318 



The Shrinkage of Soils 



The volume of water requiring to be added to 100 grms. of air-dry 

 soil to produce maximum plasticity together with the mean total linear 

 shrinkage expressed as a percentage in each case is given below. 



Volume of water required 



to produce maximum Mean linear 

 plasticity. C.c. per 100 grms. shrinkage 



air- dry soil per cent. 



A. 37-0 c.c. 13-0 per cent. 



B. 360 „ 12-1 „ 



C. 26-0 „ 8-8 „ 



D. 24-0 „ 6-0 „ 

 E 190 „ 2-9 „ 



The physical composition of each of the soils in question as deter- 

 mined by Osborne's beaker method are given below: 



An examination of the above figures will show that although a rough 

 proportionality exists between the shrinkage observed and the content 

 of particles of the fine silt and clay order of magnitude the proportion- 

 ality is by no means exact, and in the case of the samples C and D the 

 physical analysis would lead one to expect that a slightly greater 

 shrinkage would be found to occur in the case of D than that of C while 

 in fact the reverse is actually the case. 



In the case of the various experiments the series of trials were in 

 the majority of instances repeated a considerable number of times and 

 the results obtained represent the mean of a number of independent 

 determinations. It was found that this was the best plan to obtain 

 readings which would give smooth curves, as, in individual instances, 

 tendencies to depart from the smooth form were usually observed. 

 These irregularities most usually tended to occur at the commencement 



