ConHnuing our problem, we shall seek the time required for 50 percent consoli- 

 dation to occur in the layer 8 to 32 cm. H is equal to 24 cm. The ratio, U, of the 

 initial stress at the surface to the initial stress at the bottom of the compressible 

 layer must be computed before the N factor can be determined. These figures are 

 obtainable from curve B in Figure 25: at 8 cm, 53.4 g/cm^ and at 32 cm, 18.9 

 g/cm2. Thus, U is 53.4/18,9 or 2.8. N is found to be about 0.35 from Figure 28 

 (after Palmer, 1953, p. 50). 



At the averaae void ratio of 2.41 (Table 9), the extrapolated Cy from Figure 10 

 is about 0.01 cmvminute. This computation is 



_ N h2 _ 0.35 (24)2 



rc;n 2 - Z ~ U.Ulo years 



1.3 X 10^ Cy 1.3 X 10*^ (0.01) 



The time required for nearly 100 percent consolidation to occur (N = 5, from 

 Figure 28) is about 0.22 years. 



In conclusion, one should keep in mind the admonition of Taylor (1948, p. 300) 

 that "settlement analyses usually give results which at best are crude estimates." 



58 



