AllRounder.ai
Chapters in this course

Enrol to start learning

Reading is open to everyone. Enrolling is free, and it is what unlocks the audio lessons, practice tests and progress tracking.

Enrol free

13. Triaxial Tests

The chapter discusses triaxial compression tests used for soil analysis, highlighting procedures for conducting these tests on sands and clays. Various types of triaxial tests are outlined, along with their methodology for determining shear strength parameters using Mohr’s circles. Significant equations and principles related to effective and total stress are presented to aid in understanding soil behavior under applied pressures.

Sections

Triaxial Tests

Triaxial tests assess the shear strength of soil by applying controlled pressure and monitoring failure conditions in soil specimens.

1 Section Overview

Start current section content and materials

1.1 Types of Triaxial Tests

Triaxial compression tests assess the shear strength of soil by varying confining pressures and stress conditions.

1.2 Consolidated-drained test (CD test)

The CD test is a type of triaxial test used to analyze the behavior of saturated soils under consolidated drainage conditions.

1.3 Consolidated-undrained test (CU test)

The Consolidated-undrained (CU) test is a triaxial test procedure for soil samples that evaluates their shear strength under undrained conditions while considering both effective and total stress.

1.4 Unconsolidated-undrained test (UU test)

The Unconsolidated-undrained (UU) test is a triaxial compression test that measures the shear strength of saturated clay soils without allowing for drainage.

1.5 Shear Strength Parameters

This section covers shear strength parameters determined through triaxial compression tests on soils, specifically highlighting testing methodology and the interpretation of results.

1.6 Total Stress Mohr’s Circles

This section introduces total stress Mohr's circles as part of triaxial tests conducted on soils, detailing various test types and their applications in determining shear strength parameters.

1.7 Effective Stress Mohr’s Circles

This section introduces the concept of effective stress in soils and its graphical representation through Mohr’s circles during triaxial tests.

1.8 Pore Water Pressure Parameter

The section discusses the pore water pressure parameter and its role in triaxial tests conducted on soils, especially clays.

1.9 Triaxial Test Equipment

The triaxial compression test is a pivotal soil testing method that evaluates the strength characteristics of sands and clays under various stress conditions.

Learning Objectives

  • Triaxial tests are essential for evaluating the mechanical properties of soils, including shear strength.

  • Three main types of triaxial tests can be conducted on clays based on drainage conditions: CD, CU, and UU tests.

  • The Mohr-Coulomb failure envelope is critical for determining the shear strength parameters of soils.

Key Concepts

Triaxial Test

A laboratory test for determining the strength and stress characteristics of soil by applying confining pressure and axial stress.

Shear Strength Parameters

Parameters (cohesion c and angle of internal friction ϕ) used in the Mohr-Coulomb failure criterion to describe soil strength.

Mohr's Circle

A graphical representation of the state of stress at a point, which helps in understanding the failure conditions of materials.

Effective Stress

The stress that contributes to soil strength, calculated by subtracting pore water pressure from total stress.

Pore Water Pressure

The pressure exerted by water within the soil pores, affecting the effective stress and shear strength of soils.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting

Get your answers marked and your progress tracked

Enrol free