Converting Uncontrolled Fill Sites Into Controlled Engineered Fills Through Rapid, Cost-Effective, and Quantifiable Impact Rolling-Paper

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Impact rolling offers a rapid, lower-cost alternative to excavating and replacing uncontrolled fill. A heavy, non-circular roller is towed across the ground, delivering repeated high-energy impacts that can densify fill to depths of approximately 1.5–4 m. Real-time roller measurements and follow-up testing can identify areas needing further treatment and verify improvement.<br /><br />The paper describes a former quarry in rural New South Wales, backfilled without documented engineering control. Investigations found fill generally comprising sandy clay, with some gravelly sand, at depths of about 3–6 m. The project first limited the fill depth to 4 m, then used impact rolling alongside instrumented Dynamic Probing Super Heavy (DPSH) tests, nuclear density tests, boreholes and moisture assessments. Testing and treatment were repeated until the fill passed site-specific compaction criteria or further rolling proved ineffective. Local areas that could not be adequately compacted—often because of moisture-sensitive material—were excavated, moisture-conditioned and conventionally replaced.<br /><br />For this site, DPSH tip resistance of 3.5 MPa generally indicated the required 98% Standard compaction. Lower thresholds were accepted in certain wetter conditions or where density testing confirmed compliance. The remediated fill was accepted by the local council for the specified compaction requirement and assessed as suitable for industrial development, subject to further design review and consideration of settlement where buildings cross the boundary between natural and filled ground.<br /><br />The approach can reduce excavation, imported material, haulage, fuel use, emissions and project duration while providing measurable quality assurance. However, effectiveness depends on fill type and moisture conditions; impact rolling may be less suitable for very soft clays or organic-rich soils. Investigations should also assess buried services and contamination before treatment. The authors conclude that, with appropriate screening and site-specific validation, impact rolling can convert suitable legacy fills into controlled engineered platforms.

Keywords

impact rolling

fill remediation

quarry backfill

dynamic probing super heavy

compaction testing

dense fill

site investigation

soil densification

nuclear density tests

engineered platform