含水合物砂土力学特性及本构模型

Mechanical Properties and Constitutive Model for Hydrate-bearing Sand

天然气水合物(以下简称水合物)的不当开发可能会带来一系列的地质灾害和环境问题,因此,开展含天然气水合物地层开采过程中的安全稳定性评估显得尤为重要,而建立能有效描述含水合物沉积物的力学行为的本构模型是安全稳定性分析的核心前提。在分析含CO_2水合物砂土的三轴力学特性的基础上,把含水合物沉积物视为水合物和土颗粒骨架组成的复合胶结性材料,参考胶结土体的建模思路,引入附加内变量描述水合物对土体的胶结影响,建立了含水合物砂土的屈服函数和非关联流动法则,建立了含水合物砂土的本构模型。通过模型验证及分析,模型能较好地模拟不同围压下和不同水合物含量下含水合物砂土的应力应变曲线,反映含水合物砂土的力学特性。

A series of geological disasters and environmental problems may occur during gas hydrate exploitation.So it is crucial to evaluate the stability of gas hydrate-bearing sediment. In the whole evaluation,developing an effective constitutive model is a key step. Based on the mechanical characteristics of CO_2hydrate-bearing sand performed by author previously,a constitutive model was developed referring to the approach of developing a constitutive model for cement soils. In the proposed model,hydrate-bearing sediment was considered analogous to the bonding soil consisting of hydrate and soil skeleton. In addition,additional internal variables were employed to describe the bonding properties of hydrate to soil. Finally,the stress-strain relationship curves of CO_2hydrate-bearing sand were used to verify the proposed constitutive model. It is shown that the proposed model can describe the stressstrain behavior of CO_2hydrate-bearing sediments primely,which demonstrates the validity and reasonability of this model.