巴东组岩石加卸荷力学性质及卸荷本构模型  

Loading and unloading mechanical properties of rocks of Badong formation and its unloading constitutive model

作　　者：温韬[1,2] 唐辉明 范志强[1] 蔡毅 汪丁建[1] WEN Tao;TANG Huiming;FAN Zhiqiang;CAI Yi;WANG Dingjian(Faculty of Engineering,China University of Geosciences,Wuhan,Hubei 430074,China;Geosciences School,Yangtze University,Wuhan,Hubei 430100,China)

机构地区：[1]中国地质大学工程学院,湖北武汉430074 [2]长江大学地球科学学院,湖北武汉430100

出　　处：《中国矿业大学学报》2018年第4期768-779,共12页Journal of China University of Mining & Technology

基　　金：国家自然科学基金项目(41230637);中国博士后基金项目(2014M562090)

摘　　要：为揭示巴东组岩石在加卸荷条件下力学参数的劣化效应以及卸荷条件下的本构模型,开展巴东组第2段(b2)和第4段(b4)红层岩石的加卸荷试验,系统研究不同应力路径下不同岩石的力学性质.试验结果表明,轴向加载是岩石压缩条件下破坏的主要原因,而岩石在卸荷条件下破坏的主要原因是横向扩容.与b4岩石相比,同围压下b2岩石的强度更高,b2岩石随围压增大的延性特征以及低围压下岩石峰后多级破坏现象更明显.卸荷条件下,b2峰值强度对应的内聚力和内摩擦角分别是压缩条件下的96.8%和92.9%,b4分别为96.6%和60.7%.卸荷量可用来表征岩石在卸荷条件下变形参数的劣化性质,并适用于卸荷屈服段的本构关系研究;提出的能量降比参数能反映峰后应力跌落阶段特征,从而建立各个阶段的岩石卸荷损伤本构模型,通过试验验证其合理性.此外,基于能量降比参数提出了残余强度的计算公式.研究表明,建立的卸荷损伤本构模型曲线与试验曲线较为吻合,能反映卸荷条件下的岩石变形特征.In order to reveal the degradation properties of mechanical parameters of red bed rock of Badong formation under loading and unloading conditions and its unloading constitutive model,triaxial compression tests and triaxial unloading tests on the rock of Badong formation Section 2（b2）and Section 4（b4）were conducted respectively,and the mechanical properties of different rocks were analysed.The results show that the axial loading is the main cause of rock failure under compression while the failure of rock under unloading conditions is mainly due to the lateral dilatancy.Compared with the rocks of b4,rock strengths of b2 are higher under the same confining pressure,and the multistep-failure after post peak strength and ductility characteristics of b2 rocks are more obvious.Under unloading conditions,cohesion and internal friction angle of b2 rocks corresponding to peak strength are 96.8%and 92.9%of that under compression,respectively.While these values are 96.6% and 60.7% for b4 rocks.Unloadingquantity is used to represent the degradation degree of deformation parameters under unloading conditions,and to study the constitutive relation at unloading stage.Energy reduction ratio proposed in this paper is used to study the degradation effect of mechanical parameters at postpeak stress drop stage.Thus,unloading damage constitutive model for rock is established,and the rationality of this model is verified.In addition,the calculation formula of residual strength is put forward based on the energy reduction ratio.The research demonstrates that the proposed constitutive model is consistent with the test results,and it can reflect deformation characteristics of rock under unloading conditions.

关 键 词：巴东组 岩石 卸荷 变形模量 能量降比 本构模型 

分 类 号：TU45[建筑科学—岩土工程]