Use of Oedometer Equipped with High-Suction Tensiometer to Characterize Unsaturated Soils

Suction-controlled triaxial tests have been used extensively to characterize unsaturated soils. However, this type of tests requires sophisticated and therefore expensive equipment and is very time-consuming. These limitations have been the main obstacles for research, dissemination, and implementation of unsaturated soil mechanics in engineering practice. Compared with the suction-controlled triaxial test apparatus, an oedometer for saturated soils is much simpler. It is 300 to 400 times more efficient to run a constant water content oedometer test for unsaturated soils than a suction-controlled triaxial test. The major disadvantage of the constant water content oedometer test is that its stress path is difficult to analyze and no method is available to take advantage of the test results for constitutive modeling purposes. In this paper, a conventional oedometer for saturated soils was modified to characterize unsaturated soils under constant water content compression. An analysis method was also developed to use the results directly from constant water content oedometer tests for constitutive modeling. A series of constant water content oedometer tests was used to demonstrate the application of the proposed method from which the capability and the effectiveness of the proposed developments were evaluated. With developments in equipment and analysis, it is now possible to characterize unsaturated soils rapidly in a simple and efficient way.