[barnes-hayward- EXPANSIVE FORCE OF ICE 45 



MCLEOD] 



400 lbs. per square inch. It was found, however, that the ice block 

 first yielded at approximately half the crushing strength, and that 

 what we have called the crushing strength was the pressure per square 

 inch which caused the ice block to burst. 



If we take in round numbers the crushing strength to be 400 

 pounds, as C. A. Mees has done in his paper on design of dams, then 

 we find with him, that the thrust for various thicknesses of ice can 

 be taken as follows: — 



Tensile Strength. 



The best tests which we have seen on the tensile strength of ice 

 have been made by Mr. George G. Bell (Maine Society of Civil En- 

 gineers, Vol. 1, page 41, 1911). 



The American Civil Engineers' Pocket Hand Book gives a range 

 of 142 to 223 pounds per square inch. 



Mr. Bell employed a cement testing machine. The samples of 

 ice were prepared in two different ways. The first lot by filling 

 cement moulds with water which were allowed to freeze. In these 

 samples the air bubbles arranged themselves perpendicular to the 

 surface of the ice in contact with brass, forming a core in each end, 

 and when tested, failure occurred along the line containing the points 

 of contact, and the core. The second set of samples was prepared by 

 cutting the ice to nearly the proper size. These pieces were set in 

 the moulds and the remaining space filled with water and frozen. 



The following table contains Mr. Bell's results: — 



