Application of Cross-Borehole Electromagnetic Computerized Tomography in Karst Detection along Yangtze River Levee

Computerized tomography(CT)of cross-borehole electromagnetic is an advanced technology which successfully uses the principle of CT of medicine in geology.It reflects the physical parameter distribution in scenographic profile according the propagation of electromagnetic waves in lossy media and definite relation between physics and mathematics,finally gives the results by images.The Yangtze River Levees near the Wuhan section are in the area of carbonate rocks,as low-lying and the dynamic changes of Yangtze River water level which make underground water to erode limestone,generates more developed fissures,karst,fractures and so on,causing enormous hidden danger and risk to Yangtze River levee and affecting adjacent industry and agriculture production as well as the security of residents.Through electromagnetic wave CT in cross-borehole test at 90 observations,we have found that 28 observations are anomalous.This detection could provide accurate and reliable subsurface geological information for the safety assessment and early warning of the adjacent area around Yangtze River Levee.