Determining the Geotechnical Parameters of Rock Mass via Non-invasive Geophysical Methods

Rock mass reliability classification is carried out via geotechnical parameters, such as rock mass integrity index (Kv), volume joint number of rock mass (JV), rock core index (RCI), average joint spacing (dP), modulus of elasticity (E) and rock quality designation (RQD) etc. Such geomechanical parameters, however, are traditionally obtained from the expensive drilling tests. Therefore, it is never an easy task to acquire engineering parameters in the frequent borehole tests. Furthermore, such tests cannot provide volumetric evaluation of subsurface geological units. So, an attempt to minimize lots of drilling tests and to correctly estimate geotechnical parameters is essential for appropriate designs of engineering infrastructures. We propose an empirical-based geophysical approach of non-invasive geophysical method, namely controlled-source audio-frequency magneto telluric (CSAMT). Useful equations are obtained by the integration of limited boreholes and geophysical data, which provides determination of geomechanical parameters for all geophysical measurements over the complete site where even no well is available. This approach offers a thorough insight into the subsurface geology by 2D and 3D mapping of engineering parameters, eradicates the subsurface ambiguities due to limited wells, and fills a gap between the perfect geotechnical models and the inadequate drilling tests.