Special procedures such as:

a) Tests with lubricated ends;

b) tests with local measurement of strain or local measurement of pore pressure;

c) tests without rubber membranes;

d) extension tests;

e) shearing where cell pressure varies;

f) shearing at constant volume (no pore pressure change)

are not covered.

The conventional triaxial apparatus is not well suited for measurement of the initial moduli at very small strains. However, strains halfway up to failure are considered to be large enough to be measured in conventional triaxial cells.

NOTE "Water-saturated" refers to the in-situ condition. The material tested need not necessarily be saturated at all stages during the laboratory testing.

The bulk density of a soil is useful in the determination of the in-situ overburden stresses at various depth (geostatic stresses). Furthermore, bulk and dry density can qualitatively describe the mechanical characteristics of a soil via empirical relationships which are to be found in the technical literature. Such relationships should be used only as guidelines and should be supplemented by direct measurements of the mechanical characteristics.

This document describes three methods:

a) linear measurements method;

b) immersion in water method;

c) fluid displacement method.

The linear measurement method is suitable for the determination of the density of a specimen of cohesive soil of regular shape, including specimens prepared for other tests. The specimens used are normally in the form of either rectangular prisms or straight cylinders.

The immersion in water method covers the determination of the bulk density and dry density of a specimen of natural or compacted soil by measuring its mass in air and its apparent mass when suspended in water. The method is employable whenever lumps of material of suitable size can be obtained.

The fluid displacement method covers the determination of the bulk density and dry density of a specimen of soil by measuring mass and displacement of water or other appropriate fluid after immersion. The method is employable whenever lumps of material of suitable size can be obtained.

The unconfined compressive strength of cohesive soils is a measure of the apparent cohesion. A cohesive soil behaves as if it is truly cohesive, e.g. clay and clayey soils, but most soils in this group behave cohesively due to negative pore pressure and friction and not due to actual cohesion.

This test method is useful to derive the undrained shear strength of soil. It should however be noted that no provisions are taken to prevent drainage. The derived value for undrained shear strength is therefore only valid for soils of low permeability, which behave sufficiently undrained during testing.

The method is not appropriate for fissured or varved clays or silts or peats.