含气水合物沉积物弹塑性损伤本构模型探讨

A constitutive model coupling elastoplasticity and damage for methane hydrate-bearing sediments

天然气水合物的开采会带来一系列的岩土工程问题,为了保障相关工程设施的安全,有必要建立一个合理的水合物沉积物本构模型。通过深入分析水合物沉积物力学特点,从颗粒间的作用机制出发,认为水合物沉积物的力学响应是沉积物中土体颗粒间摩擦与水合物胶结二者共同作用的结果;考虑到摩擦与接触特性不同的力学机制,分别采用修正剑桥模型和弹性损伤模型对土体骨架及水合物胶结的应力-应变关系进行描述;通过假定水合物胶结的损伤演化规律,并认为在受力变形过程中二者的应变始终相等,初步建立了一个水合物沉积物的弹塑性损伤本构模型。不同水合物饱和度沉积物应力-应变曲线的模型预测结果与室内三轴排水试验结果吻合良好,表明了所建模型的可行性和合理性。

The extraction of methane hydrate in the seabed will result in a series of geotechnical engineering problems and disasters. In order to ensure the safety of the related engineering facilities during the extraction, it is necessary to build reasonable constitutive model for methane hydrate bearing sediments. Based on the thorough study of the geomechanical characteristics of hydrate bearing sediments and the contacts between soil grains, the authors suppose that the geomechanical behavior of hydrate bearing sediments resulting from the combination of the friction between soil grains and cementation due to methane hydrate. Considering the different mechanical mechanisms of the friction and cementation, the modified Cam-clay model and elasticity damage model are employed to describe their mechanical responses respectively. By assuming that soil skeleton and cementation have the same strain during the loading, a constitutive model coupling elastoplasticity and damage for methane hydrate bearing sediments is then established based on a simplified damage evolution law. The calculated results are compared with the experimental data of methane hydrate bearing sediments with different hydrate saturations. It is shown that the proposed model can describe the stress-strain behavior of methane hydrate bearing sediments quite well, which demonstrates the validity and reasonability of this model.