2. The elastic theory equation with empirical coefficients is valid for all 

 of the data obtained so far. However, because it is empirical, it might not 

 provide accurate predictions at sites with different soils. Also there is no 

 theoretical justification for applying elastic theory to problems with pres- 

 sures near the bearing capacity. The fact that it seems to function well for 

 these three test sites may be due to compensating errors. 



For field predictions settlements should be calculated using both 

 procedures. If the trend followed by the data of these three test series is 

 continued, the settlement predicted by the bearing capacity solution will 

 either lie within or below the 95% confidence limits of the elastic solution 

 prediction. In this situation the elastic solution will give the most conserva- 

 tive and probably the most nearly correct estimate. However, if the bearing 

 capacity solution yields a larger settlement than the elastic solution upper 

 confidence limit, it is possible that the empirical elastic coefficients are no 

 longer applicable. The bearing capacity solution should then be used as the 

 more conservative result. 



APPLICATION 



Summary of Settlement Prediction Scheme 



The following scheme is suggested for predicting the immediate 

 settlement of a round or square footing at a seafloor site where the distribu- 

 tion of vane shear strength with depth has been measured. 



1. Fit a straight line through the vane shear strength data according to the 

 principle of least square. The line will have a slope and intercept K' and H' 

 defined by the equation 



c = K'(H' + z) 



where c = vane shear strength 

 z = depth below surface 



Only the vane shear strength data for the depths z = 0toz = 2D should be 

 considered. (D = plate width or diameter.) 



2. Calculate the quantity H/D letting H = H'. Use this value to obtain p/K S 

 from Figure 17. 



3. For the design footing pressure p, determine the expected value and 

 confidence limits of A(p) from Figure 18. 



27 



