Empirical formulas to calculate the group efficiency

Emperical formulas to calculate the group efficiency 

Here are some empirical formulas used to calculate the group efficiency like the Converse Labarre formula and Felds rule.

1. Converse Labarre formula 

ήg= 1- θ/90 [(n-1)m+(m-1)n]/mn 

Here, 

θ = inv(tan(d/s))        θ in degrees 

Where, 

m = no of rows

n = no of piles in a row

d = diameter of Piles 

S= Spacing of piles

2. Felds rule 

According to this rule, the value of each pile is reduced by 1/16 on account of the the effect of nearest pile in each diagonal or straight row of which the pile in question is a member

2 piles at 15/16

Ng = 2*(15/16)/2*100

Ng = 93.75%

 

 

 

 

 

 

3 piles at 14/16

Ng = 3*[(14/16)/3]*100

Ng = 87.75%

 

 

 

 

 

 

 

 

 

 

 

4piles at 13/16  and 1 pile at 12/16

Ng = {[4*(13/16)]+[1*(12/16)]}*100

Ng = 80%