基于细观变形理论的盐岩塑性本构模型研究

Mesoscopic deformation based plastic constitutive model of salt rock

唯象学本构模型不能很好解决诸如夹杂含量、温度、应变速率等对盐岩力学性质的影响,更难以解释盐岩变形机制。盐岩为石岩晶体组成,其变形机制主要由多晶结构所控制,故基于固体位错理论研究方法建立的盐岩塑性本构模型更能反映盐岩的变形机制。研究表明,盐岩的塑性-蠕变交互作用机制是(亚)晶粒内部位错的滑移与(亚)晶界及其干涉面内位错的攀移运动之间的耦合。基于此,可确定亚晶(或晶粒)平均尺寸与流动应力之间的关系、(亚)晶内的位错平均密度;建立微观参量(位错、亚晶直径、亚晶界宽度等)演化模式;根据Orowan定律建立盐岩微观-宏观变形联系,从而导出盐岩塑性本构方程。导出的本构方程体现了盐岩塑性-蠕变变形的物理机制,相对于传统的塑性本构方程具有更好的物理意义。

The existing phenomenological constitutive model is hard to describe how the impurity content, temperature and strain rate affect the mechanical behavior of the salt rock. It is more difficult to explain its deformation mechanism. Salt rock mainly consists of halite crystal. The deformation mechanism of salt rock is controlled by the polycrystalline structure. Therefore, it is more appropriate to build the plastic constitutive model using solid dislocation theory for the description of the deformation of the rock salt. The mesoscopic mechanism of the plastic-creep is the coupling of dislocation sliding of inner crystal grains and dislocation climbing-sliding of boundaries and their interference surfaces of inner crystal grains. According to the above hypothesis, the relationship between the average scale of the subgrain（or grain） and flow stress, the mean density of dislocation of inner grains and evolution model of microscopic parameters（including dislocation, subgrain diameter and boundary width between subgrains） are obtained sequentially. Finally the meso-macroscopic deformation and then plastic constitutive equation of salt rock are established using Orowan’s law. The obtained equation can reflect the physical mechanism of plastic-creep deformation of salt rock and has an improved physical significance, comparing with traditional plastic constitutive model. This constitutive model could only be obtained through observation and research on mesoscopic structure of rock salt.