Figure 1 illustrates the variation of blow counts vs. depth at a site with a silty sand fill deposit overlying an older, pre-Holocene windblown sand deposit. The silt content of the upper sand varies from about 5 to 40%, with an average value of about 20%. (a) Plot N60 and (N1)60 as a function of depth. For (N1)60, use the overburden correction factor (CN) from Boulanger (2003). (b) Estimate the relative density of each layer using penetration resistance data using the relation DR =(N1) 60/46. 0 10 20 Depth (ft) N ER/60 Well graded silty, brown sand, loose to medium dense GWT at 10 ft Fig. 1: Log of boring B-1 (for use with Problem #1). N is blow count. ER/60 is measured energy ratio divided by 60. FILL 0.88 0.94 1.01 1.03 4 1.09 1.1 18 1.11 ALLUVIUM 26 1.12 20 1.14 Poorly graded tan sand, dense to medium dense 17 1.15 27 1.16 31 1.18 26 1.17 40 23 1.18 20 1.16 32 1.17 50 28 1.18 60 60