Abstract
Laboratory experiments on fluid flow through fracture are important in solving the fluid-in-rush problems that happen during the tunnel excavation. In order to study the mechanism of fluid flow through a rough-walled microfracture, fluid flow experiments were carried out and the fiber Bragg grating (FBG) strain sensors were applied to monitor the deformation of the microfracture surface during the seepage process. Considering the difficulty of collection of undisturbed rock samples from the deep locations, a methodology to simulate fluid flow through a fractured rock mass using analog materials containing a single fracture was developed. This method is easy to simulate the fluid flow through a fracture of certain aperture. Experimental data showed that Forchheimer equation could provide an excellent description of the nonlinear relationship between hydraulic gradient and flow velocity, and the variations of Forchheimer coefficients with joint roughness coefficient (JRC) were studied. It was found that the deformation of the microfracture surface subjected to seepage could be accurately captured by the quasi-distributed FBG strain sensors. The test results also demonstrated that the surface strain is significantly affected by hydraulic pressure.
Highlights
The coupling effect of stress-seepage in fractured rock mass has played an increasingly important role in the geotechnical engineering activities, such as for construction of dam foundations, ore mineral extraction, water inrush prevention, and grouting activities [1,2,3,4,5,6]
It has been found by researchers that fluid flow behavior through a rock mass is affected by many factors, such as the fracture geometry, fracture surface irregularities, fracture in-filling materials, fluid pressure, and confining pressure [11,12,13,14]
Fluid flow properties may not be modelled using cubic law because of the rough and irregular of fracture making contact with each other at discrete points could lead to the development of nonlinear flow
Summary
The coupling effect of stress-seepage in fractured rock mass has played an increasingly important role in the geotechnical engineering activities, such as for construction of dam foundations, ore mineral extraction, water inrush prevention, and grouting activities [1,2,3,4,5,6]. Single fracture is the basic unit of rock mass fracture network, and its hydraulic characteristics affect the seepage law of rock mass [7,8,9]. To investigate this phenomenon, a number of theoretical models had been proposed, in which the cubic law is most popular. Rock fracture in realistic situations has very complicated geometric characteristics and obviously deviated from a parallel-plate model [10]. It has been found by researchers that fluid flow behavior through a rock mass is affected by many factors, such as the fracture geometry (width, density, aperture, orientation), fracture surface irregularities (roughness), fracture in-filling materials, fluid pressure, and confining pressure [11,12,13,14]
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