| With the increase of mining area and depth,the ground subsidence caused by orebody mining-out has a great impact on the production and living safety of the mining area,as well as on the ecological environment and sustainable development of the mining area.Since land subsidence began to appear in an iron mining area in Ma'anshan City in2017,the land subsidence range has been expanding continuously.Even after the treatment measures of-150 m mined-out area filled underground,the maximum cumulative settlement and settlement speed of the mining area are still accelerating,threatening the safety production of the mining area,the cemetery and filling station on the ground.However,the formation reason and mechanism of land subsidence in this mine have not been clarified yet,which cannot provide scientific basis for the subsequent development of land subsidence engineering measures.To this end,the ground subsidence in this paper,the mining area as the study object,in the full collection and sorting out existing geological,hydrogeological reports and maps in the study area,on the basis of such information,in the study area 91 statistical analysis of land subsidence monitoring data using the probability integral method and grey model to predict land subsidence,mining area and analysis of the space-time evolution characteristics of land subsidence.Finally,the mechanism of land subsidence is clarified,and the following main study results are obtained:(1)Based on the probability integral method,the ground subsidence caused by-150 m mined-out area was predicted under the condition that only-150 m mined-out area was completely collapsed,and the maximum predicted value of ground deformation was obtained.And the predicted value of the monitoring point on the section ?-??.By comparing with the actual monitoring value,it is concluded that the-150 m mined-out area has limited influence on the land subsidence in the study area,and there are other factors that promote the development of land subsidence in the study area.(2)Based on the monitoring data of land subsidence in the study area,Grey model of non-equispaced sequences is adopted to model the monitoring points which do not reach the predicted value of probability integral method in the ?-?? profile and the settlement rate of the maximum monitoring point 4-2.The prediction results show that the-150 m mined-out area has less and less influence on ?-?? profile with the passage of time.In addition,the maximum monitoring point 4-2 of the subsidence rate first entered the active subsidence period on February 4,2021.(3)Through the mathematical statistics of the monitoring data of land subsidence in the study area and the analysis of its spatial evolution characteristics,the results show that the cumulative settlement amount and cumulative settlement rate increase with the increase of the cumulative days,and the development trend of land subsidence in the study area extends to the northeast direction and the north-south direction simultaneously.(4)Through time and space evolution characteristics of ground subsidence and land subsidence prediction results and the current iron ore mining situation and geophysical interpretation results in the study area of the comprehensive analysis,that caused the outcome of the study area is the main factor of ground settlement-150 m mined-out area,ongoing iron ore mining activity and the filling process at present.(5)According to the study of the mechanism of land subsidence,a new monitoring scheme and prevention measures of land subsidence are put forward.Five monitoring lines A,B,C,D and E and 20 monitoring points are planned to be laid in the northeast of-150 m mined-out area to monitor the land subsidence in the study area.Ground drilling was used to grouting and filling the-150 m mined-out area and its overlying loose area.At the same time,the filling technology of mined-out area and the strength of filling body are improved to achieve the purpose of restraining ground subsidence and continuing development. |
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