# Civil Engineering - Soil Mechanics and Foundation Engineering - Discussion

Discussion Forum : Soil Mechanics and Foundation Engineering - Section 1 (Q.No. 1)
1.
In a liquid limit test, the moisture content at 10 blows was 70% and that at 100 blows was 20%. The liquid limit of the soil, is
35%
50%
65%
none of these.
Explanation:
No answer description is available. Let's discuss.
Discussion:
123 comments Page 1 of 13.

Liquid limit is defined as the moisture content at which a groove made in a pat of soil will flow through a distance of 13mm under an impact of 25 blows. Using linear interpolation with the help of flow curve we can get the above.

Liquid Limit= W * (N/25)^0.121.

where,

W= water content at N blows.
N= no.of blows.

We can find the flow index 1st using.

I = (w1 - w2)/log(n2/n1) and then find the water content corresponding to the 25 blows using this flow index value.

Ravi Verma said:   1 decade ago
Just simply apply interpolation with 25 blows.

ASHISH WAGHMARE said:   1 decade ago
STEP1: just draw the rough graph on which, no. of blows on X-axis and moisture content on Y-axis.

80%.
M C 70%. .A(10,70%)
O O 60%.
I N 50%.
S T 40%.
T E 30%.
U N 20%. .B(100,20%)
R T 10%.
E(%)0% . . . . . . . . . . . .
0 10 20 30 40 50 60 70 80 90 100 110
NO. OF BLOWS

STEP2: Join the coordinates A and B.

STEP3: draw the vertical line from 25 no. of blows to the line AB and mark it.

STEP4: Draw horizontal line from the marked point on line AB To the pt. on Y-axis, that same will give us the liquid limit of soil sample(ie. 65%).

(NOTE: ALL STEPS ARE TAKEN FROM EXPERIMENT OF DETERMINATION OF LIQUID LIMIT BY USING LIQUID LIMIT DEVICE)
(1)

Sagar Shah said:   1 decade ago
If we use flow index than the answer coming is 50. And plot shall be along log scale wouldn't rough idea from that be wrong?

Sharda charan said:   1 decade ago
Given;

n1=10; w1=70%.
n2=100; w2=20%.

Flow index (I)=(w1-w2)/log(n2/n1) = 50;.
wL = Ilog(n2/25)+w2;.
wL = 50.10%.

V RAMESH said:   1 decade ago
Liquid Limit= W * (N/25)^0.121.

where,

W= water content at N blows.
N= no.of blows.

Liquid limit = 70*(10/25)^0121 = 89.55%.
Liquid Limit = 20*(100/25)^0.121 = 23.65%.
required liquid limit = 88-23 = 65%.