Details zur Publikation
|Titel (primär)||CPT based seismic methods for geotechnical applications|
|Titel (sekundär)||EGCON 2021 International Conference on Recent Advances in Geotechnics 9 - 11 December 2021 (Virtual Conference)|
|Autor||Fechner, T.; Ködel, U.; Mackens-Siemes, S.; Karl, L.|
|Topic||T5 Future Landscapes|
|Abstract||The Cone Penetration Test (CPT) or Direct-Push technology (DP) has become internationally one of the most widely used and accepted in-situ geomechanical testing methods to determine geotechnical engineering properties of soils and to delineate soil stratigraphy in soft silts, clays to rough cohesive soils (Lunne et al. 2002, ISO, 2009 & 2012) and provides as well as hydrogeologic information (static and dynamic pore pressure, hydraulic conductivity). A CPT machine pushes an instrumented steel cone under a controlled speed vertical into the ground and records the resistance to penetration of the cone and the surface sleeve continuously. CPT is standardized for geotechnical applications (ASTM Standard D 3441, ASTM, 2004, ASTM D-5778). Using the CPT probing method detailed geotechnical profiling can be done. The CPT method provides a near continuous log of the site lithology and geotechnical design parameters such as tip resistance and sleeve friction, pore pressure and friction ratio.
The greater speed and lower costs allow for a greater density of measurements than can affordably be obtained by monitoring wells installed using standard drilling techniques (Maliva, 2016). Thus, the installation of Direct-Push based boreholes are approximately three to five less costly compared to PVC cased boreholes. The Direct-Push technology therefore offers a broad applicability for investigation of unconsolidated sediments being mobile, flexible and cost efficient (Leven et al. 2011).
Anyhow, there is a strong dependency on heterogeneity of local geology and on the distance between the CPT locations, i.e. the one-dimensional CPT information cannot be interpolated between CPT locations without knowledge of the heterogeneity. Geophysical data may fill the interpolation gap between single CPT locations. Especially, seismic data are close to geotechnical parameters if soil dynamic parameters are requested. With the help of seismic data soil dynamic parameters can be recorded integrally, spatially and non-destructively.
If boreholes are available cross-hole seismic tomography offers an approach for characterizing geological heterogeneities at a high resolution. Uncertainty of the beforehand mentioned interpolation between CPT locations could be reduced by applying cross-hole seismic tomography. Therefore, a combination of CPT and cross-hole seismic tomography should allow the transfer of 1D point information from CPT to a 2D-plane or even into the 3D-space by linking seismic velocity to soil dynamic parameters. The paper introduces a novel combination of CPT measurements and seismic methods.
|Fechner, T., Ködel, U., Mackens-Siemes, S., Karl, L. (2021):
CPT based seismic methods for geotechnical applications
EGCON 2021 International Conference on Recent Advances in Geotechnics 9 - 11 December 2021 (Virtual Conference)
Indian Society of Engineering Geology (ISEG), Kolkata,