Cross-Hole Computed Tomography in Geological Investigation of Shenzhen Metro Complex Karst Section

［Objective］ The geological survey of Shenzhen Metro complex karst section requires high accuracy, and it is necessary to study the different CT (computed tomography) methods commonly used in karst exploration. ［Method］ Based on the practice of karst exploration on Shenzhen Metro Line 16 and other projects, various geophysical prospecting methods such as elastic wave CT, electromagnetic wave CT and resistivity CT used in karst exploration in Shenzhen are analyzed. The test results of various CT methods are compared, and their advantages and applicability are analyzed by combining the verification information of the probe/detection holes. The detection results are verified in combination with the practical application effect of Shenzhen Metro Line 16. ［Result & Conclusion］ The electromagnetic wave CT method is not as precise as the elastic wave CT method in depicting the rock surface, but the electromagnetic wave CT method has advantages in terms of long detection hole distance. The working efficiency of elastic wave CT method is higher than that of the electromagnetic wave CT method. Compared with resistivity CT method, the interpretation results of elastic wave CT method are closer to the actual strata. The elastic wave CT method is susceptible to environmental vibration interference, and the resistivity CT method is susceptible to electromagnetic environmental interference. The practical application effect of Line 16 shows that results obtained by using elastic wave CT method as the main karst exploration geophysical means are relatively reliable.