Rock Mechanics IRock Mechanics ICourse CEE9577

Introduction

Rock Mechanics Applications:Rock Mechanics Applications:

• Rock Slope EngineeringT lli d U d d O i i R k• Tunnelling and Underground Openings in Rock

• Foundations on Rock• Rock Excavation – Blasting and Tunnel Boring Machine

Excavation

Topics Covered in Rock Mechanics I

Fundamental Concepts in Rock Mechanics

• An Overview of Rock Engineering Problems and ApplicationsAn Overview of Rock Engineering Problems and Applications

• Geological and Engineering Classifications of Rocks

• Index Properties of Intact Rocks

• Classification and Fundamental Properties of Rock Discontinuities• Classification and Fundamental Properties of Rock Discontinuities

• Classification of Rock Masses

• In‐situ Stresses in Rocks

• Strength and Deformation Behaviour of Rocks• Strength and Deformation Behaviour of Rocks 

• Failure Theories and Rock Mass Strength

• Special Rock Characteristics

Examples of Rock Mechanics Problems in Slopes

Site of Landslide - China

Major Landslide on Kaolin Infilled Joint at Fei Tsui Road – Hong Kong

Edge of freshwater reservoir

Kaolin infilled jointon sliding surface

Examples of Rock Mechanics ProblemsVajont Dam Before and After Slope FailuresUpstream of the Dam

Visible scar on the unstable slope atMount Toc

Mound of debris

The Vajont dam during impoundment of the reservoir

During the filling of the Vajont reservoir, the toe of the slope on Mount Toc was submerged and this precipitated a slide.

The very rapid descent of the slide material of the reservoir displaced the water in the reservoir causing a 100 m high wave to overtop the dam wall.

The dam itself was largely undamaged.

Examples of Rock Mechanics ProblemsConsequence of Slope Failure Upstream of Viajont DamAfter Impoundmentp

The town of Longarone, located downstream of the Vajont dam, before the M t T f il i O t b 1963

The remains of the town of Longarone after the flood caused by the overtopping of the V j t d lt f th M t TMount Toc failure in October 1963. Vajont dam as a result of the Mount Toc failure. More than 2000 persons were killed in this flood.

Example of Wedge Failure on Slope

Example of Planar Failure on Slopes

Examples of Rock Mechanics Problems inHighway Rock Cuts

Plane failure along persistentbedding planes

Lar

Failure of a Large wedge formed by two Intersecting planes dipping out of the slope face

Examples of Rock Mechanics Problems in Slopes

Wedge Failure inWedge Failure in an Open Pit Mine Slope

Examples of Rock Mechanics Problem in SlopesEffect of Sheeting Joint on Slope Stability

Examples of Tunnel Side Wedge Failure 

Examples of Rock Mechanics ProblemsSan Paulo Tunnel Collapse, Brasil

Sao Paulo Tunnel Collapse – Brazil January 15 2007Failure occurred at the intersection of 18m dia. Station tunnel and the 40m dia. 40m deep shaft, due to fracture rock at the roof of that tunnel and insufficient support on the sidewall and at the roof of tunnel

Examples of Rock Mechanic ProblemsAthens Metro Tunnel Collapse, Greece

Athens Metro Tunnel Collapse – Construction 1991-1998R lli f d d t i t l th d d hi hl t t i dRavelling of ground due to intensely weathered and highly tectonizedAthenian Schist resulting in uncontrollable overbreak during TBM drive

Examples of Rock Mechanic ProblemsLane Cove Tunnel Collapse, Sydney Australia

Lane Cove Tunnel Collapse – Australia November 2 2005Collapse of the ventilation tunnel at intersection with the main tunnel was dueCollapse of the ventilation tunnel at intersection with the main tunnel was due to “rock slippage” along a dyke which was not detected during investigation, and under-design of the rock bolting system at the intersection. The collapse resulted in a 10mx10mx25m crater below an apartment building.

Examples of Rock Mechanic ProblemsLane Cove Tunnel Collapse, Sydney Australia

Lane Cove Tunnel Collapse – Australia November 2 2005Creating 10mx10mx25m sink hole and causing damage of surface structure

Tunnel Boring Machine (TBM) Excavation Niagara Tunnel (14.4 m dia), Niagara Falls , Canada

Examples of Rock Mechanics ProblemsRock Failure at Roof of Niagara Tunnel Behind TBM

Roof Failure at Niagara Tunnel

Examples of Rock Mechanics ProblemsRock Failure at Roof of Niagara Tunnel

Rock Failures at the Haunches ‐ Niagara Tunnel

Ramp to Grout Intake Tunnel – Niagara Tunnel ProjectExcavated by Drill and Blast Method

Controlled Blasting of Slope at Fiesta Texas Theme Park, U.S.

Controlled Blasting of Slope at Fiesta Texas Theme Park, U.S.

Cumberland Gap Tunnel , U.S.Bench Excavation

Multi‐boom Drill Jumbo for Drilling Blast Holes in Drill and Blast Excavation

Cumberland gap tunnel, U.S.

Harlan Flood Diversion Tunnel, U.S.Supported by Shotcrete and Rockbolts

Exchange Place Improvements ProjectDowntown New Jersey, NJ, New York‐Multiple Openings in Underground Complex

Underground Research Laboratory, Pinawa, CanadaExcavation by Controlled Blasting

Road Header for Tunnel Excavation

Underground Test Adit – SAB 3 ProjectNiagara Falls – Excavated using Road Header

Types of Conventional Tunnel Boring Machine (TBM)

1. Open Gripper Machine2. Double Shield, Telescopic3. Open with Boting Shield4. Closed Face, Ring Thrust

Tunnel Support in TBM Excavations

Rock Bolt and Mesh Support

Precast Concrete Liner Support

Mine Access Tunnel – Donkin Morien Coal Mine Excavated by TBM (7.6 m dia)

Rock Cores Recovered from Investigation

Basic Sizes of Core Used in Geotechnical Investigations

Six Basic Sizes Available E – PSix Basic Sizes Available E  P

– E 22 mm core, 38 mm hole, 36.5 mm RX casing will go in hole

– A 25‐34 mm core, 48 mm hole, 46 mm EX or EW casing

– B 33‐44 mm core, 60 mm hole, 57 mm AX or AW casing

– N 45‐55 mm core, 76 mm hole, 73 mm BX or BW casing

– H 61‐75 mm core, 93‐99 mm hole, 89 mm NX or NW casing

– P 83‐85 mm core, 123 mm hole, 114 mm HX or HW casing

– Some larger Z plus specialsSome larger, Z, plus specials

Typical Core bits for Drilling Investigations

Typical Core Log Showing Core Recoveries and Rock Quality Designation (RQD)

03-1001-014Module 1Unit 1

Deere’s Classification ‐ RQD

RQD is defined as the percentage of intact core pieces longer than 100 mm (4 inches) in the total length of core. The core should be at least NW size (54.7 mm or 2 15 inches in diameter) and should be drilled with a double tube core barrelor 2.15 inches in diameter) and should be drilled with a double-tube core barrel.

If rock cores are not available

RQD = 115 – 3.3 Jv (after Palmstrom, 1982)

Where Jv is the total number of Jointsper cubic meter

References for RQD Calculations Based on Core Sizes (Heuze’s Recommendations)

03-1001-014Module 1Unit 1

Mapping of discontinuities using handheld devices