深部采动围岩宏观变形破坏的力学演化规律

Mechanical Evolution Law of Macroscopic Deformation and Failure of Surrounding Rocks in Deep Mining

  • 摘要: 为了研究深部采动围岩变形失稳的宏观破坏特征和应力分布的时空演化过程,文章采用计算机数值模拟和实验室相似模型试验方法,探讨了深部采场顶板裂隙场、覆岩位移场和围岩应力场的力学演化规律。结果表明:深部采动围岩经历了瞬时突变、间跃发展、循序卸载、连续传递的渐变破坏过程,覆岩裂隙场具有卸压失稳、起裂张开、萌芽发育、渗透贯通、萎缩拟合、封闭稳定的时空演化特征。岩层运移呈现出较强的“临位空间效应”:顶板围岩离煤层越近,位移测线的影响越为强烈,空间影响的范围越为集中,岩层连续移动的阶段可控性越弱;反之顶板岩层距离煤层越远,临位空间的影响机制减弱,覆岩下沉量变小,应力传递与荷载转移的灵动性渐趋惰性。深部采动围岩的应力分布具有近场力学效应影响显著、远场力链承载体系减弱的区间性演化特点,围岩应力短时间内的骤然增大和不规则开采引起的高应力集中叠加效应是诱发采场冲击性动力失稳灾害事故的力学根源。

     

    Abstract: In order to study the macroscopic deformation-failure characteristics and time-space evolution rules of stress distribution of surrounding rocks in deep mining, mechanical evolution laws of roof crack field, overlying rock displacement field and surrounding rock stress field in deep mining were studied by using the methods of computer numerical simulation and laboratory similar model test. The results show that the surrounding rock has experienced gradual failure process of transient mutation, jump development, sequential unloading and continuous transmission,overlying rock fissure field has the time and space evolution characteristics of pressure relief induced instability,crack opening, crack development, through- penetration, shrinking fitting and closed stability. The migration of strata has a strong influence on“adjacent space effect”: the roof surrounding rock is closer to the coal seam, the influence of displacement measurement line is stronger, and the range of spatial effect is more concentrated, the stage controllability of the strata movement becomes weaker, otherwise when the distance between the roof layer and the coal seam is larger, the impact mechanism of adjacent space decreases, overburden subsidence is smaller, the stress transfer and load transfer mobility is inert. The stress distribution of surrounding rock in deep mining has interval evolutionary characteristics of the significant influence on the near field mechanical effect and the weakening of the far field force chain bearing system. The sudden increase in stress of surrounding rock in short time and superposition effect of high stress concentration caused by irregular mining are the mechanical causes of impact dynamic instability of mining field.

     

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