The permeability of a fissured rock mass in a dam foundation is usually determined by means of the Lugeon permeability test. This in situ test requires strict fulfilment of the conditions proposed by M Lugeon in 1933, with the purpose to obtain the flow rate of water through the rock mass. The non-compliance of these conditions implies the careful analysis of the results obtained in order to transform them into equivalent Lugeon units (ELU). At the same time it demands the development of a model, in which the different variables affecting the test are taken into account:
• Borehole dip.
• Pressure sequence during the test.
• Total pressure and duration of each pressure level.
• Length of the test section.
The relationship between the total pressure of water injection and the absorbed flows allows the determination of the behaviour of the rock mass as well as the evolution of the permeability during the test.
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