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

Abstract

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 pre-tightening 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.

Keywords

• impact dynamic load
• high-frequency low-energy
• anchoring structure
• cumulative damage
• progressive failure