初应力条件下超临界CO_2气爆致裂规律模拟研究

Simulation of fracture law of supercritical CO_2 explosion under initial stress condition

考虑到超临界CO_2气爆技术应用环境多受到初始地应力作用,利用自主研发的超临界CO_2气爆发生装置,在电液伺服三轴加载平台上进行了初应力条件下超临界CO_2气爆混凝土试件实验,得到了气爆冲击压力时程曲线和不同载荷工况下试件的破坏形貌。利用JWL状态方程拟合气爆冲击压力时程曲线确定的参数计算气爆过程中超临界CO_2的相变过程,通过开发程序将材料拉伸和压缩硬化引入Johnson-Cook模型,联合使用SPH和FEM对不同初应力条件下超临界CO_2气爆致裂过程进行了模拟计算,实验和数值模拟一致表明:超临界CO_2气爆后试件形成粉碎区和裂隙区,粉碎区是由气爆冲击波将气爆孔附近介质压碎形成的,初应力对粉碎区的形状和范围影响不大;裂隙区主要是由爆生气体的气楔作用形成的,且主裂隙方向与最大初始压应力方向一致,初应力对垂直于自身方向裂隙的扩展具有抑制作用;随着初始压应力的增大,相同爆破条件下裂隙生成条数和裂隙扩展的总长度都降低。计算结果与实验结果的一致性表明改进后的JC模型适用于超临界CO_2气爆的模拟。

The application environment of supercritical CO2 explosion technology is mostly affected by initial stress,considering that feature and developed a supercritical CO2 gas explosion device. A series of experiments were carried out with concrete specimens under the initial stress conditions on the electro-hydraulic servo triaxial loading platform,time history curve of the impact pressure and damage profiles of the specimen under different load conditions were obtained.The parameters,obtained from the gas burst impulse pressure time history curve fitted by JWL equation of state,were used calculate phase transition process of supercritical CO2 in gas explosion. The tension-hardening and compression-hardening were introduced into the Johnson-Cook model in an innovative way. SPH and FEM were used to simulate the process of explosion induced by supercritical CO2. Experimental and numerical simulations are consistent. After the explosion,specimen formed pulverization zone by shock wave crushing medium near the blasthole,with the effect of gas wedge,fracture zone was formed around pulverization zone. The direction of the main fracture is the same as that of the maximum initial compressive stress. The initial stress has an inhibitory effect on the propagation of the crack perpendicular to its own direction,and has little effect on the shape and extent of the pulverization zone. With the initial compressive stress increases,the number and total length of cracks are reduced. The agreement between the calculated and the experimental results shows that the modified JC model is suitable for the simulation of supercritical CO2 gas explosion.