Lugeon

The Lugeon value is a unit of measure used in hydrogeology and geotechnical engineering to quantify the permeability of rock. Specifically, it represents the water loss in liters per minute per meter of borehole length at a pressure of 10 bars (approximately 1 MPa) during a pressure test (Lugeon test). The Lugeon test, also known as a water pressure test or packer test, is performed to assess the hydraulic conductivity of fractured or jointed rock masses.

A Lugeon value of 1 LU (Lugeon unit) corresponds to a flow rate of 1 liter per minute per meter of borehole at a pressure of 10 bars. Higher Lugeon values indicate higher permeability, suggesting more fractures or larger fracture apertures in the rock. Conversely, lower Lugeon values suggest lower permeability and less fractured rock.

The Lugeon test involves isolating a section of a borehole using inflatable packers and injecting water at increasing pressures. The flow rate required to maintain each pressure step is measured. The Lugeon value is then calculated based on the observed flow rate, the borehole section length, and the applied pressure.

Lugeon values are commonly used in the design and construction of dams, tunnels, underground excavations, and other geotechnical structures. They provide valuable information for evaluating the potential for water leakage, assessing the effectiveness of grouting programs, and predicting groundwater flow patterns in fractured rock. However, Lugeon values are empirical and can be influenced by factors such as borehole diameter, rock type, and stress conditions. Therefore, they should be interpreted in conjunction with other geological and hydrogeological data.