Field measurement of rock mass permeability is essential that numerous factors influence its directional magnitude. Lugeon test is a popularly conducted field instrument in order to measure hydraulic conductivity of a rock mass. Discontinuity orientation, spacing and discontinuity surface quality, infill presence and type play essential role in permeability of the rock mass in addition to rock material itself. Geological Strength Index (GSI) is a parameter used in Gen. Hoek-Brown failure criterion and supporting empirical equations in order to estimate rock mass strength and deformability parameters. Frequently used Rock Quality Designation (RQD) and GSI and Lugeon values were combined in order to generate a relation among them. The proposed relationships are produced by interpretation of geotechnical core logging and Lugeon test results.
Groundwater has great influence on rock engineering structures. Difficulties may include construction operations, rock mass deformation and stability. Hydraulic conductivity, pore water pressure, water pressure acting along the joints are all important as well as water sensitivity of the rock material. Understanding of groundwater condition is crucial for surface structures on rock masses, foundations, slopes [1, 2, 3]. For underground rock structures, information about ground water pressure and water inflow rate is essential [4, 5] since it strongly influences operational issues as well as stability of the structure and supports. Operational issues may include pump selection and infrastructure design for water discharge, foreseeing a need for grouting, water sealing. Permeability character of ground plays important role for also surface structures such as dams and foundations [6, 7].
For water flow through a saturated granular material, Darcy's law  is widely accepted:
Total flow (Q in m3/s) is directly proportional to the cross-sectional area of flow (A in m2), hydraulic conductivity (or called as coefficient of permeability in m/s) and hydraulic gradient i. i is a ratio of pressure difference (Δh) along a particular flow length (l in m) can be represented as:
In addition to the intrinsic permeability of the geological material represented by ki, hydraulic conductivity, K is dependent on the fluid properties which are unit weight γ and viscosity μ: