关键词: 灰岩, 酸腐蚀, 腐蚀时间, 应变率, 动态力学性能

Abstract: Rock is usually corroded by chemicals in groundwater. Meanwhile, deformation and failure of rock occur frequently due to the dynamic load in underground engineering. Hence, this study aims to investigate dynamic mechanical properties of limestone corroded in an acid environment. Limestone samples were firstly soaked at pH=3 of KHSO4 solution and NaCl solution for different days, respectively. Then, the porosity, pore size distribution and magnetic resonance image of some samples were obtained by using the nuclear magnetic resonance (NMR) test. Finally, uniaxial dynamic compressive tests were conducted at five strain rates by using the split Hopkinson pressure bar (SHPB) system. The experimental results showed that the porosity of limestone increased sharply with increasing the corrosion time. After 28 d corrosion, the porosity increased from 0.26% in the natural state to 3.20%. Besides, the micro-pores in limestone samples expanded obviously with the corrosion time. It is found that the dynamic compressive strength was significantly reduced (30.3%) and can be divided into two stages according to the descent rate. Moreover, the dynamic elastic modulus and specific energy-absorption decayed exponentially with time. Under natural state and post-corrosion state, limestone samples both exhibited similar responses to the strain rate. Specifically, the failure mode changed from the typical splitting failure to the tensile-shear failure, shear failure, even powders with increasing strain rate. Moreover, the dynamic compressive strength and elastic modulus increased linearly. However, these two mechanical parameters of limestone were both more sensitive to the strain rate in a natural state than post-corrosion. It is proven that the effect of acid corrosion on the dynamic carrying capacity and anti-deformation capacity of limestone is significant, which should be taken into account in practical engineering.

Key words: limestone, acid corrosion, corrosion time, strain rate, dynamic mechanical properties