Application of CPTU-based soil classification methods in Hong Kong-Zhuhai-Macao Bridge

The parameters obtained from the piezocone penetration tests (CPTU) have been widely used for soil profiling and geostratigraphy over the decades. In this study, large amount of CPTU soundings and parallel drilling borings and laboratory tests are performed to characterize the soils in the projects of Hong Kong-Zhuhai-Macao Bridge. The soil types determined from six CPTU-based soil classification charts are compared with those of the laboratory tests. It is shown that the soil classification charts using the non-normalized CPTU data are the worst performers with an accuracy of 80%. The normalized CPTU-based charts provide a more accurate evaluation of the soil type. However, the soil boundaries given by the normalized charts are not consistent with the soil types determined by the China's standard. Moreover, the accuracies of the normalized charts are over-estimated since a wide range of soil zones (e.g., zone 4 to 5) are used to characterize one single soil (e.g., silt). The CPTU-based soil classification chart modified for the China's practice is the best performer with an accuracy of 90%.