Study On The Roof Damage Evolution Test And Mechanical Properties In Fully-Mechanized Top Coal Caving Mining

Exploring the damage and breaking rules of coal rock under different stress environments is of great significance to the safe and efficient production of mining enterprises.In this thesis,the MTS815 rock electro-hydraulic servo testing machine was used to conduct rock mechanics test on the roof rock of a coal mining surface in Huating City.The mechanical properties,damage evolution and energy evolution of mudrock under uniaxial compression test,uniaxial cyclic loading test and triaxial compression test were obtained.The main research contents of this thesis are as follows:(1)Two damage equations were established using acoustic emission signals as indicators of change.The acoustic emission signal of the mudstone test piece under oneway load was collected.The ringing count,time and stress relationship were fitted,and the corresponding change relationship with the internal damage of the mudstone was analyzed.The acoustic emission signal was used as an index to describe the entire process of deformation and rupture evolution of the roof plate.An injury equation based on the relationship between the two functions was constructed based on the different coupling relationships between the ring count and time.(2)A unified constitutive equation for mudstone damage was established.The triaxial compression test was carried out on the processed mudstone specimens to obtain their basic mechanical indicators.The variation law and deformation characteristics of the mechanical property curve of the specimen were analyzed.The constitutive equation was established based on statistical damage mechanics and combined with the stress characteristics under triaxial compression of mudstone.(3)The characteristics of elastic strain energy,dissipative energy and total input energy of mudstone specimens under cyclic addition and unloading were elucidated.The uniaxial cyclic addition and unloading test was carried out on the mudstone specimens,and the obtained mechanical indicators were compared with the results obtained by uniaxial compression,and it was found that the three basic mechanical indicators were generally improved.According to the cyclic addition and unloading curve,the dissipative energy and strain energy were calculated,and the energy change and distribution characteristics during the destruction of mudstone were studied.(4)The stress,displacement and plastic zone range of the working surface roof during the coal seam excavation process were obtained.Numerical simulation of coal seam excavation,in the process of coal seam excavation,the stress on the roof gradually increased,and the displacement change also increased.The farther the working surface was propelled,the more the goaf area was broken.Large shear damage began to occur,and the scope of shear failure continued to increase.