ISC7

Seismic P-, SH- and SV-Wave Cross-Hole Testing Using Direct-Push Technology for the Determination of Geotechnical Parameters

  • Fechner, Thomas (Geotomographie GmbH)
  • Koedel, Uta (Helmholtz Centre for Environmental Research)
  • Mackens-Siemes, Sonja (Geotomographie GmbH)

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Seismic surveys are often carried out between two or more pre-installed boreholes to assess the unknown geological situation in the subsurface with high resolution. However, the cost of installing boreholes is often a budgetary constraint. Therefore, the Direct-push technology, where rods are pushed into the subsurface, is a more suitable tool and by incorporating seismic sources and receivers into the push rods, geophysical methods become more flexible and adaptable, especially for larger areas of investigation or sites in harsh environments. In this presentation, we show field results using such a direct-push seismic system as a cost-effective alternative to standard borehole-based investigation techniques. Using this technique, a complete cross-hole dataset of P, SV and SH waves was acquired between previously installed PVC cased boreholes and the direct-push borehole [1]. The in-situ profiles of the paired shear wave velocity profiles (SH and SV) were used to evaluate the stress history of the soils by deriving the over-consolidation difference (OCD) [2]. Many geotechnical parameters are influenced by the soil stress history, such as deformation properties and soil stiffness, but in the calculation of parameters such the lateral stress state (K0), consolidation coefficient and liquefaction response the OCR also play an important role. The tests also showed that direct-push based techniques make even seismic methods more flexible, as test positions can be easily adapted and changed according to the results, local conditions or client requirements.