A novel approach to determine rock mechanical parameters using non-invasive geophysical methods

Engineering design of the major infrastructures mainly relies on determination of rock mechanical parameters. However, such indexes are traditionally acquired from the borehole tests of the construction site. The drilling test is generally time-consuming and costly procedure. Further, such tests provide geology information only at some specific points, need more equipment, are hardly carried out in the high topographic sites, and often leave ambiguity in the subsurface interpretation. Alternatively, geophysical research of ERT (electrical resistivity tomography) is swift, user-friendly, inexpensive and non-destructive, and can provide a bridge between the limited drilling tests and a true geotechnical model of the subsurface. In the present research, we introduce a novel geophysical approach to estimate rock mass integrity index (Kv) via integration between the ERT-based electrical resistivity and the limited borehole-based Kv. The obtained Kv offers 2D and 3D evaluation of rock mass integrity along all ERT profiles for large coverage of the project site where even no borehole data exist. Furthermore, uncertainty in the evaluation of water-clay distinction was removed by the integration of IP (induced polarization) with ERT. Our research, compared to the conventional geotechnical investigations, removes uncertainties in the geotechnical model and offers more accuracy in rock mass quality classification for various types of rock units. This approach removes the extensive drilling tests and offers a comprehensive assessment of rock mass integrity to achieve the proper design of engineered infrastructures in the highly heterogeneous terrains.