DESIGN OF TSUNAMI-PROTECTIVE EMBANKMENTS WITH A COMPLEX FRONT SURFACE

The most effective and reliable means of protecting coasts from tsunamis is to construct special engineering structures. Shore embankments and walls are constructed for protection against tsunamis. The height of the embarkrnents is determined on the basis of the maximum overwash of the design tsunami with a frequency of once in 100 years. The embankments are calculated for a hydrostatic load with reflection of the tsunami; the seismic stability of the slopes is checked without fail. The necessary stability of the embankments is provided by making the slope more gentle or by reinforcing the body of the embankment. The steepness of the slopes is usually 1:3. The front slope of the embankment is reinforced with stone or concrete slabs. For protection from possible erosion in the case of brief overflow of water, the crest and rear slope of the embankment are faced with stone, concrete, or polymer materials [1, 2]. When constructing tsunami-protective embankments, it is expedient to construct the fi'ont (i.e., seaward) side of the embankment in the form of a system of terraces. This provides better dissipation of the energy of the tsunami due to increased friction losses by the water flow forming during run-up of the wave on the embankment. The size of these terraces can be determined form the following considerations. It is known that when a fluid flow with velocity v strikes a plane at angle/3, a jet stream, the velocity of which (u) is severalfold greater than the velocity of the incident flow, "beats" along the plane. The velocity of this jet stream is determined by the relation [5, 6]