1. HIGHWALL STABILITY DUE TO GROUND VIBRATIONS FROM BLASTING Dr. Kyle A. Perry Dr. Kot F. Unrug Kevin Harris Michael Raffaldi

2. PURPOSE Objective: Study the effect of blast vibrations on the stability of highwalls and web and barrier pillars Methods Numerical Modeling Field Testing Laser Scanning Vibrations Monitoring

3. PROGRESS SASW Testing Numerical Modeling FLAC3D – Web and Barrier Pillars –Stress Distribution –Pillar Stability 3DEC – Highwall Modeling –Laser Scanning –Displacement/Velocity Field Data Collection

4. SASW Testing Dynamic Material Properties Shear Modulus Damping Ratio Modulus/Damping Reduction Curves Dynamic Model Calibration Iterative Numerical Process

5. SASW Testing

6. Numerical Modeling Sub-Objective 1: Evaluate the influence of highwall mining progression on web/barrier pillar stability using FLAC3D Methodology Simplification – 2D Section Validation – Mark-Bieniawski 5 Case Studies

7. Material Properties Coal Material Model Strain Softening Mohr-Coulomb Roof/Floor Interface Bi-linear Mohr-Coulomb PropertyValue Elastic Modulus (GPa)3 Poisson Ratio0.25 Cohesion (MPa) Initial1.81 Final0.41 Friction Angle (deg) 28 Plastic Strain Range0.015

8. Material Properties Rock Material Model Ubiquitous Joint Model with Softening Rock Matrix PropertiesBedding Plane Properties UCS Elastic Modulus Poisson Ratio Friction Angle Cohesion Tensile Strength Dilation Friction Angle Cohesion Tensile Strength MPaGPa---DegMPa DegdegMPa SS 100400.254013.525.812306.764.64 SH30100.25207.31.741970.50.17 Matrix Softening CohesionTensile StrengthDilation MaximumResidualRange*MaximumResidualRangeMaximumResidualRange* MPa ---MPa ---Deg --- SS13.5200.0055.800.0011200.005 SH7.300.0051.7400.0011900.005 Bedding Plane Softening CohesionTensile StrengthDilation MaximumResidualRange*MaximumResidualRangeMaximumResidualRange* MPa ---MPa ---Deg --- SS6.760.680.0054.6400.0011200.005 SH0.50.051.0050.1700.0011900.005

9. Model Validation

11. Material Properties Peak Strength Calibration Reasonable Web/Barrier Pillars “Infinite Length” Assumption 2D Cross Section Plane Strain Validation

12. Case Study Results CaseHeight (m)Web (W/H)Barrier (W/H)Cover (m) C11.2190.75345.7 C21.2191460.9 C31.2191.25470.1 C41.2191.5591.4 C51.2191.756.5118.9

13. Mining Progression Results

14. Important Findings Tributary Area Loading Common Assumption Arching Effect – Geology Dependent Importance of Barrier Pillar Design Mining Progression De-stressing near Barriers Asymmetric Loading Probability of Pillar Failure/Highwall Collapse Dynamic Impact on Web/Barrier Pillars

15. Numerical Modeling Sub-Objective 2: Correlate active highwall sites with 3DEC for validation and additional testing Methodology Routine trips collect scan data Digitize geometry for mesh generation within 3DEC

16. Primary Mine Site Pine Branch Mine Perry County, KY Mountaintop/Contour Hazard 7 – Hazard 10 seams 200’ – 300’ Highwall Massive Sandstone Important Mine Data Corehole Data Mapping

17. Primary Mine Site

18. VIBRATION AND SCAN DATA Laser Scanning Pre/Post Blast Capture Mesh Generation for 3DEC Geologic Data –2 Primary Joint Sets –85 Degree Dip –110, 185 Direction Seismograph Deployment Highwall Peak and Bottom Single Event Vibration Data

23. SUMMARY HIGHWALL STABILITY STUDY MODELING FIELD DATA LIDAR VIBRATION RECORDS DESIGN CALIBRATION FIELD TESTING LITERATURE/ EMPIRICAL COMPLETED MODEL BLAST AND DAMAGE CORRELATION NUMERICAL STUDY DRAW CONCLUSIONS

24. Project Direction FLAC3D Modeling Probability of Pillar Failure/Highwall Collapse Dynamic Impact on Web/Barrier Pillars 3DEC Modeling Solidify Static Model Quantify/Correlate Damage and Vibrations Sensitivity Studies –Ratio of PPV –Geology –Highwall Geometry

25. QUESTIONS?