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IS 4968:1976 Part 1 is the Indian Standard (BIS) for method for subsurface sounding for soils - static cone penetration test. This standard outlines the method for conducting a Static Cone Penetration Test (CPT) to determine soil properties for geotechnical investigation. It specifies the dimensions of the apparatus (cone and friction sleeve), the procedure for pushing the cone into the ground at a constant rate, and the requirements for recording and reporting the cone resistance (qc) and sleeve friction (fs). This data is used for soil profiling and estimating engineering properties of soil strata.
Describes the method for conducting the static cone penetration test (CPT) for subsurface investigations.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This is the 'Heavy' DCPT, distinct from the lighter versions used for pavement subgrade analysis. The 65 kg hammer is the key differentiator.
! The test is faster and more mobile than the Standard Penetration Test (SPT), making it suitable for preliminary investigations or sites with difficult access.
! Results (Nc values) are often correlated with SPT 'N' values and soil parameters like CBR, but these correlations are site-specific and should be used with caution.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
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International Equivalents
Similar International Standards
ASTM D3441-16ASTM International, USA
HighCurrent
Standard Test Method for Mechanical-Friction Cone and Piezocone Penetration Tests of Soil
Both standards provide procedures for CPT using a mechanical cone penetrometer.
ISO 22476-1:2012International Organization for Standardization, International
MediumCurrent
Geotechnical investigation and testing — Field testing — Part 1: Electrical cone and piezocone penetration test
Both define methods for cone penetration testing, but the IS code is for mechanical cones while ISO focuses on modern electrical/piezocones.
ASTM D5778-20ASTM International, USA
MediumCurrent
Standard Test Method for Electronic Friction Cone and Piezocone Penetration Testing of Soil
Both cover cone penetration testing, but this standard is specific to modern electronic cones (CPTu), whereas IS 4968 is for older mechanical systems.
BS EN ISO 22476-1:2012+A1:2018British Standards Institution, UK / European Committee for Standardization, Europe
MediumCurrent
Geotechnical investigation and testing. Field testing. Electrical cone and piezocone penetration test
European adoption of the ISO standard, sharing the same scope overlap regarding the fundamental test but differing in technology.
Key Differences
≠IS 4968 specifies a mechanical cone (Dutch mantle cone) where forces are measured at the surface via inner rods. Modern international standards (ISO 22476-1, ASTM D5778) primarily focus on electrical cones with strain gauges for direct measurement at the tip.
≠The Indian standard does not include provisions for measuring pore water pressure (it is a CPT, not a CPTu). Key international standards like ISO 22476-1 mandate piezocone (CPTu) testing for a more complete soil characterization.
≠In IS 4968, cone resistance (qc) and sleeve friction (fs) are measured sequentially in discrete steps. In modern electrical CPT(u), qc and fs are measured simultaneously and quasi-continuously.
≠Data acquisition in IS 4968 is manual, relying on reading hydraulic gauges at specified depth intervals (e.g., 20 cm). International standards for electrical CPT use electronic data acquisition systems recording data at much smaller intervals (e.g., 1-2 cm).
Key Similarities
≈The fundamental principle is identical: pushing a standardized cone into the ground at a controlled rate to measure soil resistance.
≈The basic geometry of the penetrometer cone is highly standardized and consistent across both IS 4968 and international standards, featuring a 60° apex angle and a 10 cm² projected base area.
≈The standard surface area for the friction sleeve is specified as 150 cm² in both the Indian standard and international norms like ISO 22476-1.
≈The target rate of penetration is very similar, with all standards centering around a rate of 20 mm/s (2 cm/s) to ensure comparable dynamic effects during testing.
Parameter Comparison
Parameter
IS Value
International
Source
Cone Type
Mechanical (Dutch mantle cone)
Mechanical-Friction Cone and Piezocone
ASTM D3441-16
Cone Apex Angle
60°
60° ± 0.5°
ISO 22476-1:2012
Cone Projected Area
10 cm²
10 cm²
ISO 22476-1:2012
Friction Sleeve Surface Area
150 cm²
150 cm²
ISO 22476-1:2012
Rate of Penetration
10 to 20 mm/s
20 ± 5 mm/s
ISO 22476-1:2012
Pore Pressure Measurement (u)
Not specified
Required (Piezocone), with specified filter locations (u1, u2, u3)
ISO 22476-1:2012
Data Reading Interval
Every 20 cm of penetration
≤ 20 mm (for electrical cones)
ISO 22476-1:2012
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Weight of driving hammer65 kg
Free fall height of hammer75 cm
Cone apex angle60 degrees
Cone base diameter50 mm
Penetration increment for recording blows10 cm
Key Formulas
qc = Q_c / A_c — Cone resistance = Total force on cone / Area of cone base
fs = (Q_t - Q_c) / A_s — Local sleeve friction = (Total force - Cone force) / Surface area of sleeve
What is the weight and drop height of the hammer used in this test?+
The standard specifies a 65 kg hammer with a free fall of 75 cm (Clause 3.1).
What does the Nc value from a DCPT represent?+
Nc is the number of blows required to drive the cone through a depth of 10 cm (Clause 4.1).
What are the dimensions of the cone?+
The cone has an apex angle of 60 degrees and a base diameter of 50 mm (Clause 3.1.5).
Is this test suitable for all soil types?+
No, it is not recommended for gravelly soils or ground containing boulders, as this can damage the cone and produce misleadingly high resistance values (Note under Clause 4.1).