Impact of Flow-Driven Debris on Coastal Structure During Tsunami Bore
Tsunami impact on infrastructure along the coast causes severe destruction, loss of human lives and negative influence on the economy. When tsunami propagates towards the coastline, the flow often resembles a bore which propagates with a high velocity and takes everything on its way, including heavy objects. When reaching the structure, this water-driven debris induces a kind of impact force and magnifies the load on structures along the coast. The present study is aimed to measure the load of tsunami-borne debris on a building constructed near the shoreline. In many situations, tsunami or any flood nearshore resembles a surge caused by a dam-break event; therefore, to model this process, we conducted our experiments by setting up a dam-break arrangement in a wave flume of 72.5 m length, 2 m wide and 2.5 m deep at the Department of Ocean Engineering, IIT Madras, India. A Froude scale of 1:20 was adopted for modelling the coastal structure and the debris placed over a beach slope of 1:30. The hydraulic bore was generated by a sudden opening of the gate of the tank. We considered three water depths of 0.8, 0.9 and 1.0 m. The debris was modelled as a box-shaped structure weighing 4.2, 5.6 and 6.0 kg. A video camera was used to capture the surging of the hydraulic bore and to study the character of debris motion during impact. The impact forces acting on the structure due to debris were measured with a load cell. The acquired data were further analysed and discussed.
KeywordsCoastal structures Tsunami bore Dam-break set-up Impact force Debris
The paper was developed during the collaborative research project work Indian Institute of Technology, Madras and Nizhny Novgorod State Technical University n.a. R.E. Alekseev, Russia on Impact of waterborne debris on the nearshore structures during extreme coastal floods funded by Department of Science and Technology, Government of India (Grant agreement no. INT/RUS/RFBR/P-203) and RFBR (15-55-45053). The author would like to thank Department of Ocean Engineering, IIT Madras for providing facilities for conducting the experiment.
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