This standard specifies the material, dimensional, and constructional requirements for mild steel thin-walled sampling tubes, commonly known as Shelby tubes. These tubes are designed to obtain relatively undisturbed soil samples, primarily from cohesive soils, for laboratory testing of geotechnical properties.
mild steel thin-walled sampling tubes and sampler heads
Quick Reference Values
Maximum recommended Area Ratio (Ar) for sensitive clays< 10%
General upper limit for Area Ratio (Ar)20%
Recommended Inside Clearance Ratio (Ci)1 to 1.5%
Maximum Inside Clearance Ratio (Ci)3%
Standard nominal inside diameter for tubes50, 75, or 100 mm
Cutting edge included angleapprox. 20 degrees
Key Formulas
Area Ratio (Ar) = [(Dw² - De²) / De²] x 100
Inside Clearance Ratio (Ci) = [(Di - De) / De] x 100
Practical Notes
These tubes are best suited for soft to stiff cohesive soils and are not intended for use in gravelly ground or very hard strata, where the cutting edge can be damaged.
The Area Ratio (Ar) is a critical indicator of sample disturbance. For high-quality samples in sensitive clays, ensure the tube's Ar is less than 10%.
Always inspect the cutting edge for sharpness, straightness, and any nicks before use, as a damaged edge will cause significant sample disturbance.