Table 2-3. Estimated Values for Cohesionless Soil Properties 



Soil Description 



Friction Angle, (j) 

 (deg) 



Buoyant Unit Weight, 

 kg/m 3 (lb/ft 3 ) 



Sandy silt 

 Silty sand 

 Uniform sand 

 Well-graded sand 



20 

 25 

 30 

 35 



880 (55) 

 880 (55) 

 880 (55) 

 960 (60) 



2.2.2 Shallow Water 



At shallow water sites, it may be less expensive and technically 

 preferable to use adaptations of terrestrial survey techniques that 

 provide data similar to those recommended for deep water surveys. In 

 shallow water sites, cohesionless soils will be more common, and the use 

 of the Standard Penetration Test will allow the determination of the 

 friction angle. When adaptations of terrestrial survey techniques 

 cannot be used, it is recommended that a shallow water survey follow 

 along the lines of the recommended deep water survey. 



2.3 RECOMMENDED PROCEDURES WHEN SITE SURVEY IS LIMITED 



Because the seafloor is primarily a depositional rather than an 

 erosional environment, more uniformity of sediments and sediment 

 properties can be found there than would be found on land. Properties 

 based on known environmental conditions can often be estimated accu- 

 rately enough for site selection and preliminary design. Even in more 

 complex areas where a site survey is definitely required, an estimate of 

 properties to be encountered will aid in designing the survey and 

 influencing initial thinking about the facility. Lee and Clausner (1979) 

 have procedures for estimating the necessary properties, and those 

 procedures are presented herein. 



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