The Lugeon test is a kind of water pressure test of the permeability test introduced by M. Lugeon for measuring permeability of the good foundation rocks of dams. Strictly speaking, it is distinguished from the ordinary permeability test, because it is not always based on Darcy's law. However, Lugeon test is extensively used as the permeability test for the foundation rocks of dams.
In recent years, dams have been constructed not only on the hard bedrocks but also on the weak rocks, cracky rocks with wide open cracks, etc. Therefore, corrections and adjustments have been applied in testing procedures and interpretation methods.
However, in case of bedrocks both with small critical injection pressure and under the condition of deep groundwater level, the proper Lugeon value within critical injection pressure cannot be easily obtained and larger Lugeon value is often gained, for hydrostatic head exceeds the bedrocks' own critical injection pressure and hydrofracturing occurs.
In order to refrain from its phenomenon, injection pressure should be provided near the test stage, not on the ground. Therefore, lately improved Lugeon test method using the borehole multistage constant permeability test method have developed. As a result, the above mentioned problems were almost resolved.
While, in case of huge permeable bedrocks with wide open cracks, Lugeon value resulted from the ordinary Lugeon test is often considerably smaller, because of huge pipelines friction due to turbulent flow. However, according to the writer's experiences, Lugeon value nearly equal to the real permeability under a laminar flow can be obtained by means of the above mentioned method.
