含水合物泥质粉细砂三轴试验及本构模型

Triaxial Test and Constitutive Model for Hydrate-bearing Clayey Sand

为了得到不同有效围压和水合物饱和度对含水合物沉积物强度和刚度的影响规律,并得出相应数学表达式,以南海北部沉积物土样级配作为参考,配制人工泥质粉细砂,利用自主研发的含水合物沉积物三轴试验机,制备不同饱和度的含CO 2水合物沉积物,在1,2,4 MPa有效围压下等向固结并进行三轴剪切试验。由于围压能自动根据气压的变化而变化,所以在水合物生成过程中有气体消耗但有效围压保持不变。试验结果表明:初始弹性模量随水合物饱和度的增加而增加,与有效围压无关;初始泊松比随着有效围压增加而减小,而随水合物饱和度的增加而增加;黏聚力随水合物饱和度的增加而增加,而内摩擦角与水合物饱和度无关。在邓肯-张模型的基础上,引入参数水合物饱和度,建立了含水合物沉积物的非线性弹性本构模型。最后,用试验数据对模型进行了验证,其结果符合较好。

Triaxial shear tests were conducted on self-prepared hydrate-bearing sediments to obtain the influences of effective confining pressure and saturation on the strength and rigidness of hydrate-bearing sediments.The test specimens were made from artificial clayey fine sand in reference to the particle size distribution of sediment in the north part of South China Sea.CO 2 hydrate-bearing sediments with different saturations were prepared by a self-developed triaxial test machine,and the triaxial shear tests were carried out under the effective confining pressure of 1 MPa,2 MPa,and 4 MPa.As confining pressure changes automatically with gas pressure,the effective confining pressure remained unchanged during the formation of hydrate when gas was consumed.The experimental results reveal that the initial elastic modulus increased with the rising of hydrate saturation,while independent of the effective confining pressure.The initial Poisson ratio decreased with the increase of effective confining pressure while grew with the rising of hydrate saturation.The strength index cohesive force increased with the increase of hydrate saturation,while the internal friction angle was independent of hydrate saturation.In addition,the nonlinear elastic constitutive model for hydrate-bearing sediment was established by introducing a parameter hydrate saturation based on Duncan-Chang’s model,and the proposed model was validated by test data.