The influence mechanism of interface dip angle on the synergistic bearing characteristics of rock-backfill composite
Constructional backfill mining is a technology to solve the problems of high cost of backfill and relatively low efficiency of backfill,etc.The core of constructional backfill mining is form a synergistic bearing structure of backfill-direct roof,utilize the bearing capacity of the direct roof and reduce the backfilling rate.To explore the influence mechanism of different dip angles on the synergistic bearing capacity of backfill-direct roof composite structure,a uniaxial compressive stress experiment of rock-backfill composite with interface dip angle of 0°-60° were designed,and the failure characteristics of composite samples were tested using acoustic emission and digital image correlation,and the interfaces were mechanically analyzed.The re-sults indicate that the strength and elastic modulus of the composite decrease with the increase of the interface dip angle.Strength synergies and deformation synergies are easier to achieve in low-interface dip angle composite samples than in high-interface dip angle composite samples.The final failure of the rock-backfill composite is presented in three forms,namely,synergistic penetration failure,partial interface cementation slip failure and overall sliding failure along the interface.When the dip angle of the rock stratum is less than 30°,the interface compressive stress is greater than the strength of the backfill,and the composite body achieves synergistic bearing and failure.The single largest ringing count of acoustic emission appears in the post-peak stage,which is generally caused by the failure of the siltstone or the detachment of the combination block.When the dip angle of the rock stratum exceeds 30°,the composite body has the problem of insufficient shear slip resistance at the interface,and the composite body does not achieve synergistic failure.The single largest ringing count of acoustic emission ap-pears before the peak,and the apparent fissure development of the concentration is not obvious.This study is important to the design of backfill-direct roof synergistic bearing struc-ture in goaf under different rock dip angles when the backfill is arranged in intervals in struc-tural filling mining.
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