Dynamics of Water-Rock Interaction in Rock Scour

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Scour of rock by running water is an important phenomenon in landscape evolution and it has been identified as a critical issue facing many of the world's dams. Field observations at numerous dam sites and in mountainous creek channels show that surprisingly large blocks of rock can be plucked from the stream channels by relatively small volume of water as long as it flows at sufficiently high velocity. In the case of dam spillways, several recent events have produced erosion that threatened the actual stability and safety of the dams themselves and resulted in very costly emergency actions. This research is an interdisciplinary effort aimed at developing a better physical understanding of the process. Laboratory experiments in a flume and field observations will be used to create a mathematical model for the evaluation and prediction of the severity of the process. The ultimate goal is to enhance the safety of existing dams by being able to predict the critical zones which need to be strengthened in order to prevent scour from developing. This effort is particularly important in view of the increasing extreme weather patterns being observed as a consequence of climate change. The broader impacts of the award will be a new understanding of landscape evolution by stream erosion, an improved understanding of the risks to dams as a result of potential overtopping and catastrophic flooding, and the introduction of new concepts in undergraduate and graduate earth science and engineering education. Current scour prediction models are limited to very-simple representation of the geometry and structure of the rock discontinuities in 2D, and do not adequately account for the effect of joint orientation on the removability of rock blocks. Furthermore, these approaches do not account for the potential for the kinematics of the block erosion/removal due to hydrodynamic forces beyond simple sliding or uplift. This research is an integrated program of laboratory and field studies to obtain high resolution field data, including velocity and dynamic water pressure measurements, from field prototype and scaled model hydraulic laboratory tests. The objective is to use the experimental and field data to develop a better understanding of the mechanics of scour of blocky rock masses and to develop appropriate analytical tools capable of capturing the dynamics of fluid-blocky rock interaction.