Introduction to Mining: Rock Engineering PDF

30/09/2024 PMY 121 Introduction to Mining Rock Engineering Learning Outcomes Understand the following: 1) Introduction to Rock Mechanics 2) Importance of Rock Mechanics in Engineering 3) Rock Engineering Overview 4) Key Concepts in Rock Mechanics 5) Rock Properties and...

30/09/2024 PMY 121 Introduction to Mining Rock Engineering Learning Outcomes Understand the following: 1) Introduction to Rock Mechanics 2) Importance of Rock Mechanics in Engineering 3) Rock Engineering Overview 4) Key Concepts in Rock Mechanics 5) Rock Properties and Classifications 6) Rock Behavior Under Stresses 7) Virgin Stress and Stress Fields 8) Applications of Rock Engineering 9) Challenges and Future Trends 1  30/09/2024 Introduction to Rock Mechanics Definition: Study of the mechanical behavior of rocks under different physical and environmental conditions. Focus Areas: Rock material strength Deformation and failure modes Interaction between rock and engineered structures Applications: Mining, tunneling, reservoir management Importance of Rock Mechanics in Engineering Ensures stability of underground structures Critical for design of safe and cost-effective engineering projects Prevents geological hazards like landslides and collapses Supports extraction of natural resources like mining, oil/gas drilling 2  30/09/2024 Rock Engineering Overview Definition: Application of rock mechanics principles to design and construct structures interacting with rocks. Disciplines: Geotechnical, mining, petroleum engineering Objective: Stability, safety, and long-term performance of rock structures Key Concepts in Rock Mechanics Stress & Strain: Interaction of forces and deformations within rocks Stress (σ): Force per unit area inside the rock mass Strain (ε): Deformation as a result of stress Types of Stresses: Compressive: Pushes rock together Tensile: Pulls rock apart Shear: Forces rock to slide along planes Elastic vs Plastic Deformation: Elastic: Reversible deformation Plastic: Permanent deformation before failure 3  30/09/2024 Rock Properties and Classifications Physical Properties: Density, porosity, permeability Mechanical Properties: Strength, elasticity, hardness Rock Classifications: Igneous: Formed from magma (granite) Sedimentary: Compacted sediments (sandstone) Metamorphic: Transformed under pressure/heat (marble) Rock Behaviour Under Stresses Brittle Behaviour: Sudden failure upon reaching maximum stress, with little deformation. Common in strong, hard rocks (e.g., granite). Ductile Behaviour: Rock deforms significantly before failure. Observed in weaker or deeply buried rocks (e.g., shale). Elastic Behaviour: Rock returns to its original state once the stress is removed (up to a limit called elastic limit). Failure Mechanisms: Tensile Failure: Rock fails when stretched. Shear Failure: Occurs due to sliding along failure planes. Compressive Failure: Rock breaks when compressed. 4  30/09/2024 Virgin Stress and Stress Fields Virgin Stress: Also called in-situ stress, it refers to the natural state of stress within the Earth's crust before any human interference. Types of Virgin Stresses: Vertical stress (σv): From the weight of overlying material. Horizontal stress (σh): From tectonic forces. Magnitude: Vertical stresses increase with depth due to the weight of overlying strata. Typical Values: Vertical stress increases roughly by 25 MPa per kilometer of depth. Stress Fields: Describe how stress varies across a region or volume of rock. Principal Stresses: The three mutually perpendicular stresses: σ1: Maximum principal stress. σ2: Intermediate principal stress. σ3: Minimum principal stress. Importance in Engineering: Understanding these stress fields helps in predicting rock behavior, especially around excavations. Impact of Underground Excavations on Stress Fields Stress Redistribution: Excavations cause changes in the stress field around the opening. Stress Concentration: Increased stress around the edges of an opening, leading to potential failure (e.g., cracking, spalling). Stress Release: Areas where stress is reduced after excavation. Excavation-Induced Stresses: Tensile Cracking: Occurs at the boundary of the excavation due to stress release. Shear Zones: Form around tunnels and caverns due to stress redistribution. Rockbursting: Sudden and violent failure of overstressed rock in deep underground excavations. Support Systems: Installation of rock supports (bolts, shotcrete) is critical to stabilize excavations. 5  30/09/2024 Applications of Rock Engineering Tunneling: Stress analysis to ensure stability during tunnel excavation. Slope Stability: Analyze stress conditions to prevent landslides. Dams & Reservoirs: Evaluate stress distribution to avoid foundation failures. Mining: Safe extraction methods under high-stress environments. Underground Storage: Stress management in caverns storing gases or hazardous materials. Overview of Surface Mine Support Strategies Objective: Ensure stability of slopes, benches, and highwalls in surface mining operations to prevent collapse and landslides. Key Support Strategies: Slope Design Optimization: Proper bench height, slope angle, and berm design to minimize failure risks. Reinforcement Systems: Rock bolting, mesh, and shotcrete for reinforcing steep slopes or unstable areas. Drainage Control: Preventing water accumulation, which weakens rock masses and increases failure risk. Monitoring and Prevention: Continuous monitoring of slope movement using instruments such as inclinometers and radar. 