Question

A 3 x 3 (total 9 piles) group of piles are to be constructed at a site. Assume that the piles are embedded in a saturated homogeneous clay having a cu = 90 kN/m2. Given: diameter of piles (D) = 316 mm, center-to-center spacing of piles = 600 mm, and length of piles = 20 m. Find the allowable-load carrying capacity of the pile group. Use F=3.

Answer 1

Maximum allowable load for a group pile =4.752kN

while allowable load for a group pile = 1.584kN

Step-by-step explanation:

Given

diameter of piles (D) = 316mm = 0.316m

center-to-center spacing of piles = 600 mm= 0.6m

length of piles = 20 m.

Factor of safty=3

cu = 90kN/m2

the allowable-load carrying capacity of group pile is gotten by the allowable-load carrying capacity of a single pile multiply by quantity.

therefore,

allowable-load carrying capacity of a single pile, Q =
`(A*3.619 Cu)/(l/r)` =

where,

A= cross -sectional area of the pile= πr² = 3.142*0.158² = 0.078m²

l= length of the pile=20m

r= radius of the pile base= 0.158

Q=
`(0.078*3.619 *90)/(20/0.158)` = 22.25/126.6 = 0.176kN or 175.7N

allowable load for a group pile = 0.176 * 9 = 1.584kN

Maximum allowable load for a pile = Q* factor of safety = 3*1.584 =4.752kN