CHAPTER XL 



VARIOUS TYPES OF BREAKWATERS. 



Classification of breakwaters Vertical types Mound types Action of waves 

 against vertical faces Timber-framed breakwaters Breakwaters with side 

 walls of masonry and hearting of loose rubble Kilrush pier Wick breakwater 

 Danger of loose rubble hearting Advantages of using large blocks in con- 

 structing breakwaters Breakwaters formed of concrete blocks laid in horizontal 

 courses Defects of system Batter undesirable Stone facing Breakwaters 

 formed of blocks resting on base of mass-concrete Monolithic system of 

 construction Methods of depositing concrete under water Causes of failure 

 Concrete bag-work Fraserburgh breakwater Wave-breaker Breakwaters of 

 blocks laid in sloping courses Advantages of system Colombo, Mormugao, 

 and Manora (Kurrachee) break waters Large blocks used at Re'union Mound 

 breakwaters Angles of slopes indicative of extent of exposure Plymouth, 

 Kingstown, Table Bay, and Portland breakwaters Pitched slopes Disturbance 

 of rubble by wave-action Holyhead breakwater Madras breakwater Sorting 

 rubble for breakwater mounds Cause of trouble at Plymouth breakwater 

 Alderney breakwater Causes of failure Mounds of pell-mell blocks on rubble 

 bases Mounds of rubble, faced and capped with pell-mell blocks Mounds of 

 pell-mell blocks, backed with rubble Mounds of pell-mell blocks with super- 

 structures Rubble mound with pell-mell block facing and superstructure 

 Economy and advantages of using large blocks General observations on rubble 

 and concrete block mounds Failures of pell-mell block breakwaters Particu- 

 lars relating to various pell-mell block breakwaters Rubble mound breakwaters, 

 faced and capped with stepped blocks in courses Particulars of cost, rate of 

 progress, maintenance, etc., of various existing breakwaters. 



BREAKWATERS may be classed generally under two main heads, 

 viz. the vertical type and the mound type. 



Of the vertical type, which must be taken to include struc- 

 tures with " battered " or slightly inclined faces, we find 



1. Timber framing filled with rubble stone. 



2. Outer walls, formed of masonry or concrete blocks (either 

 laid " dry " 1 or in cement), with a hearting of " dry " rubble. 



1 Without mortar of any kind. 



