Author(s): S. A. Sannasiraj; P. V. Chandramohan; S. Tharaniraja; D. Monica
Linked Author(s): Sannasi Annamalaisamy Sannasiraj
Keywords: No Keywords
Abstract: Breakwaters are constructed in the sea to resist the energy of the oncoming waves, so that the lee of the structure will be tranquil. The breakwater construction in deeper waters requires heavier armour units due to larger wave loads. The stability of the breakwater is largely influenced by the storm duration. But on the other hand, breakwaters should be able to resist the waves without undergoing distress themselves. Predominant wave action will be on the side slope facing the sea. The stones on this side will be protected by concrete amour blocks. The blocks will be subjected to relentless onslaught of waves. Besides, waves impinge on the structure in every ten second or so. Based on this principle, during the last few decades, various shapes of armour blocks have been developed. Efficiency of the shape could be established by model studies. Efficiency of the block is generally characterized by its Hudson’s stability number or KD value. Hudson’s formula is used worldwide for finding out the weight of the armour block required for a particular wave and breakwater scenario. The higher the Kd value, the lower will be weight of the armour block required. A new type of amour block named INDOPOD is developed for resisting waves. Indopod is a further modification of Kolos. The armour block consists of two hexagonal masses connected together by a hexagonal stem. These hexagonal masses provided very good interlocking properties to the blocks. To study the overall stability of the structure in order to arrive at the stability co-efficient for Indopod units, well-known Hudson’s formula is used for both the trunk and head sections. Studies to establish its stability co-efficient were carried out in a wave flume at IIT Madras. The breakwater section was tested for the determination of its stability parameters under different wave conditions. The total percentage of damage of any breakwater cross section can be assessed either by profiling the damaged portion or by counting the number of units displaced. Most importantly, due attention was given to observe the extent and pattern of subsequent damage initiated. The breakwater sections armoured with INDOPOD was tested for establishing the hydraulic stability parameters of INDOPOD by subjecting the section to action of random waves through a well-controlled experimental program (Fig. 2). Both breaking and non-breaking conditions is been considered in theexperiments. It was observed that even after the initial damage of about 2% (maximum), the armour units in the neighbourhood have realigned itself to cover the void space thus preventing the infliction of further damage. To be on the conservative side in order to arrive at the KD value, the maximum allowable damage level is fixed as 2%, which is less than the maximum percentage of damage level. In non- breaking conditions, the damage is almost nil till the verge of its breaking which is almost negligible. From the experimental results, Stability co-efficient Kd for INDOPOD Trunk and Head sections is established for three hours storm duration.
Year: 2024