The main difference between consolidated undrained (CU) and unconsolidated undrained (UU) test is the amount of time the soil sample is subjected to external pressure before testing. In CU test, the sample is first consolidated under a constant load and then tested, while in UU test, the sample is tested without any consolidation. This difference in procedure affects the results and interpretations of the tests.
Consolidation is important in soil testing because it simulates the gradual increase in load that a soil layer experiences in real-life situations. This allows for a more accurate assessment of the soil's behavior and strength under different loading conditions.
Consolidated undrained test can provide more accurate results compared to unconsolidated undrained test, as it takes into account the effects of consolidation on the soil sample. It is also preferred for cohesive soils as it can better capture their behavior under load and provide more reliable data for engineering design.
Consolidated undrained test should be used when the soil being tested is expected to experience gradual increase in load, such as in cases of embankments, dams, or earth retaining structures. It is also recommended for cohesive soils that may undergo significant changes in volume under load.
The main limitation of consolidated undrained test is that it does not take into account the effects of drainage in the soil sample. This can be problematic for soils that are prone to high levels of pore pressure buildup, as the test does not allow for dissipation of excess pore water pressure. Additionally, it may not accurately represent the behavior of soils that experience rapid loading or cyclic loading.
