Relative Density of Sand (D R ) 

 0.5 



long 



rectangular 



foundations 



Figure 1. Types of failure at different relative depth (D/B) of foundations 

 in sand. (From A. B. Vesic. 6 © Highway Research Board. Used by 

 permission.) 



Geological Oceanographic Parameters 



Assessment of the geological oceanographic parameters for each site 

 is required for evaluation of the stability of the site. For example, the bottom 

 topography could reveal important features that indicate high currents, slide 

 debris, slide scarps, or tension cracks which are significant to the stability of 

 the structure. 



The subbottom geological structure must be defined in the evaluation 

 of the stability of a given site. Such features as faults, joints, discontinuities, 

 strata, and depth to bedrock must be properly recognized to make an adequate 

 evaluation of the site. As the number of these structural features increases, 

 the problem of predicting foundation behavior becomes increasingly more 

 difficult and less accurate. In general, the subbottom features at each site 

 must be evaluated individually. For example, in the case of slopes with bed- 

 ding with various dips, the slope with the beds dipping in the direction of the 

 slope and with the beds intersecting the sediment surface are usually less stable 

 than slopes with beds dipping opposite to the slope. The geological structure 

 should therefore be considered in careful detail. 



