基于巴西劈裂试验的岩石应力–应变曲线荷载速率依存性研究

Loading rate dependency of rock stress-strain curve based on Brazil splitting test

岩石荷载速率依存性是岩石类材料流变力学研究的基本内容之一。通过对井口砂岩、江持安山岩及田下凝灰岩开展交替荷载速率条件下的巴西劈裂试验,分析交替荷载速率条件下岩石巴西劈裂破坏过程及应力–应变曲线的峰前和峰后荷载速率依存性特征,结果表明:(1)交替荷载速率条件下岩石巴西劈裂裂纹先从试件中心起裂并逐渐沿劈裂面向两端扩展,其破坏过程可分为4个阶段;(2)采用交替荷载速率试验得到的巴西劈裂试验曲线,可以清晰地观察到岩石在峰值前和峰值后阶段应力–应变的荷载速率依存性特征;(3)岩石巴西劈裂强度随加载速率的增大而增大,表现出了明显的荷载速率依存性,并通过计算荷载速率依存性系数n值,定量分析了3种岩石的荷载速率依存性特征。

Loading rate dependency is basic content of rheological mechanics of rock material. Brazilian split tests on Jingkou Sandstone,Emochi andesite and Tage tuff were performed under the condition of alternating loading rate. The Brazilian splitting failure process and the loading rate dependency characters about stress-strain curve of pre-and post-peak were analyzed and the following conclusions were found：（1） In the case of alternating load rate,the Brazil splitting crack first starts from the center of the specimen and gradually extends to the two ends of the split face,and the failure process can be divided into four stages.（2） The stress-strain curve of Brazil splitting test,which is obtained by the high and low alternating load rate test,can clearly observe the characteristic of the load rate dependence of rock at pre-and post-peak stage.（3） The splitting strength of rock in Brazil increased with the increase of loading rate,and showed a significant dependence on the load rate. By calculating the loading rate dependence coefficient n value,quantitative analysis about loading rate dependence of the three rocks was performed.