Ground engineering · Sand piles & stone columns

Stone columns (Priebe) calculator

Area replacement ratio and basic settlement improvement factor for a stone column grid.

Standard: Priebe (1995) basic improvement factor n0

Inputs in the worked example

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

Result	Value	Unit
Column area Ac	0.503	m²
Unit cell area A	3.464	m²
Area ratio Ac/A	0.145
Kac = tan²(45 − φc/2)	0.217
Improvement factor n0	1.80
Improved settlement s0/n0	83	mm
Equivalent unit cell diameter	2.10	m

Diagram for the worked example

Ac/A = πd²/4 ÷ (0.866s² triangular or s² square)
n0 = 1 + (Ac/A)·[(5 − Ac/A)/(4Kac(1 − Ac/A)) − 1] (μs = 1/3)
Basic factor only: Priebe's corrections for column compressibility and overburden are not applied

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