Consolidated-undrained test or Consolidated quick test

Wednesday, September 28, 2011 15:11
Posted in category Soil Mechanics 2
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Consolidated-undrained test (CU test) or Consolidated quick test

In consolidated-undrained test or consolidated quick test no excess load is applied. Usually normal load is applied and then sample is allowed to consolidate. Which allows drainage during consolidation process. It reduces the pour pressure to zero. After reaching this condition without allowing any drainage one normal stress is increased rapidly, until the sample fails.

During the shearing phase, the provided pore pressure is being measured. The results are then explained in terms of total or effective shear parameters.

On engineering scale, CUor quick test strengths are used to sole the stability problems in which the soils have first become fully consolidated and are at equilibrium with the previously existing stress system. When no drainage is occurring, for some reason additional stresses are applied quickly. In most of the projects unconsolidated-undrained test (UU test) and consolidated-undrained  test (CU test) are performed simultaneously. In this process moisture is drawn out. Practical examples include earthen dams stability slopes.

The unconsolidated un-drained (CU) or quick test is performed by placing the sample in the chamber and introducing the confined pressure. The sample is then allowed to consolidate under all around confining pressure by leaving  the drain lines open. The drain lines are then closed and the axial stress is increased without allowing further drainage.

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