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SI Scope Calculator

Estimate soil-investigation scope: boreholes, depth and total drilling metres.

What this tool does

A preliminary estimator for the scope of an onshore geotechnical soil investigation (SI). It derives the recommended number of boreholes, borehole depth and total drilling length from the plot area, an investigation-intensity grid and the building loading (storeys/height and/or foundation width). The result feeds the SI Cost Estimator.

Scope logic
  • Borehole count = max(ceil(area / d²), 3), where the grid spacing d is 25 m (Robust) / 35 m (Standard) / 50 m (Preliminary).
  • Depth is the greater of the height-derived and foundation-derived depths, plus embedment, floored at a 10 m minimum.
  • Total drilling (lm) = boreholes × depth.

It is advisable to obtain at least three formal quotations from qualified soil investigation contractors before finalising the investigation budget.

EN 1997-2:2007 — Eurocode 7: Geotechnical design — Part 2: Ground investigation and testing, Annex B.3.

BS 5930:2015+A1:2020 — Code of practice for ground investigations.

ASTM D420 — Standard Guide to Site Characterization for Engineering Design and Construction Purposes.

Orycta Orycta
No. of Boreholes
EN 1997-2:2007 §B.3(1) · Minimum 3 boreholes
Depth of Boreholes
Width > 150 m — multiplier reduced to 0.8 (Orycta practice)
You can enter both height and foundation width — the deeper result governs.
Each basement adds ~3.5 m to embedment depth.
Added on top of governing depth.
science

Enter the plot area and building details — the recommended investigation scope appears here.

Scope Estimate
—
No.
Boreholes
—
m BGL
BH Depth
—
lm
Total Drilling
You can enter these values into the Cost Estimator Tool.

Disclaimer

This tool provides an indicative estimate of the recommended geotechnical investigation scope based on the user inputs and selected methodology. The suggested number of boreholes, investigation depths, testing locations, and associated quantities are estimates only and shall not be used as the sole basis for project design, procurement, tendering, or construction. The final investigation scope shall be reviewed, verified, and determined by a qualified geotechnical engineer considering the project-specific conditions, design requirements, ground conditions, applicable standards, and engineering judgement. Orycta makes no representation or warranty regarding the accuracy, completeness, or suitability of the results generated by this tool and accepts no liability arising from its use.

EN 1997-2:2007 Annex B.3 · BS 5930:2015+A1:2020