What is a large shear box used for?

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.

IS 11593

: 1986

shear box (large) for testing soils

CurrentSpecializedSpecificationGeotechnical · Soil and Foundation Engineering

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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.

shear box (large) for testing soils

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

Practical Notes

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.