Test Roll Inspections for Earthworks Compaction

Atlas Engineering and Technology Group provides comprehensive Test Roll Inspections as a crucial component of our earthworks compaction testing services in Sydney. Ensuring the stability and long-term performance of your construction project starts from the ground up, and test rolling is a vital quality assurance measure to verify the adequacy of prepared surfaces.

What are Test Roll Inspections?

Test Roll Inspections, also known as proof rolling, are a qualitative assessment method used to evaluate the stiffness, uniformity, and stability of compacted earthworks layers, subgrades, and pavement bases. The process involves observing the ground surface's response as a heavy, specifically weighted construction vehicle or roller traverses it. This practical assessment helps identify any localised soft spots, insufficiently compacted areas, or unsuitable materials that may not be solely apparent through point-based density testing.

Our inspections are conducted by experienced geotechnical personnel in accordance with relevant Australian Standards, including AS 3798 "Guidelines on earthworks for commercial and residential developments," and project-specific requirements.

The Purpose of Test Roll Inspections

The primary objectives of conducting Test Roll Inspections include:

  • Identifying Unsuitable Areas: Detecting soft, yielding, excessively deforming, or unstable zones that require remediation (e.g., drying, re-compaction, or removal and replacement) before further construction proceeds.
  • Assessing Compaction Uniformity: Verifying that the compaction effort has been applied consistently across the entire area, highlighting variations in support conditions.
  • Validating Compaction Effectiveness: Providing a practical, large-scale check on the adequacy of the compaction achieved for the entire lift of material.
  • Ensuring Specification Compliance: Confirming that the prepared surface meets the project's geotechnical requirements and design specifications for stability and load-bearing capacity.
  • Minimising Future Performance Risks: Helping to prevent long-term issues such as differential settlement, pavement failure, structural distress, or serviceability problems.

When are Test Roll Inspections Performed?

Test Roll Inspections are typically carried out at critical stages of earthworks and pavement construction:

  • After the compaction of each fill layer, or at specific lift intervals as defined in the project specification.
  • On the prepared subgrade surface before sub-base or base course materials are placed.
  • On completed pavement layers (e.g., sub-base, base course) prior to placing the subsequent, often more expensive, layer or surfacing.
  • As a final acceptance test for completed earth pads or pavement foundations.
  • When visual signs of instability, poor compaction, or excessive moisture are observed.

The Test Roll Procedure

Our experienced geotechnical field technicians and engineers conduct Test Roll Inspections systematically:

  1. Equipment Selection:
    • A suitable test vehicle is chosen based on project specifications and the nature of the material being tested.
    • Commonly used equipment includes a heavily loaded tandem-axle truck (e.g., minimum 7-tonne gross mass, or as specified), a large static roller, or a heavy vibratory roller (with vibration turned off for the test, unless specifically required for specific materials and conditions). The tyre pressures and load distribution are key considerations.
  2. Defining the Test Area and Coverage:
    • The inspection is performed over the entire surface of the layer under assessment.
    • The vehicle traverses the area in a systematic pattern, often involving longitudinal passes with sufficient overlap to ensure complete coverage. Transverse or diagonal passes may also be included.
  3. Observation and Assessment:
    • As the test vehicle moves across the area at a slow, steady speed (typically 2-4 km/h), our technicians meticulously observe the ground surface directly in front of, beneath, and behind the loaded wheels/drum for any signs of distress or excessive deformation. Key observations include:
    •  
      • Rutting or Deflection: Visible sinking or depression of the wheels/drum into the material beyond acceptable limits (e.g., typically <25mm, but project-specific).
      • Pumping: The ejection of water and fines from the surface as the load passes, indicating saturated and unstable material.
      • Weaving, Rolling, or Sponginess: A noticeable elastic or plastic wave-like movement of the surface under the load, indicating instability or lack of stiffness.
      • Cracking or Shearing: Visible cracks appear on the material's surface or lateral shoving.
  4. Marking and Reporting:
    • Areas that exhibit unsatisfactory performance (i.e., fail the test roll) are clearly marked on-site (e.g., with spray paint) for immediate attention and remediation.
    • All observations are meticulously documented, including the type of test vehicle used, coverage patterns, locations and extent of any failed areas, and apparent reasons for failure.
    • A comprehensive field report outlines the inspection findings and recommendations for any necessary corrective actions.

Understanding Test Roll Outcomes

A successful test roll indicates that the compacted layer is generally firm, stable, and capable of supporting the applied test load without undue deformation or distress. This provides confidence that the layer will perform adequately under subsequent construction loads and long-term service conditions.

If areas fail the test roll, it signifies that the material in those locations has not achieved adequate compaction, stiffness, or stability. Common reasons for test roll failure include:

  • Insufficient corrective effort applied.
  • Material moisture content is either too high (wet of optimum) or too low (dry of optimum).
  • Presence of unsuitable, deleterious, or oversized materials within the layer.
  • The layer thickness is too great for effective compaction with the plant being used.
  • Poorly prepared or unstable underlying material.

Our experienced team will work collaboratively with site personnel to help identify the cause of any failures and advise on appropriate and effective remedial actions.