修正的盐岩扩容模型及扩容界限研究

摘要

With the increasing of deviatoric stresses,the dilatant phenomena would occur in salt rock.The dilatant behavior of salt rock can be divided into short-term dilatancy and long-term dilatancy.According to experimental data of the triaxial compression tests and the rheological tests,the compression-dilatancy boundary effects greatly on the dilatancy behavior both in short and long term.Namely,the salt rock material would be contracted and the behavior of self-healing in salt rock would take place when the stress state is under the compression-dilatancy boundary.In the contrary,the salt rock would be dilatant when the material subjects to a stress state that is above the compression-dilatancy boundary.In this paper,the dependences of volumetric strain on the deviatoric stresses of salt rock have been studied,a modified incremental dilatancy model was developed that is able to describe commendably the relationship between the deviatoric stresses and the volumetric strain.The results of the calculation using different confined stresses showed that the deviatoric stresses for the dilatancy onset and the largest deformation increase along with the increase of the confined stress.The compression-dilatancy boundary that affected on the permeability and porosity of salt rock could represent the alert thresholds of the failure of salt rock.%偏应力持续增加将导致盐岩发生扩容,盐岩扩容分为瞬时扩容和蠕变扩容.对盐岩三轴压缩试验以及三轴分级加载流变损伤试验数据进行分析,发现压缩-扩容边界对瞬时扩容和蠕变扩容都有影响,即应力状态未超过压缩-扩容边界时,盐岩体积不断减小;应力状态超过压缩-扩容边界时,盐岩将发生扩容,即体积增大.通过研究盐岩试件体积应变随偏应力变化规律,提出了修正的增量形式扩容模型,该理论模型计算结果与实验数据吻合较好.改变围压进行计算,结果表明,随围压增加,扩容起始点偏应力增大,最大压缩量增大.压缩-扩容边界可以作为盐岩储库围岩破坏的警戒点.