6  30/09/2024 Common Surface Mine Support Technologies Rock Bolts and Cable Bolts: Function: Reinforce rock slopes by increasing the cohesion and stability of fractured rock masses. Types: Grouted bolts: Provide long-term stabilization by bonding fractured rock. Cable bolts: Used in highwall stabilization, especially for deeper failures. Geosynthetic Reinforcement: Function: Enhances the structural integrity of soil and weak rock layers. Types: Geogrids, geotextiles, and geomembranes placed within slopes to increase tensile strength. Application: Stabilization of loose material in overburden piles and spoil heaps. Slope Retaining Structures: Gabion walls and retaining walls to prevent slope failures at mine edges. Application: For highwall and overburden stability, especially in steep pit edges. Advanced Technologies in Surface Mine Support Remote Monitoring Systems: Ground Penetrating Radar (GPR): Tracks real-time slope movement and detects potential failure zones. Inclinometers and Extensometers: Measure deformation and displacement in slopes and benches. Drones and LIDAR: Used for continuous mapping and monitoring of surface changes, enabling rapid response to stability concerns. Seismic Monitoring: Function: Detects seismic activity caused by rock movements or mining operations, providing early warnings of potential failures. Application: Installed in large open-pit mines to monitor highwall and bench stability. Vegetation and Soil Bioengineering: Reinforcement through planting: Vegetation used to bind soil particles and reduce erosion. Application: Stabilization of overburden piles and mine waste dumps to prevent surface failures and landslides. 7  30/09/2024 Underground Support Techniques and Technologies Objective: Stabilize excavations and prevent collapse by controlling rock movement and stress redistribution. Key Support Strategies: Active Support: Reinforcing the rock mass itself to enhance stability. Rock bolts, cable bolts, grouted anchors Passive Support: Structures that carry load transferred by the rock. Steel arches, shotcrete, wire mesh Preemptive Support: Applied before or during excavation to prevent damage. Ground freezing, pre-tensioned bolts Combination Approaches: Often, a combination of support methods is used to address complex underground conditions. Common Underground Support Technologies Rock Bolts: Function: Increase rock mass integrity by holding rock layers together. Types: Grouted bolts, friction bolts, tensioned bolts. Application: Tunnels, mining shafts, underground caverns. Shotcrete (Sprayed Concrete): Function: Provides surface stabilization by adhering to rock walls. Advantages: Quick to apply, effective at reinforcing loose or fractured rock. Application: Tunnel linings, underground facilities. Steel Sets: Function: Passive support used in highly fractured or weak rock conditions. Structure: Arched or straight steel members installed along the excavation. Application: Long-term support in tunnels or large underground openings. 8  30/09/2024 Advanced Technologies in Underground Support Fiber-Reinforced Shotcrete: Improvement over traditional shotcrete by incorporating fibers (steel or synthetic) for increased tensile strength. Application: Tunnels in high-stress environments or in seismic zones. Ground Freezing Technology: Function: Temporarily stabilizes ground by freezing water content in the rock mass. Application: Provides support in weak, water-bearing rock during tunnel construction. Monitoring and Real-Time Support Systems: Sensors and Remote Monitoring: Embedded in rock mass to measure displacement, stress, and rock movement. Application: Used in large projects such as metro tunnels and mines for continuous safety evaluation and dynamic support adjustments. Case Study Example: Gotthard Base Tunnel Project: Excavation of the longest railway tunnel beneath the Alps. Challenges: Complex geological conditions, high in-situ stress. Solution: Comprehensive stress analysis and advanced support systems were used to maintain tunnel stability and prevent rockburst. 9  30/09/2024 Challenges in Rock Mechanics and Rock Engineering Heterogeneous Rock Mass: Varying properties and behaviors of rock layers. Environmental Factors: Impact of water, temperature, and weathering on stress fields. Uncertainty: Difficulty in predicting exact behavior under stress conditions. Technology Integration: Use of advanced numerical modeling and AI for real-time monitoring. Future Trends in Rock Mechanics and Rock Engineering Improved Modeling: Advanced numerical methods and AI tools. Sustainability: Focus on environmentally friendly excavation and stabilization methods. Automation: Use of robotics and remote sensors in excavation monitoring and control. Resilience: Designing structures that can withstand extreme environmental and stress conditions. 10  30/09/2024 Thank You #UPMiningMatters 11