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

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

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

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

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

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

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 20-30 meters high Typical pillars dimensions about 10 meters in diameter SWEMP 2002, October 7 – 10, 2002, Cagliari, Italy

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

sI=sz=1.21 MPa at the upper surface of the model MATERIAL PROPERTIES Homogeneous and isotropic with indefinite elastic behavior E= 7.5 1010 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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