单轴压缩下尾砂胶结充填体细观能量耗散与损伤表征研究

Study on mesoscale energy dissipation and damage characterization of cemented tailings backfill under uniaxial compression

尾砂胶结充填体在两步骤回采中充当人工矿柱支撑采场顶板,其稳定性对矿柱的安全回采至关重要。基于室内试验进行尾砂胶结充填体细观参数标定,建立了尾砂胶结充填体颗粒流模型,开展了单轴压缩下尾砂胶结充填体细观力学特性研究,构建了尾砂胶结充填体细观能量指标体系,探讨了尾砂胶结充填体细观能量演化及耗散特征,揭示了尾砂胶结充填体破坏形式;结合能量耗散理论,考虑残余应变能影响,引入修正系数λ,提出了改进的损伤变量D,较好地表征了尾砂胶结充填体损伤演化过程。研究结果表明:尾砂胶结充填体细观能量主要由边界能输入,一部分通过能量积聚转化为平行黏结应变能和线性应变能,另一部分通过能量耗散转化为黏结阻尼能、摩擦能、介质阻尼能和动能;尾砂胶结充填体细观能量演化过程具有阶段性特征,包括能量积聚和能量释放两个阶段,在能量耗散阶段体现明显的延性破坏特征;尾砂胶结充填体细观损伤表象为颗粒错动和黏结破坏,考虑残余应变能的改进损伤变量更准确,能较好地反映尾砂胶结充填体延性特征。研究成果可为尾砂胶结充填体稳定性控制提供理论指导。

Cemented tailings backfill(CTB)acts as an artificial pillar to support the stope roof in twostep mining,and its stability is very important for safe mining of pillar. Based on the laboratory test,this paper calibrated the mesoscale parameters of CTB,established the particle flow model of CTB,and investigated the mesoscale mechanical properties of CTB under uniaxial compression. The mesoscale energy index system of CTB was proposed,the mesoscale energy evolution and dissipation characteristics of CTB were discussed,and the failure mode of CTB body was revealed. Combined with the energy dissipation theory,the effect of residual strain energy was considered,and the modified damage variable D was proposed by introducing the correction coefficient,which can better characterize the damage evolution process of CTB. The results show that: (1)The mesoscale energy of CTB is mainly input by the boundary energy. One part is transformed into parallel bond strain energy and linear strain energy through energy accumulation,and the other part is transformed into bond damping energy,friction energy,medium damping energy and kinetic energy through energy dissipation;(2)The mesoscale energy evolution process of the CTB is characterized by stages,including energy accumulation and energy release. The ductile failure characteristics of the CTB are reflected in the energy dissipation stage.(3)The mesoscale damage of the CTB is manifested as particle dislocation and bond failure. The improved damage variable considering the residual strain energy is more accurate,which can better reflect the ductility characteristics of the CTB. The research results can provide theoretical guidance for stable control of CTB.