Why a trial is needed
Ground response depends on soil type, density, fines content and groundwater, all of which vary. A trial replaces assumptions with measurements before the whole site is treated. That reduces risk for the client, the consultant and the contractor.
What a trial includes
- A location that represents the site and, where conditions vary, its most difficult part.
- Baseline tests before treatment, such as CPT.
- Treatment using the proposed parameters, sometimes with more than one spacing or energy level.
- Measurement of the ground response during treatment.
- Tests after treatment at the same positions, compared with the baseline and the acceptance criteria.
What is measured, by method
| Method | Response measured during the trial |
|---|---|
| Dynamic Compaction | Crater depth after each drop, heave around the print, induced settlement |
| Rapid Impact Compaction | Foot penetration per blow and total penetration per point |
| High Energy Impact Compaction | Surface settlement against number of passes |
| Vibro Compaction | Vibrator power and holding time per stage, at different point spacings |
What the trial delivers
- Production parameters: energy, spacing, number of drops, blows or passes.
- Stopping criteria that can be checked at every point.
- The verification regime: which tests, where, and how long after treatment.
These are recorded in a trial report and agreed with the consultant before production starts.
When to repeat it
If the ground changes across the site (a different fill, a higher water table, more fines), the original trial may no longer apply, and a further trial in the new conditions is justified.