Research purposes: In the construction of karst tunnel of high-speed railway, it is necessary to find out the hidden karst at the bottom of the tunnel, which affects the safety of the tunnel, and what method can be used to quickly find out the depth, nature and range of the karst, therefore, the seismic imaging method is proposed and studied in this paper.
Research conclusions: (1) Using the migration distance and fault width characteristics of the seismic imaging method, the plane physical connection with the adjacent survey line in oblique direction and short distance with the same characteristics, and the positive calculation and statistics of karst wave velocity, it is feasible to karst morpolohgy and drill holes to quickly discover the depth, nature and range of the hidden karst at the bottom of the tunnel which affects the safety of the tunnel. (2) It can detect the karst development and karst development, clay-filled karst caves, cavity karst caves and residual slag in different depths under the maximum depth of 30 m under the multiple survey lines at the bottom of the tunnel, and carry out engineering treatment, it is necessary to determine the best and effective scheme, which corresponds to cement grouting, high-pressure jet grouting pile, pile-board structure or masonry buttress, removal of residual slag, and the strength of the tunnel bottom after treatment is stable and does not sink or arch, and to ensure the smooth discharge of karst water, can ensure the safety of the tunnel. (3) We should pay attention to the inspection of the construction quality of the secondary filling layer of the inverted arch at the bottom of the tunnel. (4) The research results can be used to quickly find out the depth, nature and range of the hidden karst at the bottom of the tunnel, which affects the safety of the tunnel, to determine the best effective treatment program for reference.