Evaluate the Behavior of Fluid Flow in Rock Mass According to the Result of Water Pressure Tests in the Bakhtiari Dam Project

Abstract

This paper aims to evaluate the behavior of fluid flow in rock fractures in a scale larger than the laboratory scale and to study the results of a number of water pressure tests in the Bakhtiari dam. The flow pattern of the fluid in the fractures existing in the tests or the relationship between the flow rate and fluid pressure has been divided into three groups comprising Darcy linear behavior, nonlinear behavior induced by inertial effect and nonlinear behavior under the influence of the fracture dilatation. The nonlinearity induced by inertial effect has been studied using nonlinear fitting of the water pressure test results. This analysis depicts that the Forchheimer equation properly describes the nonlinear behavior of fluid flow in the rock mass. Besides, the linear and nonlinear coefficients of the Forchheimer equation have been determined using a nonlinear fitting. By use of the quantitative criterion for flow nonlinearity in laboratory tests, a method has been presented for estimating critical Reynolds number in field tests. This quantification helps to estimate the critical Reynolds number and to determine the deviation from linear to nonlinear flow to better understand the fluid behavior in field tests such as water pressure test.