Coefficients of Friction Between Cobesionlefts SoilB and 

 Some Marine Construction HaterialE (Valeot, 1979) 



a. Cohesionless Seafloor 



- Trapped water dissi- 

 pates rapidly. |J up 

 to 0.8 possible ((|) 

 = 38°); simple fric- 

 tional behavior con- 

 trols. 

 - Friction coeffi- 

 cient dependent on 

 surface smoothness, 

 anchor material, 

 sand type. 



b. Cohesive Seafloor 



|j (immediate) can be < 0.1 (attributed to thin film 

 trapped water between anchor and seafloor) . 



[J (short term - normally consolidated seafloor) can be 

 0.15-0.2 



Soil 



Internal 

 Friction 

 Coefficient 



Surface Friction Coefficient for — 1 



Soootfa 

 Steel 



Rough 

 Steel 



Smooth 

 Concrete 



Rough 

 Concrete 



Snooth 

 PVC 



Quartz 



Sand 



Coralline 



Sand 



Oolitic 



Sand 



Foras 



Sand-Silt 



0.67 

 0.67 

 0.79 

 0.64 



0.27 

 0.20 

 0.23 

 0.40 



0.60 



0.63 

 0.56 

 0.66 



0.60 

 0.63 

 0.58 

 0.67 



0.69 

 0.66 

 0.7A 



0.33 

 0.20 

 0.26 

 0.40 



R 

 n_ 



5.7 



where 



5.7 ~ 



Anchor bearing capacity 

 Anchor-soil shear resistance 



Value (5.7) assumes adhesion between anchor base and soil equals 

 soil undrained shear strength. 



|J (long term) 

 |J (short term 



up to 0.7 for 



drained 



= 35' 



over consolidated seafloor) depends upon soil 

 strength, anchor roughness. 



c. Effect of Sloping 

 Seafloor 



- Low initial |J 

 can cause in- 

 stability on 

 sloping sea- 

 floors. 



- Deadweights on 

 slopes ~ 10° 

 have slid under 

 own weight. 



- Avoid use on 

 sloping sea- 

 floors. 



- Sloping clay 

 seafloors 

 likely over 

 consolidated; 

 down slop creep 

 possible. 



iJ Holdinf Ctpadty lUda fot Dcadwq|hi 



26 



