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岩体工程如地下洞室、边坡工程等的施工,大多采用分层开挖的方式。其在开挖卸荷的过程中,特别是高应力条件下常表现出显著的时效变形特征。为探究分级卸荷量对岩石卸荷蠕变特性的影响,以雅砻江锦屏I级水电站大理岩为研究对象,开展相同初始高应力状态条件下恒轴压分级卸围压三轴卸荷蠕变试验。试验结果表明:分级卸荷量越大,大理岩破坏时偏应力越小且破裂角越大,每级荷载作用下蠕变变形趋于稳定所需时间越长,分级卸荷瞬时应变和蠕应变越大。采用Burgers模型对各试件的卸荷蠕变特性进行描述并拟合相关参数,然后对分级卸荷量与理论模型参数间的相关关系进行分析。研究成果表明,分级卸荷量越大,瞬时弹性模量值越小,且应力状态对瞬时弹性模量随分级卸荷量的变化率影响很小。根据这一规律提出瞬时弹性模量随分级卸荷量变化的计算公式;而随分级卸荷量的增大,参数η1和η1’逐渐减小,η2/G2 和η2 /G2 逐渐增大。研究成果表明分级卸荷量对大理岩卸荷蠕变特性有较大影响,在理论分析和实际工程运用中应予以重视。 2/ G2 and η2’/ G2
Rock works such as underground caverns, slope construction works, most of the way by stratified excavation. In the excavation and unloading process, especially under high stress conditions often show significant aging deformation characteristics. In order to investigate the effect of graded unloading on the unloading creep characteristics of rock, taking the marble of Jinping I Hydropower Station in Yalong River as the research object, the uniaxial unloading creep under uniaxial compression and unloading at the same initial high stress condition test. The results show that the larger the grading and unloading, the smaller the deviatoric stress and the larger the rupture angle when the marble is damaged, and the longer the creep deformation tends to stabilize under each load, the instantaneous strain and creep strain The bigger The Burgers model was used to describe the unloading creep characteristics of each specimen and fit the relevant parameters. Then the correlation between the grading unloading amount and the theoretical model parameters was analyzed. The research results show that the larger the grading unloading, the smaller the instantaneous modulus of elasticity, and the less influence of the stress state on the rate of change of instantaneous elastic modulus with the grading unloading amount. According to this law, the formula of instantaneous elastic modulus with the change of grading unloading is proposed. With the increase of grading unloading, the parameters η1 and η1 ’gradually decrease and η2 / G2 and η2 / G2 increase gradually. The research results show that the grading unload amount has a great influence on the unloading creep property of marble, and should be paid attention to in theoretical analysis and practical engineering application. 2 / G2 and η2 ’/ G2