Foreman Dig's site hut

Foreman Dig runs the Geotechnical department from a site hut at the edge of an excavation. The floodlight outside is on, it is raining, and the whiteboard keeps count of the days since the ground last moved. Everything in the hut that is not a kettle is one of the department's calculators. Click it to open it.

Geotechnical engineering deals with the one material nobody manufactures: the ground. Soil is a mix of grains, water and air; its strength depends on how much water it holds and how hard it has been squeezed in the past, and it changes from one borehole to the next. The calculators here cover what a footing can bear, how much a clay layer settles and how long that takes, what a pile carries through its shaft and its tip, whether a slope stays put and what a retaining wall has to resist.

Every number in this field rests on soil properties that come from a site investigation. The calculators show how those properties drive the answer; they do not replace the boreholes and lab tests that should supply them.

“Soil under a footing doesn't crush straight down: it fails by sliding along curved surfaces out to the sides.” — Foreman Dig

In this office

• Soil Bearing Capacity: Ultimate and allowable bearing capacity of a strip footing (Terzaghi-form equation with Prandtl–Reissner and Hansen factors)
• Slope Stability: Factor of safety of a uniform slope by Bishop's simplified method, searching for the critical slip circle
• Consolidation Settlement: Calculate primary consolidation settlement
• Pile Capacity: Ultimate and allowable capacity of a single round pile from unit skin friction and unit end bearing
• Retaining Wall: Active earth pressure on a retaining wall (Rankine), the overturning moment it causes, and a rule-of-thumb base width

Project guides

• Build a Retaining Wall: Check the ground under and around a retaining wall before sizing the wall itself, so you're not designing a wall on soil that can't hold it.

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