A discussion on the interpretation of the water pressure tests (Lugeon test) is made by the authors. Laminar and turbulent flow regimens are considered in the analysis which is based on some results of laboratory tests using granite fractures with varying opening and roughness.
The water pressure test as it is performed nowadays derives from the original proposal by M. Lugeon (1933) to characterize pervious regions into the rock mass volume being studied. In Brazil, these tests are often performed using five steps of pressure as following: minimum corresponds to the coefficient of pressure, Pmin=0.10 kg/c?2 ( used at the beginning and end of tests); maximum pressure, Pmax = 0.25 kg/cm2 per meter of packer depth and intermediary pressure, Pint = Pmax/2. The total pressure adopted in estimative of k, the water pressure test is a resultant also from the head losses occuring during the test which include that on the fracture entrance (Risslet, 1978). In recent years changes in the effective pressure during the test execution are often read in the centre of the test interval using electronic devices and pressure transducers .
