不同破坏准则下水合物沉积物的统计损伤模型

利用连续介质损伤力学理论与概率统计方法，假设水合物沉积物微元强度服从Weibull分布，在现有室内三轴和直剪试验数据的基础上，考虑水合物饱和度的影响，分别建立了基于修正Mohr-Coulomb强度准则和修正Lade-Duncan强度准则的水合物沉积物统计损伤本构模型，并将理论模型预测结果与室内试验进行对比，验证了模型的有效性。结果显示：基于Lade-Duncan强度准则的损伤本构模型能够较准确地反映水合物沉积物峰前的应力?应变规律，而基于修正Mohr-Coulomb强度准则的损伤本构模型则对于模拟峰后的应变软化特征有较好的适用性。对于在低有效围压、不同水合物饱和度条件下的水合物沉积物，基于修正Mohr-Coulomb强度准则的损伤本构模型的模拟精确性要优于基于修正Lade-Duncan准则的损伤模型；而在同一饱和度、不同有效围压条件下，基于修正Lade-Duncan强度准则的损伤本构模型的模拟结果则要优于基于修正Mohr-Coulomb强度准则的损伤本构模型。

Statistical damage models for hydrate-bearing sediments based on different failure criteria

On the basis of triaxial and direct shear tests, modified Mohr-Coulomb strength criterion and the modified Lade-Duncan strength criterion in which the effect of methane hydrate saturation is considered are used to describe the strength of micro-elements for methane hydrate-bearing sediments. Based on the results, statistic damage constitutive models for methane hydrate-bearing sediments are put forward using the theory of continuous damage mechanics together with statistical theory. Then, by comparing the results obtained from theoretical models to those from laboratory tests, the validity of statistical damage models based on different strength criteria are verified. The results show that the damage constitutive model based on the modified Lade-Duncan strength criterion can accurately simulate the stress-strain curves of hydrate-bearing sediments before reaching the peak stress, while the damage constitutive model based on the modified Mohr-Coulomb strength criterion can capture the strain-softening characteristics after the peak stress observed in the experiments. For the experiments with different hydrate saturations and lower effective confining pressure, the simulation accuracy of the damage constitutive model based on the modified Mohr-Coulomb strength criterion is better than that based on the modified Lade-Duncan criterion. On the contrary, under the same hydrate saturation and different effective confining pressures, the simulation results of the damage constitutive model based on the modified Lade-Duncan strength criterion are better than those based on the modified Mohr-Coulomb strength criterion.