Weak subgrade under roads, yards and working platforms
Roads, storage yards and working platforms need a stiff surface layer. On weak subgrade, wheels and outriggers push through the fill, leaving ruts and unsafe platforms.
How it is recognised
- Low CBR or low plate load modulus at formation level.
- Rutting or pumping under construction traffic.
- Heavy point loads from cranes and piling rigs.
Why it matters
Pavements deform and need early repair; a platform that fails under a crane or piling rig is a serious safety hazard.
Methods usually considered
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Geogrid
Reinforcing the granular layer so it spreads load more widely.
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Geocells
Confining the fill where the subgrade is very weak or fill is limited.
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HEIC
High Energy Impact Compaction
Improving the near-surface subgrade itself over large areas.
Which method fits depends on the site investigation and the performance requirement. More than one may be combined.
How the choice is made
- Subgrade strength and its variability.
- Traffic and equipment loads.
- Available fill and layer thickness.
- Design life: temporary platform or permanent pavement.
How the result is verified
Stiffness of the finished layer is verified by plate load tests, with density tests on the fill.
Tests typically used
Other ground problems
Have this ground problem on your site?
Share the site investigation report and the performance requirement.