Soil Mechanics / What soil mechanics is

What ground information does a project need?

An interactive: match a project to the ground questions it must answer.

Lesson review: expert verification remains open

This lesson has received a full-context editorial review and a check of its technical explanations. Selected arithmetic has been checked separately. This is not independent engineering sign-off.

Corrections checked in this pass

Clarified that the questionnaire suggests investigation priorities and does not define the full investigation scope.

Checks needed for project use

A geotechnical reviewer must check laboratory interpretation, classification conventions and the limits of drained, undrained and one-dimensional idealisations.
Investigation scope/depth and additional hazards require project ground model.

These are educational models and exercises. Check their assumptions before using the results. The full technical content and every diagram have not yet been independently verified.

Concrete and steel calculations retain their stated first-generation Eurocode teaching basis. Use the standards and amendments specified for your project; do not mix generations without an appropriate design basis.

Read the lesson register and outstanding review notes

Why this matters

Before any ground investigation is planned, an engineer has to know what questions the ground must answer for this particular project. A tall building, a road embankment and a deep excavation ask very different things of the ground. Getting this right is the difference between an investigation that de-risks a project and one that wastes money finding out the wrong things.

Different projects load and interact with the ground differently, so they need different information:

A building applies concentrated loads through footings — it mostly asks about bearing capacity and settlement beneath those footings.
A bridge combines heavy, sometimes eccentric foundation loads with sensitivity to differential settlement between piers, and often sits near water — so scour and groundwater matter too.
A road spreads modest loads over a wide area but is sensitive to near-surface soils, drainage and frost/moisture changes.
An embankment is a load: it can cause the ground beneath it to settle and, if built too fast on soft clay, to fail — so soft-ground strength, consolidation and rate of construction are the questions.
A retaining wall must resist lateral earth and water pressures, so the strength, groundwater and drainage behind it govern.
An excavation removes load and can let water in — so groundwater, base stability and the strength of the soils being cut are the questions.

Try it

Ground-information planner

Select the main priorities for this simplified example. Other selected questions may still matter on a real site; the exercise is not an investigation specification.

Project

How to think about it

Ask what the project does to the ground: apply load, remove load, or hold back soil and water.
The right questions come from the load, geometry, groundwater and construction method — not the project's size alone.

Select the questions this project must answer, then press Check.

Check yourself

For a new embankment across soft estuarine clay, which single concern is usually the most important to establish early?

Summary

Decide what the ground must tell you before planning how to investigate it.
Buildings ask about bearing and settlement; embankments about soft-ground strength and consolidation; excavations and walls about groundwater and lateral pressure.
The project type, loads, geometry, groundwater and construction method set the questions.