulic gradient, the Forchheimer equation is selected as control equation; the parameters of a and b can be calculated according to the empirical formula. This study can propose useful suggestions to the determination of critical hydraulic gradient and the selection of governing equations when calculating fluid flow in fracture networks.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2016年第11期3165-3174,共10页
Rock and Soil Mechanics
基金
国家重点基础研究发展计划(973)项目(No.2013CB036003)
国家自然科学基金(No.51379117
No.51579239
No.41427802)~~
关键词
裂隙网络
透水试验
非线性渗流
纳维-斯托克斯方程
临界水力梯度
fracture network
water permeability test
nonlinear flow
Navier-Stokes equations
critical hydraulic gradient
