Pile Group Spacing for a Target Efficiency
The center-to-center spacing that reaches a target Converse-Labarre efficiency.
Example
You enter
- Pile rows n 3
- Pile columns m 3
- Pile diameter d (in) 12
- Target efficiency Eg (0-1, e.g. 0.75) 0.75
You get
- Spacing (in) 39.56
- Angle theta = atan(d/s) 16.88 deg
Details, formula, and sources
theta = (1 - Eg) x 90 m n / ((n-1)m + (m-1)n), then s = d / tan(theta). A 3x3 group of 12 in piles targeting Eg 0.75 needs about a 39.6 in (3.3d) spacing. Answers 'how far apart for this efficiency' instead of the efficiency from a set spacing. Spacing must be at least one diameter. An empirical hand check; block failure and settlement are separate; the geotechnical engineer of record governs.
theta = (1 - Eg) x 90 m n / ((n-1)m + (m-1)n) [deg]; s = d / tan(theta). The inverse of Eg = 1 - atan(d/s) x ((n-1)m + (m-1)n) / (90 m n); spacing must be at least one diameter (theta <= 45 deg).
Converse-Labarre pile-group efficiency (standard geotechnical practice), solved for the spacing, by name; the geotechnical engineer of record and a load test govern.
The Converse-Labarre efficiency is a published empirical relation in standard foundation-engineering texts; the target efficiency comes from the group design.
Estimate. AHJ and licensed professional govern.
Field names used by the API: rows_n, cols_m, diameter_in, target_eg, spacing_in, theta_deg
- Spacing for efficiency s = d / tan((1 - Eg) x 90 m n / ((n-1)m + (m-1)n))Converse-Labarre
- Minimum spacing spacing must be at least one diameter; that sets the lowest reachable efficiencyConverse-Labarre
- Scope friction-pile hand check; block failure and settlement are separatescope of this tile