Triaxial method - Lab Report Example

Unconsolidated-Undrained Triaxial method IntroductionInsitu soil material is tested in during subsurface phase. This phase is an investigation stage that will help prepare design a waste containment facility or structures. The tests done will be used for structural fill, recompacted soil layers, and any other engineering components. These forms of tests are called conformance tests and are performed before any construction starts. Appropriate ASTM test methods must be followed when performing tests of materials.

The common tests applied in geotechnical investigation are; Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions ASTM 3080, Standard Test Method for Unconsolidated-Undrained Triaxial Compression Test on Cohesive Soils ASTM 2850, Standard Test Method for Unconfined Compressive Strength of Cohesive Soil ASTM 2166, Standard Test Method for Consolidated-Undrained Triaxial Compression Test for Cohesive Soils ASTM 4767 and Standard Test Method for One-Dimensional Consolidation Properties of Soils ASTM D 2435.1.1 Theoretical BackgroundThe purpose of this test is to establish the undrained shear strength of soil and applied to scenarios where fine-grained soils will be saturated and loading expected at a rate that overwhelms the ability of soil materials to dissipate excess pore water pressure.

The shear strength parameters of fine and course grained soils in undisturbed or remolded state is quickly established. In a situation where the rate of construction is slow and allows the soil to consolidate this test is not required. Confinement from surrounding soil in the ground can be simulated through addition of water. This makes it differ with UCS which is unconfined. Therefore, this test represents insitu material where construction rate is very first and the pore waters have no time to dissipate.

The results are quickly obtained through this testing procedure that is economical. Equipment used are triaxial machine, specimen preparation equipment, sample extruder and a balance.During the test, a cylindrical specimen always in a membrane is placed in a triaxial chamber. This chamber has a top and bottom plate with a stiff walled cylinder. In the triaxial chamber, a confining pressure from a fluid and air is created. The axial load exerts pressure on the specimen until it fails. During the process, no drainage is allowed (ASTM, p.2).Work CitedASTM, Designation: D 2850-95; Standard Test Method for Unconsolidated-Undrained Triaxial Compression Test on Soils. ASTM; U.S.A. 1999. 1-6. Print.