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基于目前未能对岩石蠕应变的内涵进行分类研究,提出岩石黏弹塑性应变分离的蠕变试验方法和数据处理技巧。以金川二矿区的二辉橄榄岩为例,探讨该类岩石的三轴黏弹塑性变形特性。岩石的瞬时应变分离为瞬弹性和瞬塑性应变,二辉橄榄岩的瞬弹性响应近线性,而瞬塑性模量随偏应力水平的增加而增大;蠕应变分离为黏弹性和黏塑性应变,岩石黏弹性应变曲线呈现衰减蠕变的特性,而黏塑性应变曲线呈现出衰减蠕变,稳定蠕变,甚至加速蠕变的特性,黏弹性应变、黏塑性应变和定常蠕变率与受载偏应力水平之间表现为非线性关系;侧向黏弹塑性应变特性与轴向相似,在未破坏级偏应力下侧向蠕变应变为轴向蠕变应变的25%~30%。将Burgers模型和非线性M-C塑性元件串联组合建立新的BNMC蠕变损伤模型,该模型认为加速蠕变是岩石强度迅速降低和黏塑性变形高度发展,塑性失稳的阶段。依据FLAC3D所提供的二次开发程序接口,采用VC++编程方法实现BNMC蠕变损伤本构模型的二次开发,提出BNMC蠕变损伤本构模型参数的辩识方法。
Based on the current failure to classify the connotation of rock creep strain, creep test methods and data processing techniques for rock viscoelasto-plastic strain separation are proposed. Taking the lherzolite in Jinchuan No.2 mine as an example, the triaxial visco-elastic plastic deformation of this kind of rock is discussed. The instantaneous strain of rock is separated into instantaneous and transient plastic strain, the instantaneous elastic response of lherzolite is near linearity, and the instantaneous plastic modulus increases with the increase of the level of deviatoric stress. The creep strain is separated into viscoelasticity and viscoplastic strain, The viscoelastic strain curve of rock exhibits the characteristic of decay creep, while the viscoplastic strain curve shows the characteristics of decay creep, steady creep and even accelerated creep. The viscoelastic strain, viscoplastic strain and constant creep rate are proportional to the loaded deflection The nonlinear viscoelasto-plastic strain behavior is similar to that of the axial direction. The lateral creep strain is 25% -30% of the axial creep strain under the unsafe grade stress. A new model of BNMC creep damage is established by combining Burgers model and nonlinear M-C plastic element in series. The model predicts that accelerated creep is a stage of rapid decrease of rock strength and high development of viscoplastic deformation and plastic instability. According to the secondary development program interface provided by FLAC3D, the secondary development of BNMC creep damage constitutive model is realized by using VC ++ programming method, and the identification method of BNMC creep damage constitutive model parameters is proposed.