Analysis Of Deep Mining And Upward Mining Subsidence Patterns In Weakly Cemented Overburden At The Ningdong Mine

The Ningdong mining area is extensively stockpiled with coal resources and lies within weakly cemented Jurassic and Cretaceous strata.Recent studies have shown that the physical and mechanical properties of the rocks in this area differ significantly from the Carboniferous and Permian rocks in the eastern mining areas.Under the same mining conditions,the surface movement and deformation pattern in the Ningdong mining area also has obvious peculiarities.As the focus of coal mining in China shifts to the west year by year,local ecological and environmental problems are becoming more and more prominent,with mining-induced subsidence being one of the main causes of ecological damage.Therefore,accurate monitoring and prediction of mining subsidence is crucial to environmental protection.As mining continues to extend deeper and deeper,some mines are also subject to repetitive mining operations,and their mining subsidence patterns change compared to previous ones.To address the above issues,the Yangchangwan coal mine in the Ningdong mining area was selected as the study area,and the study focused on the 150202 working face of the Yangchangwan coal mine on the basis of the existing data from the 130201 working face.The main research contents and results of this thesis are as follows:(1)The observation data of the 130201 working face was collated and the surface subsidence and movement deformation curve of the 130201 working face was drawn.The duration of surface movement is short,especially during the onset and recession periods,and the active period accounts for a greater proportion of subsidence,which is faster during the active period,up to 98.5 mm/day.During the mining process there is a concentration of subsidence,the surface subsidence rate is high and the dynamic deformation is intense and concentrated.The surface movement angle parameters and the expected parameters of mining subsidence were obtained to provide a basis for the design of the 150202 working face observation station.(2)A surface movement observation station was designed for the 150202 working face using the relevant parameters of the 130201 working face,and an unmanned aerial vehicle(UAV)was used to carry out comprehensive observations of the mine area at the same time as the conventional observations.The overall subsidence contour map of the mine area was obtained and the relevant surface movement angle parameters were calculated.The strike direction observation line was placed close to the downhill direction and the deformation of the 150201 working face did not propagate to the observation line.The 150202 working face in the up-hill direction has a much smaller boundary angle than the 130201 working face due to the superimposed influence of the150202 working face;both the movement angle and the full mining angle are also smaller than the 130201 working face,and the surface deformation caused by deep mining is greater and the influence is more obvious,and the surface flat bottom area is more expanded,which has a greater impact on the geological environment.150202 working face surface The active phase of movement accounts for a longer duration of overall surface movement than the 130201 working face,but the maximum value of the surface subsidence rate of 150202 is much smaller than that of the 130201 working face,and the surface subsidence rate is not significant in the case of deep mining.150202 working face is affected by the remaining deformation of the 150201 working face that has been mined next to it,and the start of the mining impact period is significantly shorter.(3)150202 working face is affected by 150201 working face and it is not clear the specific magnitude of 150201’s influence on it,so it is difficult to set boundary conditions,so the data of 130201 working face is used for numerical simulation.The numerical model of the 130201 workings was established and the model parameters were optimised so that the surface subsidence was in line with the measured conditions,and after the upstream mining simulation,all the angular parameters became smaller compared to the initial mining,and the upstream mining subsidence coefficient increased significantly compared to the traditional repeated mining.