Group Pile

Determination of load-bearing capacity of group piles is complicated. If piles are closely placed to each other it will reduce the load bearing capacity of piles

Dynamics Formulae


Qu = R + P + W

Piles in Clay

Piles in Sand

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Pile group capacity, Q = q0 X B2 + 4 x B x L x f
(Square)

It is based on simplified analysis to obtain the efficiency for friction piles. The piles may act in one of two ways:-


  • As individual piles, Qu = (p)(L)(fave)


  • As a Block with,Lg X Bg X L, Qg(u) = (fave)(Pg)(L)


Steps to determine the efficiency of the pile
group :


1.Determine Total Qu = (n1)(n2)(Qb+Qs)
2.Calculate Qg(u) = Qb(g) + Qs(g)


Compare 1 and 2 and take the lower value

Qall = Qu/FS


*(FS≥2.5)

R = (W(nH)n)/(s + c/2)

Settlement of Pile

Elastic

Consolidation

Use 2:1 distribution method which consists of 5 steps

If the pile material is assumed to be elastic, the deformation of the pile shaft can be evaluated in accordance with the fundamental principles of mechanics of materials as

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Step 2 :

  • Assume load Qg is transmitted to the soil beginning at a depth of 2L/3 from top of pile Qg spreads out along two vertical to one horizontal line from this depth

Step 3 :

  • calculate
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Step 1 :

  • the group is subjected to a total load of Qg
    • if pile cap is below original ground surface, Qg is equal to total load of the superstructure on piles minus the effective weight of soil above group pile

Step 4 :

  • Calculate
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Step 5 :

  • Total cosolidation settlement, ΔSc(y) = ΣΔSc(i)