摘要
在实际基坑和硐室的开挖过程中,岩体多处于环向卸荷的应力状态.不同于以往常规路径下的岩石蠕变特性研究,采用全自动岩石多场耦合三轴伺服仪,以红砂岩为试验对象着重研究了岩石环向卸荷路径下的蠕变力学特性.试验结果表明,与常规路径下的蠕变试验相似,岩石环向卸荷路径下的蠕变过程,同样由衰减蠕变到稳态蠕变再到非线性加速蠕变这一典型岩石流变三阶段所组成.随着围压的逐级卸载,轴向或者侧向蠕变变形,蠕变变形相对该级荷载下的瞬时变形的百分比,蠕变变形占总变形的比例,都整体呈现增大的趋势.侧向的蠕变速率、瞬时变形、蠕变变形在这一过程中逐渐超过轴向相应值,并最终达到轴向的2~3倍,出现明显的侧向扩容.基于经典弹塑性理论公式,绘制了塑性应变与偏应力水平的关系曲线,采用多种不同方式确定并比较了红砂岩卸荷蠕变过程中的长期强度.
In the excavation process of practical foundation pits and chambers,the rock mass is often in a stress state of lateral unloading.Unlike previous investigation of creep properties of rocks under conventional stress paths,this paper focuses on the creep mechanical properties of rocks under lateral unloading paths using the autocompensated multi-field coupling rock testing system with sandstone as the test object.The test results show that,similar to creep tests under conventional paths,the creep process under lateral unloading paths is also composed of the typical three stages of attenuated creep,steady-state creep,and nonlinear accelerated creep.With the unloading of confining pressure,the axial or lateral creep deformation,the percentage of creep deformation to instantaneous deformation under the same stress level,and the proportion of creep deformation to total deformation,all exhibit an overall increasing trend.The lateral creep rate gradually exceeds the corresponding axial value during this process and eventually reaches 2-3 times of the axial value,exhibiting significant lateral expansion.Based on the classical elastic-plastic theory,the plastic strain-deviatoric stress curves are plotted,and various methods are used to determine and compare the long-term strength of sandstone during unloading creep process.
作者
童飞虎
朱其志
张瑨
TONG Feihu;ZHU Qizhi;ZHANG Jin(Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University,Nanjing 210098,China;Geotechnical Engineering Research Institute,Hohai University,Nanjing 210098,China)
出处
《河南科学》
2024年第4期537-546,共10页
Henan Science
基金
国家自然科学基金资助项目(51679068,11902111)
国家重点研发计划项目(2017YFC1501100)。
关键词
红砂岩
多级卸荷流变
侧向扩容
长期强度
red sandstone
multi-level unloading creep test
lateral expansion
long-term strength
