珊瑚礁灰岩平板撞击试验与状态方程研究

Plate impact test of coral reef limestone and its state equation

为研究强动载下浅层珊瑚礁灰岩的冲击压缩特性和状态方程,采用一级气体炮试验装置对浅层珊瑚礁灰岩开展了200~500 m/s冲击速度下的平板撞击试验。基于试样自由面粒子速度时程曲线,分析了浅层珊瑚礁灰岩孔隙演化与冲击波传播的相互作用,确定了一维应变条件下浅层珊瑚礁灰岩的动态强度和冲击绝热关系。试验结果表明:冲击波压缩过程中,浅层珊瑚礁灰岩因孔隙塌缩和基质滑移产生塑性变形,导致冲击波在试样中展宽为“弹性先驱波-变形波”的双波结构,变形波的传播速度和能量随冲击压力的增大而增大;2.9×10^(4)~7.5×10^(4)s^(−1)应变率下,浅层珊瑚礁灰岩的Hugoniot弹性极限值和动态屈服强度分别为0.109±0.03 GPa和0.074±0.02 GPa;建立了0.4~1.2 GPa压力范围浅层珊瑚礁灰岩的Hugoniot线性关系,将其压力-比容(P-V)关系分成弹性段和压实段,浅层珊瑚礁灰岩相比于陆源多孔石灰岩在强动载下的压缩性更大;最终建立了可描述浅层珊瑚礁灰岩低压区孔隙压实过程的压力-孔隙度(P-α)状态方程。

To study the shock compression behavior and equation of state of shallow coral reef limestone subjected to high-intensity dynamic loadings,we conducted plate impact tests using a one-stage gas gun technique at impact velocities ranging from 200 m/s to 500 m/s.Based on the particle velocity histories of samples free surface which were obtained by all-fiber displacement interferometer system for any reflectors,the interaction between the shock wave propagation and the evolution of internal pores was analyzed.The dynamic strength and the shock adiabatic relationship of shallow coral reef limestone under one-dimensional strain shock wave loading were determined.The results indicate that the shock wave expands into a two-wave configuration,comprising an elastic precursor wave and a deformation wave,within the tested samples.This phenomenon arises from irreversible plastic deformation mechanisms,including pore collapse and matrix slippage,under shock wave compression.The propagation speed and energy of deformation waves increase with rising impact pressure.The Hugoniot elastic limit value and dynamic yield strength of shallow coral reef limestone are 0.109±0.03 GPa and 0.074±0.02 GPa respectively under the strain rate range from 2.9×10^(4)s^(−1)to 7.5×10^(4)s^(−1).A Hugoniot linear relationship for shallow coral reef limestone was established within the pressure range of 0.4 GPa to 1.2 GPa,and the corresponding pressure-specific volume curve exhibits distinct elastic and compaction stages.It is also found that compared with the shock adiabatic data of terrigenous porous limestone,the shallow coral reef limestone shows greater compressibility under intensive dynamic loadings.Eventually,the P-α equation of state was established to describe pore compaction process of shallow coral reef limestone at the low pressure region.