Civil Engineering - UPSC Civil Service Exam Questions - Discussion

Ysat= W/V.
=(0.3+1) /(0.2+0.3+0.5),
= 1.3g/cc.

e = volume of void / volume of solid
= (0.2 + 0.3) / 0.5 = 1 x 100 = 100%.

Sr = Vw / Vv = 0.3 / 0.5 = 0.6 x 100 = 60%
w = Ww / Ws = 0.3 / 1 = 0.3 x 100 = 30 %.

G = ( Sr x e) / w = (0.6 x 1) / 0.3 = 2.

Ysat = Yw x (G + e) / (1 + e) = 1 x (2 + 1) / (1+1).
= 1.5 g/cc.
So, option B is Right.

Ysat = (.3+1)/(.2+.3+.5).

For Saturated unit weight = 1.5 g/cc.

For fully saturated soil all the voids r filled with water, so total voids Vv= Va+Vw.

And Total weight W= Ww+Ws= 0.3+1+0.2(It is the wt of water which is filled in 0.2 cc which is prior volume of air) and 0.2cc has 0.2g wt as given in ques that 0.3 cc has 0.3g wt.

Ysat= W/V.
=(0.3+1+0.2) /(0.2+0.3+0.5),
= 1.5g/cc.

1) Soil is partially saturated at degree of saturation (S) = Vw/Vs = 0.3/0.5 = 60%.
2) Void ratio (e) = Vv/Vs = 0.2+0.3/0.5 = 100%.
3) Water content (w) = Ww/Ws = 0.3/1.0 = 30%.
4) Saturated unit weight (Ysat).

Note: Each milliliter of water weighs 1gm. Hence, if the soil mass is to saturate the volume of water is the same as the weight of water. As a result weight of water is to be added is 0.2gms for full saturation.

Ysat = 0.2+0.3+1.0/1 = 1.5 g/cc.

Vol Of voids= Va+ Vw.

e = (Va+ Vw)/Vs= .5/.5= 1.

The void ratio=volume of voids/volume of soil.
e=.2/.5=.4 i.e=40%.

How void ratio comes 1? Please explain.

Option B is correct.

No,

Degree of saturation =60%. ("")
e = 1 (X)
w= 30% ("")
Saturated unit weight = 1.3 g/cc (X).

Yes, Mrinmoy Void ratio is 1 and the right answer is B.