湿载耦合作用下黄土结构性损伤演化及本构关系

STRUCTURAL DAMAGE EVOLUTION AND CONSTITUTIVE RELATION OF LOESS UNDER COUPLING OF STRESS AND MOISTURE

针对增湿、加荷作用下黄土结构性损伤演化的变形问题,通过压缩变形特性和三轴剪切变形特性,分析黄土结构性损伤的宏观力学反映。分析结果表明,土的含水量增加、固结压力增大和剪切作用均会引起黄土的结构性损伤。随着含水量的增大,压缩作用损伤和剪切作用损伤更加突出;固结压力较大时,压剪作用对土原生结构破损更突出,其次生结构和剪缩性增强。将结构性损伤土视为原状结构体和完全损伤体的复合体,综合应用应力比损伤方程和应变损伤方程,在比较原状土与饱和重塑土应力比建立结构性参数的基础上,建立黄土的结构性损伤演化方程;在原状结构体服从弹性定律、完全损伤体服从修正剑桥模型的基础上,从结构性损伤土变形为原状结构体弹性变形和完全损伤体弹塑性变形叠加出发,建立结构性土的损伤弹塑性本构方程。同时,比较分析不同湿度黄土试验测试的应力–应变曲线和损伤弹塑性本构方程描述的理论曲线,两者比较一致,验证了该本构关系的合理性。

In order to study the deformation of destructured loess induced by structural damage under coupling of stress and moisture, the macromechanics reflection of structured loess is analyzed, which is induced by structural damage development, by analyzing the deformation of structured loess under compression tests and triaxial tests. The analysis result shows that water content increasing, consolidation pressures increasing, and shearing would cause structural damage of loess. With the water content increasing, structural damage of loess is more prominent by compression and shearing. When consolidation pressures are much larger, structural damage of intact loess by compression and shearing is significant, and the secondary structure and shearing-compression are increasing. Based on structural parameter proposed by comparing with the stress ratios of intact loess and saturated remolded loess during triaxial experiments, and utilizing the stress ratio damage equation and strain damage equation, the structural damage evolution equation is proposed by regarding structural damage loess as complex materials composed of intact loess and destructured loess. Based on the intact loess following Hooke＇s law and normal consolidation loess following modified Cambridge model, the elastoplastic damage constitutive equation is proposed by regarding deformation of destructured loess as elastic deformation of intact loess and elastoplastic deformation of normal consolidation loess. Meanwhile, the rationality of constitutive relationship is tested and verified by comparing and analyzing test curves under different moistures and theoretical curves described by the elastoplastic constitutive model proposed in this paper.