INTRODUCTION 

 General 



Objects either partially or completely embedded in soil often require 

 forces greater than their own weight to dislodge them. This additional force 

 requirement, termed the breakout problem, enters into the planning and exe- 

 cution of many Navy undersea operations. Among these are the salvage of 

 sunken vessels and ordnance, the retrieval of bottom-sitting devices or struc- 

 tures, and the use of embedment anchors. In each of these cases, it would be 

 desirable to be able to predict in advance the magnitudes of these breakout 

 forces so that the elements of the operation would be selected and used 

 appropriately. 



The overall problem of breakout is very extensive. However, it is 

 possible to divide it into several subprobiems which are less broad and, there- 

 fore, simpler to study. Division can be made along lines of object embedment 

 depth, soil type, and nature of breakout operation. 



A convenient division point for the object embedment depth is the 

 smallest lateral dimension of the object (width). If the object is embedded by 

 an amount greater than its width, breakout usually occurs through failure of 

 the soil above the base of the object. This is the principle of embedment anchor 

 utilization. If the embedment depth is less than the object width, the breakout 

 force problem is mainly concerned with factors below the object base. This 

 latter case will be referred to in this report as the breakout of partially embed- 

 ded objects. 



Soil can be roughly divided into two general types: cohesive and 

 cohesionless. Cohesive soils (clays) are very fine grained and relatiygjy imper- 

 vious to water flQwTcoTiesfoh less soils (sands) are coarse grained and very 

 permeable. Shallow breal<'6u"t from cohesionless soils generally requires only 

 -'Very little force in addition to the object weight. The breakout force required 

 with cohesive soils, however, may be substaotjal. 



TheTiature of the breakout operation can be separated into aided and 

 unaided breakout. Unaided breakout involves solely a direct upward pull on 

 the embedded object; aided breakout includes the performance of other activ- 

 ities in addition to direct pull. Included are water jetting, excavation beneath 

 the object, and rolling of the object prior to force application. 



