Sergio Cristiá Abad, Espoo, Rock mechanical modelling and analysis CAVERN DESIGN AND OPTIMAL LOCATIONS Sergio Cristiá Abad Laguna-LBNO extended site investigation Rock engineering meeting August 26 th 2014

SUMMARY List of tasks 1)Optimal shapes 2)Optimal locations 3)Long-term stability 4)Stability during excavation 5)Cavern reinforcement 6)Earthquake / Blasting 7)Thermal analysis 2 Sergio Cristiá Abad, Espoo,

1) OPTIMAL SHAPES Introduction (brittle rock, local and general damage) The problem (assumptions, approach) Solution Recomended shapes 3 Sergio Cristiá Abad, Espoo,

2) OPTIMAL LOCATIONS Geologial conditions Defining the locations Valiation / Mutual influence between caverns 4 Sergio Cristiá Abad, Espoo,

INTRODUCTION -High quality rock mass (high strength massive or moderately jointed material) -High stress -Looseing of confinement ↓ Brittle behavour ↓ STRESS INDUCED SURFACE DAMAGE 5 Sergio Cristiá Abad, Espoo,

INTRODUCTION Two thresholds: - Crack propagation(CD) Short term response of the rock - Crack Initiation (CI) Long term response of the rock 6 Sergio Cristiá Abad, Espoo, Diederics 2012

INTRODUCTION Damage around excavation in brittle hard rock In large excavations: – LOCAL DAMAGE excavation, excavation order / damage created by opening of “partial” spaces during the excavation (excavation stages) – GENERAL DAMAGE final shape 7 Sergio Cristiá Abad, Espoo,

THE PROBLEM: ASSUMPTIONS 8 Sergio Cristiá Abad, Espoo, ASSUMPTIONS CHILE material MODEL REALITY Complex interactions of many factors UNCERTAINTIES How the foliation affects the cavern?

THE PROBLEM: INITIAL CONDITIONS Optimization according the stress field – σH = 65MPa – σh = 38MPa – σz = 43MPa The material CHILE (Continuous Homogeneous Isotropic Linear Elastic material) LAr 1 → Mafic LAr 2 → Felsic LSc → Felsic 9 Sergio Cristiá Abad, Espoo,

69m diameter 34.1m walls 12m dome Architechtural boundaries Minimum space requirement for placing a tank with a certain dimensions → minimum requirement Rock mechanical boundaries “Friendly” with the in- situ stress field. 10 Sergio Cristiá Abad, Espoo, THE PROBLEM: BOUNDARIES / RESTRICTIONS

OPTIMAL SOLUTION Is that which fulfil the architectural requirements causing the less, or an assumable, amount of surface damage being always realistic and usable 1 optimal solution Closed range of solutions THE TARGET Evaluate and minimize the areas where the stress could likely overstep the RM strength 11 Sergio Cristiá Abad, Espoo,

WORKFLOW Separate partial effects 12 Sergio Cristiá Abad, Espoo, HORIZONTAL SECTION Relation between horizontal ppal stresses Avoid ”notcht” shapes on the vertical section ROOF HEIGTH Bending in of the walls Posible tension WALL CURVATURE Discharge of load on the roof

13 Sergio Cristiá Abad, Espoo, K= σH/σh = b/a=1.7 b=a*K=71 a=41m b=?m a=41m b=71m HORIZONTAL SECTION: LSr CAVERN

σ 1-σ3≥CI CI_mafic=98.5 (MPa) CI_felsic=87.5 (MPa) 14 Sergio Cristiá Abad, Espoo, In mafic material, the damage is gone On the other hand, in felsic material, this damage doesn’t disappear  5m HORIZONTAL SECTION: LSr CAVERN Curve the walls

15 Sergio Cristiá Abad, Espoo, K= σH/σh = b/a=1.7 b=a*K=118 a=69m b=?m a=69m b=118m HORIZONTAL SECTION: LAr CAVERN

σ 1-σ3≥CI CI_mafic=98.5 (MPa) CI_felsic=87.5 (MPa) 16 Sergio Cristiá Abad, Espoo, b=69m b=90m b=120m b=110m b=100m HORIZONTAL SECTION: LAr CAVERN

17 Sergio Cristiá Abad, Espoo, HORIZONTAL SECTION: LAr CAVERN

18 Sergio Cristiá Abad, Espoo, HORIZONTAL SECTION: LAr CAVERN

19 Sergio Cristiá Abad, Espoo, HORIZONTAL SECTION: LAr CAVERN

20 Sergio Cristiá Abad, Espoo,

WALL CURVATURE 21 Sergio Cristiá Abad, Espoo, Make arch-corners round #1 #2 #3 #4 #5 #6 #7 #8

ROOF HEIGH 22 Sergio Cristiá Abad, Espoo, ,5m roof height15m roof height σ1max  83MPa σ1max  79,5MPa Note: Pictures show results for the the LAr cavern Same behaviour in both LAr and LSc caverns

FINAL SHAPES – LSc 23 Sergio Cristiá Abad, Espoo, m 49.1m 70 m 84.1m 41m

FINAL SHAPES – LAr 24 Sergio Cristiá Abad, Espoo, m 69 m 100 m

OPTIMAL LOCATIONS-GEOLOGY 25 Sergio Cristiá Abad, Espoo, Model of the geology for the implementation in the rock mechanical analysis #3 cutting planes: Felsic Mafic Orebody Weakzone Pegmatite N E Z

GEOLOGICAL OUTPUT 26 Sergio Cristiá Abad, Espoo, Felsic Mafic Orebody Weakzone Pegmatite CUT AT -1300m

GEOLOGICAL OUTPUT 27 Sergio Cristiá Abad, Espoo, Felsic Mafic Orebody Weakzone Pegmatite CUT AT -1405m

GEOLOGICAL OUTPUT 28 Sergio Cristiá Abad, Espoo, Felsic Mafic Orebody Weakzone Pegmatite CUT AT -1500m

OPTIMAL LOCATIONS 29 Sergio Cristiá Abad, Espoo, Felsic Mafic Orebody Weakzone Pegmatite CUT AT -1400m Hanging-wall of the mine Posible weak plane No room 1LAr influence ≈ 80m

VALIDATION 30 Sergio Cristiá Abad, Espoo, σH = 65 MPa Minor mutual influence in σ1 More influnece than LAr caverns ↓ Effect of the z direction

VALIDATION 31 Sergio Cristiá Abad, Espoo, σh = 38 MPa Minor mutual influence in σ3

Thank you all for your attention! 32 Sergio Cristiá Abad, Espoo, questions