See Report for more information and pictures. In general, it can be said that the construction was mainly subject to local failure mechanisms, which increased over time. The only global failure mechanism to which the structure is subject is the shearing of the entire structure downwards. Due to the rough and cohesive structure, the construction has a high resistance to shear, as it was well anchored in the ground at both ends. The downward drag of the structure could be observed at the anchors at the bottom of the structure. These began to fold over to the right, due to the acting perpendicular force as a result of the water pressures. Because the structure lasted a long time, it was decided on day 2 of the tests to inflict damage to the side of the structure with a shovel. The wooden beams, that serve to prevent water infiltration, were broken. By inflicting this manual damage, the water was able to penetrate along the side of the structure. This was not a problem at first, as the pit is covered with the vapor-tight foil. Due to this watertightness of the well, there is no contact between the water and the underlying soil. As a result, no erosion can occur in the well itself. Of course, with a permanent load, damage will occur because the soil on the side of the pit will erode. Because the water always chooses the path of least resistance, there will be an increasing water load in the well itself. As a result, the foil will eventually fail and the construction itself can be lifted in the event of extreme water pressures. In that case we speak of the global failure of the structure.

After the first discharges of water were released over the dike, we especially noticed a lot of turbulence in the water around the first transverse wooden beam. Due to the downward flow of the water, a strong water pressure was exerted on the wooden beam, which translates into a normal force in tension on the ground anchors. After 6 minutes, the first local damage was noted. Due to the ever increasing normal force on the tension anchors, the resistive normal force was exceeded at a certain point. As a result, the ground anchors were pulled out of the ground and the wooden beam was dragged down under the influence of the water current. Secondly, we noticed that the vapour barrier, which was partly anchored over the wooden panel structure, was subject to enormous tensile forces. These tensile forces are the result of the water flow and the impact of the waves on the structure. The ground anchors, which ensure that the vapor barrier does not wash down, offer a certain resistance to shear. The fibers around the openings where the anchors are located are very locally subject to large normal stresses. These normal stresses spread over a larger area, which largely cancels out the effect of the tensile action on the vapor barrier. Due to the high tensile strength of the vapor barrier, no initial cracking occurred. Furthermore, under the influence of the continuous loading of the water waves, local damage was found in the middle part of the structure. There, the vapor barrier was anchored to the panel structure via wooden transverse beams. Due to the presence of strong turbulent vortices in these zones, the vapor barrier at this location ruptured and the middle plate was exposed. A few moments later, the vapor barrier also began to fail at the bottom of the structure. This local failure of the structure does not affect the overall stability of the structure. When the overtopping tests were carried out further, severe forces were exerted on the vapour barrier at the top of the structure. Because the top wooden beam was already washed away initially, water started to seep in under the screen. This flow of water infiltration was very limited, and therefore did not lift the overall structure. Due to the continuous water flow on the vapor barrier, some ground anchors were pulled out of the ground. The areas around the anchors also started to show cracks, and the gaps of the resulting holes kept getting bigger. In addition to local damage to the vapor barrier, damage was also found on the side of the construction towards the end of the tests. There, lateral water seepage was avoided by the use of a large wooden beam. Due to the strong forces of the water, this wooden beam was pulled out of the ground and dragged down. This had no effect on overall stability, as the small wooden bars prevented lateral water seepage.

The repair measure lasted longer than we initially expected. Over time, and with increasing wave load, the entire structure gradually began to slide downwards. The vapour barrier came off first, which in itself was not a major concern as the film in the well was unharmed. The test results clearly show that bridging the damage to the dike has an effective effect. The most critical points of the construction are the top and sides, as these places allow water infiltration. This water barrier in particular ensures the water-resistant effect, and so contact between water and the underlying ground is avoided as much as possible.