深埋隧洞硬岩板裂化过程试验研究

Experimental study on slabbing process of hard rock in deep tunnels

基于含孔花岗闪长岩试件成功再现了深部隧洞硬岩板裂化过程,并结合实时监测系统、光学显微镜、声发射监测系统对板裂过程、“V”型板裂破坏带、板裂微观机理、特征应力、碎屑及裂纹演化特征进行详细分析。结果显示:通过不断加载的应力路径可再现板裂化过程,板裂主要在压应力集中区域开始孕育,在微观上以穿晶、张性、膨胀性裂纹相互作用、联合贯穿,并以33.42°~41.91°的角度相交于临空面或洞壁,于潜在“V”型坑附近形成一系列薄岩板,岩板厚度通常为101.38~120.9μm;岩板不断向外鼓胀、屈曲折断,最终在压应力集中区域形成近似对称的“V”型板裂带。板裂前期,声发射信号主频主要集中在260~340 kHz,幅值主要集中在40~60 dB,以产生高频、低幅、小尺度裂纹为主要特征;板裂后期,25~75 kHz的低频声发射信号开始出现,且在25~350 kHz整个区间均有分布,大于80 dB的高幅信号出现,以低频、高幅值裂纹号出现,低、中、高频和低、中、高幅值裂纹共存为主要特征;板裂中期,以主频、幅值特征介于上述二者之间的裂纹为主要特征。

Using the perforated granodiorite specimens,the slabbing of hard rock in deep tunnels is successfully reproduced.The real-time monitoring system,optical microscope and acoustic emission(AE)system are used to investigate the slabbing process,V-shaped slabbing band,micro-fracturing mechanism,characteristic stresses,fragments and crack characteristics.The results indicate that the slabbing can be reproduced by the continuously loaded stress paths.The slabbing is mainly inoculated in the region of compressive stress concentration.From a microscopic perspective,the extensile and dilatant cracks,generated in the form of trans-granular cracking,continue to interact and coalesce and then intersect with the free surface at the angle of 33.42°~41.91°,forming a series of thin plates with the thickness between 101.38~120.9μm near the potential V-shaped pits.Subsequently,the plates continue to bulge outward,buckle and fracture,and finally form an approximately symmetrical V-shaped band.In the early stage,the dominant frequency of AE is mainly concentrated in 260~340 kHz,and the amplitude is mainly concentrated in 40~60 dB.This stage is mainly characterized by the cracks with high frequency,low amplitude and small rupture.In the later stage,the AE with the low frequency of 25~75 kHz begins to appear,resulting in a signal distribution from 25 to 350 kHz,and the AE with high amplitude larger than 80 dB appears.This stage is characterized by the appearance of cracks with low frequency and high amplitude and the coexistence of cracks with low,medium and high frequencies and low,medium and high amplitudes.In the medium stage,the cracks with the frequency and amplitude between the two are produced.