分级加载养护对矸石胶结充填柱力学和变形性能的影响

Effects of curing under step-by-step load on mechanical and deformation properties of cemented gangue backfill column

利用分级加载来模拟采空区矸石胶结充填柱硬化过程中的加载历史。通过电阻率和超声设备监测试件在硬化期间和单轴压缩测试期间的内部损伤。结果表明:1)加压硬化试件32 d的单轴抗压强度和弹性模量高于无压力硬化的对照试件,分别为对照试件的0.5%~20.2%和7.1%~52.3%,且受初始加载龄期和应力-强度比的影响;硬化期间施加在矸石胶结充填柱上的应力-强度比不应超过80%。2)初始加载龄期越早,总变形越大,应力-强度比越高,总应变越大;蠕变应变随着应力-强度比的增加而增加,且可以用Burgers黏弹性蠕变模型来描述;当应力-强度比小于80%时,初始加载龄期越早,最后一步加载后的蠕变应变就越小。3)可以根据超声波脉冲速度和电阻率的变化来监测早龄期矸石胶结充填柱在压力下的稳定性。

A step-by-step load was utilized to mimic the load history of the backfill column in the in-situ curing process.The inner damage of the specimen during curing and uniaxial compressive testing was monitored by electrical resistivity and ultrasonic equipment.Results show that:1)Uniaxial compressive strength(UCS)and elastic modulus(EM)of the samples curing under pressure are higher than those of the control samples without pressure,ranging in ratio from 0.5%to 20.2%and 7.1%to 52.3%,respectively,and are influenced by the initial loading age(ILA)and stress strength ratio(SSR).The SSR during curing should not exceed 80%.2)The earlier the ILA is,the higher the total strain becomes.The higher the SSR applies,the larger the total strain gets.The creep strain increases with the increase of SSR and can be described by Burger’s viscoelastic creep model.When SSR is less than 80%,the earlier the ILA is,the smaller the creep strain becomes after the last step-loading.3)The stability of the early age backfill column under pressure can be monitored based on the change of ultrasonic pulse velocity(UPV)and electrical resistivity.