Question

A group of concrete piles (3×3) is driven into a uniform layer of medium dense sand, which has a unit weight of g_t = A kN/m³ and a friction angle of f = B^o. The water table is C m below the ground level. Each pile has a diameter of 400mm, a length of 10m. The centre-to-centre spacing of the piles is s = D m.

Assume proper values for A, B, C and D.

1. Calculate the ultimate vertical capacity of a single pile.
2. Find the allowable load capacity of the pile group, based on individual pile failure. Use a factor of safety of 2.5 and a pile group efficiency of 0.9.
3. Based on Hansen’s equations, find the allowable block capacity of the pile group. Use a factor of safety of 3.5. Assume the average unit weight of concrete piles is 25 kN/m³.

Answer 1

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