Lecture 4 Tunneling Through Fault Zones and Melanges BIMROCKS SHORT COURSE Dr. Edmund Medley Consulting Geological Engineer, Belmont, California, USA emedley@bimrocks.com Geological Engineering Department, Haceteppe Univ, Ankara June 22 and 23, 2004
Much of this lecture is possible thanks to the use of slides and photographs permitted by: Gruppe Geotechnik Graz, Austria Prof. Dick Goodman Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 2
BIG CONCLUSION 1: Remember this picture!!! Matrix Proposed Tunnel Blocks, inclusions, lenses, etc Scale: 1:?????? Matrix Actual Distribution of Blocks Medley, 2000
BIG CONCLUSION 2: Remember this picture as well!!! Matrix Proposed Tunnel Matrix Apparent Distribution of Blocks Willis, 2000
Tunneling failures can occur in relatively coherent rock-masses Photo: courtesy Prof. R. Goodman Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 5
Some Rock Mass BEHAVIOUR TYPES Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 6
Tunneling in in fault rocks and melanges can result in in failures Collapsed Tunnel M2, Egnatia Motorway, Greece Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 7
Tunnel Collapse in in unexpected bimrock Galgenberg Tunnel, Austria Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 8
Example Case Hepp Study Kavsak of of Geotechnical (Turkey) Hazard Assessment Project Data Upgrading of the river for energy production. Headrace tunnel (length 9km, diameter 9,0m Power house Tasks Geotechnical hazard assessment and optimization of design prior to construction Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 9
Geotechnical Longitudinal Section for for the the Tender Design faulted Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 10
Site mapping in in faulted rocks Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 11
Site mapping Geotechnical Hazard Assessment Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 12
Site mapping of of geological structures Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 13
Site mapping of of bimrock... Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 14
Revised Geotechnical Longitudinal Section Fault zones with bimrocks Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 15
Geotechnical Longitudinal Section for for the the Tender Design faulted Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 16
BIMROCK EFFECTS in in TUNNELS Mixed face conditions require different excavation methods on the same section Strong variation of rock mass quality Stress redistribution and deformations extremely influenced by arrangement of blocks and matrix Prediction of displacements and lining utilization extremely difficult Danger of brittle failures in blocks Difficulty of determination of proper support Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 17
BIMROCK EFFECTS PROBLEMS of DISPLACEMENTS IN MATRIX IN RELATION TO BLOCK DISTANCE Displacements depend on the length of the weak zone between two stiff blocks 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180-0,20-0,25-0,30-0,35-0,40 Δr 5 length of 20 weak zone 40 m 75 m Δr -0,45 Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 18
BIMROCK EFFECTS DISPLACEMENTS Final displacements influenced by zone length and stiffness contrast between blocks and matrix 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180-0,20-0,30-0,40-0,50-0,60-0,70-0,80 E 1 /E 2 = 1,5 E 1 /E 2 = 2,0 E 1 /E 2 = 4,0-0,90-1,00-1,10 Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 19
BIMROCK EFFECTS STRESS DISTRIBUTION Stress concentration in blocks depend on stiffness contrast and distance between blocks σ1/p1 40,0 50,0 60,0 70,0 80,0 90,0 100,0 110,0 120,0 130,0 140,0 150,0 160,0 170,0 180,0 2,70 2,60 2,50 2,40 2,30 2,20 2,10 2,00 1,90 1,80 F 1,5 / Var 8 F 2,0 / Var 8 F 4,0 / Var 8 Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 20
BIMROCK EFFECTS STRESS CONCENTRATIONS Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 21
BIMROCK EFFECTS MODEL 1.1 STIFF advance SOFT STIFF STIFF-SOFT-STIFF FINAL SETTLEMENTS FINAL STRESSES NORMALISED σ Z / σ [-] V,PRIM settlement [m] stress σz / σv,prim [-] normal chainage [D] 2/3 E stiff 1/2 E stiff 1/4 E stiff Relative stress increase in stiff material Relative stress decrease in soft material Trough shaped displacement chainage [D] VECTOR ORIENTATION TREND +1/2 D verctor orientation [ ] normal Change of displacement vector orientation near transition Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 22 chainage [D]
BIMROCK EFFECTS BLOCK REINFORCEMENT Stress concentrations can cause brittle failure in stiff blocks Resulting stress redistribution leads to additional displacements in the matrix material Knowledge of the spatial distribution of blocks and matrix essential to properly estimate stress situation Short term prediction and prediction of displacements extremely important Support / reinforcement of blocks necessary to avoid brittle failure and long term stress redistribution, frequently mistaken for creeping Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 23
BIMROCK EFFECTS CASE STUDIES Location Map Tunnel Spital, Austria Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 24
BIMROCK EFFECTS: Case Study Project data : Tunnel Spital, Austria Twin 2,2 km long freeway tunnels in the Semmering region, eastern Austria Alignment along a major fault zone Excavation area 70 90 m2 Underpass of a railway line and built up area average overburden 30 m, maximum 80 m Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 25
BIMROCK EFFECTS CASE STUDY Tunnel Spital, Austria Geological overview Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 26
BIMROCK EFFECTS CASE STUDY Geological sections at tunnel faces at various tunnel locations 1773 1785 1777 1788 1779 1790 Tunnel Spital, Austria Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 27
BIMROCK EFFECTS CASY STUDY Geological overview Nord tube: 1870-2000m South tube: 1700-1800m Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 28
BIMROCK EFFECTS Case study Heterogeneity - Displacements Tunnel Spital, Austria Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 29
BIMROCK EFFECTS CASE STUDY Block effect on displacement settlement crown / top heading Block Tunnel Spital, Austria Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 30
BIMROCK EFFECTS: COLLAPSE at at GALGENBERG TUNNEL, AUSTRIA A fatal collapse July 1994 at station 1330 m. Eight meters of heavily supported tunnel section collapsed at the face. A miner, and equipment was buried Redesign and maintenance work lasted for two months. Collapse caused by brittle failure of stiff rock outside of excavation Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 31
BIG CONCLUSION 1: Remember this picture!!! Matrix Proposed Tunnel Blocks, inclusions, lenses, etc Scale: 1:?????? Matrix Actual Distribution of Blocks Medley, 2000
BIG CONCLUSION 2: Remember this picture as well!!! Matrix Proposed Tunnel Matrix Apparent Distribution of Blocks Willis, 2000
Copyright: Dr. Edmund Medley, PE CEG Consulting Geological Engineer emedley@bimrock.com 34
ex po po nent (ik-spo nent) n. 1. One who expounds or interprets.