Study On Deformation Characteristics Of Loose Bed In Fudong Mining Area Tested By Combined Well-Ground Electrical Method

Coal seam mining will cause a series of damage effects to the overlying strata such as deformation and damage.At the same time,the environmental problems caused by coal mining have been concerned for many years.The loose layer covered by the mine in the east of China is thick,which in the process of mining not only causes the surface subsidence and other environmental negative effects,but also damages the building of the industrial square and causes the fracture of the shaft,which seriously harms the safety production of the mine.Due to the lack of research on the internal deformation characteristics of loose layer,the research and observation of its internal deformation subsidence mechanism are not enough.Therefore,it is of great theoretical and practical significance to explore the geophysical exploration means for the observation of loose layer deformation.In this paper,the working surface of a mine in Fudong Mining area is covered with extremely thick loose strata as the research object.Based on the extraction and analysis of borehole logging curves,combined with the indoor resistivity test of in-situ borehole coring,geoelectric parameters and physical characteristics required by numerical simulation and similar simulation are selected.The geoelectric model of loose bed segment was constructed,and the test simulation study was carried out through the twodimensional borehole-ground combined electrical method observation system model and three-dimensional borehole-ground combined electrical method observation model.The physical observation test was carried out on the internal deformation characteristics of loose bed under mining conditions,and the field test was carried out combined with the in-situ characteristics of loose bed in the study area.The following results have been achieved:(1)The lateral resistivity distribution of borehole was obtained by using borehole logging data in the study area.In situ coring was carried out in the engineering field,and resistivity test was carried out in the laboratory.Based on the above data results,the numerical simulation of geoelectric field parameters was designed,and the mining control group was set up to carry out the test simulation of different types of the combined well and ground electrical method observation system.The study showed that the combined well-ground electrical method was able to distinguish the formation information with differentiated distribution of the resistivity of the loose layer,and demonstrated that by increasing the number of electrodes in the observation system and reducing the electrode spacing,the ability to identify more accurate stratification effects could be obtained.The feasibility of the combined well-ground testing technique for the observation of loose layer deformation is verified.(2)The 3D physical similarity simulation test was designed,and the dynamic capture data of the loose layer deformation field by the combined well-ground electrical testing technology was obtained based on the mining conditions.Through the ratio analysis between the resistivity test results and the background values in different mining stages,combined with the field test process,when the ratio results reach 3.5 times,the formation deformation of " Fourth aquifer " is obviously observed.With the advancing of the working face,the maximum ratio result of the influence of the internal deformation of the overlying loose layer in the working face is 7 times.At the same time,as the influence of mining intensifies,the ratio results show that the formation deformation gradually develops upward to the " Second aquifer " strata.Corresponding to the stoping schedule,the ratio results show that the combined testing system can realize the dynamic capture of formation deformation under the influence of mining advance.The effectiveness of the combined well-ground testing technique for loose layer deformation capture is comprehensively verified by physical similarity simulation test.(3)Field test was carried out to further explore the effective detection of geological target body around borehole and the differentiated resolution effect of loose strata by the combined well ground electrical method.The field test results can correspond to the actual stratum profile,and the test effect is good.The field measurement of combined well-ground electrical method provides a new technical idea and basic data support for measuring the internal deformation of loose layer.Due to the influence of the mining schedule,the dynamic measurement of the combined well and ground electrical method will be carried out in the future,to strengthen the further study of the deformation characteristics of the loose layer.Figure [37] Table [17] Reference [80]...