Experimental study of the effect of holes number and arrangement of lattice pounder on offshore dynamic compaction

In offshore dynamic compaction, the water effect on the depreciation of the pounder impact velocity on seabed and the crater depth created in the soil is always a major challenge. In this paper, the water entry problem of lattice pounders of 9, 16, and 25 holes, with 3x3, 4x4, and 5x5 matrix arrangement respectively, the effect of the number, dimensions and arrangement of the pounder holes, on the impact velocity with simulated soil of the seabed and the crater depth created in it was studied experimentally. The results showed that the impact velocity of the lattice pounders depends on the holes area, and the crater depth created in the soil, the amount of energy transferred from the pounder to the soil and the improvement radius and depth of soil depend on the area of the pounder's lattice web. Therefore, in dynamic compaction of the seabed, increasing the pounder weight without reticulating it cannot considered as a suitable solution to increase the impact velocity on seabed and the effective factor on soil settlement and compaction. Also increasing the pounder weight and its drop height over the optimum drop height lead to increasing the operating costs, and it requires the use of large barges and long cranes with a high load capacity.