TEST PROCEDURE AND RESULTS 



A list of the tests which would be performed was compiled before the 

 testing program was begun. It was decided that the parameters to be varied 

 would be the soil strength, S; the embedment depth, D; the object width, B; 

 and the relative breakout force, f^^/fn, (for the long-term tests). To be inves- 

 tigated were two soil strengths (10 and 20 psf), three object widths (3, 6, and 

 9 inches), and a variety of embedment depths (ranging between and 4.5 inches) 

 Relative force levels ranging between 0.2 and 1 .0 were also to be considered. A 

 list of the various permutations of these parameters was made and randomized. 

 Two tests with each permutation were eventually performed. A few additional 

 tests were performed when it appeared that data for a particular range of param- 

 eter values were lacking. 



Each test was begun by thoroughly mixing the soil in one of the two 

 drums. Either additional dry soil or water was added until the desired shear 

 strength was obtained throughout the drum. The soil was then vibrated to 

 increase the degree of saturation. An object was placed to a predetermined 

 embedment depth and the soil smoothed about it. About 1 foot of water 

 was added to cover the soil and object, and the lever— weight-holder system 

 was rigged. Weights were added so that the weight of the object was supported 

 and virtually no force, positive or negative, was transmitted to the soil. This 

 condition was maintained for about 24 hours. 



At the end of the waiting period, additional weights were placed on 

 the weight hanger. If the test was to be an immediate breakout test, weights 

 were placed until breakout occurred. For a long-term test, a predetermined 

 weight was placed on the holder, and the time required for breakout was 

 recorded with the electric-clock— mercury-switch system. The upward move- 

 ment of the object was measured as a function of time after load application. 



After a test was completed, the water was drained from the drum, 

 and the characteristics of the hole left by the object were measured. The 

 shear strength of the soil was then measured at four different depths (1,4, 

 7, and 1 3 inches) beneath the hole center and at the same four depths at an 

 offset distance of 8 inches from the hole center. For use in analysis, these 

 were averaged as follows: 



(a) With the 3 x 3 x 3-inch block, the strengths at depths of 1 and 

 4 inches and offset distances of and 8 inches from the hole center were 

 averaged to yield one shear strength, S. 



(b) With the 6 X 6 X 6-inch and 9 x 9 x 6-inch blocks, the strengths at 

 depths of 1 , 4, and 7 inches at the two different offset distances were averaged. 



The data from these tests are included in Table 2 of the main text of 

 this report. 



37 



