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The comparisons between model predictions and type one test are shown in Figure 14 in terms of the stress-strain-volume relationship on NRFM. The unextended M-A model overestimates the deviatoric stress especially under unloading-reloading conditions (Figure 14(a)), while the extended model proposed in this paper could well predict the stress-strain-volume behaviour of NRFM under CSR loading (Figure 14(b)).
The extended model considering the effect of stress path can well capture the stress-strain relationships of NRFM (Figure 15(b)), while the model without considering the effect of stress path cannot well represent the stress-strain relationship (overestimating the dilation of the NRFM).
A micromechanical model considering the effect of stress path was proposed for NRFM. The main conclusions and discussion are summarized below.
Corresponding to these engineering conditions, two types of triaxial drained tests were conducted to simulate the actual stress variations of the NRFM. In the first type of test, no failure occurred, and the NRFM exhibited contraction during the entire loading period.
At the particle length scale, the movements of the local contacted planes can well reflect the deformation behaviour of the NRFM sample.
For the NRFM under unloading-reloading conditions, the new stiffness of the particles can well predict the linear relationship of the stress-strain curves; for the tests under the stress transition path, the local dilatancy angle can well describe the volume of the sample changing from contractancy to dilatancy.
Caption: FIGURE 2: Particle size distribution of NRFM.
Caption: FIGURE 11: Stress-dilatancy relations for selected contact plane orientations for NRFM.
Caption: FIGURE 13: Comparisons between three types of model simulations and test results on NRFM: type one test, (a) and (c): type two test, (b) and (d).
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- NRG Energy, Inc.