A Treatise On The Principles And Practice Of Harbour Engineering

BREAKWATER DESIGN. 129 During the early hours of the morning of 27th November, despite the faet that the outline of the mole was almost completely obscured by foam and spray, the shelter wall of the outer arm was observed to be split into several sections for a distance of 500 feet from its junction with the inner arm. Some of these sections had merely shifted in position, but others had been completely over- turned on to the inside quay. As the day ad- vanced the breach was extended, until eventually it was 65 feet wide, the wall continuing to break away and small portions of it to be swept into the harbour. Fig. 109 is a plan of the damaged portion, and figs. 110, 111, and 112 are cross sections at various points. In the first length, A.B., for a distance of about 230 feet from the commencement of the bend, the pitching or oovering of artificial stone blocks was torn off to depths varying from 6 feet 6 inches to nearly 20 feet, the blocks in some cases being deposited along the outer slope, and in other cases projected a long way out side. The protecting apron was com- pletely swept away, but the founda- tion of the mole structure was not damaged beyond a few cracks near the base, which were neither large nor deep. In the length B.C., the topmost course of artificial blocks of stone was overturned, and the lower courses were dislocated and partially damaged. The shelter wall was broken into five 108. —Section of Galliera Mole as constructed. each on enormous blocks, of which four were ; shifted parallel to their original posi- tion and one (number IV. on plan) was over- turned on to the quay. Detailed particulars of the blocks are as follows : — aij No. of Block on plan. Volume in cub. ft. Weight in tons. I. 15,510 1,012 II. 6,980 455 III. 4,935 322 IV. 13,395 894 V. 14,030 915 Il In the length C.D. the shelter wall was entirely demolished and the artificial blocks disturbed, though not to the extent experienced in the