Construct Secant Pile Wall—Guide Wall Sequence Checklist

Construct secant pile wall—guide wall and sequence is the focus of this practical, job-ready checklist for site engineers and inspectors. It covers secant bored piles with clear emphasis on guide wall construction, primary and secondary pile offsets, and drilling tolerance control. You will verify alignment using total stations and templates, manage drilling verticality, and sequence primaries then secondaries to achieve the designed overlap. This checklist deliberately excludes diaphragm walls to keep the scope precise and avoid method confusion. Following it helps prevent misaligned guides, inadequate interlock, overbreak, and costly rework while delivering a watertight, dimensionally accurate wall ready for excavation support. Each step calls for tools, acceptance criteria, and evidence such as photos, batch tickets, and survey files. Use the interactive features to tick items, add field comments, and export your records to PDF/Excel with a secure QR for authentication.

• Ensure guide wall accuracy, pile set-out, and drilling tolerances are controlled from day one. The sequence mandates primaries before secondaries, protecting interlock and water cut-off, with survey checks, template verification, and documented acceptance at each hold point.
• Improve construction reliability by validating primary/secondary offsets with total station data and drilling logs. Capture concrete placement evidence, verify verticality, and compare placed volumes to theoretical values to flag anomalies early and reduce rework and delays.
• Interactive online checklist with tick, comment, and export features secured by QR code.
• Produce defensible, audit-ready records. Photos, batch tickets, survey files, and signed inspections demonstrate conformance per approved project specifications and authority requirements, de-risking approvals and enabling confident handover before excavation.

Survey & Controls

• 1. Verify site control points and benchmarks with total station and digital level; positional error ≤ ±5 mm and elevation ≤ ±5 mm. Upload survey report, instrument calibration certificates, and georeferenced photos.
• 2. Set out pile centerline and stationing on the guide wall footprint; transverse offset ≤ ±3 mm, chainage ≤ ±5 mm. Record as-built coordinates and attach layout sketches with station references.
• 3. Scan for underground utilities using GPR and verify clearances; mark no-drill zones. Evidence: utility permits, GPR map, and signed clearance form per approved project specifications and authority requirements.

Guide Wall Construction

• 4. Construct guide wall to drawings; top elevation within ±5 mm and thickness within −0/+10 mm. Verify reinforcement and cover with bar schedules and photos before casting. Record concrete delivery tickets and pour times.
• 5. Check guide wall alignment parallel to design line using total station; straightness deviation ≤ 5 mm over 10 m. Document with alignment shots at 5 m intervals and a signed inspection sheet.
• 6. Install steel drilling templates/sleeves fixed to the guide wall; hole centers within ±2 mm of set-out and plumbness ≤ 1:500. Upload template survey, plumb gauge readings, and fixation details.

Pile Layout & Offsets

• 7. Confirm design diameters and center-to-center spacing for secant interlock; acceptance: spacing within ±5 mm of approved drawings. Evidence: layout table, total station shots, and CAD overlay check.
• 8. Mark primary pile locations in one color and secondary in another on the guide; include chainage tags. Photo-document color coding and station references at every 10 m.
• 9. Before drilling secondaries, re-verify offsets from as-built primaries; acceptance: center shift of secondaries ≤ ±5 mm from design and overlap per approved design. Upload comparison report.

Drilling (Primary Piles)

• 10. Drill primary piles through guide sleeves to design toe level using CFA/rotary tools; verticality tolerance ≤ 1:100. Capture rig inclinometer logs and depth records; photo of kelly scale at toe depth.
• 11. Maintain bore within guide opening; top-of-hole deviation ≤ ±2 mm at guide elevation. Evidence: feeler gauge check at sleeve, total station shot of bore center, and supervisor sign-off.
• 12. Clean bore base; residual sediment thickness ≤ 50 mm or stricter per specifications. Verify with weighted tape or slurry sampler; upload measurement photos and timestamps.

Concreting & Reinforcement

• 13. Place primary pile concrete by tremie from toe upward; maintain concrete head ≥ 1 m above groundwater. Record start/finish times and batch tickets; acceptance: continuous pour without interruption.
• 14. Confirm primary concrete achieves minimum handling strength prior to adjacent drilling as specified. Evidence: field cube/cylinder results or maturity log and authorization to proceed.

Drilling (Secondary Piles)

• 15. Re-survey guide sleeves and set-out for secondaries; acceptance: center deviation ≤ ±3 mm at guide. Attach re-survey file and sleeve condition photos.
• 16. Drill secondary piles cutting into primaries to achieve designed overlap; verify verticality ≤ 1:100. Evidence: drilling logs, torque trends, and visual confirmation of primary material in cuttings.

Concreting & Reinforcement

• 17. Inspect secondary pile reinforcement cage: diameter, splice, and centralizers at ≤ 3 m spacing; concrete cover ≥ design. Upload cage checklist, heat numbers, and photos showing spacers.
• 18. Tremie concrete secondary piles in one continuous operation; acceptance: placed volume within −5%/+10% of theoretical unless justified. Record tremie embedment and concrete head; attach batch tickets.

Verification & Records

• 19. Survey as-built pile centers at guide level after each shift; acceptance: wall alignment within ±15 mm cumulative over 25 m. Upload CSV coordinates and comparison plot to design.
• 20. Verify designed overlap indirectly from spacing and verticality; acceptance: overlap meets or exceeds design per approved project specifications. Provide calculation sheet and engineer approval.
• 21. Perform integrity testing on selected secondary piles per ITP (e.g., low-strain PIT). Acceptance: no major defects indicated. Upload test reports and mark tested piles on plan.
• 22. Protect and trim piles to cut-off; acceptance: cut-off elevation within ±10 mm and no damage to interlock. Evidence: photos with staff gauge and supervisor sign-off.

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