In the rugged terrain of northeastern Yunnan, China, a groundbreaking study is shedding new light on the intricate stresses and strains deep within the Earth’s crust, with implications that could reshape mining and energy extraction practices. Led by Hui Wang from the BGRIMM Technology Group in Beijing, this research delves into the complex in situ stress fields and mechanical properties of rocks in deep mines, offering a roadmap for safer and more efficient underground operations.
The Maoping lead-zinc mining area, a vital metal mine site in the region, served as the primary study area. Wang and his team conducted hydraulic fracturing in situ stress testing and ultrasonic imaging logging, collecting a wealth of data to analyze the stress field characteristics. “The in situ stress in the mining area is significantly high and increases with depth,” Wang explains. This finding is crucial for understanding the structural integrity of deep mines and the potential risks associated with excavation and extraction.
The study revealed that the stress state in the mining area is dominated by strike-slip stress, where the horizontal stress (σH) is greater than the vertical stress (σV), which in turn is greater than the minimum horizontal stress (σh). This stress regime is characterized by a maximum horizontal principal stress direction trending northwest, a critical piece of information for engineers designing mine tunnels and support structures.
One of the most innovative aspects of the research is the development of a new method to determine stress direction using borehole breakouts and drilling-induced fractures. This technique promises to enhance the accuracy of stress field mapping, a vital tool for disaster prevention and mitigation in deep mining operations.
The research also explored how the mechanical properties of dolomite, a common rock type in the region, evolve with burial depth. “Rocks with higher elastic modulus and strength tend to accumulate more energy, leading to higher in situ stress levels,” Wang notes. This insight is invaluable for predicting rock behavior and designing appropriate support systems in deep mines.
The implications of this research extend beyond the mining industry. In the energy sector, understanding in situ stress fields is essential for the safe and efficient extraction of geothermal energy, as well as for the development of underground energy storage solutions. The findings could also inform the design of deep geological repositories for nuclear waste, a critical component of the nuclear energy cycle.
As the demand for metals and energy continues to grow, so too does the need for safe and efficient deep underground operations. This research, published in the journal Deep Underground Science and Engineering (translated from Chinese), provides a significant step forward in our understanding of the complex stresses and strains that govern the behavior of rocks deep within the Earth’s crust. By informing the design of mine tunnels, support structures, and disaster prevention strategies, this work could help to unlock the full potential of the Earth’s deep resources, while minimizing the risks associated with their extraction. As the energy sector continues to evolve, the insights gained from this study will be invaluable in shaping the future of deep underground operations.