Study On The Damage Characteristics Of Solidified Body And Coal Pillar And The Movement Law Of Overburden In Continuous Driving And Gangue Backfilling

The combination of continuous driving and gangue backfilling(CDGB)conduces to realizing gangue discharge reduction and ground subsidence control.Meanwhile,it can release the coal buried under buildings,railways and water-bodies and the irregular residual coal,so that such coals become minable.In this paper,we use theoretical analysis,mechanical experiments and numerical simulations to investigate the law of overburden movement in the process of CDGB.The main results are as follows :(1)The results of uniaxial compression experiments show that t the free area can be used as a quantitative index to evaluate the stability of the combined system of rock mass and coal pillar at the site of continuous excavation filling.The compressive strength,axial peak strain and weakening modulus of the specimen are negatively correlated with the free area,and the increase of the free area weakens the bearing capacity of the specimen and reduces the brittleness of the specimen.When the free area is greater than the critical value(free area ratio > 1.13),the relationship between the deformation resistance of the specimen and the free area changes from positive to negative correlation.(2)Compared with the single filling body,the stress-strain curve of the composite support does not show a sharp decrease in compressive strength during the damage stage,and there is a certain residual support strength,and the phenomenon of sudden collapse of coal pillars due to stress concentration is significantly improved,which can effectively protect coal pillars.(3)The monitoring of the loading process of different shaped specimens by the acoustic emission acquisition system shows that: the cylindrical specimens do not appear to be suddenly broken during the loading process,but the microfractures start to gather through the accumulation of energy and then release and finally present a step damage;the peak count of the post-peak stage of the square(vertical tangent)specimens is concave and the energy accumulation paragraph feeling is not strong,showing the characteristics of " The peak count of the square-shaped specimen in the pre-peak stage is very small,and the highest peak count point is in the post-peak stage.(4)When the filler is filled,it has two effects on the surrounding rock: firstly,the coal column is deformed by lateral expansion or even rupture,and the filled filler plays a lateral supporting role on the coal column;secondly,when the filler is connected to the top,it plays a bearing role on the roof together with the coal column;the filler-coal column bearing system is established and its action process is divided into three stages:the filler is not connected to the top and the coal column is supported independently,the filler starts to play a role,and the filler-coal column carries the load together.(5)From the numerical calculation model,it can be seen that the overall increase of overburden settlement in the three stages of continuous excavation and gangue filling but the increase gradually decreases,and the increase in each stage shows different characteristics;the vertical stress distribution of overburden in the three stages of continuous excavation and gangue filling is an elliptical high stress area in the area of supporting coal pillar,and the extreme value of high stress increases with the increase of the number of excavation in the supporting tunnel,and the stress concentration caused by excavation shows different characteristics in the three stages,in which the coal pillar shows stronger stress concentration compared with the filling body,and the stress concentration of the filling body increases with the increase of filling time.