What is group efficiency of pile ?

The group efficiency of a pile is defined as the ratio of the ultimate load of the group to the sum of individual ultimate loads.

𝜂𝑔 = Qug/ n Qup  

Where,

Qug = load carried by a group of friction piles 

Qup = load carried by each friction pile

n = number of piles

ηg = efficiency of pile group