Intelligent detection and numerical simulation analysis of concrete abrasion of a stilling basin floor

The abrasion damage of hydraulic concrete is the main reason for the destruction of stilling basins. The long-term development of damage will threaten the safety of flood discharge in the flood season. Manual inspection is often used to evaluate the erosion condition of the stilling basin bottom plate in a project, which requires pumping and desilting. The inspection cost is high and cannot be determined during operation. Based on intelligent detection using a remotely operated vehicle (ROV), this research uses the abrasion evaluation method of the two-dimensional aggregate exposure ratio (AER) of hydraulic concrete to study the abrasion distribution of a stilling basin bottom, which has considerable application research value.

In this paper, the surface flow stilling basin of a large water conservancy project in Southwest China is taken as the study site. The detection equipment is a self-developed, ROV that has the functions of underwater crawling, floating, bottom plate dredging, and underwater acoustic positioning. The vehicle is equipped with a high-definition camera and can comprehensively detect the bottom plate abrasion damage of a stilling basin. According to the abrasion process of hydraulic concrete, an abrasion characteristic classification table is proposed, the abrasion damage degree is quantitatively characterized according to the AER, and the abrasion distribution of the bottom plate of the stilling basin is clarified. On this basis, the influence of hydrodynamic factors on the abrasion of the bottom slab of the stilling basin is further analyzed using three-dimensional numerical simulation.

The results showed that: (1) The distribution law of the abrasion damage of the bottom plate of the stilling basin was basically consistent with the AER distribution. The AER could effectively reflect the abrasion damage of hydraulic concrete. (2) The abrasion in the front and rear sections of the stilling basin was severe, and there were different degrees of concrete mortar damage, aggregate exposure, falling off, and other undesirable phenomena. (3) The water flow in the stilling basin of the surface outlet fluctuateed violently, and the bottom velocity reached the maximum in the front area of the stilling basin; thus, this region was prone to scour, abrasion, and other damage. (4) Influenced by the tail sill of the stilling basin, the water flowed back in front of the tail sill, forming a vortex. The sand and stone deposition oscillated with the backflow vortex, continuously scouring the bottom plate of the stilling basin, resulting in an increase in the degree of abrasion in this area.

The AER can reflect the abrasion damage of the stilling basin bottom plate concrete to a certain extent and can be used to supplement the abrasion quantitative evaluation index system. The high flow velocity and backflow caused by sedimentation near the end sill are important factors leading to the erosion of the stilling basin floor. The research results have considerable application value and promotion importance for the safe operation and evaluation of a stilling basin structure.