Construct DSM Cutoff Wall Checklist and QA Guide

The checklist

Pre-Construction & Submittals

1. 1Confirm approved DSM mix design and wall geometry; record binder type, water-to-binder ratio, target diameter, and permeability criteria per approved project specifications and authority requirements; attach signed approvals and latest revisions.
2. 2Stake wall alignment and top-of-wall elevation using total station/GNSS; maintain horizontal tolerance ±20 mm and elevation ±10 mm; upload coordinate file, stake-out report, and photos of control points.
3. 3Verify materials traceability: cement/binder lot numbers, delivery tickets, and storage conditions; acceptance: tickets match mix design, moisture protected; upload tickets and silo level logs.
4. 4Approve construction method statement explicitly excluding secant and diaphragm wall methods; include sequencing, overlap geometry, spoil management, and contingency plans; evidence: signed method statement and ITP.

Equipment Calibration & Mixing Energy Control

1. 5Calibrate torque and rotation sensors on the DSM rig; acceptance: within ±2% of reference across operating range; attach calibration certificates and before/after check readings.
2. 6Calibrate grout flowmeter and pressure transducer with a prover tank; acceptance: flow error ≤ ±3%, pressure ≤ ±2% of full scale; upload calibration sheet and photos.
3. 7Configure data logger to capture depth, torque, RPM, penetration/withdrawal rates, flow, and pressure at ≥1 Hz; verify time sync; evidence: sample log file and timestamp check.
4. 8Complete trial columns to establish baseline energy curve versus depth; acceptance: actual curve within ±10% of target over 90% of length; attach plots and trial reports.

Wet Mixing Operations & Overlap Continuity

1. 9Survey start point and verify drill to design depth (toe elevation) with depth encoder; tolerance: depth −0/+100 mm; evidence: log extract and stake photo.
2. 10Maintain penetration and withdrawal rates per procedure (e.g., 0.2–0.6 m/min); acceptance: within specified band; upload rig trend chart showing steady rates without stalls.
3. 11Control binder dosage via flow vs. advance rate; acceptance: dosage within ±5% of target; capture flow/pressure plots and batch records for each column.
4. 12Ensure column overlap meets design (≥150 mm or ≥15% of diameter, whichever is greater); verify by layout checks and drilling logs; evidence: as-built overlap calculations and field photos.
5. 13Monitor real-time energy index (torque×revs) and set low-energy alarms; acceptance: not below target for more than 0.5 m of depth; attach alarm screenshots and corrective action notes.
6. 14Check tool verticality with inclinometer; tolerance: deviation ≤ 1:100; capture inclinometer readings at start, mid-depth, and toe for each column.
7. 15Observe and record returns/spoil consistency to confirm mixing; acceptance: continuous returns without segregation; upload photos and supervisor sign-off.

Quality Assurance Coring & Lab Testing

1. 16Select core locations using a risk-based plan covering overlaps and variable soils; mark on as-built; evidence: core location map with coordinates and IDs.
2. 17Extract 100 mm diameter cores after specified curing (e.g., 7/28 days); seal ends to prevent moisture loss; evidence: core logs, photos, and chain-of-custody.
3. 18Test UCS and lab permeability per approved project specifications; acceptance: parameters meet target values; attach lab reports with sample IDs and curing records.
4. 19Assess core quality (RQD-like assessment, defects, inclusions); acceptance: no open voids or unmixed zones; upload inspection sheets and annotated photos.

In-Situ Permeability Verification

1. 20Conduct falling-head or single-hole packer tests in selected columns; acceptance: hydraulic conductivity meets target (e.g., ≤ 1×10⁻⁷ m/s) per approved specifications; attach raw data and calculations.
2. 21Investigate anomalies (rapid head loss or high k) by coring or GPR; implement remedial re-mixing or grout injection; evidence: corrective action record and passing retest.

Documentation & Acceptance

1. 22Compile daily reports with instrument logs, batch tickets, crew notes, and weather; supervisor signs; upload PDF and native data files.
2. 23Produce as-built wall plan showing column centres, diameters, overlaps, and test locations; georeference to site grid; evidence: CAD/PDF and exported coordinate list.
3. 24Complete final acceptance review against ITP: mixing energy compliance, overlap continuity, core and permeability results; obtain client/engineer digital signatures.
4. 25Archive all records with QR-linked index; store photos, logs, approvals, and test certificates; verify backup to project server/cloud.

