Proof-Roll Subgrade: Identify Soft Spots, Remediate, and Accept

The checklist

Pre-rolling Preparation

1. 1Confirm subgrade elevation within design tolerance using a level/total station; moisture within OMC ±2% with a moisture meter; record readings and survey shots.
2. 2Define proof-rolling limits, lot size, and pass layout on a plan; mark boundaries with paint/flags; attach a markup and photos for evidence.
3. 3Ensure surface drains freely with no standing water; pump or cut shallow reliefs to dewater; acceptance: firm, non-glossy surface; photo evidence.
4. 4Remove loose debris, organic pockets, and large clods with rakes and blades; acceptance: uniform, tight surface; photo before/after.

Equipment and Calibration

1. 5Verify proof-rolling vehicle type and axle load meet project requirements; weigh axles on portable scales; acceptance: within specified kN per axle; log kN values.
2. 6Check tire inflation pressure with a calibrated gauge; acceptance: within ±10 kPa of target; record pressures and gauge calibration date.
3. 7Confirm travel speed between 3–8 km/h using GPS or tachometer; acceptance: average within range; record start/end times and distance to compute speed.
4. 8If using a smooth-drum roller, operate in static mode unless authorized; record vibration status and amplitude if permitted by specifications.

Proof-rolling Execution

1. 9Establish straight, parallel passes with 50% overlap; paint alignment lines; acceptance: full coverage with no missed strips; attach a coverage map.
2. 10Run initial passes along the roadway alignment; if specified, add a transverse set; record number and direction of passes per lot.
3. 11Observe live response: rut depth, deflection, weaving, and pumping; call out chainage and offset; video or photo each anomaly for the log.
4. 12Measure rut/deflection with a 3 m straightedge and ruler; acceptance: ≤ 25 mm or per approved specifications; record mm at three points.
5. 13Note environmental conditions (temperature, recent rainfall, cloud cover); acceptance: conditions recorded to contextualize results; photo sky/ground conditions.
6. 14Log axle load, tire pressure, speed, pass count, and coverage for each lot; acceptance: complete entries; exportable worksheet attached.

Soft Spot Identification

1. 15Flag locations exhibiting pumping, shear cracking, or bounce; stake corners; acceptance: each soft spot uniquely ID’d with chainage/offset; geo-tagged photos.
2. 16Delineate soft spot limits by two confirming passes around the perimeter; mark boundaries with paint; sketch limits on the plan.

Remediation

1. 17For shallow weakness (<150 mm), scarify with a grader to target depth, moisture condition to OMC, and compact; acceptance: density per spec; nuclear density results attached.
2. 18For deep weakness, undercut to firm bearing layer measured by probe/plate; acceptance: firm base passes spot proof roll; record undercut depth (mm).
3. 19Backfill with approved granular material in ≤150 mm lifts; compact each lift; acceptance: density ≥ target per spec; field test results and lift photos.
4. 20Install separator geotextile where fines pumping persists and is authorized; acceptance: product per approved submittal; delivery tickets and installation photos.
5. 21Trim and re-establish design elevation using total station; acceptance: elevation within ±10 mm; upload survey file and as-built shots.

Re-proof and Acceptance

1. 22Allow moisture to equilibrate if wet conditioned; acceptance: surface firm and non-tacky; record elapsed time and field moisture check.
2. 23Re-proof roll remediated areas using the same axle load and speed; acceptance: no pumping and rutting ≤ 10–15 mm; record measured mm and photos.
3. 24Spot check 5–10 m beyond boundaries to confirm no extension; acceptance: no new soft responses; update map and log.
4. 25Obtain inspector/engineer sign-off per approved project specifications and authority requirements; acceptance: digital signatures captured; distribute signed report.

Preview the printable checklist

Preview page one below. Open the image or download the PDF for all pages.

At a glance

• Systematically plan, execute, and document proof rolling to reveal weak subgrade areas before paving. The checklist standardizes loads, speed, and overlap, enabling consistent coverage and comparable observations across crews and shifts with clear, practical tolerances.
• Quantify rut depth and visible deflection with simple tools, then classify severity and limits. Recommended remediation options focus on undercut and replacement, moisture conditioning, recompaction, and geotextile separation when pumping fines are observed and permitted.
• Re-proof corrected areas under the same axle load and speed to verify improvement. Acceptance relies on minimal rutting, absence of pumping, compliant density, and documented survey elevations, signed off per approved project specifications and authority requirements.
• Interactive online checklist with tick, comment, and export features secured by QR code. Capture calibrated measurements, geo-tagged photos, and signatures, then export as PDF/Excel for traceable quality records that integrate smoothly with project document control.

