Applications of ground penetrating radar in the Three Gorges Project, China

During the Three Gorges Project (TGP) on the Yangtze River in China, a number of complicated engineering and geological problems had to be solved. A quick and high resolution non-destructive method was needed to find buried geological defects and engineering quality problems in order to guarantee the project schedule and engineering quality. Ground penetrating radar (GPR) was one technique which was effectively applied to detect the extension of inhomogeneous weathering of granite prior to excavation, to map the extent and attitude of large faults and weathering of alternative layers, and to check the engineering quality of concrete work for TGP during construction. In this paper, three case histories are discussed.nThe detection results proved consistent with the results of excavation with the performance of GPR obvious. As a large scale, high technology and difficult construction, The Three Gorges Project(TGP) is the largest and most ambitious infrastructure project in the world. Geological exploration and surveys have been conducted for more than 30 years providing a wealth of data prior to construction. Like other large hydroelectric engineering projects, the TGP was faced with many complicated engineering, geological and technology problems during construction, such as outlining inhomogeneous weathering layers in granite during excavation, determining the occurrence of large faults and weathering of alternative layers, detecting the position of seepage in the embankment, checking the engineering quality of the work, and so on. If these problems could not be rapidly solved during construction, they would delay the construction process and affect construction quality. As a high resolution non-destructive detection technique, GPR was able to rapidly and economically solve some of the problems encountered during TGP construction which other geophysical methods could not accomplish. Through test, research and practical application, successful results were obtained using GPR to solve the engineering problems mentioned. In this paper, three case histories are presented. The first shows the delineation of inhomogeneous layers in granite, the second illustrates the definition of faults and weathering of alternative layers, and the third demonstrates the checking of the engineering quality of work for the TGP. The detection results were confirmed by on-site inspection.