Stress measures on the Bimont dam: our experts mobilized

Located at the base of the Sainte-Victoire mountain, this 87-meter-high dam, put into water for the first time in 1854, regulates and secures water supply for the Aix region and the city of Marseille. As some well-identified areas of the structure are subject to a phenomenon of swelling of the concrete by internal sulphate reaction, since 2009 it has been the subject of a major renovation program, in which this measurement campaign took place. It consisted in carrying out a series of overcoring tests at different depths to sample the thickness of the dam as much as possible.

Overcoring is a method of determining relaxation stresses: a deformation measuring cell is first installed in a small diameter borehole. The measurement cell is then overcored using a larger coring bit, which relieves the stress acting on the wall. The induced deformations are then recorded by the sensors of the cell, and inverted to determine the state of stress in situ.

These stress measures will be used by the input data operator to complete the understanding of the dam's evolution and its monitoring during the re-flush.