含天然气水合物沉积物损伤统计本构模型

A statistical damage constitutive model of hydrate-bearing sediments

水合物含量、有效围压是影响含天然气水合物沉积物力学性质的主要因素,在忽略其他次要因素(包括水合物种类、试样颗粒大小、试验条件等)的情况下,水合物含量和有效围压是决定试样弹性模量的两个关键参数。在分析等效弹性模量与水合物含量相互关系的基础上,考虑有效围压的影响,建立了弹性模量与有效围压的幂函数关系;同时采用Drucker-Prager破坏准则来表示含天然气水合物沉积物微元强度,并假设其微元强度服从Weibull分布,从而建立了含天然气水合物沉积物的损伤统计本构模型,与不同有效围压下的试验结果及已有研究成果相比较,表明了所建模型能够很好地模拟三轴剪切条件下含水合物沉积物试样的应力-应变关系特性。此研究成果可对含天然气水合物沉积物工程性状的数值模拟提供参考。

Hydrate saturation and effective confining pressure can significantly influence the mechanical behaviour of hydrate-bearing sediments.In the case,that the effects of the hydrate type,grain size,and testing conditions are excluded,these two variables are the critical factors that determine their elastic modulus.Based on the relationship between equivalent elastic modulus and hydrate saturation,a power function is established for the damage variable,which takes into account the influence of effective confining pressure.Drucker-Prager failure criterion is adopted to describe the strength of a micro-element of hydrate-bearing sediments.By assuming that the variation of the micro-element strength follows Weibull’s distribution,a statistical damage constitutive model of hydrate-bearing sediments is developed.By comparing the simulated results with the experimental data available in the literature,we show that the proposed model can describe the stress-strain behavior of the hydrate-bearing sediments very well under the triaxial shearing condition.The results can provide reference for numerical simulation of engineering properties of gas hydrate sediments.