| The construction of tunnels in complex mountainous areas in the west is an important guarantee for the in-depth implementation of the “Belt and Road” strategy and a strong transportation country.Efficient and accurate survey work is the decisive factor for the scientific design and safe construction of deep-buried tunnels.The geological survey in the high and cold environment in the western mountainous areas is faced with huge challenges such as complex terrain and geological conditions,harsh climatic conditions,and fragile ecological environment.Due to the complex terrain and dense vegetation,the geological surveying and mapping work is extremely difficult.In order to ascertain the geological conditions of the tunnel,a large number of deep holes are required,but the construction period is long and the cost is high.Therefore,the establishment of high-efficiency,environmentallyfriendly and safe new survey models,innovative high-precision information processing methods and other core technologies are critical technical problems that need to be solved urgently.At present,electromagnetic method has been widely used in railway tunnels,hydropower tunnels and other systems,and has become an important survey method.However,highway deep buried tunnels have their own characteristics.Compared with railway tunnels and hydropower tunnels,the width of the tunnels is wider(mostly double lines),and there are more geological problems to be faced.Moreover,the audio magnetotelluric method is mainly used in the electromagnetic exploration of long and deep tunnels at home and abroad(There is a blind area about 50 m in the shallow buried section,which can be used for reference for the full depth exploration within 2000 m of deep buried tunnel by electromagnetic method.With the support of the Sichuan Provincial Transportation Science and Technology Program and the Queershan Tunnel,Erlangshan Tunnel and other major national engineering projects,based on the basic theory of electromagnetic method,the principle of electromagnetic method,numerical simulation,key processing technology,engineering application and other aspects are carried out.After detailed studies,a new survey model for deep-buried highway tunnels was established,and this model was applied to specific projects to achieve good application results and promote the application of geophysical prospecting technology in highway construction.Through theoretical model analysis,experimental research,engineering verification and other means to carry out technical research,the main innovation results have been achieved:Opposing Coils Transient Electromagnetics(OCTEM)is introduced into the highway tunnel survey for the first time,which overcomes the blind area of the electromagnetic method for shallow detection,and realizes the full depth e l e c t r o m a g n e t i c e x p l o r a t i o n w i t h i n 2 0 0 0 m e t e r s o f t h e d e e p t u n n e l.(2)A formula of apparent resistivity ratio method is put forward,which effectively suppresses the low-resistance shielding effect,realizes the weak anomaly extraction under the low-resistance coverage of the electromagnetic method,and effectively improves the resolution.A new two-dimensional inversion initial model method is constructed,which effectively solves the limitations of the traditional method of initial model construction in solving geological problems in complex areas.(3)A new model for comprehensive investigation of highway tunnels under complex terrain and geological conditions dominated by electromagnetic methods was created,which effectively solved key technical problems such as lithology division,rock mass integrity evaluation,structural identification and unfavorable geological research and judgment in deep buried tunnels.The research results provide scientific industry basis and standard for electromagnetic exploration of highway tunnels in complex mountainous areas,and provides a complete set of geological surveys for the Sichuan-Tibet Expressway and Sichuan-Tibet Railway Examples for reference.The research results have been successfully applied to the new Erlang Mountain Tunnel(length 13.4km,maximum burial depth about 1600m)known as the "Sichuan-Tibet First Tunnel",the world's first ultra-long tunnel with an altitude of more than 4300 meters-Queer Dozens of super projects such as mountain tunnel(maximum altitude 5050 m,buried depth greater than 700m),Kangba No.1 Zheduoshan tunnel(length 8.4km,maximum buried depth nearly 800m)have also been successfully promoted to Huiqing Expressway in Guangdong and Yunnan The survey of highway tunnels outside Zhanhui Expressway and other provinces,as well as the survey of railway tunnels such as Sichuan-Tibet Railway and Zhengwan High-speed Railway,has greatly shortened the survey period,with significant economic and social benefits. |
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