JIANG Ming-jing, FU Chang, HE Jie, et al. Distinct element simulations of exploitation of methane
hydrate bearing sediments with different methods[J]. 2015, 36(S2): 639-647.
DOI:
JIANG Ming-jing, FU Chang, HE Jie, et al. Distinct element simulations of exploitation of methane
hydrate bearing sediments with different methods[J]. 2015, 36(S2): 639-647.DOI: 10.16285/j.rsm.2015.S2.091.
Distinct element simulations of exploitation of methane
hydrate bearing sediments with different methods
天然气水合物以胶结及孔隙填充等形式存在于深海能源土中,开采时因其分解会劣化地层力学特性进而引发海底事故,使得人们对能源土开采过程进行中力学特性的变化愈发重视。在前期室内试验的基础上,将一个温度-水压-力学二维微观胶结模型引入离散元商业软件PFC2D中,通过对排气、排水性较好的土体进行升温及降压法开采进行数值模拟,并将模拟结果与相同条件下的室内试验结果对比,验证了该胶结模型的适用性。进一步分析了颗粒接触分布与颗粒平均纯转动率(averaged pure rotation rate
Methane hydrate bearing sediments(MHBS) are usually found undersea
which is generally categorized into different types
i.e. bond
pore-filling and so on. The mechanical properties of MHBS will be deteriorated as methane hydrate (MH) dissociates and many marine accidents will be caused; thus a lot of attention has been attracted in investigating MHBS properties changes during exploitation. A newly proposed 2D temperature-water pressure-mechanical bond model is implemented into PFC2D
the commercial software of the distinct element method (DEM)
to simulate the dissociation of MH by thermal recovery and depressurization using soil in good exhaust and drainage conditions. By comparison with laboratory test results
it is validated that the newly proposed model is applicable to simulate the mechanical behavior of MHBS. At the same time
the micromechanical properties are also analyzed. With temperature increasing during thermal exploitation
the anisotropic degree of total contact distribution increases; the amount of bond contact
whose principal direction is horizontal all the time
decreases and the amount of unbonded contact
whose principal direction is vertical all the time
increases; the value of averaged pure rotation rate (APR) and its concentration degree increases all the time. With back (water) pressure decreasing during exploitation by depressurization
the total contact distribution changes from isotropic to anisotropic with a vertical principal direction
and the value of APR is small and uniformly distributed. After the recovery of back water pressure
the sample is damaged further
and the anisotropic degree of total contact distribution increases. Besides
the value of APR increases and the concentration degree of positive and negative value increases.