Abstract
A cone penetration test (CPT) is the most common geotechnical testing method used to estimate in situ the strength properties of soil. Although CPT provides valuable information, this information is restricted to the location of the measurement. We propose a new concept to integrate shallow S-wave reflection seismic data with CPT data in order to obtain laterally continuous subsoil information. In this vein, a valid quantitative means to relate seismic reflections to CPT data is a primary requirement. The approach proposed here is based on the characterization of the scaling behavior of the local fine-scale S-wave velocity information extracted from the seismic reflection data and the same behavior of the CPT cone resistance. The local velocity contrast information is extracted by linearized Zoeppritz inversion of the amplitude-preserved prestack reflection data. We have formulated a multiscale analysis approach employing the continuous wavelet transform in order to quantitatively characterize the nature of change at an interface of the local S-wave velocity contrast and the CPT cone resistance and to illuminate any relation between these two. The multiscale analysis estimates the singularity parameter α, which indicates the nature of the interfacial change.
The application of our method to the field data has uncovered a striking relation between the nature of variation of the local S-wave velocity contrast and that of CPT cone resistance; otherwise, such a relation was not visible. Detailed analyses of two extensive field datasets have shown that the lateral fine-scale variation of soil strength, as seen by CPT cone resistance, has a close resemblance with the variation of the local S-wave velocity function as seen by angle-dependent reflection measurements. This leads to a unique possibility to integrate two very different in-situ measurements—reflection seismic and CPT—providing laterally continuous detailed information of the soil layer boundaries.
