Study On Strata Imaging Technology For Distributed Tunnel Advance Detection

With the rapid development of China’s economy,investment in highways,railways and other people’s livelihood projects has increased in recent years,coupled with China’s special geographical environment,the number of tunnel projects in China has increased dramatically.A distributed seismic exploration system independently developed by my laboratory,using the flexibility of the distributed system,multiple collectors are connected in a cascade manner to increase the number of collectors,reduce the number of explosives excitation,and achieve less gun excitation 3.Multi-point reception data collection,advance the detection of the tunnel by improving the spatial positioning accuracy and reducing the construction risk.In this paper,based on the distributed tunnel seismic exploration system,the research on stratigraphic imaging technology is carried out.With such instruments,the processed seismic signals are converted into useful geological structure information and presented in the form of images.The main technical links involved in this article are: filtering,first arrival pick-up,extraction of reflected waves,separation of transverse and longitudinal waves,velocity analysis,migration imaging,reflection layer extraction,etc.This article introduces all the technical aspects of distributed tunnel stratum imaging technology,clarifies the role of each link in imaging technology,introduces the technology involved in each link,and includes three very critical links: first pick,Wavefield separation and migration imaging have been studied in detail.Starting from the principle of the first-come-first-pick function,this paper has studied a variety of traditional first-come-first-pick methods,and the traditional firstcome-first-pick-up algorithms through laboratory measured tunnel seismic signals include: energy ratio method,long-time short-time average ratio method The AIC method was compared and verified with each other.On this basis,an improved study on the first-to-first-picking algorithm for long-term and short-time mean ratio was proposed.Then the two links involved in wave field separation: reflected wave extraction and transverse and longitudinal wave separation are studied in detail in this paper.The reflection wave is extracted because the reflection wave of the seismic signal in the tunnel is the desired useful signal;there is a difference between the transverse and longitudinal waves,and the imaging processing after separation can improve the accuracy of data interpretation.Study the application of F-K transform and Radon transform in the extraction of reflected waves,and the application of apparent velocity method and polarization filtering method in the separation of transverse and longitudinal waves.In this paper,Kirchhoff method is used for migration imaging,and the imaging data is reflected in the form of an image.Based on the principle of migration imaging,the applicability of Kirchhoff’s method in this link is studied.From the wave equation,using Green’s theorem,the integral formula of Kirchhoff’s method is derived,and the migration formula of Kirchhoff’s method is further derived.The formation imaging technology studied in this paper has a very important guiding role for the distributed tunnel seismic exploration instrument system developed by our laboratory.It can lay a solid foundation for achieving the entire process from data acquisition to data interpretation for the laboratory,reduce the cost of detection,and enhance the competitiveness of independently developed instruments which designed by our laboratory.