Soil Mechanics / module 3
Ground investigation and ground profiles
Finding out what is in the ground: the desk study and phased investigation, intrusive and in-situ methods, sampling and groundwater, and building a ground model that is honest about its uncertainty.
What you will understand
- Explain why ground investigation is phased and risk-driven, starting with a desk study
- Match investigation methods to the ground and to what must be measured
- Distinguish disturbed, bulk and undisturbed samples and their uses
- Apply the standard SPT energy normalisation and know its limits
- Assemble borehole logs into a ground profile, and state its residual uncertainty
Lessons
Why investigate, and the desk study
The ground model, uncertainty, phased investigation, and the desk study that leads it.
Methods, sampling and groundwater
Intrusive and in-situ methods, sample quality, and measuring groundwater.
Building and using the ground profile
From borehole logs to a ground model, and living with residual uncertainty.
Module summary
- Ground investigation is phased and risk-driven, starting with the cheap, high-value desk study.
- Methods are matched to the ground and to what must be measured; sample quality limits what can be tested.
- SPT N is normalised to N₆₀; specific correlations and standards must be verified against the current edition.
- Logs become a ground model with a stated uncertainty; the observational method manages what remains.
Teaching basis and review status
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 notesCheck your understanding
Check yourself
You need the undisturbed shear strength and consolidation behaviour of a soft clay. Which sample type is required?
Practice
An SPT records N = 15 with a rig energy ratio of 80%. What is N₆₀?