3.2.2 Sampling shall be performed as below;
3.2.2.1. Disturbed samples shall be obtained from a boring using a split barrel sampler in accordance with ASTM.
3.2.2.2. Undisturbed samples of cohesive soil shall be obtained from a thin-walled tube sampler in accordance with boring using ASTM.
3.2.2.3. Undisturbed samples should comply with the followings;
Soil samples shall be taken wherever major change in soil type is evident and at every 3m (max.) in an apparently homogeneous stratum.
Soil samples should contain no visible distortion of strata, or opening or softening of materials.
Specific recovery ratio (length of undisturbed sample/length of sampling push) should exceed ninety five percent (95%).
Area ratio (annular cross-sectional area of sampling tube/full area of outside diameter of sampler) should be less than fifteen percent (15%).
All undisturbed samples shall be properly packed by air tight sample tube to prevent change in natural moisture content and shall clearly be labeled.