冻融循环作用下贺兰山遗址区岩石损伤特征研究

Study on damage characteristics of rock in Helan Mountain site under freeze-thaw cycle treatment

针对宁夏环境致贺兰山遗址区岩石风化严重的问题,首先对取自贺兰山遗址区的岩样进行冻融循环试验,设置循环次数分别为0、10、20、30、40次,测量岩样的质量、纵波波速及有效孔隙率,并分析冻融循环次数对它们的影响;然后开展单轴压缩和声发射试验,绘制应力-应变曲线,分析其变化规律;最后基于弹性模量与累积振铃计数,定义损伤变量,建立温度-水-力三场耦合作用下的损伤本构模型。研究结果表明,有效孔隙率和波速降低比率在20次循环周期后均有所下降,此时岩样出现颗粒剥落现象,二者的变化能够反映岩石表面损伤情况;损伤变量经历了平稳阶段、缓慢增加阶段和陡然上升阶段,对应于应力-应变的变化规律;构建的损伤本构模型能够描述贺兰山岩石的损伤演化过程,为进一步认识贺兰山遗址岩石的病害机理提供了理论依据。

In view of the serious weathering of rocks in the Helan Mountain site area caused by Ningxia environment,firstly,the freeze-thaw cycle tests were carried out on the rock samples taken from the Helan Mountain site,and the cycle times were set as 0,10,20,30 and 40 times respectively.The mass,longitudinal wave velocity and effective porosity of the rock samples were measured,and the influence of the cycles on them was investigated.Then,uniaxial compression tests and acoustic emission tests were performed;the stress-strain curves were obtained,and their variation laws were analyzed.Finally,the damage variable was defined,based on the elastic modulus and cumulative ringing count,and the damage constitutive model under the coupling action of temperature-water-force was established.The study results show that the effective porosity and the reduction ratio of wave velocity decrease after 20 cycles.At this time,the particle spalling phenomenon occurs in rock samples,and the changes of two indexes can reflect the damage of rock surface.The damage variable has experienced a steady stage,a slowly increasing stage and a steep rising stage,which corresponds to the change law of stress-strain.The constructed damage constitutive model can describe the damage evolution process of rocks in the Helan Mountain,which provides a theoretical basis for further understanding the disease mechanism of rocks in the Helan Mountain site.