Geotechnical Engineering · Course
Soil Mechanics
Understanding how soil, water and loading interact.
The ground is the one material an engineer does not manufacture. It is natural and variable — made of particles, water and air, shaped by its geological and stress history, and governed by drainage and time. This course builds the physical understanding a geotechnical engineer needs: how to describe and classify a soil, how water flows through it, how stress is shared between the soil skeleton and the porewater, how it settles with time, how strong it is, and an accessible framework that ties these together. Design of foundations, slopes and retaining structures is reserved for later courses; the aim here is the knowledge you need before you begin them.
Who it is for
- Civil and geotechnical engineering students after introductory mechanics
- Structural and civil engineers who want to understand the ground their structures sit on
- Graduates preparing for geotechnical design courses
- Engineers returning to soil mechanics after time away
What you should already know
- Basic force and moment equilibrium (statics)
- Comfortable rearranging simple formulae and working with ratios
- Stress and strain from strength-of-materials is helpful but not required
- No previous soil mechanics is assumed
The syllabus
Fifteen modules in four stages, from describing a soil to an accessible critical-state framework. Live modules link through; planned modules are labelled.
The physical soil
- 01Open →
What soil mechanics is
Soil as an engineering material, why the ground is uncertain, and how it can control an otherwise adequate structure.
- 02Open →
Geology, soil formation and fabric
Where soil comes from and why that matters: weathering, transport and deposition, the clay minerals, and the particle arrangement (fabric) that controls how a soil behaves.
- 03Open →
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.
- 04Open →
Particle size, description and classification
Gravel to clay, grading curves and their D-values, and how a soil is described and classified — with its limits.
- 05Open →
Phase relationships and soil states
Solids, water and air — the void ratio, water content and saturation that describe a soil's state, and the unit weights that follow from them.
- 06Open →
Soil compaction and earthworks
Densifying soil by expelling air: the compaction curve, optimum water content, the zero-air-voids ceiling, and how compaction is specified and controlled on site.
Water, stress and loading
- 07Open →
Water in soil and Darcy's law
Heads and hydraulic gradient, Darcy's law, seepage velocity and layered permeability — how water moves through the ground.
- 08Open →
Effective stress and stress in the ground
Total stress, porewater pressure and Terzaghi's effective-stress principle — the single idea that governs soil strength and settlement.
- 09Open →
Stress paths, drainage and loading
Following the stress state as a load is applied: the Mohr circle and its invariants, total and effective stress paths, and why drained and undrained loading trace different routes to failure.
Time, strength and testing
- 10Open →
Consolidation and settlement with time
Why saturated clay settles slowly: excess pore pressure and its dissipation, the compression a load causes, and how that settlement unfolds over time.
- 11Open →
Shear strength of soils
Why and how soil fails in shear: friction and interlocking, the Mohr–Coulomb criterion on effective stress, peak, critical and residual states, and drained versus undrained strength.
- 12Open →
Laboratory and field testing
How the numbers are obtained: what each test measures, the drainage condition and stress path it imposes, and whether it represents the field problem you are designing for.
Frameworks and integration
- 13Open →
Critical-state soil behaviour
One framework that ties the course together: the critical state a soil reaches at large strain, the critical-state line, and how a soil's state relative to it predicts strength, volume change and pore-pressure response.
- 14Open →
Two-dimensional seepage and flow nets
Water seeping around walls and beneath dams: flow lines and equipotentials, the flow net as a graphical solution, the seepage flow rate, and the exit gradient that governs piping and heave.
- 15Open →
Integrated soil interpretation
Putting the whole course to work: a way of reading any ground and any project — what governs, what is missing, and which later course you would turn to for the design itself.