Dear Leidy,

Your question is very interesting and you have mentioned clearly that in UU test the soil sample is not allowed to consolidate during the shearing but in CU test the shear load is applied after completing the consolidation. In CU test in the initial stage, the soil is consolidated and shear is applied in the second stage by increasing the additional axial load. This clearly shows that the additional load is required to make soil fail is high in CU test as compared to UU test. Here, i would like to mentioned that the above statement is true for the initial moisture content and void ratio is same for both the specimen tested for UU and CU test..ok all the best in your research..

Dear Leidy. I assume you did not measure the excess pore pressures during undrained shear in the CU tests?, because if you did, which is the current practice, you will obtain effective strength parameters in the CU test, and the results are not comparable. Even, if you did not measure excess pore pressures during undrained shear, you will have different conditions, and rather than asking what is lower or higher, you should figure out which test is representing better your conditions in the field. In CU tests, you will change the effective stresses during consolidation, thus, the larger the consolidation stress the larger the shear strength you must obtain for each point in the test. That can represent stage construction where you may have change in the in-situ s'vc due to preconstruction and a rapid failure. The UU on the other hand represents rapid failure but additionally you never change the effective stress before shear, so the condition is always undrained. Please be careful that running UU tests on unsaturated clays may give you unrealistic phi values.

Mr.Elimar,

I fully agree to your point and thank you for giving more details on the discussion with highlighting the importance behind application rather than comparison of UU and CU results.

Thanks Karthigeyan, regards.