Study On The Ground Movement And Deformation Of Affiliated Architecture In Eastern Area Of Cheng-chao Iron Mine

Study on ground movement and deformation of man-made architecture induced by sublevel caving in underground metal mine are not well known and have not been extensively described. As the deepening of mining level, deformation of strata become more complicated due to increase of multiple impact factors. As a result, subsidence area often extended beyond preplanning which pose a great threat to security of mining activity. Therefore, research on deformation of strata and man-made architecture induced by sublevel caving in underground metal mine with complex geologic setting is of great necessity and value in ensuring the safety of mining activity and preventing disaster happening.On account of gradually aggravated situation on stability of ground surface and affiliated architecture under complex geological setting in eastern area of Cheng-chao iron mine, the Cheng-chao iron mine was selected as the representative case study in this paper. By means of geological analysis, highly precise three-dimensional monitoring on surface movement and fissure deformation and numerical simulation, detailed study on surface movement and architecture deformation were carried out. The main research results are as follows:Firstly, the effect on subsidence exerted by geologic and mining parameters was revealed. Results shows that the existence of gob resulting from the sublevel caving method adopted in mining account for mostly the appearance of surface movement and fissure displacement, and the development of gob either in spatial or temporal dimension along with the schedule of mining greatly determined the trend of surface movement and fissure deformation.Secondly, the discrepancy in mechanism of structure damage between eastern main shaft and western ventilating shaft were figured out. The southern part of eastern main shaft area is a sliding slope induced by underground mining which provide certain free surface for area behind; As a result of that area in the vicinity of shaft suffer from toppling failure along steep joints, the surface movement was magnified by highly weathered strata with depth approximate to fifty meters and underground water. As for western ventilating shaft, the fluctuation of horizontal displacement result from its relative location with two gobs and high quality wall rock deferred the development of damage to some extent.Thirdly, thorough investigation concerning mechanism of ground movement was carried out. In the initial stage of mining activity, surface subsidence was mainly caused by vacuum sucking-off brought by dewatering and failure of hollow structure in marble. As the deepening of mining activity, the gob dimensions extended greatly and lean toward south with an obtuse angle, which aggravate the movement of wall rock.Fourthly, two and three dimensional numerical simulation was carried out by utilizing commercial program UDEC and FLAC3D respectively. Characteristic of distribution of stress and deformation in rock strata as well as limit of subsidence area were analyzed. By comparing simulated outcome with that obtained from on the spot monitoring, the feasibility of numerical tools is conformed. In order to make good use of each one's advantage, these two numerical tools should be combined in practice.Fifthly, six stages of movement of rock strata in metal mine adopting sublevel caving method was determined.1. Relative stable stage 2. Local collapse stage 3. Durative collapse stage 4.stage of surface subsidence 5. Stress loading of wall rock in pit 6. Gradual development stageFinally, based on the fruit of study mentioned above, corresponding remedy measures were proposed. As for the western ventilating shaft, reinforcement work needs to be done for fear that the occurrence of abrupt subsidence. Remedy work in eastern shaft should mainly concentrate on foundation reinforcement and construction of drainage system, what is more, the interactive and periodic excavation of ore deposits in the two sides of shaft can mitigate the deformation of ground surface and architectures to some extent. In addition, backfilling subsidence pits also make a difference in reducing the magnitude and extent of subsidence.