Step (2): compul-e the sum of the natural overburden stress and the computed 

 pressure exerted by the load (Table 8). This computation of pressure in the direction 

 of the vertical or z axis, p^^, of the load can be simplified by dividing the surface 

 area into four rectangles (squares in the example given) to determine the pressure at 

 the corner of each rectangle (see Fig. 26). A graphical solution (Fig. 26), from 

 tables by Newmark (1935), is made for p , using coefficients m and n that are defined 

 in Table 8 and Figure 26 (after Palmer, 1953, p. 39). 



Step (3): load plus overburden stress from the last column in Table 8 is plotted 

 (Fig. 25, curve B). Settlement is assumed negligible when curve B becomes asymp- 

 totic to curve A; 32 cm is selected as the lower limit of the compressible stratum in 

 this problem (Fig. 25). 



Step (4): an average initial void ratio must next be computed. Depth as a 

 function of void ratio for core A 31 is shown in Figure 27. Curve B arbitrarily is 

 divided into 5-cm intervals from 8 to 32 cm (Table 9). A void ratio is determined 

 every 5th cm from Figure 27, and an average initial void ratio of 2.41 is computed 

 (Table 9). 



Step (5): compute the average final void ratio. Values of load plus overburden 

 stress at each depth given in Table 9 are determined from curve B, averaged, and an 

 average final stress of 29 g/cm'^ is computed in Table 9. When this figure is entered 

 on the laboratory-determined virgin compression curve of Figure 10, it is found that 

 the average final void ratio is 2.08. 



Step (6): compute settlement. Knowing the compressible thickness, H|, to be 

 32 - 8 or 24 cm, the total settlement, S, finally can be computed by use of equation 

 14, 



_ e. _ ef 2.41 - 2.08 - , _ - _ 



S = H: = 24 cm = 2.0 cm . 



1 + ei ' 1 + 2.41 



Time rate — The preceding settlement analysis indicated that the load in the 

 problem will very slowly sink about 2.3 cm deeper than 8 cm as a result of the gradual 

 consolidation of the sedimentary stratum upon which it initially rested. 



5 



The average initial void ratio also can be obtained another way. At 8 cm, the sedi- 

 mentary overburden stress is 3.4 g/cm"^, at 20 cm (1/2 layer thickness), 9.2 g/cm^; 

 and 32 cm, 15,3 g/cm (Fig. 25). These stresses correspond to void ratios of 2.53, 

 2.32, and 2.21 (Fig. 10); and e; Is computed to be 2.35 by averaging these numbers. 

 Using this value In equation 14 settlement Is computed to be 1 .9 cm. 



53 



