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Methane hydrate as a “new energy”                                 259

           sample, equivalent to an experimental test. The controlling parameters are given in
           Fig. 7.22.
              The DEM simulations of thermal recovery are shown in Fig. 7.23, while the DEM
           simulations of depressurization process are illustrated in Fig. 7.24. By comparing
           Figs. 7.16 and 7.19 with Figs. 7.23 and 7.24, it is evident that the DEM simulations
           of thermal recovery and depressurization process capture the sample responses as
           observed in laboratory tests. The most important advantage of DEM simulation is that
           it can visualize the micromechanism in a granular material. Some good examples are
           given in the following section.


           7.5.2 Micromechanism associated with MH dissociation

           There are two types of contacts in MHBS, i.e., the bonded contact and the unbonded
           contact. In order to study the effects of temperature and applied deviator stress during
           thermal recovery, the distributions of the total, bonded, and unbonded contacts in


                                                          Fig. 7.22 Temperature and
                                                          confining pressure vs time in
                                                          laboratory test and DEM
                                                          simulation (A) thermal
                                                          recovery and
                                                          (B) depressurization [19].
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