Research On Transient Electromagnetic Method Detection In Goaf Of Hangshaotai Railway

The goaf is a huge potential threat to high-speed rail tunnels and bridges.Especially in some old mines,the mining history is long,the underground goaf is complicated,and there may be harmful gases such as gas.Most of them are accompanied by some roadway collapse,water accumulation,and even old kiln water accumulation problems,and It is difficult for old gobs to enter their interior for verification.Tunnel and bridge construction will cause secondary disturbances in the goaf,breaking the existing stress balance in the goaf.Such problems may have an adverse impact on railway construction and later operations.Therefore,the use of geophysical methods to detect goaf has important practical significance,and also provides a basis for subsequent evaluation of goaf stability.According to the characteristics of the goaf passing through,a detection and verification system for the goaf is established,and special geological surveys are carried out within the scope that may affect the safety of the line.It is implemented by integrated geological survey methods combining data collection,geological mapping,geophysical exploration,drilling,testing and testing to identify the safety boundaries of goaf and railway lines.The main research results are as follows:(1)Determine the geophysical methods applied to the detection of goaf based on the collection and evaluation of relevant goaf data.(2)Layout of the geophysical detection cross section,using high-precision antimagnetic transient electromagnetic method to delineate the geophysical anomaly area.Verify that there is an empty space in the abnormal area by drilling.Therefore,it is further verified that the diamagnetic transient electromagnetic system is an effective method for detecting shallow goaf.(3)The traditional transient electromagnetic method causes the measured signal to be distorted at an early stage due to the mutual inductance effect,and then there is a detection dead zone in the shallow surface of the earth.The transient electromagnetic system based on the equivalent diamagnetic flux theory is verified by setting the double-transmitting coil to cancel The influence of the induced electromotive force of the transmitting coil improves the early data quality and realizes the shallow detection,which can achieve good results in the detection of shallow goaf.(4)According to the analysis of comprehensive exploration results,the exploration work will be further strengthened for the areas where the goaf is present,and the stability analysis and safety evaluation of the goaf will be made and the recommended measures for remediation will be given.