Imaging of karst cave using ground penetrating radar and electrical resistivity tomography: a case study in Shandong, China

Abstract

A denudation-dissolution hilly area about 20km southeast of Jinan city, Shandong Province, China is characterized by karst features. The upper part of the area is covered by quaternary Holocene flood and slope deposits, and the lower bedrock is Ordovician limestone, which is a moderately weathered massive structure with developed joints and fissured fractures, and solution grooves can be seen locally. The local government to better serve the surrounding residents and the surrounding facilities, here is planned for the substation, for later security construction, electrical resistivity tomography (ERT) method and ground penetrating radar (GPR) method were used to investigate the underground karst caves. The aim of the joint use of the two methods is to better describe the characteristics of karst landform, a 160 MHz shielding antenna was employed in the GPR survey, while the frequency limits the scope of the depth of the electromagnetic waves can reach. However, it provides a lot of shallow stratigraphic information, which well represents the boundary between overburden and bedrock and the development of karst. The use of ERT method further makes up for the depth defects of the GPR method, and two-dimensional imaging of underground resistivity distribution was carried out, which also helps to further identify the characteristics of underground karst. The combination of the two geophysical methods can accurately delineate the development of underground karst, which also proves that the combination of the GPR method and ERT method has good application value in karst landform detection, and can also be applied to a similar geological survey.