Surrounding Rock Deformation Mechanism And Application For Gob-side Entry Retaining In Deep And Large Height Coal Seam With Fully Mechanized Gangue Backfilling Mining

As a non-pillar mining technology,Gob-side Entry Retaining(GER),advanced in raising the resource recovery rate,reducing the driving rate and optimizing ventilation in work-face,is a significant orientation in green mining technology.However,at the present stage,GER along with caving method for roof management is applied not effectively in deep large height working face.Therefore,as an effective method to break this technical bottleneck,research for GER with gangue backfilling technology has been an urgent task in deformation mechanism and control technology of surrounding rock under the condition of deep large mining height.In this thesis,laws of strata behavior,roof structural characteristic,material properties of roadside support body(RSB),stability of RSB and control technology of surrounding rock under the condition of deep large mining height was studied systematically by laboratory test,theoretical analysis,numerical simulation,similarity simulation test and field monitoring.The primary innovation and achievements are as follows:(1)The effects of water-cement ratio,aggregate and age on the compressibility of gangue concrete,the speed of resistance increasing,the compressive strength and the post-peak bearing capacity were studied.Combined with laws of strata behavior of gob-backfilled GER,adaptability of gangue concrete using as RSB material was discussed.The sensitive regulation range of water-cement ratio to the mechanical properties of gangue concrete is 0.46-0.60.(2)A model for analysis of roof deformation of GER with mechanized gangue backfilling and stability of RSB under the condition of deep large mining height was established to deduce the predictive formula of roof subsidence.By the analysis of the key parameters,the load-bearing characteristic of backfilled region is determined as the main control factor of the main roof deformation.The firm-soft combining supporting structure applicable to gob-backfilled GER was proposed innovatively.(3)The criterion of sliding and rotary instability in the limit equilibrium state of RSB in gob-backfilled GER are obtained.Combined with the numerical simulation method,the influential law of the roadside support parameters on the stability of the surrounding rock in the gob-backfilled GER is revealed.The optimal design method of the key parameters of the RSB is obtained.(4)Mechanical model of the floor of GER with mechanized backfilling gangue under complex load was established to figure out the analytical expressions of stress field and displacement field of the floor strata,revealing the distribution rule of principal stress field and plastic zone of the floor.It is found that,the external factors such as the stress concentration factor of the solid coal side and the support resistance of the RSB impact on the destruction features of the floor,by changing the horizontal stress of the floor.In this paper,the control principle of the floor heave in GER with mechanized gangue backfilling was further discussed from the aspects of improving the mechanical properties of the rock strata,adjusting the principal stress of the floor and optimizing the upper load on the floor.(5)The bearing characteristics of the backfilling area,the law of strata behavior and the load transfer mechanism in the advance process of face are clarified,using the method of numerical simulation.Multi-software coupling model was established by calibrating the mesoscopic mechanical parameters of creep constitutive model of broken gangue combined with experiment,revealing the time-varying evolution rule of root subsidence and stability of RSB in the process of backfilling in GER.(6)Similarity simulation test of gob-backfilled GER considering the circulation push effect of backfilling area was first carried out by using self-developed physical simulation test system containing horizontal push apparatus.The influence of horizontal push pressure and structure of RSB on the bearing characteristics of the backfilling area,the deformation law of roof and the convergence deformation of roadway were analyzed.The stage characteristics of stress evolution rules of broken gangue in GER(active compaction,passive compaction,and stress-steady phase),obtaining the dominant factor and the control principle of roof rotary deformation.(7)Technical system for the deformation control of surrounding rock in GER with mechanized gangue backfilling in deep large-height mining,on the core of the firm-soft combining RSB,technical parameters design of backfilling area,lateral pressure control in backfilling area,local reinforcement design of floor,was proposed based on the design principles of key technical scheme and geological conditions of the test mine.The technical scheme was implemented successfully,verifying the rationality and practicability of the research results.