| S.No. | Checkpoint | IS Requirement | Status |
|---|---|---|---|
| A. PRE-BACKFILL CHECKS & MATERIAL APPROVAL | |||
| A1 | Foundation work completed and approved — structural concrete cured, formwork removed, no defects outstanding Acceptance: Structural engineer inspection report filed; foundation ready for backfill notification issued | Mandatory | OK NC NA HOLD |
| A2 | Waterproofing and DPC (Damp Proof Course) completed if specified — all surfaces sealed, joints sealed, no defects Acceptance: Waterproofing contractor inspection report; all coats applied as per spec; curing time observed before backfill | Conditional | OK NC NA HOLD |
| A3 | All services and pipes protected — utility lines, drainage pipes cased or marked to prevent damage during backfill compaction Acceptance: Service drawings marked on site; pipes protected with casing or sand bedding; location flagged | Conditional | OK NC NA HOLD |
| A4 | Backfill material approved by site engineer — source certified, visual inspection passed, free from organic matter/oversized particles Acceptance: Material approval certificate; max particle size 75mm; no roots, wood, plastic; material classification per IS 1498 | Mandatory | OK NC NA HOLD |
| A5 | Laboratory Proctor test (IS 2720 Part 7 or 8) completed — MDD (Maximum Dry Density) and OMC (Optimum Moisture Content) established Acceptance: Test report filed; MDD ≥1.60 t/m³ typical for granular soil; OMC recorded; test date within 6 months of backfill start | Mandatory | OK NC NA HOLD |
| A6 | Compaction specification finalized — target density (≥95% MDD or ≥90% MDD) and compaction equipment (plate compactor, roller) defined Acceptance: Method statement signed; equipment type and passes specified; frequency of density testing defined | Mandatory | OK NC NA HOLD |
| B. BACKFILL MATERIAL QUALITY CHECK | |||
| B1 | Material free from organic matter — no peat, soil with OMC >10%, vegetation, wood, trash, or plastic Acceptance: Visual inspection; no discoloration indicating organic content; rejected batches noted and removed | Mandatory | OK NC NA HOLD |
| B2 | Particle size within specification — max 75mm diameter, no oversized particles in backfill Acceptance: Sieve analysis from Proctor sample; any particles >75mm removed from pile before placement | Mandatory | OK NC NA HOLD |
| B3 | Moisture content within acceptable range — between OMC-2% and OMC+2% (ideal for compaction) Acceptance: Field moisture content test on incoming material; if too dry, sprinkle water; if too wet, air-dry before use | Mandatory | OK NC NA HOLD |
| B4 | No frozen lumps or chunks — material thawed if stored in cold weather; uniform consistency across pile Acceptance: Visual inspection; material spreadable; no ice or frozen clods; allow thawing time if frozen | Conditional | OK NC NA HOLD |
| B5 | Material grading matches approved specification — sieve analysis result within design range (IS 1498 classification) Acceptance: Grading curve plotted; material classification confirmed; deviations within ±5% acceptable | Conditional | OK NC NA HOLD |
| C. BACKFILL PLACEMENT & LAYER CONTROL | |||
| C1 | Layer thickness controlled — max loose layer thickness 200-300mm, compacts to 150-200mm finished (typical for cohesive; granular 300-400mm) Acceptance: Layer thickness measured with ruler/tape; marked on formwork; compaction depth per spec | Mandatory | OK NC NA HOLD |
| C2 | Material placed in horizontal layers — layers parallel to ground surface; no lenses or wedges Acceptance: Visual inspection during placement; levels checked; excavator operator trained on layer placement | Mandatory | OK NC NA HOLD |
| C3 | No free-fall dumping against structures — material spread from side or top, no direct drop onto foundations/walls Acceptance: Visual inspection during placement; dumping method supervised; no impact on structure | Mandatory | OK NC NA HOLD |
| C4 | Adequate moisture for compaction — material moisture checked and adjusted (spray water if dry) to OMC ±2% Acceptance: Field moisture test on each layer before compaction; moisture adjusted within ±2% of OMC | Mandatory | OK NC NA HOLD |
| C5 | Material spread uniformly — no heaping or thin sections; thickness uniform across width and length Acceptance: Visual inspection; excavator operator spreads evenly; manual leveling if needed; theodolite check for large areas | Mandatory | OK NC NA HOLD |