Recognition Research And Application Of Audio-frequency Magnetotellurics And High Density Resistivity Method For Tunnel Karst

The mountain tunnel is the difficult problem in the construction of road traffic,especially in the western mountainous area.The terrain structure is complex and the geological causes are diverse,which have a serious impact on the tunnel design and construction.Because of the irregular distribution and the diversity of the form,the single drilling is difficult to understand its shape and distribution effectively.The accurate and effective exploring method is our research focus.In the preliminary survey of the tunnel,drilling can be directly reflected by the geological information.But because of the constraints of work cost and terrain,we usually use geophysical exploration methods.In this paper,the starting point is the actual tunnel engineering survey.Then,through collecting a large number of Geological data,paper and previous experiences from pioneers,this paper summarizes the electromagnetic response characteristics of the common geological bodies(such as fault zone,surface unevenness,etc.)in the tunnel survey,which is collected from a large number of collected data and previous experience.This paper analyzes the advantages and disadvantages and the limitations of the relevant survey methods,and establishes the high and low resistance model,the graben basement model,the surface heterogeneous body model,the fault crushing With the model of several geoelectric model,analysis of their electromagnetic response characteristics,and finally applied to the actual tunnel project,through drilling to verify the feasibility of this study.Firstly,the methodological research of the tunnel survey technology in the actual work area is carried out to study the applicability and limitation of the tunnel survey-related methods,and the relevant electromagnetic response characteristics of the area are summarized,and the high and low resistance model suitable for the work area is established.The method of surveying four kinds of geoelectric model of the fault zone model,the surface heterogeneous body model and the fault zone model.Then,based on the model,the principle,device and technical characteristics of the high density resistivity method and the magnetotelluric sounding method are analyzed and summarized,and the two geophysical methods are combined and applied to the actual tunnel engineering survey.In the tunnel survey,the results and limitations of the survey are obtained.The conclusion that the magnetotelluric sounding method is very poor and the static effect is very large,and the high density resistivity method is shallow and the high resistance is serious.Reflecting the rough shortcomings,the two joint interpretation can effectively solve the relevant geological problems.Finally,the drilling area of the predicted anomaly is verified,and the geologic characteristics and geologic anomalies of the work area are compared with the drilling data.The validity of the joint exploration between the magnetotelluric sounding method and the high density resistivity method is proved in practice.In this paper,the actual survey of tunnel engineering as the starting point,to solve the problem of tunnel geological survey technology research summary,through the location model simulation,the actual engineering application,field drilling verification,proved a single geophysical method of the limitations of the use of magnetotelluric measurements Deep and high density resistivity method for joint exploration of tunnels,learn from each other,mutual verification,can effectively solve the engineering geological problems of tunnel survey,the future similar projects provide a good reference and experience.