Preview the printable checklist

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

At a glance

• Establish a robust QA/QC regime around DSM mixing energy, penetration/withdrawal rates, and binder dosage to achieve uniform soil–cement. Validate overlap geometry and verticality to avoid windows that create seepage pathways, and verify permeability through lab and in-situ tests tied to traceable locations.
• Drive reliability with instrumented rigs, calibrated torque, RPM, and grout flow meters logging at 1 Hz or better. Use alarms for low energy or flow anomalies, and base corrective actions on real-time dashboards and daily reviews. Align sampling, coring, and testing frequency with risk and geology variability.
• Interactive online checklist with tick, comment, and export features secured by QR code. The QR-backed workflow links field data, photos, and signatures to each task, enabling faster nonconformance closure, transparent approvals, and searchable archives for audits and closeout documentation across contractors and owner teams.
• Document wall continuity through as-built mapping of column centrelines, diameters, and overlaps. Integrate GNSS/total station coordinates, drilling depth profiles, and energy curves to demonstrate conformance. Where deviations occur, implement targeted re-mixing or grout injections and retest to confirm permeability recovery before acceptance.

How to Use the DSM Cutoff Wall Interactive Checklist

1. Preparation: gather approved mix design, method statement, ITP, rig calibration certificates, and survey control. Ensure access, spoil management, lighting, and emergency equipment. Equip the crew with PPE, tablet/phone, and camera for logging evidence.
2. Open the checklist on your device and switch to interactive mode. Assign roles to crew members so torque/RPM monitoring, survey, batching, and QA sampling tasks have clear owners.
3. During production, tick each task as completed, attach photos (stake-out, instrument screens), and upload data logs. Use comments to record anomalies, pauses, and corrective re-mixing.
4. At verification stages, add lab reports and field test sheets. Cross-reference sample IDs to column numbers and depths to maintain traceability.
5. Export progress snapshots to PDF/Excel for daily briefings. Share links with stakeholders to review comments and request clarifications before the next shift.
6. Sign-Off: obtain digital signatures from contractor, engineer, and owner. Generate a QR-linked final export and place it on the as-built drawing set for quick authentication.

Control Mixing Energy for Uniform DSM Columns

Mixing energy unifies soil and binder into a low-permeability matrix. Track torque, rotation speed, penetration/withdrawal rates, grout flow, and pressure against target curves. Calibrate sensors so the energy index reflects true conditions. Use alarms to flag low energy that might create unmixed streaks or lenses. Trial columns help tune tool selection, blade wear limits, and rate bands before production. During drilling, aim for steady torque and RPM; spikes may indicate obstructions or overly rapid advance. Document any pauses and corrective passes. Align binder dosage with advance rate to avoid under-cemented zones that elevate hydraulic conductivity. Daily reviews of depth-registered plots catch trends like energy decline with wear or water ingress. When deviations occur, stop, re-mix the affected interval, and annotate logs so laboratory results correlate with field actions.

• Calibrate torque, RPM, flow, and pressure instruments.
• Log depth-indexed data at 1 Hz or better.
• Use alarms and pause to re-mix low-energy intervals.
• Tune penetration/withdrawal to maintain steady torque.
• Correlate dosage with advance rate and depth.

Assure Overlap Continuity and Verticality

Continuity depends on precise layout, verticality control, and disciplined sequencing. Set out centers with the required offset to achieve designed overlaps, and verify with survey before drilling. Inclinometer checks at start, mid, and toe keep deviations within tolerance. Plan a systematic column sequence to minimize time between adjacent columns, preventing slurry loss and soil relaxation that can open windows. Review returns visually to confirm intermixing at overlaps. Where verticality or position drifts, adjust subsequent centrelines or perform corrective columns. Document each overlap’s achieved geometry in an as-built and flag any potential gaps for targeted verification. Avoid mixing adjacent columns too far apart in time or depth; consistent energy during overlap passes is essential for continuity.

• Stake centers to deliver the designed overlap.
• Check verticality; target deviation ≤ 1:100.
• Sequence columns to limit gap time between overlaps.
• Inspect returns for continuous intermixing.
• Record achieved overlaps in as-built maps.

Verify Performance with Coring and Permeability Testing

QA coring and permeability testing demonstrate the cutoff’s hydraulic integrity. Choose core locations to sample overlaps, variable strata, and critical zones such as under utilities or near tie-ins. Extract and seal cores after designated curing periods to preserve moisture. Laboratory programs typically include UCS and permeability; where needed, add index tests to diagnose variations. Complement lab work with in-situ falling-head or packer tests to confirm performance in place. If results exceed target conductivity, execute corrective re-mixing or injection and retest until compliant. Maintain traceability by linking samples to column IDs, depths, and energy logs so nonconformances can be resolved efficiently. Acceptance is based on meeting permeability targets and demonstrating continuity, not on structural capacity.

• Select cores using a risk-based plan.
• Seal and label cores with chain-of-custody.
• Test UCS and permeability against targets.
• Use packer or falling-head tests in situ.
• Retest after any remedial works.