Quality Protocol ID: GAT-STD-2024 • Scope: Geotechnical Sampling & In-Situ Verification Protocols • Jurisdiction: Queensland, Australia
1. Laboratory Soil Testing (AS 1289 Series)
All empirical data cited within GAT (QLD) Pty Ltd advisory monographs is derived from testing procedures conforming to the Australian Standard AS 1289 'Methods of testing soils for engineering purposes'. Essential laboratory tests include:
- Atterberg Limits (AS 1289.3.1.1 / 3.9.1): Liquid limit (wL), plastic limit (wP), and plasticity index (IP) to classify soil expansiveness.
- Shrink-Swell Index (AS 1289.7.1.1): Direct measurement of core shrinkage and swell strain under inundation to establish the Iss reactivity value.
- Particle Size Distribution (AS 1289.3.6.1): Sieve analysis and hydrometer sedimentation for coarse and fine fractions.
- California Bearing Ratio (AS 1289.6.1.1): Standard compaction with 4-day soaking for flexible pavement subgrade evaluation.
2. Earthworks Supervision & Compaction Control (AS 3798)
Structural fill placed beneath building footprints, roads, and retaining walls must satisfy Level 1 geotechnical inspection and testing according to AS 3798:
- Continuous Inspection: Full-time presence of a qualified geotechnical technician during stripping, benching, moisture conditioning, and rolling.
- Density Ratio: Minimum 95% or 98% Standard Maximum Dry Density (SMDD) depending on structural loading criteria.
- Moisture Control: Moisture content held within ±2.0% of Optimum Moisture Content (OMC).
3. In-Situ Field Penetration Testing
Standard Penetration Tests (SPT - AS 1289.6.3.1) and Dynamic Cone Penetrometer (DCP - AS 1289.6.3.2) provide continuous profiling of non-cohesive and cohesive strata. SPT 'N' values and DCP blow counts are correlated against allowable bearing capacity (qa) limits.
