Author(s): Arkal Vittalhegde; Sooraj Mohan; Sharhabeel P S
Linked Author(s): Arkal V Hegde
Keywords: Semicircular breakwater; Incident wave steepness; Dimensionless stability parameter; Dimensionless depth parameter
Abstract: The semicircular breakwater (SBW) is a composite breakwater. The prototype consists of a semicircular caisson made up of pre-stressed concrete resting on a rubble mound. The caisson of the SBW is hollow and it is resting on a rubble mound foundation, thus the weight of the structure and materials get reduced. The wave pressure on the semicircular surface passes through the centre of the circle, so no overturning moment is induced by the wave pressure. The lateral wave force component acting on a semicircular breakwater is smaller than that of vertical component, so the stability against sliding is good. As a whole SBWs are technically advanced, economically viable and aesthetically pleasing. The present paper discusses the results of series of experiments conducted in a two dimensional monochromatic wave flume to determine the critical (minimum) weight required to resist sliding of an emerged nonperforated SBW model. The critical weight required to resist sliding is expressed in terms of dimensionless stability parameter W/γH i 2, where W is the critical (minimum) weight required to resist sliding per unit length of the model, γis the specific weight of water and H i is the incident wave height. The variation of W/γH i 2 with incident wave steepness H i /g T 2 for different values of dimensionless depth parameter ranges d/g T 2, for a constant R/h t =0.92were plotted graphically to analyse the influence of dimensionless depth parameter and other wave parameters on the critical weight required, where d is the depth of water, T is the wave period, R is the radius of the semicircular caisson and h t is the total height of the structure. The wave climate of the Mangaluru coast in India was used for arriving at the various model wave parameters. Incident wave heights (H i) used in the flume experiments varied from 3 to 18 cm, wave periods (T) ranged from 1.4 s to 2.5 s, water depths (d) varied as 35 cm, 40 cm, 45cm in the experiments and the model scale adopted is 1:30.