The role of hydromechanical coupling in fractured rock engineering

Abstract

This paper provides a review of hydromechanical (HM) couplings in fractured rock, with special emphasis on HM interactions as a result of or directly connected with human activities. In the early 1960s, the coupling between hydraulic and mechanical processes in fractured rock started to receive wide attention. A series of events-including dam failures, landslides, and injection-induced earthquakes-were believed to result from HM interaction. Moreover, the advent of the computer technology in the 1970s made possible the integration of nonlinear processes such as stress-permeability coupling and rock mass failure into coupled HM analysis. Coupled HM analysis is currently being applied to many geological engineering practices. One key parameter in such analysis is a good estimate of the relationship between stress and permeability. Based on available laboratory and field data it was found that the permeability of fractured rock masses tends to be most sensitive to stress changes at shallow depth (low stress) and in areas of low in situ permeability. In highly permeable fractured rock sections, fluid flow may take place in clusters of connected fractures that are locked open as a result of previous shear dislocation or partial cementation of hard mineral filling. Such locked open fractures tend to be relatively insensitive to stress and may therefore be conductive at great depths.Because of out the great variability of HM properties in fractured rock, and the difficulties in using laboratory data for deriving in situ material properties, the HM properties of fractured rock masses are best characterized in situ.

Estimation of fracture flow parameters through numerical analysis of hydromechanical pressure pulses

“…[14] Most hydromechanical models have been developed from laboratory experiments and describe fracture hydromechanical behavior as a function of normal stress [Rutqvist and Stephansson, 2003]. Because of the difficulties in developing laboratory measurement facilities for shear-slip experiments, only a few models have been proposed for understanding fracture hydromechanical behavior under shear stress [Makurat et al, 1990;Olsson and Barton, 2001].…”

“…Fluid flow in such fractured rock is often complex because of heterogeneities, both at the scale of the single fracture and the entire fracture network. Numerous laboratory, field, and modeling investigations have shown that fluid flow in a single deformable fracture can depend on a number of factors such as the fracture hydraulic and mechanical parameters, the effective stresses applied on the fracture plane, the amount of surface contact area and voids, and channeling [Rutqvist and Stephansson, 2003]. For example, any variation in stress on fracture changes the geometry of its void space, which in turn changes its global permeability and preferential flow paths [Pyrak-Nolte and Morris, 2000].…”

Hydromechanical modelling of pulse tests that measure fluid pressure and fracture normal displacement at the Coaraze Laboratory site, France

“…For example, Hopkins et al [61] show that joint normal stiffness in laboratory samples can vary over several orders of magnitude, along with the percentage of contact area within the joint. On a larger scale, measurements of fault aperture in the field have shown that a shear offset results in an undulating pattern of variable fracture aperture [44,62]. Faults would then be represented better with a variable width of void space and a variable contact area, to take into consideration the variability of hydraulic aperture and normal stiffness [17][18]23,63].…”

Influence of Landscape Coverage on Measuring Spatial and Length Properties of Rock Fracture Networks: Insights from Numerical Simulation

“…These naturally occurring discontinuities often form complex, hierarchical networks over a broad range of length scales, and dominate the bulk behaviour of geological media (Bonnet et al 2001). It is, therefore, important to understand and characterise the distribution of natural fractures in geological formations, which is relevant to a variety of engineering applications such as hydrocarbon extraction, geothermal production, groundwater remediation and geological disposal of radioactive waste (Rutqvist and Stephansson 2003;Lei et al 2017).…”