Cause of failure at Endhó dam spillway: Physical modeling

Abstract

Over last decades, water demand has increased, and with it the need to store runoff artificially. This way reservoirs have emerged; structures considered high risk, in the event of failure. The work of spillway of the Endhó dam presents important water shocks in the coating slabs of the discharge channel, specifically in the final part of the rapids in relation to the trajectory, which delivers water to the buffering pond, which puts at risk the reservoir stability. According to the geological and hydraulic features of the work, it is probable that the subpressure force is the main cause of the wear, rupture and detachment of the slabs. To determine the causes that originate the failure, a 1:100 scale physical model was built. In this, the laws of resemblance (Froude) and similarity (geometric, kinematic and dynamic) were met, and the underground flow with soil from of the dam was simulated. The maximum flow that was passed on the spillway work was 11 l/s (equivalent to 1 100 m³/s in the prototype), it was operated for 240 continuous hours. With seven pressure sensors the values were recorded in the area of interest and data up to 9 220 kgf/m² (prototype) were obtained. The subpressure values obtained in the physical model were higher than those estimated with Lane's methodology. The structural analysis indicates that the weight of the structure is not sufficient to counteract the subpressure in the rapid parabolic.