Foundations · Pile groups & caps

Pile group efficiency & settlement calculator

Group capacity from single-pile capacity with efficiency, block failure check in clay and group settlement from a single-pile test.

Standard: Converse–Labarre · Vesić group settlement · Terzaghi–Peck block

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Input	Value	Unit
Rows m	3
Columns n	4
Spacing s	1.5	m
Pile diameter D	0.5	m
Pile length	15	m
Single pile ultimate capacity	1500	kN
Single pile settlement at working load	8	mm
Clay cu at base (0 = sand, skip block)	60	kPa
Average cu along shaft	45	kPa

Result	Value	Unit
θ = atan(D/s)	18.43	°
Efficiency Eg (Converse–Labarre)	0.710
Group capacity Eg·n·Q1	12,777	kN
Block failure capacity	22,248	kN
Governing group capacity	12,777	kN
Group settlement s1·√(Bg/D)	21.2	mm

Diagram for the worked example

Eg = 1 − θ[(n − 1)m + (m − 1)n]/(90mn)
Block: Qb = 2(Bg + Lg)·L·c̄u + Bg·Lg·Nc·cu, Nc = 9 × (1 + 0.2Bg/Lg) ≤ 1.5 × 9 (simplified)
Vesić: sg = s1·√(Bg/D)
Driven piles in sand often have Eg ≥ 1; Converse–Labarre is conservative there

Pile cap (2/3/4 piles) — Truss-method tie force and steel, strut angle, pile load and column punching.
Pile group loads (rigid cap, any layout) — Axial load in every pile of a vertical-pile group under axial load and biaxial moments, with compression and…
Raked pile group (2D rigid cap) — Axial force in vertical and raked piles under a rigid cap carrying vertical load, horizontal load and…
Pile cap for 2 to 9 piles — Standard pile cap layouts from 2 to 9 piles (line, triangle, square, square with centre pile, 2 × 3, hexagon…
Pad footing — Square pad: bearing, flexural steel, one-way shear and punching shear.
Bearing capacity — Ultimate and allowable bearing pressure for strip or rectangular footings with shape and depth factors.

For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.