GENERAL FEATURES OF VARIOUS ANCHORS 



Deadweight Anchor 



permitting shorter 



se most holding force due to 



Large vertical reaction compo 



line scope 



No setting distance 



Reliable holding force, becau 



anchor mass 



Simple, on-site constructions feasible, tailored to task 



Size limited only by load-handling equipment 



Economical; weighting material readily available 



Reliable on thin sediment cover over rock 



Mooring line connection easy to inspect and service 



d in conjunction with 

 piles, embedded plate anchors) 



Good energy absorber when 



"non-yielding" anchors (i- 



Good reaction to vertical load components; works well in 



combination with drag embedment anchors permitting short 



mooring line scopes 



Lateral load resistance low compared to other anchor types 



Usable water depth reduced; deadweight can be undesirable 



obstruction 



Plate Anchor 



High capacity (greater than 100,000 lb) achievable 



sts uplift as well 

 moorings 



lateral loads enabling short scope 



Anchor dragging eliminated 



Higher holding capacity to weight ratio than any other type 

 of anchor 



Handling 

 1-* . -u. 



1.* 



simplified due to relatively light weight 



can function on moderate slopes and in lithified 

 s 



implified due to possibility of instan- 



Installation i 

 taneous embedment 



afloor contact 

 Accurate anchor placement possible 

 Does not protrude above seafloor 



Can accomodate layered seafl 



2,3,4* 



stance bee 

 expenditure during pe 



ors or seafloors w 

 f continuous power 



' ' Penetration is controlled and can be monitored 



Susceptible to cyclic load strength reduction when used in 

 taut moorings in loose sand, coarse silt seafloors 



For critical moorings, soil engineering properties required 



Anchor plate typically not recoverable 



'" Special consideration needed for ordnance 



Anchor cable susceptable to abrasion/fatigue 



Gun system not generally retrievable in deep water (>1,000 ft) 



Surface vessel must maintain position during installation 



Operation limited to sediment seafloors 



2,3,4* 

 2,3* 



Propellant-enbedded anchor 

 Screw-in anchor 

 Vibrated-in anchor 

 Driven Anchor 



Drag Embedment Anchor 



Broad range of anchor types and sizes available 

 High capacity (greater than 100,000 lb) achievab 

 Standard off the shelf equipment 

 Broad use experience 



provide cooti 

 exceeded 



resistance even though maxi 



Anchor is recoverable 



Usable with wire or chain mooring lines 



Anchor does not function in lithified seafloors 



Anchor behavior erratic in layered seafloors 



Low resistance to uplift, therefore, large line scopes requireii 

 to cause near horizontal loading at seafloor 



Penetrating/Dragging anchor can damage pipelines, cables, etc. 



High capacity (greater than 100,000 lb) achievable 



Resists uplift as well as lateral loads permitting use with 



short mooring line scopes 

 Anchor setting not required 

 Anchor dragging eliminated 



*Short mooring line scopes permit u: 

 room or where minimum vessel 



areas of limited sea 

 Ions are required 



Drilled and grouted piles especially suitable for hard coral or 



rock seafloor 

 Does not protrude above seafloor 

 Driven piles cost competitive with other high capacity anchors 



when driving equipment is available 

 Drilled and grouted piles incur high installation costs and 



require special skills and installation equipment 

 Wide range of sizes and shapes are possible (pipe, structural 



shapes) 

 Field modifications permit piles to be tailored to suit require' 



ments of particular applications 

 *Taut moorings may aggravate ship response to waves (low 



*Taut lines and fittings must continually withstand high 



stress levels 

 Costs increase rapidly in deeper water or exposed locations 



where special installation vessels are required 



Special equipment (pile extractor) required to retrieve or 



refurbish the mooring 

 More extensive site data is required than for other anchor type 



for any taut 



ing. 



