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IS 11594:1985 is the Indian Standard (BIS) for mild steel thin-walled sampling tubes and sampler heads. 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
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
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.
Standard Practice for Thin-Walled Tube Sampling of Soils for Geotechnical Purposes
Defines the equipment and procedure for obtaining relatively undisturbed soil samples using thin-walled tubes (Shelby tubes).
BS EN ISO 22475-1:2021BSI (UK) / ISO (International)
MediumCurrent
Geotechnical investigation and testing — Sampling methods and groundwater measurements — Part 1: Technical principles for execution
Specifies technical principles for sampling, including requirements for samplers (like thin-walled tubes) to achieve specific sample quality classes.
JIS A 1221:2009Japanese Industrial Standards, Japan
HighCurrent
Methods for undisturbed soil sampling using a thin-walled tube sampler with fixed piston
Covers the apparatus and method for obtaining undisturbed soil samples, focusing on thin-walled tube samplers.
Key Differences
≠The maximum allowable Area Ratio (Cₐ) in IS 11594 is 15%, which is less strict than the <10% required by ISO 22475-1 for high-quality (Class 1) samples and the ≤10% recommended by ASTM D1587 for sensitive soils.
≠IS 11594 allows a wider Inside Clearance Ratio (Cᵢ) of 0.5% to 3.0%, whereas ASTM D1587 suggests a tighter range of 0.5% to 1.5% and ISO 22475-1 specifies 0% to 1.5% for Class 1 samples, affecting internal sample friction.
≠The Indian standard is specific to 'mild steel' for the tubes, while ASTM D1587 provides more flexibility, allowing for steel, stainless steel, or brass, which can offer better corrosion resistance.
≠IS 11594 specifies three nominal outside diameters (50, 75, 100 mm), whereas ASTM D1587 lists common imperial sizes (2, 3, 5 inches) which are similar but not identical.
Key Similarities
≈All standards specify a similar fundamental design: a thin-walled metal tube connected to a sampler head designed for pushing into the ground.
≈The requirement for a sharpened, tapered cutting edge at the base of the sampling tube is a common feature across all standards to ensure minimal disturbance during soil penetration.
≈The sampler head must be vented (e.g., via air vents or a check valve) to allow air and water to escape as the sample enters the tube, preventing pressure buildup that could disturb the sample.
≈The primary objective of all mentioned standards is to define equipment and methods for obtaining high-quality, relatively undisturbed soil samples suitable for laboratory testing of engineering properties.
Parameter Comparison
Parameter
IS Value
International
Source
Area Ratio (Cₐ)
≤ 15%
< 10% (for Quality Class 1)
BS EN ISO 22475-1
Inside Clearance Ratio (Cᵢ)
0.5% to 3.0%
Typically 0.5% to 1.5%
ASTM D1587
Tube Material
Mild steel
Steel, stainless steel, or brass
ASTM D1587
Standard Tube OD (Nominal)
75 mm
3 in (76.2 mm)
ASTM D1587
Standard Tube OD (Nominal)
100 mm
Not a standard size; closest is 5 in (127 mm)
ASTM D1587
Sampler Head Feature
Must have an air vent
Must have a check valve and ports for venting
ASTM D1587
Minimum Tube Length
Not less than 10 times the outside diameter
Length-to-diameter ratio typically between 10 and 20
ASTM D1587
⚠ Verify details from original standards before use
Key Values6
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
Tables & Referenced Sections
Key Tables
Table 1: Dimensions of Thin-Walled Sampling Tubes and Sampler Heads
What is the common name for a tube specified by IS 11594?+
It is commonly known as a 'Shelby Tube'.
What is the purpose of the 'Inside Clearance Ratio'?+
It is a small inward bevel at the cutting edge that reduces friction between the soil sample and the inside of the tube as the sample enters, minimizing disturbance.
What is the maximum recommended Area Ratio (Ar) for these samplers?+
The area ratio should be as low as possible, preferably not exceeding 10% for undisturbed sampling in sensitive clays (Clause 4.3).
Can these tubes be reused?+
Yes, but only if they are not bent or buckled and the cutting edge remains undamaged and sharp. Any damage can compromise sample quality.