ABSTRACT
Borehole geophysical logging methods provide a complete set of direct, continuous and in situ measurements for characterization of structural, compositional, geomechanical and petrophysical rock mass properties at depth. A new concept of stackable borehole logging tools for geotechnical characterization has been implemented tested and applied. The measurements obtained cover the basic geologic and geomechanical rock mass characterization features. A combination of oriented images and borehole logs is necessary for the characterization of the compositional-petrophysical and geomechanical properties of the rocks in the subsurface. The logging devices are mounted in a stackable toolstring and can be combined to fit characterization requirements that require specific tool combinations (e.g. PVC cased holes, or open hole measurements). This design was implemented by a logging tool manufacturer and is being successfully applied in different tunnel construction projects. This type of toolstrings are also suitable to be used to for the characterization in advance of the rock mass ahead of the tunnel face in horizontal and subhorizontal holes.
