砂岩分级加卸载蠕变试验过程能量演化分析  

Analysis of energy evolution during the step loading and unloading creep experiments of sandstone

作　　者：韩超[1,2] 庞德朋[1,2] 李德建 HAN Chao;PANG De-peng;LI De-jian(State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;School of Mechanics and Civil Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China)

机构地区：[1]中国矿业大学(北京),深部岩土力学与地下工程国家重点实验室,北京100083 [2]中国矿业大学(北京),力学与建筑工程学院,北京100083

出　　处：《岩土力学》2020年第4期1179-1188,共10页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.41572334,No.11572344);国家重点研发计划(No.2016YFC0600901);中央高校基本科研业务费专项资金(No.2010YL14)。

摘　　要：对陕西柠条塔砂岩样品进行单轴分级加卸载蠕变试验,分析样品变形破坏过程中的能量演化规律。结果表明:随循环级数增加,各级耗散能非线性增长,各级塑性应变能相对稳定;耗散能超过塑性应变能可作为样品破坏的先兆能量特征。通过定义相关系数,建立能量与变形之间的关系后发现:随循环级数增加,各级塑性应变能与各级新增塑性应变呈正相关性,各级耗散能与塑性应变累积量呈正相关性。分别对加载、蠕变、卸载及恢复等4个阶段的能量计算后得出:各阶段能量演化速率均随循环级数的增加而增大。加、卸载速率恒定时,加载段能量变化率大于同级卸载段能量变化率,蠕变段能量变化率大于同级恢复段能量变化率。通过分析各级循环加载段能量变化规律,提出能量衰减系数λ,该值随应力水平增长呈幂函数形式降低,以此提出一种可以有效预测破坏应力的方法。The uniaxial step loading and unloading creep experiments were conducted on the sandstone samples from Shaanxi Province to analyse the law of energy evolution of the samples during the process of deformation and failure.The results show that with the increase of cyclic series,the dissipation energy of each grade exhibits a nonlinear increase and the plastic strain energy of each grade is relatively stable.The dissipation energy exceeding plastic strain energy can be regarded as a precursor energy characteristic of the sample failure.By defining the correlation coefficient and establishing the relationship between energy and deformation,it can be found that with increasing cyclic series,there is a positive correlation between the plastic strain energy and the new adding plastic strain of each grade,and the dissipation energy of each grade is positively correlated with the plastic strain accumulation.According to the calculation of the energy of loading,creep,unloading and recovery stages,the evolution rate of energy in each grade increases with the increase of cyclic series.When the rates of loading and unloading are constant,the change rate of energy at the loading stage is larger than that at the unloading stage,and the change rate of energy at the creep stage is greater than that at the recovery stage under the same grade.Finally,by analysing the change law of energy at each cyclic loading stage,an energy attenuation coefficientλis proposed,which decreases as a power function with increasing stress level.Thus,an effective method is introduced for predicting failure stress.

关 键 词：蠕变 砂岩 能量演化 塑性应变能 耗散能 

分 类 号：TU45[建筑科学—岩土工程]