Load and Deformation Relations of Placed Riprap Model with Toe Support

Abstract

Abstract: Rockfill dams are hydraulic structures of major importance that can be exposed to extreme flood events, leading to overtopping processes. These phenomena erode and weaken their structural and geotechnical stability. As a rockfill dam protection, ripraps are broadly used against erosion processes. For steep slopes, as the one considered in this work, riprap failure is made possible during overtopping process. Thus, understanding the riprap behavior during overtopping events is a major issue to improve construction and reinforcement techniques. In this work, datasets were obtained from an experimental model of placed riprap built in a flume. The riprap stones were placed in an interlocking pattern with a metallic support at the toe. The model was submitted to successive overtopping with increasing levels of discharge until its complete failure. A laser traverse system measured the coordinates of specific riprap stones between each discharge increase and six load cells located at the toe measured the load during the entire procedure. From the total load values, two different types of load contributions could be distinguished: the self-weight of the stones and the hydraulic load depending on the discharge level of the overflow. The present work highlights the strong relation between riprap stone displacements and axial reaction load values measured at the toe. The results demonstrate that as the hydraulic load induces 2D deformations of the riprap, a larger part of the riprap weight is supported at the toe. Thus, the measured axial load during overtopping arises both from the hydraulic load and from the load imputed to the compaction of the riprap layer. This compaction effect induces an even greater load than the one imputed to the water.