Experiments on earth dams breaching. Monitoring instrumentation and methods

Abstract

A research project on laboratorial characterization of the breach processes involved in the failure by overtopping of earth dams is currently ongoing at LNEC and IST. The breach evolution process is a complex phenomenon which requires the understanding of both hydraulic and geotechnical components involved. Laboratorial tests allowed relating the dynamics of the breach with the hydraulic and geotechnical properties of the embankments and understanding how the latter influence the failure mechanisms. In this paper four different approaches for estimating breach hydrographs are presented. Two are based on: i) stage-discharge relations; and ii) water-volume balances within the reservoir. The other two constitute a novel estimating method and are both based on velocity field maps, obtained from the application of an LSPIV algorithm and on breach area detection, delineated with the aid of a laser sheet. The technique used for combining the instrumentation and measuring methods in these different approaches for breach hydrographs estimation is herein scrutinized.