岩石黏弹塑性应变分离的流变试验与蠕变损伤模型

 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。

Rheological test of separation between viscoelastic-plastic strains and creep damage model#br#

The systematic study on the essence of creep strain has not been carried out at present. A method separating the viscoelastic-plastic strains and the techniques of data processing were proposed. The elasto-visco-plastic deformation characteristics of iherzolite at No.2 area in Jinchuan were studied. The instantaneous strain was decomposed into the instantaneous elastic and plastic strains. The instantaneous elastic response is nearly linear. The instantaneous plastic modulus increased with the increasing of stress. The creep strain was decomposed into the viscoelastic strain and the viscoplastic strain. The viscoelastic strain exhibited a creep reduction，while the viscoplastic strain exhibited the creep reduction，the steady creep，and even the accelerating creep. The viscoelastic strain，the viscoplastic strain and the steady creep rate are related to the deviatoric stress level nonlinearly. The visco-elasto-plastic strain characteristics of radial creep are similar to that of axial creep. But the radial creep strain is only 25%–30% of the axial creep strain. A new BNMC creep damage model was established by connecting the Burgers model with the nonlinear M-C plastic components in series. The accelerated creep was treated in the model as a stage that rock strength decreased rapidly and the viscoplastic deformation highly developed with the plastic instability. The BNMC creep damage model was written into FLAC3D via VC++ programming. The method of determining the unknown parameters in the creep damage constitutive model BNMC was proposed.