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Naruki Wakabayashi Shimizu Corporation Tokyo Japan

Study on the Jointed Rock Mass for the Excavation of Hyper-KAMIOKANDE Cavern at Kamioka Mine. Naruki Wakabayashi Shimizu Corporation Tokyo Japan. NNN07 Hamamatsu, Japan 3-5 October 2007. Topics 　・ Previous Geological Survey and Stability Analysis for the Hyper-K cavern

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Naruki Wakabayashi Shimizu Corporation Tokyo Japan

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  1. Study on the Jointed Rock Mass for the Excavation of Hyper-KAMIOKANDE Cavern at Kamioka Mine Naruki Wakabayashi Shimizu Corporation Tokyo Japan NNN07 Hamamatsu, Japan 3-5 October 2007

  2. Topics 　・Previous Geological Survey and Stability Analysis for the Hyper-K cavern ・Site Selection ・Isotropic Elastic FEM Analysis for the Investigation of Cavern Shape, Size and Type 　・Ongoing Investigation and Analysis for Jointed Rock Mass ・Investigation of Joint Orientation ・Obtaining In-Situ Rock Joints and Investigation of Joint Mechanical Properties ・Pull-out Test of Two Types of Cable Bolt ・Two TypeAnalysis to Consider the Influence of Joint and Support System

  3. Kamioka Mine Tokyo Hamamatsu Site Selection Kamioka Mine Location Mozumi mine Super-K Proposed Area Proposed Area in Mozumi Mine is about 10km South from the Super-Kamiokande. Tochibora mine

  4. Geological Map of Proposed Siteat Tochibora MinePlan View of + 550mEL Core Boring ”NAMARI” Fault Limestone Hyper-K proposed Site Hornblende Biotite Gneiss & Migmatite Skarn Orebody Zone Existing Tunnel Surveyed ”ANKO” Fault Biotite Gneiss ”240゜- ME” Fault Proposed Site Formation is Hornblende Biotite Gneiss and Migmatite. N 100m

  5. ”NAMARI” Fault Offset ”ANKO” Fault Spacing ”240°-ME” Fault Isotropic Elastic FEM Analysis Cylindrical Dome Larger than Super-K Two Parallel Tunnels Huge Tunnel Comparison of the Hyper-K Cavern from Various View Points Image Design of Two 250m Long Parallel Tunnels

  6. Summary ofPrevious Study Site Selection : Tochibora Mine, +480mEL~+550m EL is the most appropriate location with very competent rock condition. Cavern Design: Two 250m Long Parallel Tunnels with Section of 2,076m2 are capable of being safely excavated. This Type is possible to continue observation during Maintenance. Cavern Layout: Two Parallel Tunnels as above should be Located with 80m –100m (about 2 Diameter Distance) Spacing and 50m-100m Offset to avoid the poor Zone of Surrounding Faults. In Isotropic Elastic FEM Analysis of Previous Study, Young’s Modulus was empirically decreased as Jointed Rock Mass. It is Important and Necessary to Consider the Influence of Joint Orientation and Mechanical Properties Numerically.

  7. Equivalent Continuum Analysis Discontinuous Analysis Composition of Elastic Blocks Surrounding Joints Anisotropic Young’s Modulus Considering Joint Orientation and Mechanical Properties Key Block Damage Tensor Distinct Element Method (DEM) Crack Tensor Analysis for Jointed Rock Mass ・Characteristics of Joint Orientation ・Mechanical Properties of Joint and Rock Core ・Mechanical Properties of Support such as Cable Bolt

  8. Measurement of Joint Orientation in this Existing Tunnel Rock Types Gneiss Migmatite N +550m EL Rock Classification B Very Good CH Good CM Medium Obtaining Rock Joint (3 Places) Pull-out Tests of Cable bolt (6 Places) Investigation of Jointed Rock Mass

  9. N N N N Migmatite Gneiss E E E E W W W W Strike Joint N W E Pole S S S S S Dip × Investigation of Joint Orientation ・Major Joint Set: Strike E-W and Dip ±70～90° ・Another Joint Set : Strike NE-WS and Dip ±40～50° Projection of Poles Pole Density Contours

  10. Situation of Obtaining In-Site Rock Joints Diamond Drilling Joint Recovered Core with Joint Joint

  11. Joint Mechanical Properties Direct Shear Test of Rock Joints ・Joint Deformability Parameters such as Normal and Shear Stiffness, Dilatancy Angle ・Joint Shear Strength such as Cohesion and Internal Friction Angle Rock Joint Specimen with extensometers Normal Stress Shear Displacement Shear Test Equipment (Normal and Shear load are 1MN)

