To Study the Geotechnical Parameters for Slope Stability in Opencast Mines

Abstract

Slope stability is a critical aspect in the design and operation of opencast mines throughout the entire project lifecycle. Slope failure can lead to significant hazards including equipment damage, production delays, and worker injuries. Therefore, ensuring stable slope design is essential. The failure mechanisms are primarily influenced by geotechnical parameters such as rock mass strength, structural discontinuities, and groundwater conditions. Historically, due to limited technological advancement, slope failures were frequent, and the development of benches posed major challenges. However, modern advancements in rock mechanics, field investigations, and simulation-based software have revolutionized slope design processes. With the integration of advanced software tools and skilled personnel, slope failures can now be effectively predicted and mitigated. This study focuses on understanding and analyzing pit slope design in the context of the Singhori opencast project of Western Coalfields Limited (WCL). The project involves the use of secondary data from earlier research and government agencies, which has been numerically modeled to analyze slope behavior. The findings emphasize that final pit design is not only influenced by ore grade and economics, but also critically by rock mass strength and stability. Thus, slope stability assessments must be integral to every mining plan to ensure safe and efficient operations.

Introduction

1. Importance of Slope Stability in Opencast Mining

• Slope stability is crucial for safety, operational continuity, and economic viability in opencast mines.

• In India, slope design still largely relies on empirical methods, lacking site-specific standards, increasing risk especially in deeper mines.

• Factors affecting slope stability include excavation, groundwater fluctuations, weathering, blasting, and equipment movement.

• Economic pressures often push for steeper slopes, which increase ore recovery but also risk failure if not properly designed.

2. Technical and Environmental Challenges

• Removal of overburden creates large waste dumps, leading to land degradation and additional instability risks.

• Geotechnical complexity increases with depth: weathered rocks lose cohesion, groundwater infiltrates, and faults or joints reduce rock mass strength.

• Failures can cause production delays, equipment loss, human casualties, and in some cases, permanent loss of mine areas.

3. Modern Slope Stability Approaches

• Advanced methods now include:

  • Numerical modeling (e.g., FEM, LEM, DEM)

  • Probabilistic analysis

  • Real-time monitoring tools (piezometers, inclinometers, extensometers, radar)

• A balanced slope design requires:

  • Detailed site investigations: drilling, geophysical surveys, lab/in-situ testing

  • Integration of hydrogeological and geotechnical data

4. Literature Review – Key Studies & Findings

A series of global and Indian studies contributed insights:

5. Singhori Opencast Project – Numerical Modeling Approach

• Location: Singhori OCP, Western Coalfields Limited (WCL)

• Geological units: Soil, Weathered Zone, Kamptee Formation, Barakar Formation

• Methodology:

  • FEM (Phase2): Used Shear Strength Reduction (SSR) method to model failure zones.

  • LEM (GEO5): Bishop’s method validated the FEM results.

  • Scenarios simulated: Current operational vs. final mining stages.

  • Inputs: Accurate geological profiles, bench geometries, geotechnical parameters from field/lab studies.

• Findings:

  • Current slopes generally stable.

  • Final pit slopes may become vulnerable, especially in weathered zones and steep benches.

  • Recommended dump optimization and reinforcement to maintain acceptable safety margins.

6. Key Takeaways & Recommendations

• There is an urgent need in Indian mining to:

  • Standardize slope stability practices

  • Modernize design tools and monitoring systems

  • Improve workforce technical capacity

• The Singhori case underscores the importance of:

  • Integrated numerical modeling

  • Geologically informed design

  • Real-time risk monitoring

Conclusion

Based on the detailed geotechnical assessment and slope stability analysis of the Singhori Opencast Coal Mine, using both the Limit Equilibrium Method (LEM) and Finite Element Method (FEM), the following conclusions and recommendations have been drawn. These findings incorporate results from current and final mining conditions, under varying geological formations and slope configurations, while also considering critical factors such as water saturation and weather influences:

References

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Copyright

Copyright © 2025 Mr. Ravi Singh, Dr. Ram Chandra Chaurasia . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.