Non-Darcy Flow Experiments of Water Seepage through Rough-Walled Rock Fractures

Abstract

The knowledge of flow phenomena in fractured rocks is very important for groundwater-resources management in hydrogeological engineering. The most commonly used tool to approximate the non-Darcy behavior of the flow velocity is the well-known Forchheimer equation, deploying the "inertial" coefficient that can be estimated experimentally. Unfortunately, the factor of roughness is imperfectly considered in the literature. In order to do this, we designed and manufactured a seepage apparatus that can provide different roughness and aperture in the test; the rough fracture surface is established combining JRC and 3D printing technology. A series of hydraulic tests covering various flows were performed. Experimental data suggest that Forchheimer coefficients are to some extent affected by roughness and aperture. At last, favorable semiempirical Forchheimer equation which can consider fracture aperture and roughness was firstly derived. It is believed that such studies will be quite useful in identifying the limits of applicability of the well-known "cubic law," in further improving theoretical/numerical models associated with fluid flow through a rough fracture.

Laboratory Simulation of Flow through Rough-Walled Microfractures under High Hydraulic Gradient

“…This deviation in the flow can be a result of significant inertial effect or fracture dilation. The results are consistent with previous literature [23,26].…”

Experimental study on seepage characteristics of microfracture with different aperture

“…This difference can be attributed to the result of inertial effect or fracture dilation, with the increase of flow velocity, the effect of inertial force becomes more and more significant, and the relationship between hydraulic gradient and velocity deviates from the linear relationship more and more 12 . For samples with different aperture, with the increase of the fracture aperture, the increase rate of the average velocity decreases gradually, as has been reported in the literature 24 .…”

A Systematic Investigation Into the Control of Roughness on the Flow Properties of 3D‐Printed Fractures

“…Recent 3DP studies investigated shear response (and asperity degradation) (Ishibashi et al., 2020) and non‐Darcian flow regimes (Yin et al., 2020) in polymeric rough fractures. Attempts to more accurately replicate natural fracture material properties produced 3DP fracture replicas that were later molded into concrete (Q. Jiang, Feng, Gong, et al., 2016; Ni et al., 2018) or natural minerals (Fang et al., 2018). However, replicating fractures using higher strength materials is resolution‐limited.…”

“…Attempts to more accurately replicate natural fracture material properties produced 3DP fracture replicas that were later molded into concrete (Q. Ni et al, 2018) or natural minerals (Fang et al, 2018). However, replicating fractures using higher strength materials is resolution-limited.…”