SCREW PILES. 



395 



experiments the ground was proved to be incapable of support- 

 ing more than 700 Ibs. per square foot, which was insufficient 

 to support the working load, the following means were adopted 

 as the most expeditious and effectual for obtaining the necessary 

 supporting area. 



Timber platforms composed of whole baulks of timber 12 

 inches square were placed round each group of piles transversely 

 to the centre line of the pier, and arranged so as to break joint 

 under the main bearing-sills, or at the centre between two of 

 them. The main sills rested upon the platform and consisted 

 of baulks laid longitudinally, one on each side of the screw-piles. 

 The platforms were made on shore and floated off at high water ; 

 after being adjusted round the piles, the sills were placed in 

 position and secured. The platforms were then weighted with 



FIG. 34G. 



a load greater than would be supported by the piles on com- 

 pletion of the pier. On the platforms coming to rest with the 

 load upon them, a connection was made with the piles by cast- 

 iron discs, arranged to clamp the piles below a collar cast specially 

 on the pile shaft. 



The load on the pier is thus transmitted through the columns, 

 piles, and discs, to the bearing area of the platform, thereby giving 

 the necessary resistance to support the load (Figs. 346 to 349). 



Load on Piles. Mr. J. Gaudard, in his paper on foundations, 

 states that the load a pile driven home and secure from lateral 

 flexion can bear may be estimated at from one-tenth to one- 



eighth the crushing load. 1 



M.P.I.C.E., vol. 1. p. 123. 



