Seismic Downhole & Cross-hole Testing

The seismic downhole method provides a designer with information pertinent to the seismic wave velocities of the materials). The P- wave and S-wave velocities are directly related to the important geotechnical elastic constants of Poisson’s ratio, shear modulus, bulk modulus, and Young’s modulus. Accurate in-situ P-wave and S-wave velocity profiles are essential in geotechnical foundation designs

These parameters are used in both analyses of soil behaviour under both static and dynamic loads where the elastic constants are input variables into the models defining the different states of deformations such as elastic, elasto-plastic, and failure. Another important use of estimated shear wave velocities in geotechnical design is in the liquefaction assessment of soils.

The Downhole Test is a method that determines soil stiffness properties by analysing direct compressional and shear waves along a borehole down to about 30 m. The downhole testing aims to derive elastic rock properties such as Poisons ratio or Young’s modulus. Shear waves have to be generated at the surface.