不同恒温时间加热下花岗岩冲击压缩力学特性及破碎特征

Impact compression mechanical properties and crushing characteristics of granite at different constant temperature heating time

为研究不同恒温时间的实时高温作用对花岗岩冲击压缩力学特性与破碎特征的影响,开展了高温时SHPB冲击压缩试验及筛分试验。首先,将花岗岩加热到700℃并进行0、30、60、90及120 min这5种不同时间的恒温热处理;其次,不对试样做冷却处理,利用同步对杆装置进行高温时SHPB试验,收集破碎试件并开展筛分试验;最后,结合抗压强度、分形维数等数据,分析花岗岩的力学特性及破碎特征。研究结果表明:恒温时间对花岗岩动态抗压强度影响较大,试件抗压强度随恒温时间增加而呈明显下降趋势;花岗岩破碎程度随恒温时间增加而不断加剧,表现在破碎试件中细块数量逐渐减少,细粒数量不断增多。不同恒温时间加热下花岗岩冲击压缩破坏的分形维数集中在2.2~2.7之间,且与恒温时间呈现正相关关系。实时高温作用下花岗岩动态抗压能力与宏观破碎分形特征均具有明显的应变率强化效应。

In order to study the effect of real-time high temperature action at different constant temperature time on the mechanical properties and failure characteristics of granite shock compression,the SHPB impact compression test at high temperature and screening test were carried out.Firstly,the granite was heated to 700℃and subjected to five different time length constant temperature heat treatment of 0,30,60,90 and 120 min.Secondly,SHPB test at high temperature was carried out by synchronous rod device without cooling the sample. The crushed specimens were collected for screening test. Finally, combined with the data of compressive strength and fractal dimension, the mechanical properties and crushing characteristics of granite were analyzed. The results show that the constant temperature time has a great influence on the dynamic compressive strength of granite, and the compressive strength of the specimen decreases significantly with the increase of the constant temperature time. The degree of granite fragmentation increases with the increase of constant temperature time, which shows that the number of fine blocks in broken specimens gradually decreases and the number of fine particles increases. The fractal dimension of granite impact compression failure at different constant temperature duration is concentrated in the range of 2.2−2.7, and presents a positive correlation with the constant temperature duration. The dynamic compressive capacity and macro fracture fractal characteristics of granite at real-time high temperature have obvious strain rate strengthening effect.