Bored Pile Concrete and Rebar Calculator

Because drilling always over-excavates: bit wear, uneven walls and local collapse in sand all make the hole bigger than design, so more concrete goes in than theory allows. Ordering at 1.0 leaves every pile half a cube short, the last one waits for the next truck, and a stopped pour risks a discontinuity. Settlement also measures against the overbreak factor.

Friction piles usually run 50-80 kg/m³, end-bearing 60-100, and piles taking lateral load or uplift can exceed 120. Below 40 suggests under-reinforcement and needs a crack and bending check; above 150 is usually uneconomic and a precast or steel pile may be the better answer. Steel ratio is a core comparison between pile options.

Underwater work needs the tremie method with a highly workable mix — 180-220 mm slump, aggregate no larger than 40 mm and no more than a quarter of the clear bar spacing, plus a retarder to keep the pour continuous. In a dry hole the slump can drop to 100-140 mm and cement content falls. The wrong mix blocks the pipe, segregates or traps mud in the shaft.