均质砂岩损伤临界值的研究及SHPB试验验证

砂岩在冲击荷载下，损伤量D通常在小于1的情况下就发生破坏，存在损伤临界值.本文首先根据分形几何理论和砂岩结构特征，建立2×3的元胞模型，理论解析出砂岩的不稳定损伤临界值为0.4，阶段变化的损伤临界值为0.119.然后通过直径50 mm的SHPB试验结果分析，表明在砂岩动态损伤演化过程中有两个临界点，第1点为从线形损伤阶段到加快损伤阶段的临界点，对应的损伤量约为0.1；第2点为从损伤阶段到破坏阶段的临界点，对应的损伤量约为0.4，与理论研究十分吻合.该研究揭示了砂岩在损伤演化过程中发生破坏的临界问题. 

Theoretical Study and SHPB Experimental Verification on the Critical Damage of Uniform Sandstone

Under the impact load,sandstone usually fails when the damage quantity D is less than 1,and there exists the critical damage.Based on the fractal geometry theory and the structure features of sandstone,a 2 × 3 cellular model was established in this paper.The instability critical damage of sandstone is 0.4 after theoretical calculation,and the critical damage of stage change is 0.119.Results analysis of the Φ50 mm SHPB experiment shows that there are two critical points in the dynamic damage process of sandstone:the first critical point is from the linear damage stage to the accelerated damage stage,and the corresponded damage quantity is about 0.1;the second critical point is from the damage stage to the failure stage,and the corresponded damage quantity is about 0.4,which agrees well with the theoretical research.The study reveals the critical problem of sandstone failure in the damage process.