At around 11:00 a.m., one of four flaps on a dam on the River Meuse suddenly collapsed, unleashing a 40 cm wave that reached the following dam, located 4 km downstream. The operator alerted the communities liable to be affected. River traffic was halted on the 5-km section upstream of the first dam; it emptied itself in 3½ hours. The upstream and downstream dams opened and closed their floodgates to limit the wave’s impact.

The dam with inflatable bladders had been put in service in March 2017 in place of a needle dam. It was raised that day and then continuously monitored for 36 hours after being put back in service. River traffic upstream of the dam resumed on 7 August and the dam’s water level returned to normal on 15 August.

The flap collapsed after its bladder (an inflatable cylinder placed under the flap) burst. A 1 m L-shaped tear, stopping vertically on a seal, was found on the dam’s No. 2 bladder. According to the operator, this failure was linked to the combination of two things:

• a localised manufacturing defect:
  • lack of adhesion between the outer rubber and the central textile plies along a diameter of 80 cm;
  • a surface defect on the textile side and a lack of thickness of the inner rubber.
• eighteen months of unsuitable operating conditions, which induced ageing accelerated by fatigue;
  • the bladder, which remained deflated under water pending the completion of the work on the dam, was subjected to forced oscillations;
  • the dam’s hydraulic environment exposed the bladder to a highly turbulent flow and cross-flows.

Oscillation, combined with the lack of local adhesion, allowed the bladder’s rubber and textile plies to move relative to one another, wearing it down until it burst. A number of membranes that may have been subjected to stresses under identical conditions were identified. They were inspected, but not found to be defective. The operator changed the stages in which similar dams are built so that bladders are not exposed to abnormal stresses.

A new bladder was installed in August. The dam was returned to normal service on 4 October.