不同灰砂比岩充组合体疲劳损伤与破裂特性试验研究

Experimental study on fatigue damage and failure characteristics of rock-backfill combination specimen with different cement-tailings ratios

为了揭示地下采场中岩充组合结构体在频发应力扰动作用下的损伤演化和破裂机制,对4种不同灰砂比的岩充组合体试样开展多级增幅疲劳试验并进行试验后CT扫描。结果表明:(1)充填体的灰砂比对岩充组合体的变形、刚度劣化、损伤扩展和破坏模式均有影响。灰砂比从1:4下降到1:12,体积膨胀增加,割线模量先增加后减小。(2)提出了基于不可逆轴向应变的累积损伤演化模型,该模型与试验数据拟合良好,灰砂比为1:4和1:8的岩充组合体累积损伤呈现2阶段增加模式,即最初稳定增加,随后急剧增加。灰砂比为1:10和1:12的岩充组合体呈现倒“S”形损伤累积模式,即初始、稳定和加速增加3个阶段。(3)随着灰砂比减小,岩充组合体的宏观破坏模式从拉伸−剪切混合破坏过渡为拉伸破坏。试验后的CT图像揭示了岩充组合体细观破裂演化模式,包括充填体中的剪切破坏、沿着岩石和充填体接触面的拉伸破裂以及岩石中的拉伸和剪切破裂。采用“柔性充填体”有利于防止岩石剥落、坍塌等灾害。研究成果可为矿山充填配比优化和深部矿产资源安全开采提供理论依据。

To reveal the damage evolution and fracture mechanism of rock-backfill composite structure in mine stope under frequent stress disturbance,a series of multi-stage increasing-amplitude fatigue tests and post-test CT scanning were carried out on rock-backfill combination with four different cement-tailings ratios.The results indicate that:1)Deformation,stiffness degradation,damage propagation,and failure pattern of the rock-backfill combination are influenced by the cement-tailings ratio.Volume expansion increases,while the secant modulus initially rises and then decreases as the cement-tailings ratio decreases from 1:4 to 1:12.2)An irreversible axial strain-based cumulative damage evolution model was proposed,which aligns well with the experimental data.For rock-backfill combinations with cement-tailings ratios of 1:4 and 1:8,the cumulative damage exhibits a two-stage increasing pattern,characterized by an initial steady rise followed by a sudden increase.Conversely,for rock-backfill combinations with cement-tailings ratios of 1:10 and 1:12,an inverted S-shaped damage accumulation pattern is observed,featuring a clear three-stage progression of initial,steady-state,and accelerated increase.3)Decreasing the cement-tailings ratio transforms the rock-backfill combination samples from mixed tensile-shear failure to tensile failure.Post-test CT images depict the mesoscopic fracture evolution pattern of the rock-backfill combination,which comprises shear fractures in the backfill,tensile fractures along the rock-backfill interface,and tensile-shear fractures in the rock.The study suggests that implementing“flexible backfilling”can help mitigate disasters like rock spalling and collapse.These results offer a theoretical foundation for optimizing mine filling ratios and ensuring the safe extraction of deep mineral resources.