Earth and Environmental Science 11–12 · Year 12
Liquefaction: saturated sand losing strength when shaken
Module 6: Hazards
The idea
Shaking raises the water pressure between sand grains until they no longer touch, so saturated ground behaves as a liquid and buildings sink or tilt.
What you need
- a tray or clear box 30 cm across with 8 cm of fine sand, water to just below the surface
- a small brick or weighted model building, a ping-pong ball buried as a buried tank
- rubber mallet or a hand to tap the box side rhythmically, stopwatch
How to do it
- Level the saturated sand, stand the brick on it and bury the ball; record their positions.
- Tap the side of the box steadily for 20 s and record what happens to the brick and the ball.
- Repeat with dry sand, then with sand saturated to different depths.
- Measure how far the brick sank and how much the ball rose in each case.
- Relate the result to buildings on reclaimed land and to the Christchurch 2011 earthquake.
What you should see
In saturated sand the surface shimmers, water rises, the brick sinks or tilts and the buried ball floats to the surface within seconds of shaking; in dry sand there is no pore water to carry the load, so the brick stays upright, although tapping can settle the dry sand a little and let the buried ball work slowly upward; the learner compares how far and how fast anything moves with the saturated tray. The effect returns as the water table is raised toward the surface, so the water level, not the sand alone, controls the hazard.
What changes
- What you change
- water content of the sand
- What you measure
- settlement of the brick and rise of the ball
- What you keep the same
- sand depth
- shaking rhythm and time
- brick mass
- box
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Earthquakes open cracks that swallow buildings.
- Only tall buildings are at risk.
Safety card
Hazards
- heavy wet box
Controls
- two people to carry
Note
No hazardous chemicals or heat sources: record the activity in the school's RiskAssess risk assessment, following the NSW Department of Education Science safety and compliance page; the Chemical Safety in Schools package is not triggered.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Earth and Environmental Science Stage 6 Syllabus (2017), NESA; current, replaced by the 11–12 Syllabus (2025) from 2028EES12-13EES11/12-1EES11/12-2EES11/12-3EES11/12-4
- Earth and Environmental Science 11–12 Syllabus (2025), NESA; to be implemented from 2028, not yet taughtEES-12-02
- Australian Curriculum v9No Australian Curriculum v9 code is listed.
Sources
The pages the author read to write this activity.