Answer:
The moist unit weight of compaction = 109.05 lb/ft3
Explanation:
In order to determine the moist unit weight, the dry unit weight has to be evaluated first. If Y is the moist unit weight, then:
Y = Yd (1 + m)
Where:
Yd = dry unit weight
m = moisture content of soil = 8% = 0.08
But the dry unit weight is unknown. In order to calculate the dry unit weight, we will make use of the formula for relative density R;
R = [(Yd — Ydmin) ÷ (Ydmax — Ydmin)] × [Ydmax ÷ Yd]
Where:
R = relative density = 60% = 0.6
Yd = dry unit weight
Ydmin = minimum dry weight = 92 lb/ft3
Ydmax = maximum dry weight = 108 lb/ft3
Therefore R = 0.6 = [(Yd — 92) ÷ (108 — 92)] × [108/Yd]
0.6 = [(Yd — 92)/16] × [108/Yd], or
0.6 = (0.0625Yd — 5.75) × [108/Yd]
0.6Yd = 6.75Yd — 621
6.75Yd — 0.6 Yd = 621
6.15Yd = 621
And Yd = 100.98 lb/ft3 = dry unit weight
But we are asked to find the moist unit weight = Y = Yd (1 + m)
where Yd = dry unit weight and m = moisture content of soil = 8% = 0.08
Therefore, Y = 100.98 (1 + 0.08) = 109.05 lb/ft3.
