s 



54 DESIGN 



see Transactions of the American Society of Civil Engi- 

 neers, Vols.XLVIII, p. 180; LIV, PartF, p. 3; LXV,p.467; 

 LXX, p. 412. 



Bulkheads. In constructing artificial lakes, it some- 

 times happens that a part of the shore lies in an unstable 

 soil which cannot be excavated without flowing. To 

 construct a firm and stable shore the following method has 

 been used: 



A single row of piles close together with every fifth one 

 omitted is driven along the shore line. Then batter piles 

 are driven in the gaps at as great an angle with the vertical 

 as possible. Unfortunately with a drop-hammer machine 

 this angle cannot be made greater than about 20 degrees. 

 The piles are then all sawed off at about 1| or 2 feet below 

 the proposed water surface and a wale is framed into them 

 in such a way that the thrust of the batter pile due to lateral 

 movement of the soil is transmitted to the wale and then 

 against the vertical piles. (See Fig. 18, page 55.) 



In performing this work of cutting off the piles and 

 placing the wale in position, a trench must be excavated in 

 order to provide room for the workmen. In order to draw 

 the work together jack-screws are used and a bolt with 

 suitable washers through each pile holds it close to the 

 wale. The wale consists of an 8-inch by 10-inch timber. 

 The piles are notched to receive it, since the bolts must not 

 be required to take up much of the thrust. The material 

 on the water side of the piles can then be removed by 

 cable-way or otherwise to the full depth of the lake. 

 Good upland subsoil is then dumped in over the piles to 

 reinforce them and provide a firm shore. This soil of course 

 will sink down into the soft material below and more will 

 have to be added until no further settlement takes place. 

 It is wise to fill in considerably above the proposed grade 



