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统一黏塑性理论假设材料的应变仅由弹性应变和黏塑性应变组成。包含应力的黏塑性应变率表达方式,可以清晰地体现岩石材料应力增长率随应变加载速率相关的特性、在持续的偏压下的蠕变特性以及在恒定的应变下的松弛特性,但微分方程表示的本构模型在实际运用中存在计算上的困难。将无损伤Lemaitre统一黏塑性模型转换成关于应力的积分形式,并运用一致渐进展开算法得到其近似解,最后建立了基于近似解的牛顿迭代格式。开展了不同围压条件下泥质粉砂岩的三轴松弛试验,并将试验数据用于黏塑性模型的参数反分析,结果表明模型能够较好地反映泥质粉砂岩在长期作用下的力学行为特征。
The unified theory of viscoplasticity assumes that the strain of a material consists only of elastic strain and viscoplastic strain. The expression of viscoplastic strain rate including stress can clearly reflect the characteristics of rock material stress growth rate with strain loading rate, creep characteristics under constant bias and relaxation characteristics under constant strain. However, the differential equation The constitutive model represented has computational difficulties in practical application. The nondestructive Lemaitre unified viscoplastic model was transformed into the integrated form of stress, and its approximate solution was obtained by using the uniform evolutionary expansion algorithm. Finally, the Newton iterative scheme based on the approximate solution was established. The triaxial relaxation tests of muddy siltstone under different confining pressure were carried out. The experimental data were used to inversely analyze the parameters of viscoplasticity model. The results show that the model can well reflect the mechanical behavior of muddy siltstone under long-term action feature.