含水合物沉积物的弹塑性本构模型

土的密度对其力学特性具有明显影响.水合物以一种固相赋存于沉积物的孔隙中,使得水合物的含量和其赋存形式都会影响含水合物沉积物(GHBS)的密度,因此在研究和描述含水合物沉积物的力学性质时应考虑水合物含量和赋存形式对其密度的影响.本文基于黏土和砂土统一的本构模型(CSUH模型),首先建立水合物体积分数与压硬性参量的关系式来反映水合物对沉积物压缩规律的影响.其次,为了合理考虑水合物含量和赋存形式对沉积物密度的影响,建立了可以描述有效初始孔隙的计算式,并将其引入到状态参量中来描述水合物对沉积物剪胀性和峰值强度的影响.最后,结合CSUH模型中水滴形屈服面,建立了一个含水合物沉积物的弹塑性本构模型.通过与室内试验结果比较,验证了该模型不仅能够合理地描述不同赋存形式、不同水合物含量下含水合物沉积物的应力应变关系,而且在描述具有相同赋存形式含水合物沉积物的力学特性时,不同的水合物含量只需采用一组参数. 

AN ELASTOPLASTIC CONSTITUTIVE MODEL FOR GAS HYDRATE-BEARING SEDIMENTS 1)

The density is one of the most important factors for the mechanical behavior of soil. The content and occurrence modes of hydrates obviously affect the density of gas hydrate-bearing sediments (GHBS) because hydrates exist in the pore of sediment as solid phase. Therefore, it is necessary to consider the effect of the hydrate content and occurrences to describe the mechanical properties of hydrate sediments well. In this paper,based on the unified hardening model for clays and sands (CSUH model), the relation between the volume fraction of hydrate and the compressive hardness parameter is firstly established to reflect the influence of hydrate on the compressibility of sediments. Secondly, in order to consider the influence of hydrate content and occurrence modes on sediment density, we propose a formula to describe the effective initial void ratio, and it is then introduced into the state parameter to describe the influence of hydrate on dilatancy of sediment. Finally, combining the drop-shaped yield surface of the CSUH model, an elastoplastic constitutive model for GHBS is developed. Compared with the laboratory test results, it is verified that the model can reasonably describe the mechanical behaviors of GHBS containing hydrates with different occurrence modes and contents. For the same occurrence mode but different contents, the set of parameters is the same.