AS 1289.6.2.2:2020 pdf Methods of testing soils for engineering purposes Method 6.2.2: Soil strength and consolidation tests — Determination of shear strength of a soil — Direct shear test using a shear box
1 Scope
This document sets out a method for determining the effective shear strength of a soil by direct
shearing in a shear box. The method specified is for a single-staged test, i.e. with a single value of
applied normal stress.
This document applies to shearing of dry, fine-grained and clay soils using shear boxes having shear
plane dimensions up to a maximum of 300 mm × 300 mm.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document.
AS 1289.0, Methods of testing soils for engineering purposes, Part 0: Definitions and general requirements
AS 1289.6.6.1, Methods of testing soils for engineering purposes, Method 6.6.1: Soil strength and
consolidation tests — Determination of the one-dimensional consolidation properties of a soil
AS 1726, Geotechnical site investigations
3 Terms and definitions
For the purpose of this document, the definitions below apply.
3.1 may
indicates the existence of an option
3.2 normal
stress is one that occurs when a member is loaded by an axial force
3.3 shall
indicates that a statement is mandatory
3.4 should
indicates a recommendation
4 Principle
A predetermined normal stress is applied under one-dimensional conditions, allowing sufficient time
for any consolidation or creep to occur and then shearing the soil by displacing one half of a shear box relative to the other. Interpretation of the shearing stage of the test assumes that the soil is drained and the displacement rate is chosen so that it is slow enough to ensure fully drained behaviour. Shear boxes used allow for either circular or square specimens, with the maximum length of specimen in the direction of shearing varying from 50 mm to 300 mm. Specimens are either tested in their natural (undisturbed) state or can be prepared by remoulding or reconstitution directly in a shear box.
Different procedures for different soil types are specified.
5 Apparatus
5.1 General
The following apparatus is required:
(a) A shear box consisting of two separate halves which can be moved relative to each other to
enable shearing a soil sample along a predetermined plane.
Boxes shall be constructed of non-corrosive material such as brass. The shear box shall be
designed so that the soil sample can be subjected to a normal stress applied perpendicular to
the plane of shearing. Where drainage is required, the design shall also allow porous plates
(these could be either stone, ceramic or sintered bronze) to be placed above and below the
soil specimen. The load shall be applied through a loading cap which rests on top of the soil
specimen and upper porous plate, if used.
NOTE 1 A schematic design of a typical shear box is shown in Figure 1.
(b) An outer box or carriage (running on ball or roller races) in which the shear box can be placed
so that the specimen can be totally submerged in water.
(c) A motorized worm drive unit, capable of pushing or pulling at the level of the shear plane in
such a way that the bottom half of the shear box moves relative to the top half.
The speed at which the worm drive shears the soil shall be adjustable, typically by using
a gear box, so that a range of shearing speeds can be attained. For soil specimens where
consolidation is not rapid, the shearing speeds shall be calculated using the equations given in
Clause 6. The selected displacement rate shall not vary by more than ± 10 % during the test.
(d) A loading frame arranged so that the points of load application between the worm drive and
the bottom frame and of the reaction between the proving ring (or load cell) and the upper
half of the box shall be in the plane of shearing.
AS 1289.6.2.2:2020 pdf Methods of testing soils for engineering purposes Method 6.2.2: Soil strength and consolidation tests — Determination of shear strength of a soil — Direct shear test using a shear box
