Correlations Developed for Estimation of Hydraulic Parameters of Rough Fractures Through the Simulation of JRC Flow Channels

• Published in: Rock mechanics and rock engineering Vol. 44; no. 4; pp. 447 - 461
• Main Authors: Rasouli, V., Hosseinian, A.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.07.2011; Springer; Springer Nature B.V
• Subjects: Applied sciences; Buildings. Public works; Channels; Civil Engineering; Computation methods. Tables. Charts; Computational fluid dynamics; Correlation; Earth and Environmental Science; Earth Sciences; Exact sciences and technology; Flow channels; Fluid flow; Fluids; Fracture mechanics; Geophysics/Geodesy; Geotechnics; Hydraulic fracturing; Hydraulic properties; Hydraulics; Mechanical properties; Original Paper; Parameter estimation; Rocks; Roughness coefficient; Statistical models; Structural analysis. Stresses; Surface roughness; Walls; Water effect, drainage, ground water lowering, filtration; Fracture surface roughness; Riemannian roughness parameter; JRC flow channels; Fracture closure; Pressure drop; FLUENT; Data analysis; Roughness; Two dimensional model; Rock mass; Three dimensional model; Soil water properties; Flow(fluid); Hydromechanics; Jointed rock; Fracture surface; Simulation model; Joints; Comparative study
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-011-0148-3

The hydro-mechanical response of fractured rock masses is complex, due partly to the presence of fractures at different scales. Surface morphology has a significant influence on fluid flow behaviour of a fracture. Different empirical correlations and statistical models have been proposed to estimate the equivalent hydraulic aperture and determine the pressure drop along a fracture. However, the existing models suffer from not being adequately generalised to be applicable to a wide range of real fracture surfaces. To incorporate the effect of profile roughness in the hydro-mechanical behaviour of fractured rock masses, the joint roughness coefficient (JRC) is the most widely used empirical approach. However, the average JRC of two fracture walls in fluid flow analysis, as is a common practice, appears to be inappropriate. It will be shown how different combinations of pairs of JRCs could lead to a similar JRC value. Also, changing the position of the top and bottom walls of a fracture can significantly change the hydraulic response of the fracture while the average JRC is identical in both cases. In this paper, correlations are developed which are based on the simulation of JRCs using estimated fluid flow parameters of 2D fractures can be estimated. In order to widen the application range of the correlations, JRC flow channels were generated: these are 2D channels with their top and bottom walls being made from two of the JRC profiles. To estimate the JRC of linear profiles, a correlation developed between JRC and a newly developed Riemannian roughness parameter, D R1 , is proposed. Considering ten JRC profiles, a total of 100 JRC flow channels were generated. In order to only investigate the effect of surface roughness on fluid flow, the minimum closure between the top and bottom walls of JRC flow channels were considered to be constant. Three cases with minimum closures of 0.01, 0.05 and 0.10 cm were considered in this study. All JRC flow channels were subjected to fluid analysis using FLUENT software. Based on these results, correlations were developed between the geometrical and hydraulic properties of flow channels. Analysis of several real fractures demonstrated the applicability of these correlations.