390 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



f rictional hold on the ground to withstand the strain. Mr. J . W. 

 James, M.I.C.E., found by experiment the adhesion of ice t<> 

 timber to be 33 '32 Ibs. per square inch, therefore the force 

 exerted on the piles will be in proportion to the superficial area 

 of the portion of the timber gripped by the ice. 



Mr. James gives the following practical formula for readily 

 determining approximately the force capable of overcoming the 

 frictional resistance and drawing the pil< 



R = force in pounds required to draw the pile. 



W weight of the ram in pounds. 



F = fall of ram in inches. 



S = set of pile at last blow. 



P = perimeter or girth of the pile in inches. 



G = coefficient = 0*3285 deduced from a number of experi- 

 ments made with piles, 1 inch to 3J inches square, driven into 

 various descriptions of ground. 1 



Then 



Rx S P_Rx S xO-25 xP 

 W x F 4 WxF 



W x F x C 



0-25 x p x S 



WxFxC 



25 x P X K " 



p 

 As a pile 1 inch square has a perimeter of 4 inches appears 



in the formula. 



Resistance to Horizontal Stress. Experiments made by Mr. 

 J. W. Sandeman, M.I.C.E., with the view of ascertaining the 

 amount of resistance offered by different material, such as clay, 

 sand, ashes, to the horizontal movement of timber piling, tend 

 to show that loose ashes afford the least resistance, clay more, 

 and sand the greatest. It also appears, from the fact of all 

 these piles breaking off at 5 feet below the surface of the ground, 

 that a tie-pile driven 15 feet into the ground would meet with 

 as much resistance to horizontal stress, applied at the level of 

 the ground, as if the pile were driven to a greater depth. 2 



Sheet-piling. At the dock works near Kiel, in driving the 

 sheet-piling enclosing the works, which varied from 25 feet 6 

 inches to 37 feet long, it was found advantageous to drive two 



1 M.P.I.C.E., vol. xli. pp. 1U2, 103. 2 Ibid., vol. lix. p. 282. 



