Research On Backfilling Waste-Rock's Compressive Mechanical Properties And Overburden Control

Waste-rock backfilled mining is an important technical means to realize 'three unders'mining and an effective way to control overburden failure and surface subsidence.The compaction and mechanical properties of waste-rock is closely related to its control effect on overburden.In this paper,tangshan mine F5001 waste-rock backfilling working face as the background,by using indoor test,field measurement,PFC2D,FLAC3D and other methods,respectively from the physical and mechanical characteristics of waste-rock,compaction characteristics of waste-rock,rammed waste-rock spatial distribution,backfilling waste-rock overburden control effect and other aspects of the system research.(1)The grain density of backfilled waste-rock is about 2.903 × 103kg/m3,the bulk density is about 1.807×103kg/m3,the moisture content is about 3.95%,and the crushing coefficient is about 1.607.Particle size range is 0?50mm.Under the extreme compression state,the axial compressive strain is about 0.24,the axial stress is about 28.1mpa,the residual bursting coefficient is 1.22,and the compaction degree is 0.76.Under the lateral limit condition,the gangue hardening function is approximately He=1.3147·e18.53?,and the compression modulus has three stage characteristics of'pore compaction-particle breakage-compaction hardening' with the increase of axial strain.(2)The gob online monitoring system is built,and the sensor protection scheme of 'clean-fix-control" is proposed.Both the gob roof subsidence and the waste-rock stress value reach stability after the working face is advanced about 100m,and the stability value is about 425.50mm and 2.87mpa.The hardening function in gob is approximately H?=0.7383·e18.94?.The correction coefficient of gangue compression modulus and deformation modulus is proposed.The correction coefficient of F5001 working face ranges from 0.5616 to 0.8462,and the upper limit is reduced to 0.6351 when the gangue ultimate compression ratio is considered.(3)The horizontal stress exerted on waste-rock by the compactor during the primary compaction process is about 0.57mpa.When the lateral pressure is greater than 0.6mpa,the compaction effect is obvious.During the loading process of the tamper,a three-zone distribution of 'dense zone-transition zone-loose zone' from the bottom of the loading end to the top of the fixed end is gradually formed.The compaction degree of waste-rock in gob can be effectively enhanced by increasing compaction stroke.(4)The improvement of backfilling rate and initial compactness has obvious improvement effect on roof failure and overburden deformation.When the backfilling rate increases from 60%to 100%,the plastic failure height of roof decreases by 58.75%,the maximum settlement decreases by 83.9%,the stress peak decreases by 6.7mpa,and the stress concentration coefficient decreases by 0.33.10.0%increase in the initial compression rate of backfilling waste-rock can reduce the plastic failure height of roof by 60%,the maximum settlement by 29.5%,the stress peak by 7.0mpa,and the stress concentration coefficient by 0.35.