How to Use This Interactive Proof-Roll Subgrade Checklist

1. Preparation: Assemble a calibrated tire gauge, portable axle scales (or weigh ticket), GPS/speed readout, 3 m straightedge, ruler, moisture meter, nuclear density gauge (or approved alternative), paint/flags, and PPE.
2. Open the checklist in interactive mode on a tablet/phone. Create a lot, set chainage limits, and enter target axle load, tire pressure, and speed from the project specifications.
3. During proof rolling, tick items as you go, add comments for anomalies, and attach geo-tagged photos/videos and measurement readings directly to the relevant checklist line.
4. After identifying soft spots, switch to remediation tracking: record chosen method, depths, lift thicknesses, density results, and survey elevations without duplicating earlier entries.
5. Re-proof corrected areas and update the same lot with before/after metrics. Use the comparison view to verify rutting reduction and absence of pumping against acceptance criteria.
6. Sign-Off: Collect digital signatures from contractor and inspector, then export as PDF/Excel. Share the QR-authenticated package with stakeholders and archive it in project records.

Plan passes, loads, and observations that reveal true subgrade behavior

Effective proof rolling starts with a controlled setup: defined lots, a verified axle load or static roller weight, and a steady speed that allows observers to see movement without dynamic effects. Mark parallel passes with 50% overlap so every square metre receives at least two loadings. Log axle load in kilonewtons, tire pressure in kilopascals, and speed in kilometres per hour. During passes, watch for rutting, lateral weave, and pumping of fines. Quantify rut depth with a 3 m straightedge and a ruler instead of relying on visual estimates. Typical acceptance limits use small, recoverable deflection and rutting that does not exceed project thresholds; where not stated, many teams flag anything beyond 25 mm for review. Capture short videos and geo-tagged photos at chainage and offset so remediation crews can find the same locations. Recording weather and moisture helps interpret results and avoid over-rejecting a wet but recoverable surface.

• Use steady 3–8 km/h to minimize dynamic amplification.
• Overlap passes by 50% for complete coverage.
• Measure rut depth with a straightedge and ruler.
• Log axle load, tire pressure, speed, and weather.
• Geo-tag photos at chainage/offset for traceability.

Choose remediation that fits depth and mechanism, then verify by re-proof

Treat shallow, moisture-sensitive soft spots by scarifying, moisture conditioning to optimum, and compacting to target density. Where the weak layer is deeper or truly unstable, undercut to a firm bearing stratum and replace with approved granular material in controlled lifts. If fines pump through granular fill, a separator geotextile can stabilize the interface when permitted. Always re-establish design elevation with a survey before re-proof rolling. Re-proof at the same axle load and speed that revealed the defect to make the before/after comparison meaningful. Acceptance hinges on no visible pumping, minimal rutting (often ≤ 10–15 mm after correction), and compliant density results. Document depth removed, material placed, test results, and photos to close out the nonconformance without resorting to stabilization mix design decisions, which belong to separate engineering processes.

• Match remediation depth to weakness depth.
• Moisture condition and compact shallow repairs.
• Undercut and replace deep unstable zones.
• Use separator geotextile only if permitted.
• Re-proof at the same load and speed.

Document decisions and acceptance to reduce future paving risks

A thorough record streamlines approvals and protects the schedule. Start with a coverage plan marking all passes. For each lot, store the axle load, tire pressure, speed, weather, and moisture readings alongside rut measurements and photos. Use consistent chainage/offset and sketches to delineate defect boundaries. After remediation, attach density test reports, undercut depths, delivery tickets, geotextile approvals, and a new survey showing restored elevation. Re-proof results should be clearly compared with initial findings, referencing the same measurement points. Digital signatures from the contractor and inspector provide accountable acceptance per approved project specifications and authority requirements. Archiving as a QR-authenticated PDF/Excel package ensures field staff and paving crews can quickly verify that the subgrade met acceptance before base or asphalt placement, reducing the risk of rutting, settlement, and reflective cracking.

• Maintain a pass coverage map for each lot.
• Pair measurements with geo-tagged photos.
• Attach density and survey evidence to repairs.
• Compare re-proof to initial at same points.
• Capture digital signatures for acceptance.