Geophysical Research on Rock Mass Quality Evaluation for Infrastructure Design

Abstract

Evaluation of rock mass quality is necessary for the proper design of engineering infrastructures. Rock quality designation (RQD) is an important geotechnical parameter in the rock mass quality classification. However, given the limited data and natural heterogeneity, rock mass quality evaluation is a challenging task. Traditionally, the rock mechanical parameters are obtained from the drilling tests. However, the drilling tests only provide single-point information and thus cannot provide detailed underground information. Moreover, boreholes are costly and time-consuming, and still cannot be carried out in the steep topographic terrains. Alternatively, electrical resistivity tomography (ERT) is non-invasive, cost-effective, and user-friendly, can provide 2D plane information even 3D information, and can bridge gaps between the available well data and the accurate subsurface geological model. In this research, we establish important empirical relations between ERT and the limited borehole data. We estimated RQD along with the ERT profiles and evaluated the subsurface for rock mass quality even where no borehole exits. Furthermore, the ambiguity of water/clay distinction in the geological model was removed via integration between ERT and induced polarization. Compared with the past geotechnical studies, our work provides far better insights into the subsurface via 2D/3D evaluation of rock mass quality for the development of the engineered structures. Therefore, geophysical research based on ERT can be very helpful in the hard rock terrains lacking sufficient mechanical well data.