Determination of Fineness modulus (FM)?

Problem 1: 25% of total sand sample is retained on each of 0.60mm, 0.425mm, 0.30mm and 0.15mm sieves. Find the FM of sand sample?

Exam Name: Sylhet gas field 2017, BGFCL 2017 


Solution: 

Openings	Percentage retain	Cumulative percentage  retain
0.60 mm	25	25
0.425 mm	25	---
0.30 mm	25	50
0.15 mm	25	75

Sum of Cumulative percentage retain = 150
So that,  FM= (150/100)
                    = 1.5
Answer: 1.5

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Problem 2: Sieve analysis was performed for a coarse sand and it has been found that 100% of the sample retained No. 30 sieve. What is value of fineness modulus of the sample?
Exam Name: PGCB 2017. 

Solution: 

Sieve No.	Percentage retain	Cumulative percentage  retain
#4	0	0
#8	0	0
#16	0	0
#30	100	100
#50	0	100
#100	0	100

Sum of Cumulative percentage retain = 300
So that,  FM= (300/100)
                    =3
Answer:3

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