INTRODUCTION 



The purpose of this report is to provide techniques for predicting 

 the maximum uplift forces which may be applied to direct embedment 

 anchors without causing the anchors to pull out. These forces will be 

 identified as the anchor holding capacities. Since holding capacity 

 is not a property of a particular anchor but may vary considerably 

 with seafloor type, embedment depth, and method of loading, this report 

 shows how these factors influence holding capacity and how to design 

 anchors conservatively in a variety of situations. 



It is necessary to subdivide the holding capacity problem into 

 categories. The first subdivision is based on method of loading of 

 which three will be considered: 



(a) immediate breakout 



(b) long-term static load 



(c) long-term repeated load 



Immediate breakout describes the situation in which the anchor is 

 loaded as rapidly as possible until breakout occurs. Most field tests 

 have been conducted in this manner, and most of the theoretical results 

 are directed toward it. This loading method is presented first because 

 long-term holding capacities are usually presented as fractions of the 

 immediate capacity. Long-term static holding capacity refers to the 

 situation in which an anchor pulls out after a constant upward force 

 has been applied over a long period of time. This holding capacity 

 would be as^sociated with moored objects such as submerged buoys. Re- 

 peated loading involves a line force which varies considerably with time 

 and which can be approximated by a sinusoidally varying force with a 

 certain period and amplitude. Moored surface buoys and ships can pro- 

 vide this type of force application. For each manner of loading two 

 general types of seafloors are considered: cohesionless and cohesive 

 soil. Rock is not considered in this report. 



IMMEDIATE HOLDING CAPACITY 



The commonly used equation for representing the holding capacities 

 of embedment anchors is the following (Vesic, 1969) : 



F = A (cN + Y, DN ) (1) 



i c b q 



where F = holding capacity (lbs) 



