A triaxial shear test is a common method to measure the mechanical properties of many deformable solids, especially soil and rock, and other granular materials or powders. There are several variations on the test.

What does the triaxial test do?

A triaxial test is performed on a cylindrical core soil or rock sample to determine its shear strength. The triaxial test attempts to replicate the in-situ stresses (stresses in the original place the soil sample was taken) on the core soil or rock sample.

What are the advantages of triaxial test?

Advantages of Triaxial Test

The stress distribution on the failure plane is uniform. There is complete control over the drainage. Pore pressure changes and the volumetric changes can be measured directly.

What are the different types of triaxial test?

The types of triaxial test

There are three main types of test based on whether water flow in or out of the specimen is permitted during the consolidation and shear stages of the test: Consolidated Drained (CD), Consolidated Undrained (CU) and Unconsolidated Undrained (UU).

What is a true triaxial test?

The true triaxial apparatus is a laboratory testing equipment to study the three dimensional stress-strain-strength behavior of soil, for instance in complex stress paths. It is mainly considered as a research laboratory tool for advanced study of mechanical behavior of soil.

CE 326 Mod 12.9b Triaxial Shear Test

How do you do a triaxial test?

A typical triaxial test involves confining a cylindrical soil or rock specimen in a pressurised cell to simulate a stress condition and then shearing to failure, in order to determine the shear strength properties of the sample. Most triaxial tests are performed on high quality undisturbed specimens.

What is a consolidated undrained triaxial test?

Consolidated undrained triaxial compression tests were performed to investigate the shear strength behavior of the solidified dredged materials (SDM). ... The undrained shear strength develops slightly with the increase of applied normal stress in the preyield state.

What is triaxial compression?

DEFINITIONS. 2.1 Triaxial Compression Test—the triaxial compression test a test in which a cylindrical specimen of soil or rock encased in an impervious membrane is subjected to a confining pressure and then loaded axially to failure in compression.

What is UU test in soil?

UU (unconsolidated undrained) test: In this, cell pressure is applied without allowing drainage. Then keeping cell pressure constant, deviator stress is increased to failure without drainage. CU (consolidated undrained) test: In this, drainage is allowed during cell pressure application.

What is meant by triaxial stresses?

Triaxial stress refers to a condition where only normal stresses act on an element and all shear stresses (txy, txz, and tyz) are zero. An example of a triaxial stress state is hydrostatic pressure acting on a small element submerged in a liquid.

How is the triaxial test useful in engineering design?

Triaxial tests are often used to determine the behavior and strength characteristics of soils. Specimen size can have a significant impact on the measured shear strength. Accordingly, the selected parameters affect the related geotechnical engineering analysis and design.

Which is a demerit of triaxial test?

The following are the demerits of triaxial test: 1. Takes a longer period under drainage conditions than a direct shear test. 3.

What is triaxial compressive strength?

triaxial compression test A test for the compressive strength in all directions (compare UNIAXIAL COMPRESSION TEST) of a rock or soil sample, using a triaxial cell. Tests in which drainage is prevented are called 'undrained' tests and the strengths obtained are 'undrained' strengths.

What is the difference between UU and CU test?

The CU test includes pore pressure measurements during the shearing phase. Therefore, the effective stresses can be calculated. The UU test is a glorified unconfined compressive strength test. The CU test can model a proposed long term loading condition.

What is CD test?

Consolidated Drained (CD) Triaxial Test

Determination of strength and stress-strain relationships of a cylindrical specimen of “undisturbed” or “reconstituted” specimens. The soil specimens are isotropically consolidated and sheared in compression with drainage at a constant rate of axial deformation.

What is B value in triaxial test?

Abstract. The B-value, measured after setting up a specimen for triaxial testing, is used for evaluating the degree of saturation of a specimen.

What is back pressure in triaxial test?

The use of back pressure, common in triaxial testing, has been extended to consolidation testing. ... Use of back pressure causes the air to be dissolved in the water and eliminates the initial compression commonly found in time-compression curves from standard tests.

What is a shear box test?

A Shear Box is used for direct shear testing of soil specimens to determine the shear strength of a soil sample. These shear box apparatus' divide horizontally, allowing the application of a vertical confining load to the specimen and horizontal shearing stresses to the lower half of the box.

What is consolidation test?

Consolidation test is used to determine the rate and magnitude of soil consolidation when the soil is restrained laterally and loaded axially. The Consolidation test is also referred to as Standard Oedometer test or One-dimensional compression test.

Is code for triaxial test?

1. IS 2720(Part 11):1993 Determination of the shear strength parameters of a specimen tested in unconsolidated undrained triaxial compression without the measurement of pore water pressure (first revision). Reaffirmed- Dec 2016.

How reliable the triaxial compression tests are?

The lateral pressure is applied at the same rate selected for the axial load until it reaches the prescribed value. Once this confining pressure is reached, it should be maintained within 2% accuracy. The loading machine must be stiff and sufficient of applying the maximum required pressure for a rock specimen to fail.

Why triaxial testing is considered as test like conditions in the most natural?

Like Cone Penetration Testing, Triaxial Testing is used to measure the properties of soils, but can also be used on more solid materials like rock. Typically, Triaxial Testing is used to solve problems of stability by: Determining the shear strength and stiffness of soil when retaining reservoirs of water.

What is a plate load test?

A Plate Load Test determines the actual strength, as well as the bearing capacity of ground, and is used when the testing involves large particle sizes or soils that have a harder texture.

What is unconfined compression test?

The Unconfined Compression Test is a laboratory test used to derive the Unconfirmed Compressive Strength (UCS) of a rock specimen. Unconfirmed Compressive Strength (UCS) stands for the maximum axial compressive stress that a specimen can bear under zero confining stress.

Which of the following parameter is determined by triaxial test?

Triaxial test is used to determine the shear strength parameter of soil.