| S.No. | Checkpoint | IS Requirement | Status |
|---|---|---|---|
| A. SAMPLE DETAILS & PREPARATION | |||
| A1 | Sample identification Acceptance: Identification legible; depth ≥0.5 m below surface or as specified | Sample ID, location, depth clearly documented | OK NC NA HOLD |
| A2 | Sample preparation — passing 425 μm sieve Acceptance: Material homogeneous; all particles pass 425 μm sieve; no crushing of clay aggregates; preparation documented | Soil passed through 425 μm (No. 40) IS sieve per IS 2720 Part 5 Clause 4.1; air-dried at room temperature; lumps gently broken; no grinding to prevent crushing of clay particles | OK NC NA HOLD |
| A3 | Specific gravity determination (reference) Acceptance: Gs value documented; used for Activity & liquidity index calculations if required | Specific gravity (Gs) measured per IS 2720 Part 3; typical range 2.60–2.75 for soil minerals | OK NC NA HOLD |
| B. LIQUID LIMIT (LL) DETERMINATION | |||
| B1 | Equipment — Casagrande Apparatus Acceptance: Apparatus calibrated; groove depth 2 mm at center; impact mechanism lifts cup 10 mm at 2 drops/sec; cup smooth & undamaged | Casagrande apparatus per IS 2720 Part 5 Clause 5.1: cup height = 10 mm, groove cut per standard pattern, groove closed at end, cup angle 30° to horizontal. OR cone penetrometer method (alternative) | OK NC NA HOLD |
| B2 | Casagrande Method — Trial procedure Acceptance: Each trial: blow count 10–50 range preferred; moisture range spans LL; groove closure observed at correct section | 4–5 trials at different moisture contents: soil placed in cup, groove drawn through center with grooving tool (perpendicular to motion direction), cup dropped repeatedly, count blows until soil joins at bottom of groove | OK NC NA HOLD |
| B3 | Casagrande — Blow count & moisture recording Acceptance: Blow count accurate ±1; moisture content within ±0.5%; data tabulated: N vs w (%) | For each trial: (a) Number of blows (N) when soil groove closes; (b) Moisture content measured immediately from soil cup (oven-dry method per IS 2720 Part 2: 105°C, 24 hrs) | OK NC NA HOLD |
| B4 | Casagrande — Flow curve & LL determination Acceptance: Flow curve linear; R² >0.95; LL determined to nearest 0.5%; LL typically 20–60% for soils | Plot semi-log graph: X = log(N), Y = moisture content (%); line fitted through 4–5 points; LL = moisture content at N = 25 blows (extrapolated/interpolated from flow curve) | OK NC NA HOLD |
| B5 | Cone Penetrometer Method (alternative) Acceptance: Penetration depth recorded to ±0.5 mm; moisture at 20 mm penetration identified; method noted in report | If using cone penetrometer (IS 2720 Part 5 Clause 6.2): cone 30° angle, mass 80 g, penetration measured after 5 sec rest; LL = moisture content at 20 mm penetration; min 3 trials at different moisture contents | OK NC NA HOLD |
| C. PLASTIC LIMIT (PL) DETERMINATION | |||
| C1 | Plastic Limit thread rolling method Acceptance: Thread diameter 3.0 mm ±0.5 mm at rolling end; crumbling point clearly identified; procedure repeated min 3 times | Per IS 2720 Part 5 Clause 6.3: soil rolled on non-porous surface (glass plate) into thread of 3.0 mm diameter; at crumbling point (thread cannot be rolled further without breaking), moisture content determined = Plastic Limit | OK NC NA HOLD |
| C2 | Minimum 3 determinations for PL Acceptance: Three values recorded; range <2% (if >2%, repeat trials); consistency verified | Minimum 3 trials of plastic limit thread rolling; moisture content measured for each (oven-dry at 105°C, 24 hrs per IS 2720 Part 2) | OK NC NA HOLD |
| C3 | Average PL calculation Acceptance: Average calculated correctly; standard deviation <2%; outliers reviewed & justified | PL = average of 3 (or more) acceptable PL values; rounded to nearest 0.5% | OK NC NA HOLD |