  12. σn=10N/mm2 Cohesion=0.57N/mm2 Internal Friction angle =33° Shear Strength (N/mm2) Normal Stiffness =67N/mm2/mm Normal Stress (N/mm2) Normal Displacement (mm) Shear Stiffness=60N/mm2/mm Shear Strength Shear Stress (N/mm2) Normal Displacement (mm) Diｌatancy angle=2.4° Shear Displacement (mm) Shear Displacement (mm) Results of Direct Shear Test Normal Stress (N/mm2)

  13. Special Cable Bolt with Dimples （ST-Cable Bolt） Usual Cable Bolt without Dimples （PC-Cable Bolt） Pull-Out Test of Two Type Cable Bolts Economical Support System should be used ・Usual Support System for Large Cavern is Rock Anchor → Expensive ・Proposed Support System is Rock Bolt and Cable Bolt → Economical ・Special Cable Bolt with Dimples has very high Strength ・Mechanical Properties of Cable bolt was estimated by Pull-Out Test

  14. Inserting Cable Bolts Diamond Drilling ST-Cable Bolt PC-Cable bolt Pull-Out Test Setting up Equipments Jock and Dial Gauge Pressure Pump Situation of Pull-Out Tests

  15. Cable bolt model Strength (kN/m) Stiffness (kN/m/m) Migmatite (B) ST △Gneiss (CH) ○Migmatite(CH) △Gneiss (CH) ○Migmatite(CH) □Gneiss (B) ◇Migmatite(B) □Gneiss (B) ◇Migmatite(B) ST Stiffness (kN/m/m) PC ST Strength above 270kN/m Stiffness above 53MN/m/m Load (kN) PC Strength above 53kN/m Stiffness above 40MN/m/m PC Strength (kN/m) Displacement (mm) Results of Pull-Out Tests Gneiss (B) ST Load (kN) PC Displacement (mm)

  16. Mechanical Properties

  17. Joint Strike Huge Tunnnel W48m×H54m 2070m2 Discontinuous Analysis by DEM DEM Analysis is Performed to Establish the Behavior of Jointed Rock Mass and the Effect of Support System. Cavern Direction is East and West Cavern Shape and Direction Analysis Cases

  18. Procedure of Analysis 200m Second Step First Step Third Step Strike NS-WS Dip ± 40～50° (Another Joint Set) Fourth Step Analysis Model Joints are Generated Statistically According to the Joint Orientation Establishing Support System after Each Excavation Step 200m Strike E-W Dip ±70～90° (Major Joint Set)

  19. （kN） （kN） 45 32 35 93 37 41 618 464 620 415 89 60 67 17 13 13 284 474 (mm) (mm) 17 10 10 15 15 15 Case 1：Without Support Case 2：RB+PC-Cable Bolt (Double) Displacement of Right and Left Side Wall are nearly same because of Symmetrical Joint Dip Angle (±70～90°). Displacement of Case-3 is smaller than Case-2 because of Support Effect of ST Cable Bolts (mm) Case 3: RB+ST-Cable Bolt (Double) Displacement Vector and Cable Axial Force

  20. Equivalent Continuum Analysis by Crack Tensor Crack Tensor Analysis is Performed to Estimate the Relation between Tunnel Direction and Joint Orientation. In-Situ Stress is Isotropic σH=σv=14.4 （N/mm2） Case 1:Cavern Direction is East and West, parallel to Joint Strike Case 2:Cavern Direction is North and South, right-angled to Joint Strike Joint Strike Joint Strike Case 1 Case 2 234m Huge Tunnnel W48m×H54m 2070m2 240m 48m 240m 54m Z 240m X Cavern shape and Region (528m×528m） Model

  21. Joint Strike Joint Strike Case 1 Case 2 Displacement Side Wall Displacement of Case 1 is 2 times Larger than Case 2 because of influence of Joint Strike Direction.

  22. Summary Joint Orientation : At Proposed Site in Tochibora Mine, Major Joint Set Strike Direction is E-W and Dip Angle is ±70～90° Joint Properties : Normal and Shear Stiffness, Shear Strength are Estimated. Cable Bolt Properties: Shear Strength and Stiffness of ST and PC Cable Bolt are Estimated. Shear Strength of ST-Cable Bolt is 5 Times Higher than PC-Cable Bolt. ST-Cable Bolt is very Effective Support. Results of Analysis : Discontinuous and Equivalent Continuum Analysis are able to Estimate the Effect of Rock Support System and the Anisotropic Behavior of Jointed Rock Mass. Joint Orientation is very Important factor to decide the Cavern Direction. Further Investigation : It is Necessary for Estimation of Accurate Joint Orientation to investigate in Different Direction Tunnel or Bore Hole Additionally. Measurements of In-Situ Initial Stresses and In-Situ Tests on Rock Mass Deformability are indispensable.

  23. END

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