Soil Mechanics / Ground investigation and ground profiles
Why investigate, and the desk study
The ground model, uncertainty, phased investigation, and the desk study that leads it.
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.
Checks needed for project use
- A geotechnical reviewer must check laboratory interpretation, classification conventions and the limits of drained, undrained and one-dimensional idealisations.
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 notesWhy this matters
Ground investigation develops a ground model of the strata, groundwater and properties relevant to the project. Inadequate investigation or interpretation can leave important hazards undetected. The work begins with existing records and site observations before intrusive investigation is planned.
What you should already know
- What kinds of ground questions a project raises (Module 1)
- Basic soil types and how they form (Module 2)
Investigation is phased, each phase informing the next:
- 1.Desk study — assemble what is already known: geological maps and memoirs, historical maps, aerial photographs, previous site investigations, mining and groundwater records. Cheap, fast, and the single most cost-effective step.
- 2.Walkover survey — visit the site and read it directly: seepages, made ground, cracked structures, slope signs, vegetation.
- 3.Intrusive and in-situ investigation — trial pits, boreholes, penetration tests and geophysics, targeted by what the first two phases revealed.
- 4.Laboratory testing — classification and strength/stiffness on the samples recovered (Modules 4–11).
The aim throughout is a ground model — a defensible picture of the strata, groundwater and properties — with its uncertainty stated, not hidden.
Check yourself
Why is a desk study carried out before any boreholes are drilled?
Summary
- Ground investigation turns the unseen ground into a ground model to design against.
- It is phased: desk study → walkover → intrusive/in-situ → laboratory, each informing the next.
- The desk study uses existing information to identify hazards and target the investigation that follows.
- The deliverable is a ground model with its uncertainty stated honestly.