Detection of Unfavorable Karst Cavities in the Carbonaceous Bedrock Area at the Kaihua Segment of Hangzhou-Xinanjiang-Jingdezhen Expressway

The karst cavities can cause great harm to the construction or running of expressway. During the construction of expressway, the detection of these unfavorable geological objects is usually by use of high density resistivity method, and the physical background of the method is the combination of high resistivity of bedrock and low resistivity of karst cavities. In the study area, the Kaihua segment of Hangzhou-Xinanjiang-Jingdezhen Expressway, the widely distributed rich carbonaceous bedrock shows low resistivity, and the conventional interpretation idea of high density resistivity method is not applicable. The research results of this paper suggest that the U shape of relative high resistivity can be an indicative for detection of unfavorable geological objects such as karst cavities. 6 out of 11 boreholes drilled for purpose of calibration revealed karst cavities, and the karst ratio is from 1.2% to 10.3%, indicating the new interpretation method is feasible and reliable.