the changes to the rate of particle reorientation and the viscous 

 effects of strength. Table 2 summarizes the results of studies by 

 Sridharan and Madhav (1964) , Carlson (1948) , and Evans and Sherrat (1948) 



Table 2. Torsional Moment Versus Rate of 

 Rotation 



Reference 



Torsional Moment (%) 



Rate of Rotation 



2 /min 



6 /min 



30°/min 



Carlson 



100 



102 



117 



Evans and Sherrat 



W = 42.5* 

 W = 55.5 

 W = 61.0 



100 

 100 

 100 



116 

 127 

 120 



156 

 172 

 200 



Sridharan and Madhav 



Undisturbed 

 Remolded 



100 

 100 



110 

 108 



132 

 118 



Where W = water content of soil (%) 



Although the results are scattered, several apparent trends exist. 

 The vane shear strength of the soil increases with increasing rate of 

 rotation. The increase is generally greater for samples with higher 

 water contents, and the increase is generally greater during the 

 undisturbed test. 



The torque at failure is the sum of the opposing torques on the 

 cylinder side and on the two cylinder ends : 



T = T + T 

 Failure Sides Ends 



(7) 



11 



