不同中主应力条件下粗粒土应力变形特性试验研究

采用长江科学院大型真三轴仪,对粗粒土进行了一系列不同中主应力系数条件下的真三轴试验和平面应变试验,研究了中主应力对粗粒土的应力变形的影响规律。试验结果表明,中主应力比b一定时,应力–应变关系曲线的斜率和峰值强度随着固结压力的增大而增加,在低围压条件下,体变关系曲线在加载过程中表现为先剪缩后剪胀的特性,而在高围压下,整个加载过程中表现剪缩的特性;固结压力一定时,随着b值的增大,应力在峰值后的软化现象愈加明显,体变全过程曲线表现出剪胀特征对应的固结压力越来越低,小主应变–大主应变关系曲线的斜率绝对值增大。研究成果可为进一步研究粗粒土的本构模型奠定基础。

Experimental study on stress-strain characteristics of coarse-grained soil under different intermediate principal stresses

In order to study how the intermediate principal stress (short for IPS) influences the stress-strain characteristic of coarse-grained soil, using the large-scale true triaxial apparatus developed by Changjiang River Scientific Research Institute (CRSRI), a series of true triaxial compression tests and plane strain tests are carried out. The test results show that: (1) When the IPS ratio (also called b value) is a constant, the slope of stress-strain curves and the peak strength increase with the increasing consolidation pressure; (2) Under the relative low confining pressure conditions, with the increasing axial strain, the volumetric strain exhitits shear contracting firstly and then dilating, but when the confining pressure rises to a higher level, the volumetric strain shows shear contracting in the whole deformation process; (3) When the consolidation pressure is the same, with the increase of b value, the stress softening effect after the peak stress becomes more obvious. Under a relative lower consolidation pressure, the volumetric strain exhibits the characteristics of shear contracting firstly and then dilating. For the relation curves between the minimum and the maximum principal strains, the absolute value of slope also increases. The above results can be treated as the research foundation in establishing the constitutive model for coarse-grained soil under complex stress paths.