How do you calculate deviator stress?

2.2 Deviator Stress (Principal Stress Difference)–Deviator stress is the difference between the major and minor principal stresses in a triaxial test, which is equal to the axial load applied to the specimen divided by the cross-sectional area of the specimen, as prescribed in the section on calculations.

What is B value in triaxial test?

The B-value, measured after setting up a specimen for triaxial testing, is used for evaluating the degree of saturation of a specimen. However, the stress conditions used when measuring the B-value have not been standardized.

How long does a CU triaxial test take?

The unconsolidated – undrained triaxial test is the fastest test, typically completed under 30 minutes. It is performed on cohesive soil samples to determine the undrained shear strength of the core sample.

What is axial strain?

The strain in the direction that the load is applied, or on the same axis as the applied load.

What is triaxial test used for?

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.

How CU test is different from a test CD?

In a CU (undrained) test, pore pressure changes (U) are allowed to take place and are measured. In a CD (Drained) test drainage is allowed to prevent pore pressure changes happening. In this type of test the volume change of the sample is measured during the shear stage.

What is UU triaxial test used for?

Unconsolidated – undrained (UU) triaxial test It is performed on cohesive soil samples to determine the undrained shear strength of the core sample. It has no saturation or consolidation stage and is a short-term test to determine short-term engineering problems.

What is the triaxial test?

The triaxial test typically involves placing a cylindrical specimen of soil, ranging from 38mm to 100mm diameter, into a cell that can be pressurised. Most specimens have an approximate 2:1 height-to-diameter ratio, and are sealed within a rubber membrane.

How is the soil sheared in a triaxial test?

The soil is sheared by applying an axial strain, ε a, to the test specimen at a constant rate through upward (compression) or downward (extension) movement of the load frame platen. This rate, along with the specimen drainage condition, is dependent on the type of triaxial test being performed.

Does a triaxial specimen deform uniformly during the test?

It is thus very clear that the uniformity of stress and strain in the specimen is an essential part for the triaxial test concept. However, it is not often the case that a triaxial specimen deforms uniformly during the test.

How is triaxial compression conducted?

The triaxial compression is conducted by controlling the rate and the total value of ver- tical movement of the top rigid surface. In the case where the effects of end restraint are of interest, a total vertical movement of 0.05m is carried out during 100 days (8.64 x 106s).