基于CT技术的原状黄土细观结构动态演化特征

发布时间：2018-05-06 10:02

本文选题：土壤 + 力学特性　；参考：《农业工程学报》2017年13期

【摘要】：非饱和原状黄土具有典型的结构性,结构性对其强度、变形等特征产生重要影响,但结构性对其屈服特性的影响却鲜有报道。为研究结构性对非饱和原状黄土在各向等压加载过程中的屈服特征影响规律,以非饱和土多功能三轴仪为研究工具,对4个非饱和原状黄土试样进行控制吸力的各向等压加载试验。借助CT(computerized tomography)技术,对变形和排水稳定后黄土试样进行实时动态扫描,将加载过程中的宏观力学指标与细观扫描数据联系,以明晰原状黄土加载过程中的结构演化规律。结果表明:原状黄土屈服前,CT数ME增长缓慢,说明结构性起到了抵御外部荷载的作用;当试样屈服后,ME呈线性增长趋势,试样进入塑性硬化阶段,结构性的作用明显降低。吸力增大时,原状黄土结构性对其力学变形特征影响较小;而吸力减小时,土颗粒之间水膜润滑作用明显,结构性对于抵抗外部荷载的作用增强。施加净平均应力后的原状黄土,其内部的孔洞和孔隙会减小,但不会完全闭合,这与新形成的结构能抵御外部荷载有关。研究结果可为进一步建立原状黄土结构性本构模型提供借鉴。
[Abstract]:Unsaturated undisturbed loess has a typical structure, which has an important influence on its strength, deformation and other characteristics, but the influence of structure on its yield characteristics is rarely reported. In order to study the effect of structural structure on yield characteristics of unsaturated undisturbed loess under various isobaric loading conditions, the multifunctional triaxial apparatus of unsaturated soil was used as a tool. Four unsaturated undisturbed loess specimens were subjected to isobaric loading under controlled suction. With the help of CT(computerized tomographic technique, the deformation and drainage stability of loess samples were scanned in real time, and the macroscopic mechanical indexes during loading were connected with the mesoscopic scanning data to clarify the structural evolution law of undisturbed loess during loading. The results show that the growth of CT number ME is slow before the loess yield, which indicates that the structure has the function of resisting the external load, and the effect of the structure is obviously reduced when the specimen is in the plastic hardening stage. With the increase of suction, the structure of undisturbed loess has little effect on its mechanical deformation characteristics, but when the suction decreases, the lubricating effect of water film between soil particles is obvious, and the effect of structure on resisting external load is enhanced. When the net average stress is applied to the original loess, the internal pores and pores will decrease, but will not be completely closed, which is related to the ability of the newly formed structure to resist external loads. The results can be used for reference in the further establishment of structural constitutive model of undisturbed loess.
【作者单位】：空军工程大学机场建筑工程系;后勤工程学院土木工程系;火箭军驻北京地区军事代表局;榆林学院建筑工程学院;
【基金】：国家自然科学基金项目(51509257,11672330)
【分类号】：TU444

【参考文献】