■simpler to construct as cc^tlj forming is -avoided. Figures 138, ■139? snd 

 IhO show three types of impermeable concrete groins. Figure 138 shows a 

 combination concrete and stone semi -articulated type. Figure 139 shows 

 an all concrete articulated "type. Figure IkO sho^js an all concrete type 

 originally articulated and later solidified with a concrete cap, 



]4iiO, In Figure 138_, the precast reinforced concrete groin is con- 

 structed of vertical transverse blocks shaped like a capitcl "I", 6 feet 

 wide and U feet long. The height of the unit is equal to the vridth of 

 the unit but may vary with location, Horiaontal panels 2 feet high, 

 8 inches thick^ and 10 feet long^« with notches on either sndj are placed 

 in between the transverse blocks. Rock fill is then placed in between 

 the horizontal panels and covered with a 6-inch concrete slab cast in 

 place. The concrete slab can be used to tie the entire structure into a 

 single unit. 



iiUl. In Figure 139, the groin is composed of concrete precast 

 trapezoidal blocks, each 3 feet 3 inches high and x-jeighing 5 tons. Tvro 

 types of blocks are used. Type A„ shown in Figure 139 has a length of 

 5 feetj a top width of 2 feet and bottom width of 6 feet. Type B^ not 

 shown but similar to ty-pe A_^ has a length of 3 feet 10 inches 5 a top 

 width of 3 feet 2 inches ^ and a bottom width of 7 feet 2 inches. The 

 block at the offshore end ia the s ame as type A but with a sloping off- 

 shore face. The steel joints and r einforcing^, shown in Figure 139 5 are 

 ths 8 ame for both tj^pe A and type B. A patent on the joint is held by 

 Harrison Weber. The reinforcing bars are welded to the I-beam and the 

 channels on opposite ends cf the blockj and are placed as one unit in the 

 form for easting the concrete block. 



hk2. The blocks are placed on the beach surface, the flexible nature 

 Df the joints enabling the blocks to conform with the ground slope and to 

 undergo a measure of settlement. The height cf groin can be increased 

 by maintaining the relation»ship beti<reen height and base width. As some 

 settlement occurred ^htro this type of groins was originally placed 

 on a sandy beach^ a mat of crushed stons x-'Xas used as a foundation in 

 later installations, 



I1U3. Figure lij.O shews another tj'pe of concrete block groin which 

 is simple to cast and place^ and which has served satisfactorily in some 

 locations. The height of groin can be changed by changing the length 

 and base width of the concrete blocks, ConDrete ehannsl=ways are cast 

 in the block as a guide in placing and to tie the blocks together. No 

 special type oi; ;nd bird:?: is reijuired. Alter the blocks have settled 

 for a iM^rlcd of tl'.ie, the ccncrete cap can be poured. This cap will 

 increa-.e the heii_;ht 01 the groin somewhat ., and tie all the component 

 carts togethe""" into a monolithic groin, 



'-■^ • Steel Shc^ret .'lie '-'^gA-^:' ~ satisfactory s teel sheet pile "^roins 

 ha7£ been construct^^d i:ith straight wtb^ arch v<-eb,, or M or Z sections. 

 All of t-ese are Tiade with interlocking joints that do not pull spare- 



208 



