1.1 BACKGROUND 



Figure 1-1 illustrates several of the terms used in evaluating 

 anchor holding capacity. The depth of the anchor fluke embedded in 

 the seafloor is termed D , and the fluke width is called B . Infinite 

 strip, square, or circular flukes are generally assumed in model studies 

 or analyses. However, rectangular flukes can be evaluated by applying 

 a shape factor identical to that used by Skempton (1951) for rectangu- 

 lar footings . 



"Deep anchor failure" defines a situation in which the sediment 

 surface is not affected when the anchor is loaded to failure. As the 

 anchor is displaced, the soil tends to flow from above to below the 

 anchor. "Shallow anchor failure" defines a situation in which the soil 

 surface is bulged when the anchor is loaded to failure. As the anchor 

 is displaced, a soil plug over the anchor is pushed out of the sediment. 

 A term called the "relative depth of embedment" (D/B) is used to help 

 define shallow and deep anchor behavior. This term is a function of 

 soil type and strength, and determines which of these two modes of 

 failure will govern when an anchor is extracted. These failure modes 

 are illustrated in Figure 1-1. 



fluke 

 width, B 



Shallow Anchor Failure 



Deep Anchor Failure 



Figure 1-1. Definition of terms. 



