摘要
研究了岩样在单轴压缩条件下轴向应力-侧向或环向变形的全程曲线特征。基于考虑峰值剪切强度后微小结构之间相互影响和作用的梯度塑性理论,得到了由于剪切局部化而引起的侧向塑性变形。利用虎克定律描述了试件的弹性变形,得到了轴向应力-侧向变形全程曲线的解析解。在软化阶段,试件中部侧向变形及对靠近试件上端或下端部位的侧向变形并不相同。与轴向应力-应变曲线可能出现的回跳现象类似,试件中部轴向应力-侧向应变曲线也可能出现回跳现象。在应变软化阶段,与应力-侧向应变曲线相比,应力-环向应变曲线不容易发生回跳现象。若在试件内部出现多条剪切带,则应该以等效剪切带宽度替代本文中的剪切带宽度。随着剪切带倾角、内部长度参数的降低、剪切模量的增加及弹性模量的降低,轴向应力-侧向应变曲线越陡:甚至能出现弹性回跳。
Characteristics of complete axial stress-lateral (or circumferential) deformation curves for rock specimen subjected to shear failure are analyzed in uniaxial compression. Based on gradient-dependent plasticity considering interactions and interplaying among microstructures beyond the peak shear stress, the plastic lateral deformation due to shear strain localization is derived. The elastic lateral deformation is obtained according to Hooke's law in elastic mechanics. The total lateral deformation depending on the axial compressive stress is determined by the sum of the plastic and elastic deformations and then the analytical solution of complete stress-lateral deformation curves is proposed. In strain softening stage, the lateral deformation is non-uniform in different sections of specimen due to the assumption that a single shear band appears in the central section of specimen. Similar to possible snap-back of axial stress-axial strain curves, axial stress-lateral deformation curves can exhibit snap-back behavior. After shear localization occurs, compared with axial stress-lateral strain curves, axial stress-circumferential strain curves cannot exhibit easily snap-back behavior. If multiple shear bands are formed in rock specimen, then the thickness of shear band should be substituted for the equivalent thickness of shear band. The analytical results obtained show that lower inclination angle of shear band, lower characteristic length of rock material, larger shear softening modulus or lower elastic modulus can lead to steeper axial stress-lateral strain curves and even can cause snap-back in strain softening stage.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2004年第6期904-908,共5页
Rock and Soil Mechanics
基金
国家自然科学青年基金项目(编号:50309004)
关键词
梯度塑性理论
局部化
侧向变形
环向变形
解析解
回跳
等效剪切带宽度
gradient-dependent plasticity
localization
lateral deformation
circumferential deformation
analytical solution
snap-back
equivalent thickness of shear band
