摘要
针对白鹤滩地下厂房开挖过程中所揭露的力学响应行为十分复杂的错动带,为研究其在高应力条件下的加卸荷力学特性,开展一系列不同应力水平和应力路径下的不排水三轴常规加、卸荷试验。研究结果表明:(1)卸荷过程中,错动带卸荷应力–应变曲线特征与初始围压相关性很大,错动带向卸荷方向回弹变形显著,从卸围压开始即表现出强烈的剪胀现象;卸轴压卸围压方案比增轴压卸围压方案的侧向扩展变形表现更为显著;且在试样表面都出现了张/张剪裂纹。(2)卸荷应力路径下,错动带变形模量劣化效应十分明显,随围压的减小而逐渐降低,基本呈三次多项式递减;体积模量随体积应变的增加而减小,整体呈负指数形式降低;泊松比则随体积应变逐渐增加,整体呈近似抛物线形式递增。(3)相同初始围压条件下,相较于加荷条件,卸荷条件下错动带的破坏应力有所降低,内摩擦角明显增大,而黏聚力则明显降低;卸轴压卸围压方案下的破坏应力劣化更显著。试验所采用的应力水平和应力路径基本涵盖和反映了错动带在洞室开挖过程中所经历的复杂的应力重分布过程,具有一定的代表性,地下厂房开挖后高边墙错动带黏聚力和内摩擦角取值基本可参考卸轴压卸围压应力路径下天然含水率错动带的试验结果,为后续进一步讨论错动带强度特征并建立错动带本构模型提供了有效依据。
For staggered zones revealed in Baihetan underground powerhouse with complex mechanical response behavior, a series of undrained triaxial conventional and unloading tests under different stress levels and paths were carried out to study the mechanical properties of staggered zones under loading and unloading in high stress conditions. In the unloading process, the unloading stress-strain curves were related to the initial confining pressure, deformation rebounded in the direction of unloading and strong dilation occurred from the start of unloading. The lateral expansion in the course of the unloading of the axial and confining pressure was more significant than that in the course of loading axially and unloading of confining pressure. The tensile-shear cracks appeared in the surface of the staggered zone samples. For the stress unloading path, the deformation modulus was degraded with the decrease of confining pressure, which was described with a cubic polynomial. The bulk modulus was decreased exponentially with the increasing of volumetric strain. The Poisson＇s ratios of interlayer zone samples increased gradually with a parabola trend. In comparison to the loading conditions, the failure stress was decreased and the internal friction angle was increased and the cohesion was reduced significantly. The degradation in the course of unloading of axial and confining pressure was more significant than that in course of loading axially and unloading of confining pressure.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2016年第6期1090-1101,共12页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金国际合作重大项目(41320104005)
国家自然科学基金重点项目(11232024)
国家自然科学基金青年基金项目(51309219)~~
关键词
水利工程
错动带
卸荷试验
变形特征
强度参数
hydraulic engineering
staggered zones
unloading test
deformation feature
mechanical parameters
