Basic Study On State Monitoring And Self-sensing Of Gangue-cemented Backfilling Body During Bearing Failure

Backfilling mining has a significant advantage in the green development of coal mining,and plays an important role in controlling the rock movement and surface subsidence.Health monitoring of gangue-cemented backfilling body(GCBB)is critical to ensuring the safety of backfilling engineering in coal mining.The application value of electrical monitoring method in the health monitoring of backfilling structure has been verified,in order to improve the monitoring system of backfilling engineering.With the continuous expansion of national strategic resources,the utilization of underground space has attracted much attention in the green development of coal mining,and the role of GCBB has changed from the traditional space arbitrary piling to structural functionality,making the studied monitoring method difficult to meet the health monitoring of the GCBB constructed by functional backfilling.As a result,in order to broaden the application of electrical monitoring methods in the safety monitoring and prevention and control of backfilling in coal mining,this thesis uses the GCBB as the research object and focuses on two key scientific problems centered on the GCBB’s self-sensing performance enhancement and response mechanism and the monitoring mechanism of the GCBB’s structure state based on electrical self-sensing.Using theoretical analysis,laboratory tests and numerical simulations to carry out the mechanical and self-sensing properties of GCBB under uniaxial and triaxial loading,the mechanoelectric self-sensing response mechanism of GCBB during bearing failure,the mechanoelectric self-sensing evolution characteristics during bearing failure,and the engineering design of self-sensing monitoring of the structural state of GCBB.The main research results are as follows:(1)The variation rule between stress-strain and self-sensing response of GCBB during bearing failure was obtained in order to realize the enhancement of mechanical and self-sensing performance for conventional GCBB.The effects of conductive additive type,electrical measuring arrangement,and material grading on GCBB’s mechanical and self-sensing response performance were discovered.Carbon fiber was the best conductive additive of GCBB,and the embedded copper mesh was the best electrical measuring arrangement.The self-sensing test of GCBB under triaxial loading conditions was realized in order to restore the actual force state of GCBB,and the mechanoelectric self-sensing response mechanism of GCBB under different surrounding pressures was determined.(2)The self-sensing prediction model of GCBB with the BP artificial neural network was built from a macroscopic experimental standpoint.Using the self-sensing parameters of GCBB,this model has a good prediction effect on mechanical indexes.At the microscopic level,the mechanoelectric damage constitutive model of GCBB under uniaxial and triaxial loading were established,taking into account the restraining effect of carbon fiber on GCBB damage.To achieve the inversion of the mechanical deformation characteristics of GCBB under the loading effect by using the self-sensing parameter,the mechanoelectric response mechanism of the conductive path and electron tunneling mechanism of GCBB during bearing failure were determined.(3)Cross-sectional image analysis was used to create a mesoscopic model of GCBB with the actual aggregate morphology.By embedding the cohesive unit into model,the crack expansion of GCBB under loading was visualized.The mesoscopic evolution law of the mechanoelectric self-sensing response of GCBB under loading was revealed considering the aggregate morphology,loading method,and size factors.(4)Based on electrical self-sensing,a monitoring method for the status of functional backfilling structures in coal mining was proposed,and the influence law of shape and size factors on the self-sensing response of GCBB was obtained,confirming the feasibility of the self-sensing monitoring method.On this basis,a multivariate structural state evaluation model for GCBB containing stress,strain,FCER/%,and acoustic emission signal was built,and a method was proposed to determine the precursor of the backfilling structure’s instability based on the maximum point of the model’s first derivative.Finally,the influence characteristics of the self-sensing response of the bearing capacity of GCBB were revealed from the fine viewpoint of different backfilling interval conditions while considering the field effect of the GCBB under the structural backfilling mode.There are 126 figures,40 tables and 206 references.