Drained creep behavior of marine clays

Long-term, drained triaxial creep tests were conducted on undisturbed and reconstituted specimens of a North Central Pacific clay. The undisturbed specimens were obtained from cores taken in water depth of about 5800 m and the reconstituted samples were prepared from remixed and reconsolidated tanks of sediments. A power law, with ma being the principal creep parameter, is a good predictor of the axial strain behavior with a constant value of ma for up to 6-9 months, but decreasing values thereafter. The results from the reconstituted set of samples confirms that ma is time dependent, and to a lesser degree, stress dependent. High temperature results in higher overall strain rates and lower ma values at equivalent times, compared to a one-year undisturbed illite test. The results indicate that the strain rates would have reached the tertiary creep stage, resulting in rupture if given enough time, particularly at the higher stress level of 60% of the failure stress. The tests on both undisturbed and reconstituted samples showed that there was a significant increase in strength during long-term creep with essentially no volume change.