动静荷载作用下硬岩峰后力学试验研究

Experimental Study on Post-peak Mechanical Properties of Hard Rocks under Combined Static and Dynamic Loading

对3种典型岩石分别进行了峰后循环加卸载试验和峰后振动试验,研究了围压对岩石变形和弹性模量的影响。结果表明：抗压强度随峰后循环加载静荷载次数增加而衰减,弹性模量在循环加载中也出现软化现象;峰后每个循环的卸载过程及加载初期无明显声发射现象,在应力加载到新峰值的60%~90%时才开始出现声发射激增现象,使用＂应变历史＂作为凯瑟效应判断标准可以较好地解释这一现象;在振动荷载作用下,围压的初步增加对粉砂岩和花岗岩的损伤闭合有积极作用,但进一步增加会抑制粉砂岩损伤的继续闭合。

Experimental studies were conducted for three typical rocks under cycles of static and dynamic loading to investigate the impact of confining pressure on rock deformation and elastic modulus. Results showed that,increasing cycles of static and dynamic loading would reduce the post-peak compressive stress and result in the softening of elastic modulus. No obvious acoustic emission was observed at the initial stage of loading process and during the cyclic unloading process. However,more and more acoustic emission occurred as the load was up to 60% ~ 90% of the new peak. ＂Strain history＂as the standard of Kaiser Effect could explain this phenomenon very well. Under dynamic loading condition,an initial increase in confining pressure could promote the damage recovery of siltstone and granite,but a further increment would hinder the damage recovery of siltstone.