1. DESIGN PROCEDURE FOR UNDERGROUND QUARRIES
DIGITA
UNICA
CSGM
CNR
DESIGN PROCEDURE FOR UNDERGROUND QUARRIES
R. Ciccu1, B. Grosso1, A. Bortolussi2
Department of Geoengineering and Environmental Technologies, University of Cagliari, Cagliari, Italy
Environmental Geology and Geoengineering Institute of CNR – Cagliari Department,
Cagliari, Italy
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

2. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
Dimensional stones are commonly extracted in surface quarrying
easy application and economically convenient if compared with underground extraction;
favorable work conditions
(good air conditions, natural light and reduced noise effects);
quarry accesses are of easy and economical construction;
huge machine can be used without control system for exhaust gases;
they do not require high skilled man power.
There are, however, situations in which surface extraction is
not possible or become less and less convenient with exploitation
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

3. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

4. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

5. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
Underground development of a pit quarry
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

6. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
Underground quarrying has some advantages:
Small Dumps volume
Little Impact on Environment
Working conditions independent from weather
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

7. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
Main Characteristics of Underground Marble quarries
Marble basin of Carrara: more than 60 quarries developed underground
Exploitation Method:
Rooms and Pillars with Irregular path
Access
on the slope of a hill -
at the base of the vertical walls for pit quarries
Typical chambers dimensions
from 20 to 70 meters wide and meters high
Typical pillars dimensions
about 10 meters in diameter
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

8. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

9. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

10. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

11. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

12. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
Main problem of underground quarries is Stability
Law dispositions do not indicate
The design process to be followed
Which methods have to be used for the evaluation of the safety factor
Which type of geomechanics investigation have to be performed
How much stability analysis has to be deepen
Which methods and system have to be set up for monitoring the stability conditions
Interest for guide lines for design and monitoring
quarrying industry
designer
government control offices
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

13. methods for geomechanical design
GUIDE LINES
methods for geomechanical design
methods for stability monitoring
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

14. Activity Results Documents Geologic survey Geological model
Geological maps
Statement of the seismic characters of the region
Design earthquake
Report
Geomechanical Survey
Geomechanical model of the rock mass
Geomechanical maps including data survey position, geomechanical dominium boundaries, joint fabric parameters, intact rock parameters, original state of stress.
Quarry design activity
Geometry of the quarry and its development during exploitation.
Design maps with position and dimension of the exploitation rooms and the pillars at the various stages of the quarry development.
Stability analysis
Stress distribution on rock structure of the quarry and on supports - Stability analysis of blocks - Safety factors
Stress analysis report of the rock structures at its successive geometric configurations.
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

15. Intensively jointed rock mass Moderately jointed rock mass
GEOMECHANICAL MODEL
Intensively jointed rock mass
Moderately jointed rock mass
Little jointed or continuous rock mass
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

16. Activity Results Documents Geologic survey Geological model
Geological maps
Statement of the seismic characters of the region
Design earthquake
Report
Geomechanical Survey
Geomechanical model of the rock mass
Geomechanical maps including data survey position, geomechanical dominium boundaries, joint fabric parameters, intact rock parameters, original state of stress.
Quarry design activity
Geometry of the quarry and its development during exploitation.
Design maps with position and dimension of the exploitation rooms and the pillars at the various stages of the quarry development.
Stability analysis
Stress distribution on rock structure of the quarry and on supports - Stability analysis of blocks - Safety factors
Stress analysis report of the rock structures at its successive geometric configurations.
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

17. ASSESSMENT OF STABILITY
STRESS LEVEL IN THE ROCK STRUCTURE
ASSESSMENT OF STABILITY
EQUILIBRIUM OF BLOCKS
Block Theory and the Limit Equilibrium methods
BLOCK EQUILIBRIUM ANALYSIS
Numerical methods for stress analysis of the continuous media
Boundary Element Methods (BEM), Finite Element Methods (FEM),
Finite Difference Methods (FDM).
STRESS ANALYSIS
Numerical methods for analysis of the discontinuous media
Distinct Element Methods (DEM).
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

18. Moderately jointed rock mass
GEOMECHANICAL MODEL
OF THE ROCK MASS
STRESS ANALYSIS METHOD
Moderately jointed rock mass
Distinct Element Methods (DEM).
Little jointed or
continuous rock mass
Boundary Element Methods (BEM), Finite Element Methods (FEM), Finite Difference Methods (FDM).
Boundary Element Methods (BEM), Finite Element Methods (FEM), Finite Difference Methods (FDM).
Intensively jointed rock mass
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

19. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
STRESS ANALYSIS
EXTRACTION AND
CUTTING PROBLEM
. It can be highlighted that stress analysis is important not only for stability assessment but also for solving some particular problems related to the rock cutting and blocks extraction. SUCH AS BLOCK BREAKING DURING EXTRACTION
Block breaking during extraction
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

20. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

21. FEATURES OF THE STRESS ANALYSIS OF
UNDERGROUND QUARRIES
PROBLEM CHARACTERISTICS
MODEL CHARACTERISTICS
3D GEOMETRY
3D GEOMETRY
LARGE VOLUME (AT LEAST 100 X 100 X 100 m)
LARGE MODEL DIMENSIONS
CONTINUOUS OR SLIGHTLY CONTINUOUS ROCK MASS WITH FEW JOINTS
GENERALLY NUMERICAL METHODS FOR CONTINUOUS MATERIALS CAN BE USED (FEM, BEM, FDM)
SIMPLE CONSTITUTIVE LAW FOR THE INTACT MATERIAL CAN BE GENERALLY ASSUMED WHICH HAS TIPICALLY HIGH STRENGHT AND HIGH ELASTIC PARAMETERS
ELASTIC CONSTITUTIVE LAWS CAN BE USED UP TO THE YELD CONDITIONS
ORIGINAL STATE OF STRESS SOMETIMES INFLUENCED BY THE PRESENCE OF OTHER UNDERGROUND QUARRIES
MEASURES OF THE ORIGINAL STRESS SHOULD BE DONE
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

22. GOALS OF THE STRESS ANALYSIS
ASSESSMENT OF THE GLOBAL STABILITY CONDITIONS
EVALUATION OF THE SAFETY FACTOR IN THE RESISTENT STRUCTURES
ANALYSIS OF BREACKING MECHANISM OF BLOCK DURING EXTRACTION
3D GEOMETRY
HUGE NUMBER OF ELEMENTS AND NODES
LARGE MODEL DIMENSIONS
LARGE AMOUNT OF REQUIRED MEMORY
SMALL ELEMENTS’ DIMENSIONS FOR ACCURATE ANALYSIS
HIGH COMPUTATION COSTS
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

23. SUB-MODELING TECHNIQUE
Construction of the global model (model of the rock mass volume in which stress is influenced by the quarry development )
Analysis of the global model
Construction of the sub - model with a refined finite elements mesh (model of the volume in which detailed results are needed);
Identification of the “driven nodes” (nodes of the sub-model which boundary conditions are taken from the results of the analysis of the global model)
Stress analysis of the sub-model subjected to the boundary conditions derived from the result of the analysis performed on the global model.
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

24. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
3 – D View
Longitudinal Section
Model’s Geometry
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

25. sI=sz=1.21 MPa at the upper surface of the model
MATERIAL PROPERTIES
Homogeneous and isotropic with indefinite elastic behavior
E= Pa, n =0.3 r = 2700 kg/m3
ORIGINAL STATE OF STRESS
sI=sz=1.21 MPa at the upper surface of the model
k=sIII/sI = sx/sz =sy/sz= 0.43
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

26. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
Eight Nodes Brick Element
Mesh’s Geometry
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

27. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
SIMULATION STEPS
Simulation of the original stress conditions
First cut at the top of the first chamber
Exploitation of two horizontal slices of blocks in the first chamber
Excavation of the tunnel in the upper part of the wall of the first chamber
First cut of the second chamber
Exploitation of the rock volume of the second chamber
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

28. GLOBAL MODEL - RESULT OF STRESS ANALYSIS
AT THE DIFFERENT STAGE OF QUARRY DEVELOPMENT
ORIGINAL STATE OF STRESS
EXPLOITATION OF THE FIRST ROOM
FIRST CUT IN THE SECOND ROOM
EXPLOITATION OF THE SECOND ROOM
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

29. SIMULATION OF THE ORIGINAL STATE OF STRESS
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

30. EXPLOITATION OF THE FIRST ROOM
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

31. FIRST CUT IN THE SECOND ROOM
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

32. EXPLOITATION OF THE SECOND ROOM
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

33. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
FIRST SUB-MODEL
15 m
39,4 m
30 m
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

34. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
GLOBAL MODEL
FIRST SUB-MODEL
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

35. FIRST CUT IN THE SECOND ROOM
TUNNEL EXCAVATION
FIRST CUT IN THE SECOND ROOM .
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

36. EXPLOITATION OF THE SECOND ROOM
EXPLOITATION OF THE FIRST SLICES
EXPLOITATION OF THE SECOND ROOM
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

37. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
(s33-[MPa])
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

38. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
(s33-[MPa])
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

39. ANALYSIS OF THE STRESS EVOLUTION DURING THE BLOCK CUTTING
GLOBAL MODEL
SUB-MODEL 1
DETAIL OF THE SUB-MODEL 1
SUB-MODEL 2
2 m
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

40. SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy
CUT AT THE TOP OF THE BLOCK
CUT AT THE BASE OF THE BLOCK
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

41. CUT AT THE BASE OF THE BLOCK
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

42. CUT AT THE TOP OF THE BLOCK
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

43. CONCLUSIONS GUIDE LINES FOR DESIGN AND MONITORING
DEVELOPMENT OF OF UNDERGROUND QUARRIES
FOR DIMENSIONAL STONES EXPLOITATION REQUIRES:
GUIDE LINES FOR DESIGN AND MONITORING
METHODS FOR RELIABLE ASSESSMENT OF STABILITY CONDITIONS
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

44. GEOMECHANICAL MODEL OF THE R.M.
CONCLUSIONS
RELIABLE ASSESSMENT OF STABILITY CONDITIONS
GEOMECHANICAL SURVEY
GEOMECHANICAL MODEL OF THE R.M.
EVALUATION OF THE ORIGINAL
STATE OF STRESS
BLOCKS STABILITY ANALYSIS
LARGE VOLUME OF THE ROCK MASS
STRESS ANALYSIS
ACCURATE FOR THE EVALUATION OF THE STRESS IN THE RESISTENT ROCK STRUCTURE
MEASURE OF STRESS IN THE ROCK STRUCTURE DURING THE EXTRACTION ACTIVITY
UPDATING OF THE GEOMECHANICAL MODEL
SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy