Indian Journal of Geo Marine Science Vol. 47 (03), March 2018, pp. 681-685 Physical model studies on the stability of emerged seaside perforated semicircular breakwaters ArkalVittal Hegde 1* ,Sooraj Mohan 1 , José L S Pinho 2 & Sharhabeel P S 1 1 Department of Applied Mechanics and Hydraulics, National Institute of Technology Karnataka, Surathkal, Mangaluru, Karnataka, 575 025, India. 2 Department of Civil Engineering, University of Minho, Braga, P-4704-553, Portugal. [E-mail address: *1 arkalvittal@gmail.com; 1 srjmhn@gmail.com; 1 habeel17@gmail.com; 2 jpinho@civil.uminho.pt] Received 15 March 2016 ; revised 14 October 2016 Present study discusses experiments conducted in a two dimensional monochromatic wave flume to determine the critical (minimum) weight required to resist the sliding of an emerged seaside perforated semicircular breakwater model. It is observed from a detailed review that there is hardly any literature, stressing the critical weight determination for the sliding stability of this breakwater type. Hence, the present research was taken up to study the variations in the critical weight required for sliding stability with different wave and structural specific parameters. The variations were recorded graphically using non-dimensional parameters obtained from a dimensional analysis using Buckingham’s π theorem. [Keywords: Semicircular breakwater, Incident wave steepness, Dimensionless stability parameter, Dimensionless depth parameter, Buckingham π theorem, Sliding stability] Introduction Semicircular breakwater (SBW) have many advantages over conventional, rubble mound breakwaters. These advantages have made them popular and attract the interest of coastal scientists. The SBW has been recognized as being an excellent coastal protection structure for a wider range of water depths 1 , especially when the seaside wall is perforated 2 . SBW has high overturning stability because of its arch type shape 3 . The stability can be increased further by perforating the base slab, as this will reduce the uplift pressure 4 . The dynamic force acting on the wall of SBW always passes through the centre of the circle creating a uniform sub-grade reaction. As a result, the sub-grade reaction per unit area is minimal and hence, SBW can be installed on a relatively soft foundation 5 . The cost of construction of SBW is comparatively lower than that of conventional rubble mound breakwaters by about 20% 6 . There is also ease of construction since it is of modular type. Furthermore, arch type of construction provides an advanced aesthetic value compared to others. Sasajima et al. (1994) studied the forces and pressures on the SBW erected at the Miyazaki port in Japan 4 . The result of force and pressure variations obtained by the modified theoretical formula of Goda and Suzuki (1976) were found to be greater when compared with experimental values obtained on measured highest 1/3 rd wave pressure, pressure at the time of maximum force, and maximum wave pressure at different elevations along the seaward side 7 . Sundar and Raghu (1997) conducted experiments on wave runup, wave reflection, and dynamic pressures on SBW subjected to random waves 8 . The pressure spectrum at still water level (SWL) results in lesser energy compared to that of a location immediately below the SWL, which is due to the intermittence effect. Pressure spectra were found to decrease towards the sea bed. The 0 th spectral moment at a location (z/d=- 0.10), immediately below the SWL, was nearly 60 to 75% greater than that exerted at the SWL. The