The design and test procedures of a triaxial consolidation test apparatus, restoring the condition of in-situ one-dimensional consolidation, are described. Results of comparison between the triaxial and standard consolidation tests on an undisturbed clay have shown that;
　1) Relative amount of secondary compression in the triacial consolidation test is smaller than that in the standard test.
　2) The value of coefficient of consolidation obtained in the triaxial consolidation test is about half the value in the standard test.
　Coefficient of earth pressure at rest K0 is measured in the triaxial consolidation test. In consolidation processes, K0 is equal to unity at the start or consolidation, then it decreases with time and tends to be about 0.5 at the completion of consolidation. In the rebound processes, however, K0 increases more or less with time. K0 values at the completion of rebound are found to increase with the　overconsolidation ratio.