基于声震监测的钢纤维/混凝土裂纹扩展规律及失稳前兆

Crack propagation law and failure precursor of steel fiber reinforced concrete based on acoustic emission and microseism monitoring

对不同龄期、不同钢纤维掺量的钢纤维/混凝土(SFRC)单轴压缩过程中声发射(AE)和微震(MS)信号进行分析,探究SFRC的声震信号特征及裂纹扩展规律。结果表明:(1)SFRC加载过程中裂纹扩展可分为裂纹压密(I)、裂纹稳定发育(II)、裂纹急速扩展(III)和峰后破坏(IV)4个阶段;(2)随龄期增加,第I、第II阶段中AE、MS的能率、振率及微观裂纹和细、宏观裂纹的整体扩展速率均逐渐降低;第III、第IV阶段中AE、MS的能率、振率及微观裂纹及细、宏观裂纹的整体扩展速率均逐渐增大;(3)随钢纤维掺量增加,除第I阶段外,其余3个阶段的AE能率和振率、微观裂纹整体扩展速率均逐渐增大;各个阶段的MS能率和振率逐渐减小,MS能量突增点的时间比逐渐增大,表明细、宏观裂纹整体扩展速率降低,破坏时间延迟;(4)SFRC失稳前,AE、MS的能率和振率、MS能量占比均出现明显陡增,可作为SFRC的失稳前兆指标。

Uniaxial compression tests were performed on the steel fiber reinforced concrete(SFRC)specimens with different ages and steel fiber volume fractions.The acoustic emission(AE)and microseismic(MS)signals were monitored during the loading progress.Through the in-depth analysis of testing results,the feature of AE and MS signals and the evolution of crack propagation in SFRC were studied.The results show that:(1)The crack propagation of SFRC during uniaxial compression can be divided into four stages:Crack compaction stage(I),crack stable development stage(II),crack unstable propagation stage(III)and post-peak failure stage(IV).Different stages show different AE and MS characteristics.(2)With the increase of age,the energy rates and count rates of AE and MS in stages I and II decrease,as well as the generation rates of micro-,meso-and macro-cracks of the whole specimen.However,the energy rate and count rate of AE and MS in stages III and IV increase,as well as the generation rates of micro-,meso-and macro-cracks of the whole specimen increase.(3)With the increase of steel fiber volume fraction,the AE energy rate,AE count rate and micro-crack generation rate of the whole specimen in stages II,III and IV increase,while the MS energy rate and MS count rate in each stage decrease,and the MS energy surge time rate in each stage increase.Furthermore,the generation rates of meso-and macro-cracks of the whole specimen in each stage decrease,and the failure time is delayed.(4)Before the failure of SFRC,the energy rates and count rates of AE and MS increase sharply,as well as MS energy ratio.These variables can be used as the precursor index of SFRC failure.