Study on the mechanism of the influence of early damage of cemented#br#
backfill on later mechanical properties
GAN Deqing1，2，ZHANG Yajie1，2，LIU Zhiyi1，2，SUN Haikuan1，2
(1. College of Mining Engineering，North China University of Technology，Tangshan，Hebei 063210，China；2. Hebei Mining Development and Safety Engineering Laboratory，North China University of Technology，Tangshan，Hebei 063210，China)
Abstract：To investigate the influence mechanism of early load damage on later mechanical properties of the cemented paste backfill，four different degrees of static load damage were applied to the backfill at ages of 3，7，14 and 21 d. After 28 d of maintenance，uniaxial compression tests，ultrasonic tests and electron microscopic microstructure scans were conducted to investigate the influence mechanism of early load damage on later mechanical properties of the backfill under three scales of macro-fine-micro. The results show that：the load damage had less effect on the late compressive strength of the backfill at ages 3 and 7 d，and the late compressive strength of the backfill increased under certain load conditions. The late compressive strength of the backfill at age 14 and 21 d was weakened. The late elastic deformation capacity of the cemented backfill at each age was strengthened. The quantitative relationship between the degree of load and the physical properties of the backfill was established based on the variation of wave velocity. It finds that there was a damage threshold and a repair threshold for the backfill at 3 and 7 d of damage age. With the degree of damage load increased，the internal structure of the backfill gradually expanded from a larger number of fine fissures to a single fissure，and the connecting material at the fissure section was mainly the hydration product C-S-H reticulated gel. At ages 3 and 7 d，there were a large number of incompletely hydrated cement particles inside the backfill，and the gel products produced at the later stage of maintenance were sufficient to fill most of the damaged fissures. Therefore，the damage had a less effect on its later compressive strength. While at ages 14 and 21 d，the incompletely hydrated cement particles in the backfill were reduced，and the gel products produced at the later stage were insufficient to fill the damaged fissures. Thus，the connection between the internal structural particles was poor，and the damage had a significant weakening effect on its later compressive strength. The results of the study can provide guidance for working with mine backfilling.
甘德清1，2，张雅洁1，2，刘志义1，2，孙海宽1，2. 胶结充填体早期损伤对后期力学性能影响机制研究[J]. 岩石力学与工程学报, 2023, 42(4): 821-832.
GAN Deqing1，2，ZHANG Yajie1，2，LIU Zhiyi1，2，SUN Haikuan1，2. Study on the mechanism of the influence of early damage of cemented#br#
backfill on later mechanical properties. , 2023, 42(4): 821-832.
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2023, Vol. 42 
