天然气水合物沉积物的强度模型

Strength model for methane hydrate-bearing soil

建立有效描述含天然气水合物(以下简称"水合物")沉积物强度特性的强度模型是水合物开发前必须解决的关键问题之一。在调研前人对含水合物沉积物强度试验结果的基础上,分析了水合物存在对土体强度的两种影响机理,分别是水合物作为持力体分担土骨架部分应力以及土颗粒之间的胶结作用。在此基础上,把含水合物沉积物视为复合材料(土颗粒骨架相和水合物相复合)进行考虑,建立了含水合物沉积物的强度模型,该模型能较好地反映不同水合物赋存模式、不同水合物含量、不同围压作用下的含水合物沉积物的强度特性。同时,该模型还能很好地反映细粒土中水合物形成后内摩擦角的减小。然而,由于前期相关试验数据的缺乏,该模型的一些关系式还有所欠缺,在后期的工作中需要进一步的优化。

The strength model of methane hydrate-bearing soil is one of the vital problems to be solved in hy-drate exploiting. In this paper, based on previous tests of methane hydrate-bearing soils on strength, two reinforcing mechanisms are analyzed. The reinforcing mechanisms include hydrate transfer into bearing body which can load part stress from soil frame and cementing action between soil particles. Based on the above analyses, methane hydrate-bearing soil is considered to be composite material, which consists of soil particle phase and hydrate phase, then a strength model is established. The strength model can predict the strength values in condition of various occurrence models, various saturations and various confining pressures for methane hydrate-bearing soils satisfactorily. Meanwhile, the dropping characteristics of friction angles of fine-grained soil with hydrate are taken into account as increasing saturation of hydrate. However, in short test data on strength, some formulas are not good enough and should be optimized in the future works.