考虑应力水平和损伤的胶结充填体蠕变特性及本构模型

Creep characteristics and constitutive model of cemented backfill considering stress and damage

充填采矿法中胶结充填体处于长期荷载环境,其蠕变特性会对矿山安全开采产生重要影响。基于此,制作胶结充填体的标准圆柱体试样,采用WDW-100 kN型微机控制电子万能试验机加载系统和DS2系列全信息声发射监测系统,进行了单轴压缩、分级蠕变和声发射监测试验,获取了胶结充填体蠕变变形及振铃计数、能量和振幅等声发射特征参数。根据试验结果,探讨了不同应力水平下胶结充填体蠕变变形特征和声发射特征;对比单轴压缩试验,从宏细观角度揭示了胶结充填体蠕变破坏特征;考虑应力水平和损伤的影响,引入损伤变量、新的二次黏性元件和开关元件,构建了能表征不同应力水平下胶结充填体蠕变变形规律的改进Burgers模型,并通过试验结果进行验证。研究结果表明:①不同应力水平下,胶结充填体的蠕变3阶段变形特征差异显著,据此将荷载应力大小分为减速、等速和加速3类应力水平;②不同应力水平下,胶结充填体声发射特征与各阶段蠕变变形特征变化规律较一致:减速蠕变阶段内,声发射事件较活跃;稳定蠕变阶段内,声发射活动较少;加速蠕变阶段内,声发射事件最活跃;③对比单轴压缩破坏,胶结充填体蠕变破坏程度较为平缓,主裂纹沿扩展方向发生明显偏转,完整性较好,以结构性失稳破坏为主;④构建的改进Burgers蠕变模型能与各应力水平试验数据均有较高吻合度,较好的表征了不同应力水平下的胶结充填体蠕变变形规律。

In the filling mining method,the cemented backfill will have an important impact on the safe mining of the mine in a long-term loading environment.Based on this,standard cylinder samples were prepared for uniaxial compression test,graded creep test and AE(acoustic emission)monitoring tests by the systems of WDW-100 kN microcomputer-controlled electronic universal testing machine and DS2 series acoustic emission monitoring machine,and creep deformation and AE parameters,such as ring count,energy and amplitude,were obtained.Based on the results,the creep deformation characteristics and AE characteristics of cemented backfill under different stress levels were discussed.Compared with uniaxial compression tests,the creep failure characteristics of cemented backfill were revealed from a macro and meso perspective.Considering the effects of stress levels and damage,damage variable,a new secondary viscous body and switching component were imported to construct an improved Burgers model,which could characterize the creep rule of cemented backfill under different stress levels and was verified by experimental data.The research results show that①Under different stress levels,the three-phase creep deformation characteristics of cemented backfill are significantly different.Based on this,the load stress is divided into three types:deceleration,constant velocity and acceleration;②Under different stress levels,the AE characteristics of the cemented backfill are consistent with the changes in the creep deformation characteristics at each stage:during the deceleration creep phase,the AE events are more active;during the steady creep phase,there are fewer AE activities;during accelerated creep phase,AE events are most active;③Compared with the failure of samples under the uniaxial compression,the creep damage of cemented backfill is relatively gentle.The main crack is deflected obviously along the propagation direction.Sample presents structural instability failure with integrity failure;④The improved Burgers model constructed can be in good agreement with the experimental data of various stress levels,and it can better characterize the creep deformation rule of cemented backfill under different stress levels.