Geophysics in Service of Mining: Perspectives and Strategies - Interview with Kellwi Tejada
Advanced Techniques in Mining Geophysics - An Interview with Kellwi Tejada
The interview focuses on the experience of Kellwi Tejada, who is the head of geophysics at Anddes, and addresses the main geophysical techniques used in mining projects. Techniques such as seismic prospecting, geo-electric prospecting, and other tools like Ground Penetrating Radar (GPR) and Transient Electromagnetic (TEM) are discussed. Techniques such as electrical resistivity tomography, 2D MASW testing, and seismic refraction tomography are highlighted as the most effective for characterizing foundation soil and mining components.
What are the main geophysical techniques you have used in mining projects, and which do you consider most effective for applications in the mining industry?
I consider that my experience as a geophysical engineer is focused on applied geophysics in terrains up to depths ≤100 m, which allows obtaining high-resolution and precise data for making the best decisions in different engineering studies in mining.
The techniques I have used the most, due to their reliability and feasibility, are those found in the seismic prospecting group, such as seismic refraction tomography, seismic reflection, surface wave tests like MASW 1D/2D, passive seismic tests like multichannel analysis of microtremors and the H/V spectral ratio test. Additionally, I have experience in conducting vibration tests for blast monitoring and well seismic tests (Down hole, Cross Hole, and Up Hole). I also consistently apply geo-electric prospecting tests, such as electrical resistivity tomography, induced polarization, measurements of natural and induced electrical potential, electromagnetic tests like Ground Penetrating Radar (GPR) and Transient Electromagnetic (TEM), each for specific purposes.
Among the techniques I consider most effective of all those mentioned are 2D and 3D electrical resistivity tomography, MASW 2D testing, seismic refraction tomography, well seismic testing, and GPR. All of these techniques are aimed at characterizing foundation soil and mining components to detect any potential danger to the stability and integrity of the structure.
Could you describe a specific challenge you have faced when applying geophysical techniques in a mining environment and how you resolved it?
I remember once working in an environment with heavy vehicle traffic and production plants generating significant environmental noise, which hindered obtaining good seismic data. I resolved this by applying new passive seismic techniques such as the Multichannel Analysis of Microtremors (MAM) test. This test records signals from the abundant environmental noise in that location, allowing for good characterization of the subsurface with successful results. We had to plan the tests differently to achieve our goal, ensuring good results this time. This experience taught us that geophysical methods easily adapt to any environment or situation. While not all methods may be useful due to their advantages and disadvantages, at Anddes, we have a wide range of equipment and tests that enable us to quickly address various problems.
How do you determine which geophysical technique is most suitable for a specific mining project, considering factors such as soil type, depth, and lithology?
Several aspects must be taken into account. First, I identify the purpose of the study, the depth of investigation desired, the conditions of the terrain to be explored, and general aspects of local geology. Based on these initial considerations, I choose the most suitable technique for conducting the survey. For example, if my goal is to determine the thickness of a layer containing abundant moisture or a high water table (e.g., a bog), I cannot use seismic refraction because the presence of water distorts the arrival of P-waves. In this situation, I use electrical resistivity tomography, which characterizes such soils well as electrical current can easily transmit through them.
On the other hand, if the goal is to characterize rock type based on wave velocities, the most appropriate test is seismic refraction or MASW 2D, which has an active source. In this case, the MAM test cannot be applied because the phenomenon of wave dispersion by passive sources does not occur in such rigid materials.
What is your approach to acquiring and processing geophysical data in mining projects, especially in areas with adverse conditions or difficult access?
The key is to have a very good understanding of the environment where exploration will take place. To achieve this, it is essential to conduct a technical visit to the project site before conducting geophysical tests. This allows us to identify the best areas of the terrain to ensure that the test provides high-quality data. However, it’s not enough just to do that; it’s also necessary to evaluate the characteristics of the geophysical equipment, such as the source, power, instrument sensitivity, geometric arrangement to be used, among others. All these aspects will contribute to success in prospecting and data processing. Therefore, it’s crucial that the assigned personnel have the necessary experience to address these situations.
How does the interpretation of geophysical data contribute to planning and decision-making in the development of a mining project?
I believe that geophysical interpretation plays a fundamental role in the planning and decision-making of a mining project through the assessment and management of risks associated with mining activities, such as terrain stability, groundwater contamination, and the identification of geological-geotechnical risk zones.
Al utilizar técnicas geofísicas no solo se beneficia las empresas mineras en el desarrollo de sus proyectos de ingeniería, sino también el entorno ambiental y social. Por ejemplo, la prospección geofísica ayuda a caracterizar grandes áreas de terreno de manera precisa, eficiente y sin ser invasivo, optimizando la necesidad de realizar un número significativo de perforaciones exploratorias invasivas lo que reduce costos y el impacto ambiental asociado a la prospección del subsuelo. Finalmente, todas estas bondades que brinda la prospección geofísica promueven una gestión más eficiente de los recursos naturales, contribuyendo así a la preservación de los ecosistemas y al desarrollo sostenible de las comunidades cercanas a las operaciones mineras.
Kellwi Tejada
Head of Geophysics