Hydraulic Conductivity of Jointed Rocks

by Mahdi Zoorabadi

Institution: University of New South Wales
Department: Mining Engineering
Year: 2014
Keywords: Analytical methods; Hydraulic conductivity; Jointed rocks; JRC profiles; Nonlinear flow
Record ID: 1051519
Full text PDF: http://handle.unsw.edu.au/1959.4/54094


Hydraulic conductivity is an important characteristic of jointed rocks and methods to quantify this parameter are essential for mining and civil engineering applications. Rock discontinuities play a significant role in the circulation of water through jointed rocks, while the geometral characteristics of joints control the magnitude and orientation of the conductivity tensor. However, because of the complexity of water flow within individual fractures and the complexity of water circulation within discontinuity network, hydraulic conductivity determination is a challenge. Hydraulic behaviour of individual rock fractures, hydraulic conductivity of jointed rocks and depth dependency of hydraulic conductivity for jointed rocks were investigated in this thesis. For individual fractures, an analytical method was proposed to estimate the hydraulic aperture of rough fractures with matched surfaces under linear flow conditions. The application of this method for JRC profiles was verified by precise laboratory experiments, which provided the capability to study the hydraulic behaviour of JRC profiles under linear and nonlinear flow conditions. The unique nonlinear results of these experiments showed a reducing trend between normalised transmissivity and Reynolds number which was modelled satisfactorily by the Forchheimer equation. For the first time, empirical relationships were proposed to calculate the constants in the Forchheimer and Izbash equations. Moreover, a new empirical equation was introduced for the trend between flow friction factor and Reynolds number. The flow friction factor is a function of both Reynolds number and relative roughness, but it is more sensitive to Reynolds number. New analytical formulations were introduced in this thesis to estimate the hydraulic conductivity of jointed rocks. These formulations considered the rock discontinuities to have finite persistence with circular disk shape. Two well-known cases were used to verify the proposed formulations. These cases demonstrated that the proposed analytical method provides a valuable ability to study the parameters involved in the hydraulic conductivity of jointed rocks. Furthermore, a new empirical relationship was proposed to calculate the hydraulic aperture of rock discontinuities at different depths. This relationship can be combined with an analytical method to calculate the hydraulic conductivity of jointed rocks. This procedure was applied to a real case in Eastern Australia. Comparison of these results with the measured conductivity at different depths validated the accuracy of proposed procedure.