Application Of Comprehensive Geophysical Prospecting Method In Goaf Of Iron Mine

Goaf disaster is one of geological disasters.It is because the underground mining activities break the original mechanical balance of the underground rock mass,which makes the surrounding rock stress reconcentration and distribution.If the stress concentration exceeds the failure limit of rock mass,a series of destructive activities such as displacement,roof fall,spalling and rock burst will occur.For skarn iron deposit goaf,it is affected by metallogenic conditions and strata characteristics.The surrounding rock of iron ore body is mainly brittle rock.The deformation of surrounding rock mass after failure is severe,which is easy to cause ground collapse,ground fissures and other natural disasters,and cause damage to human life and property or production activities.Transient electromagnetic method(TEM)has been used for a long time in the exploration of iron mine goaf.Predecessors have done a lot of work on the theory and application effect of TEM.Radon measurement is mostly used in coal mine goaf exploration,less in iron mine goaf.Based on the theory of TEM,this paper firstly solves and deduces the governing equation in the process of two-dimensional profile forward modeling by establishing the transient electromagnetic field forward modeling model of goaf.Based on the two-dimensional profile difference equation,the forward modeling of mine goaf is carried out,the corresponding characteristics of low-resistivity goaf and high-resistivity goaf are simulated respectively,and the basic model of shape identification of goaf anomaly is established.Secondly,the effectiveness test of TEM and radon measurement is carried out over the surrounding known goaf.Through the section test,the response characteristics of TEM forward simulation are summarized and analyzed.Combined with the response characteristics of TEM and radon anomaly areas in the goaf of known test profiles,the interpretation principles of field production interpretation work are determined,and the goaf interpretation work is carried out for exploration profiles.Thirdly,drilling method is used to verify the abnormal range of the delineated goaf,and the comprehensive geophysical methods of TEM and radon measurement are evaluated according to the verification effect.The following conclusions can be drawn from this research:1?Through the two-dimensional forward modeling of transient electromagnetic methods,we have proved the effectiveness of transient electromagnetic methods in iron mine goaf exploration,and summarized the characteristics of transient electromagnetic anomaly response.2?By carrying out the transient electromagnetic methods and radon measurement test in the known iron mine goaf,we have a further understanding of the abnormal response state of the iron mine goaf from the actual situation,and summarized the characteristics of the abnormal response of radon gas.3?In the study area,transient electromagnetic methods and radioactive radon detection work were carried out,and the effectiveness of transient electromagnetic methods and radioactive radon measurement methods in iron mine goaf was verified by drilling verification method.The practice has proved that the application effect of the comprehensive geophysical prospecting method of transient electromagnetic methods and radioactive radon measurement in iron mine goaf detection has certain guiding significance for the exploration of the same type of iron mine goaf.