Improved simplified calibration procedure for a high-cycle accumulation model

Abstract

The high-cycle accumulation (HCA) model proposed by Niemunis et al. [16] predicts permanent deformations due to a drained cyclic loading with many small cycles (i.e. N≥103 cycles with strain amplitudes εampl≤10−3). The strain amplitude is the most important influencing parameter of the rate of strain accumulation ε̇acc. Based on tests on a medium coarse sand, a square relationship ε̇acc~(εampl)2 has been used in the HCA model so far. The new test results presented in this paper indicate, however, that the exponent of the amplitude-dependence may vary between 1.3 and 2.4, depending on the tested material. This comes out of 150 drained cyclic triaxial tests with 105 load cycles performed on 14 clean quartz sands with specially mixed grain size distribution curves. Consequently, an additional material constant Campl has been introduced into the HCA model describing the amplitude dependence according to ε̇acc~(εampl)Campl. The additional parameter requires a revision of the simplified calibration procedure proposed by Wichtmann et al. [24] which uses correlations between the HCA model parameters and granulometric (d50, Cu) or index properties (emin). Furthermore, the new cyclic test data reveal that the existing correlations are inappropriate for well-graded granular materials (Cu≥5). Enhanced correlations suitable also for more well-graded sands are proposed in the paper. The possible error of a HCA model prediction with parameters fully or partly determined from the correlations is discussed.