GATE Civil Engineering (CE) 2023 Shift 1 Solved Paper

A group of 9 friction piles are arranged in a square grid maintaining equal spacing in all directions. Each pile is of diameter 300 mm and length 7 m. Assume that the soil is cohesionless with effective friction angle 𝜙′ = 32°. What is the center-to-center spacing of the piles (in m) for the pile group efficiency of 60%?