不同加载速率下胶结充填体损伤特性与能量耗散特征分析

针对矿体回采所导致的充填体破坏可近似看作不同加载速率下的加载过程,在实验室开展了5种加载速率下的胶结充填体单轴压缩试验,在得到充填体应力-应变曲线的基础上,根据能量耗散原理及损伤力学,计算了不同加载速率下的充填体能耗值并构建了相应的损伤演化方程,研究了不同加载速率下胶结充填体的能量耗散与轴向压缩时间、应变间的内在关系,探讨了胶结充填体受压破坏的能量损伤演化过程.研究结果表明,不同于高强度的岩石,胶结充填体存在临界加载速率现象,当加载速率超过临界值后,充填体强度随加载速率增加而降低;充填体的峰前能耗量、峰后能耗量、单位体积应变能及总能耗量与加载速率呈二次函数曲线关系;充填体的总能耗量随轴向压缩时间、轴向应变的增大呈现Logistic函数形式增长规律,但加载速率的不同使得能耗值增长速率及充填体达到相同轴向变形所需能耗量存在明显差异;不同加载速率下充填体的压缩破坏均属同一类损伤过程,充填体受压破坏的能量损伤演化过程可划分为初始损伤、损伤稳定发展、损伤加速及损伤破坏4个阶段.

Research on Damage and Energy Dissipation Characteristics of Cemented Backfill under Different Loading Rates

As the destruction of the backfill caused by the mining of the ore body can be regarded as a loading process at different loading rates, a uniaxial compression test of cemented filling bodies under five loading rates was carried out in the laboratory. Based on the stress-strain curve of the filling body, according to the principle of energy dissipation and damage mechanics, the energy consumption value of the backfill at different loading rates was calcu lated and the corresponding damage evolution equation was constructed. Therefore, the internal relationship between the energy dissipation of cemented filling and the axial compression time and strain at different loading rates was studied, and the evolution process of energy damage for the cemented filling body under compression was discussed. The results show that unlike high-strength rocks, there is a critical loading rate for cemented backfill . When the loading rate exceeds the critical value, the backfill strength decreases with the increase of loading rate. The pre-peak energy consumption, post-peak energy consumption, strain energy per unit volume, and total energy consumption of the filling body have a quadratic function curve relationship with the loading rate. The total energy consumption of cemented backfill increases with the increase of axial compression time and axial strain in the form of a logistic function. However, the difference in loading rate makes the increase rate of energy consumption value, and the energy consumption of the backfill under the same axial deformation has obvious differences. The compression failure of backfill under different loading rates exhibits the same kind of damage process. The energy damage evolution process of the backfill under uniaxial loading can be divided into four stages: initial damage, stable development of damage, acceleration of damage and damage failure.