shaft which was in turn connected to a torque screwdriver handle. The vane 

 size was selected so that typical soil strengths would fall within the midrange 

 of the torque dial. The shaft without the vane was tested to determine the 

 torque lost to shaft friction. The torque device was calibrated by applying 

 a known torque and connparing with the dial reading. 



electric outlet 



displacement 



mercury 

 switch 



_2_ 



L 



test 

 object 



weight 

 y"^ stand 



knife-edge 

 support 



H 



^ 



weights 



~55-gallon drum 



Figure A-1. Setup for FY-71 laboratory tests. 



Vane tests were perfornned by pressing the vane to a particular 

 soil depth and then slowly twisting the handle until a constant reading was 

 obtained. To achieve as much consistency as possible, the same individual 

 performed all tests. A few core samples of the soil were obtained and sub- 

 jected to the more standard laboratory vane test. The results of these latter 

 tests compared favorably with the results of the tests with the hand-held vane. 

 Strengths were obtained according to the usual practice of assuming full mobi- 

 lization of strength over a cylindrical failure surface having a diameter equal to 

 the vane diameter and an altitude equal to the vane height. Mobilization of 

 strength along the ends of the cylinder was also assumed. 



35 



