This code provides comprehensive guidelines and procedures for obtaining undisturbed soil samples from boreholes, trial pits, and excavations. It specifies sampler design criteria (such as area ratio, inside clearance, and outside clearance) to minimize mechanical disturbance, ensuring accurate laboratory assessment of soil strength and compressibility.
Lays down the procedure for obtaining undisturbed soil samples for laboratory testing purposes.
Quick Reference Values
Area Ratio (Ar) for thin-walled samplers< 10%
Inside Clearance (Cr)1% to 3%
Outside Clearance (Co)0% to 2%
Recovery Ratio (for undisturbed sample)0.96 to 1.05
Key Formulas
Ar = ((Dw^2 - De^2) / De^2) * 100 — Area Ratio
Cr = ((Ds - De) / De) * 100 — Inside Clearance
Co = ((Dw - Dt) / Dt) * 100 — Outside Clearance
R = L / H — Recovery Ratio
Practical Notes
Seal the ends of the sample tube with molten paraffin wax or microcrystalline wax immediately after extraction to prevent moisture loss.
Use a stationary piston sampler for soft, sensitive clays to avoid sample disturbance and improve the recovery ratio.
A high area ratio significantly disturbs the soil structure; always verify the sampler dimensions before authorizing undisturbed sampling.