n6 RAILWAY CONSTRUCTION. 



into the ground to depths varying from 42 to 48 feet. A 

 toothed or serrated edge, as in Fig. 113, is sometimes given to 

 the lower edge for screw piles which have to cut their way 

 through a hard stratum. 



All bolting flanges should be accurately turned and fitted to 

 ensure close, parallel surfaces when bolted together. 



The joint shown at A, Fig. 112, is one the writer has used to 

 a large extent for the bolting flanges of cast-iron screw piles and 

 cylinders. It is very simple in form, readily coated with white 

 lead to ensure a water-tight joint, and as the upper length is 

 practically recessed, or let into the lower length, the exact 

 continuity of the different castings is secured. 



Solid screw piles of wrought-iron or steel, similar to Fig. 114, 

 are used for some descriptions of work. These are generally 

 made in long lengths, in sizes varying from 4 to 8 inches in 

 diameter, and with screw blades of wrought-iron or cast-iron 

 fixed in the most secure manner to resist the strain produced 

 when screwing into the ground. The couplings for these solid 

 piles must be very carefully made, all contact surfaces truly faced 

 and fitted, bolts turned, and bolt-holes drilled. 



Fig. 115 is a sketch of a hollow cylindrical water-jet pile, 

 which has been used successfully in cases of light sand. The 

 lower end of the pile is made externally in the form of a solid 

 disc, terminating in a conical point, having an aperture in the 

 centre to correspond to the water-jet. To the top of the pile is 

 secured a tight-fitting cover throurgh which a tube passes from a 

 force pump. Water at high pressure is pumped into the tube, 

 and as it forces its way out through the conical point the sand 

 is stirred up and loosened, and thus allows the pile to descend. 

 When the pile has been lowered to a sufficient depth the pumps 

 and tube are removed, and the sand settles down into its former 

 compact condition. 



Great care must be used with the first two or three lengths 

 of any screw pile to ensure the pile taking a correct or true 

 vertical position. Each series of screw piles should be properly 

 braced together to obtain stability under moving loads. 



Hollow cylinders of cast-iron, wrought-iron, or steel form 

 most efficient foundations or piers for large bridges over soft 

 ground or fresh water of considerable depth. Made open at the 

 bottom, and constructed of complete rings, or, if of large diameter, 

 of rings built up in segments and securely attached together 



