高频低能冲击扰动下锚固结构渐进失效试验研究

Experimental study on progressive failure of anchoring structure under high-frequency and low-energy impact disturbance

高频低能冲击扰动对巷道围岩及锚固结构造成持续疲劳损伤,是深部巷道趋向失稳的重要诱因,合理构建抗冲击动载巷道锚固支护体系及避免锚固结构失效已经成为深部煤炭开采面临的重要课题之一。采用理论分析、实验室试验、数值模拟等方法,研究了冲击载荷下锚固结构内部应力传递转化机制,阐明了锚固结构累积损伤与渐进失效机理,提出了冲击动载巷道控制准则。结果表明:压缩应力、拉伸应力与压拉快速转换形成的震荡效应是造成锚固结构损伤的三大要素;压缩、拉伸作用下介质抗压强度与不协调变形是导致锚固界面破坏的关键因素,锚固结构在内部法向驱动力作用下损伤累积,切线模量为负或单次动载冲击变形量持续逆势上扬时锚固结构失效,压缩、拉伸、震荡叠加影响下锚固结构预紧力损失及内部损伤存在明显的累积突变效应,内部裂隙以张拉裂隙为主,整体破坏从震荡效应向拉伸效应再向压缩破坏效应逐渐演化。通过提高围岩/锚固剂协调变形能力,增加锚固长度调动大范围岩体承载、保护锚固界面,保持锚固结构承载区抗剪阻滑强度大于动载冲击时内部法向驱动力,同时削弱震荡效应可有效降低锚固结构累积损伤程度。最后提出了降能-高阻-让压的冲击动载巷道控制技术准则,包括远场卸压、近场强支、破碎围岩改性、预紧力维持和让压结构,可为类似条件巷道维控提供指导。

High-frequency,low-energy impacts consistently inflict damage on the surrounding rock and anchoring structure in deep roadways,leading to ongoing instability.The construction of anchoring support system that can withstand these dynamic impact loads is identified as crucial in deep coal mining.Through theoretical analysis,laboratory experiments,and numerical simulations,the stress transfer and transformation mechanisms within the anchoring structure under such loads are explored.The cumulative damage and progressive failure of the structure are studied,with criteria being proposed for controlling the roadways under dynamic impact conditions.The findings reveal that three primary elements,i.e.,compressive stress,tensile stress,and oscillatory effects caused by quick transitions between compression and tension,are responsible for damaging the anchoring structure.Crucially,the failure of anchoring interface under such conditions is primarily due to the medium's compressive strength and uncoordinated deformation.Damage in the anchoring structure accumulates under internal normal forces,leading to failure when the tangential modulus turns negative or the deformation from a single dynamic impact continuously increases contrary to expectations.A significant cumulative-mutation effect is observed under the combined influence of compression,tension,and oscillation,particularly in terms of the loss of pretightening force and internal damage in anchoring structure.Internal fissures predominantly exhibit tensile fractures,with an overall deterioration transitioning gradually from oscillatory effects to tensile stress effects,and subsequently to compressive failure effects.To effectively reduce this cumulative damage,it is crucial to improve the coordinated deformation capacity of both the surrounding rock and the anchoring agent.Additionally,increasing the anchoring length not only enhances structural stiffness but also mobilizes a broader range of rock mass for load-bearing,thereby protecting the anchoring interface,ensuring that the shear resistance in the anchoring structure’s bearing area surpasses the internal normal driving force during dynamic impacts,and mitigating the effects of oscillation can effectively reduce the cumulative damage degree of the anchoring structure.Finally,a new guideline for controlling the roadways under dynamic impact loading is proposed.The guideline,characterized by low energy,high resistance,and an allowance for compression,includes strategies such as far-field unloading,strong support in the near field,modification of fractured surrounding rock,maintaining pre-tightening force,and incorporating compression structures.It aims to provide an effective guidance for the maintenance and control of roadways in similar conditions.