Applied hydrogeophysics for characterisation of tailings facilities

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Linnanmaa, auditorium IT115. Remote connection: https://oulu.zoom.us/j/61809696082

Topic of the dissertation

Applied hydrogeophysics for characterisation of tailings facilities

Doctoral candidate

Master of Science Raul Mollehuara Canales

Faculty and unit

University of Oulu Graduate School, Faculty of Technology, Oulu Mining School

Subject of study

Geophysics

Opponent

Professor Jussi Leveinen, Aalto University

Second opponent

Professor Pedro Martinez-Pagan, Polytechnic University of Cartagena

Custos

Professor Juha Pekka Lunkka, University of Oulu

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Applied hydrogeophysics for characterisation of tailings facilities

This doctoral thesis presents the results of interpreting hydrogeological and elastic properties in mining tailings storage facilities (TSFs) within the framework of hydrogeophysics.

In this research, two near-surface geophysical techniques seismic refraction (SR) and electrical resistivity imaging (ERI) were used for data acquisition in two TSF sites (Brukunga mine in South Australia, and Pyhäsalmi mine in Finland). The data acquired by seismic refraction was used to obtain seismic P-wave velocity (Vp) models while S-wave velocity (Vs) models were obtained from the same data by multichannel analysis of surface waves (MASW). Electrical resistivity imaging (ERI) was applied to obtain cross-sections of bulk electrical resistivity. The outputs of the SR method were used to set the geometric constraints for the inversion of the apparent electrical resistivity data in the ERI model.

This research shows that geophysical methods such as ERI and SR can retrieve high-resolution images of the subsurface of tailings facilities mapping the structure, the phreatic line, the dynamics of water, and detecting changes associated with the electrical resistivity response of the tailings media.

The thesis also describes the methods and workflow for establishing dependencies between the petrophysical parameters from geophysical data (i.e., compressional and shear wave velocities, electrical resistivity) and the geotechnical and water-related properties of the tailings media (i.e., elastic properties, water saturation, water content, porosity). The dependences in the form of empirical equations are key for filling the gap of theoretical deductions.

Furthermore, this thesis contributes to the research field through a unified workflow for integrating and interpreting geophysical data acquired in tailings facilities using petrophysical and ‘rock’ physics principles. The interpretation describes and estimates quantitatively the state condition of the tailings subsurface in terms of hydrogeological and geotechnical parameters.
Last updated: 17.11.2021