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IS 11593:1986 is the Indian Standard (BIS) for shear box (large) for testing soils. This standard specifies the requirements for the materials, dimensions, and construction of large-scale direct shear box apparatus. This equipment is used to determine the shear strength parameters (cohesion and angle of internal friction) of coarse-grained soils, gravels, and rockfill materials that cannot be tested in a standard small shear box.
! This apparatus is essential for testing materials with large particle sizes, such as those in rockfill dams and railway ballast, where standard shear boxes (60x60mm) are inadequate.
! Ensure the ratio of the box dimension to the maximum particle size is at least 6:1 to avoid boundary effects influencing the test results.
! Proper saturation of coarse-grained samples within the large box can be time-consuming and challenging but is critical for obtaining representative effective strength parameters.
BS EN ISO 17892-10:2018BSI (UK) / CEN (Europe) / ISO (International)
HighCurrent
Geotechnical investigation and testing - Laboratory testing of soil - Part 10: Direct shear tests
Specifies requirements for the apparatus used in direct shear tests, including large boxes, within a broader test method standard.
ASTM D3080 / D3080M - 11(2023)ASTM International, USA
HighCurrent
Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions
Defines the test method and necessary apparatus, providing guidelines for large-scale boxes based on soil particle size.
ASTM D5321 / D5321M - 20ASTM International, USA
MediumCurrent
Standard Test Method for Determining the Shear Strength of Soil-Geosynthetic and Geosynthetic-Geosynthetic Interfaces by Direct Shear
Focuses on interface shear, a key application for the large shear box specified in IS 11593, and details its apparatus.
BS 1377-7:1990British Standards Institution (BSI), UK
MediumWithdrawn
Methods of test for soils for civil engineering purposes. Shear strength tests (total stress)
Describes the classic direct shear test method and apparatus, including provisions for large specimens (300 mm square).
Key Differences
≠IS 11593 is a dedicated apparatus specification standard, whereas international counterparts like ASTM D3080 and ISO 17892-10 are test method standards that include apparatus requirements within them.
≠IS 11593 mandates a specific large shear box size of 300 mm x 300 mm. International standards are more performance-based, recommending the box dimension be a multiple (e.g., >10 times) of the maximum particle size, allowing for various 'large' sizes.
≠The Indian standard specifies the box material (mild steel or gunmetal) and that it should be 'suitably stiffened'. Modern international standards focus on performance, stating the box must be rigid enough to prevent distortion under load, without specifying material.
≠IS 11593 specifies a detailed design for the normal loading yoke and lever system (1:10 ratio). International standards are less prescriptive, allowing any system (lever arm, pneumatic, hydraulic) that can apply and maintain a constant normal stress.
Key Similarities
≈All standards are based on a common apparatus principle: a rigid, two-part box where one half can move horizontally relative to the other to shear the contained soil specimen.
≈The conceptual requirement for two independent loading systems is universal: one for applying constant normal stress vertically and another for applying a controlled rate of horizontal shear displacement.
≈All standards require the use of rigid, grooved or serrated gripper plates and porous plates/stones at the top and bottom of the specimen to ensure shear transfer and allow for drainage.
≈Instrumentation for measuring normal and shear displacements (dial gauges or LVDTs) and the applied shear force (proving ring or load cell) is a common requirement across all standards.
Parameter Comparison
Parameter
IS Value
International
Source
Standard Large Specimen Size
300 x 300 mm (square)
Min. 300 x 300 mm for interfaces; for soil, width must be >10 times max particle size.
ASTM D5321 / ASTM D3080
Specimen Height
Not explicitly defined, but box depth of 200 mm allows for ~150 mm specimen.
Minimum thickness of 6 times the max. particle diameter or 50 mm, whichever is greater.
ASTM D3080 / D3080M - 11(2023)
Initial Gap between Halves
Shall not exceed 0.5 mm
A small gap of about 0.5 mm to 1.0 mm should be present after consolidation.
BS EN ISO 17892-10:2018
Porous Plate Material
Sintered bronze or unglazed ceramic
Corrosion-resistant material such as silicon carbide, aluminum oxide, or porous metal.
ASTM D3080 / D3080M - 11(2023)
Shear Box Material
Mild steel, gunmetal or other suitable corrosion-resistant material
Not specified, but must be corrosion-resistant and sufficiently rigid to resist distortion.
BS EN ISO 17892-10:2018
Normal Loading System
Dead weight and lever arm with a 1:10 ratio.
Any system capable of applying a constant normal stress (e.g., dead weights, pneumatic/hydraulic pressure).
ASTM D3080 / D3080M - 11(2023)
Rate of Shear Displacement
Variable speed motor to give rates from 0.005 to 2.5 mm/min.
Rate is not fixed but calculated based on soil consolidation properties (e.g., time for 50% consolidation).
ASTM D3080 / D3080M - 11(2023)
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Standard shear box sizes (mm x mm)300 x 300, 600 x 600, 1000 x 1000
Minimum depth of each half of box (for 300x300mm size)150 mm
Maximum gap between shear box halves2 mm
Recommended ratio of box size to max particle size6:1 to 8:1
Displacement rate range for shearing0.0002 to 2.0 mm/min
It is used to determine the shear strength of soils with large particles like gravel, ballast, and rockfill, which are too big for a standard 60x60 mm shear box.
What are the standard sizes for a large shear box specified in this code?+
The code specifies square boxes with side dimensions of 300 mm, 600 mm, and 1000 mm (Clause 4.1).
Which IS code describes the testing procedure using this apparatus?+
The testing procedure is detailed in IS 2720 (Part 13) - Method of Test for Soils, Part 13: Direct Shear Test.
What is the maximum particle size that can be tested in a 300x300 mm shear box?+
To maintain a recommended ratio of at least 6:1 (box size to particle size), the maximum particle size should be around 50 mm.