gradually settle as transference of load from water to solids Is accompanied by a re- 

 duction in the volume of sediment equal to the volume of interstitial or pore water 

 drained . Determination of the expected amount and time rate of settlement is made 

 from results of laboratory consolidation tests. 



Amount — The amount of settlement is computed from the formula 



Settlement 



- ^f 



1 + e. 



(14) 



where e- is the initial average void ratio and er Is the final average void ratio within 

 a sediment stratum undergoing consolidation with an initial thickness of Hj . 



A problem previously was worked using data from core A 31 . It was found that 

 a hypothetical load (with a buoyed mass of 5 kg and a square surface area of 100 cm ) 

 placed on the bottom immediately sank about 8 cm because the sediment failed in 

 shear. We will continue the problem at this point and compute the amount of expected 

 settlement of the load due to sedimentary consolidation. 



Step (1): compute depth in the core as a function of sediment overburden pressure 

 (stress), d-p relationship (Fig. 25, curve A), from known values of sediment wet unit 

 weight (Table 7). 



TABLE 7. D-P COMPUTATION FROM WET UNIT WEIGHT OF CORE A 31 



Interval 

 (cm) 



Interval 



Depth, d 



(cm) 



Cumulative 



Depth 



(cm) 



Wet Unlt_ 

 Weight, p 

 (g/cm3) 



1/ 



Overburden 



Stress 



P = (P -l)d 



(g/cm2) 



Cumulative 



Overburden 



Stress / 



(g/cm2) 



0-4 



4 



4 



1.4 



1.6 



1.6 



4-15 



11 



15 



1.45 



5.0 



6,6 



15-29 



14 



29 



1.5 



7.0 



13.6 



29-46 



17 



46 



1.55 



9.4 



23.0 



46-60 



14 



60 



1.6 



8.4 



31.4 



From measurements reported by Richards (in preparation), 

 Plotted as curve A, Figure 3. 



51 



