胶结充填体损伤演化尺寸效应研究

Study on size effect of damage evolution of cemented backfill

尺寸效应是影响胶结充填体抗压强度、变形破坏及损伤演化的一个重要因素。基于此,采用WAW–300微机电液伺服万能试验机、声发射和超声波监测系统,选取尺寸为50,70和100 mm的方形试样进行单轴压缩试验,通过分析声发射参数与超声波波速变化规律,探讨不同尺寸胶结充填体损伤演化规律。研究结果表明:(1)随着尺寸的增加,胶结充填体抗压强度表现出先增后减趋势,破坏形式由劈裂破坏为主向剪切破坏为主转化;(2)声发射参数与超声波波速变化规律表现出明显的阶段性与波动性特征:随尺寸的增加,声发射振铃累计计数曲线在平静期内趋于平缓,但在活跃期内上升幅度更高,超声波波速在平静期与活跃期内下降幅度均增加;(3)胶结充填体损伤演化过程中的耗散能量是影响其抗压强度的内在因素,峰后破坏过程中的损伤程度是影响其破坏形式的主要原因。研究成果可为不同尺寸胶结充填体破裂预测提供指导。

The size effect is an important factor affecting the uniaxial compressive strength,forms of deformation and damage evolution of cemented backfill.Based on this,using WAW–300 micro-electro-hydraulic servo universal testing machine,acoustic emission and ultrasonic monitoring system,three different sizes of square samples with side length of 50,70 and 100 mm were selected for uniaxial compression test.The variation rules of acoustic emission parameters and ultrasonic velocity were used to investigate the damage evolution law of cemented backfills with different sizes.The research results show that:(1)With the increase of size,the uniaxial compressive strength of cemented backfill shows a trend of increasing first and then decreasing,and the failure form changes from mainly splitting failure to shear failure.(2)The variation rules of acoustic emission parameters and ultrasonic velocity show obviously multistage and volatility:with the increase of size,the accumulative counting curve of acoustic emission ringing tends to be gentle during the quiet period,but the increase rate is higher during the active period;and the ultrasonic wave velocity increases during the quiet period and the active period.(3)The dissipated energy in the damage evolution of cemented backfill is the internal factor which affects its compressive strength,when the damage degree in the post-peak failure process is the main reason which affects its failure form.The research results can provide guidance for the prediction of fractures of different sizes of cemented backfill.