Canada Line Project

Stability of the Twin Bored Tunnels Under False Creek

Vancouver, British ColumbiaBy: Catherine Paul, Jen Ramesch, Matt Gellis,

Matthew Yip, and Rhaul Sharma

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 22

Canada LineCanada LineCanada Line will connect downtown Vancouver with central Canada Line will connect downtown Vancouver with central Richmond and Vancouver International Airport (19.5km long)Richmond and Vancouver International Airport (19.5km long)

The Canada Line will consist of:The Canada Line will consist of:18 stations along its route18 stations along its routeone bridge crossing the Fraser Riverone bridge crossing the Fraser RiverElevated Elevated GuidewayGuideway section over the City of Richmondsection over the City of RichmondCut and Cover method tunnels (Marine Drive to Cambie Street)Cut and Cover method tunnels (Marine Drive to Cambie Street)Twin Bored Tunnel section (Cambie St. to Waterfront)Twin Bored Tunnel section (Cambie St. to Waterfront)

Anticipated commuter time of 25 to 30 minutes with Anticipated commuter time of 25 to 30 minutes with approximately 40 million boardings by the year 2010approximately 40 million boardings by the year 2010

Construction has commenced and is scheduled to be completed Construction has commenced and is scheduled to be completed by the end of 2009 (to avoid major delays and construction by the end of 2009 (to avoid major delays and construction during the Olympic Games)during the Olympic Games)

The need for Canada Line;The need for Canada Line;One of the busiest corridors in VancouverOne of the busiest corridors in VancouverRoad congestion has increased by 36% in the last 10 yearsRoad congestion has increased by 36% in the last 10 yearsCanada Line will provide the equivalent capacity of 10 arterial Canada Line will provide the equivalent capacity of 10 arterial roadsroads

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 33

Canada LineCanada LineTwin Bored Tunnel SectionTwin Bored Tunnel Section

Looking North

Looking South

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 44

Twin Bored TunnelsTwin Bored TunnelsEarth Pressure Balance Tunnel Boring MachineEarth Pressure Balance Tunnel Boring Machine

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 55

Twin Bored TunnelsTwin Bored Tunnels

Entry Point Section A – A’

A

A’

Location

Regional Geology

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 66

PhasePhase22 Analysis Analysis -- SectionsSectionsFill and Marine Sediments

Glacial TillSandstone Bedrock (weak)

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 77

Material PropertiesMaterial Properties

Peak Residual Peak Residual0.005 0.01 0 0

0.1 0.01 35 300.5 0.01 35 30

Elastic PropertiesMaterial Type

0.0113

Mohr-Coloumb 0 0.01

Strength ParametersCohesion (MPa) Dialation Angle

(deg)Friction Angle (deg)Failure Criterion

Lithologic Unit Unit Weight (kN/m3)

2225

Fill & Marine Sediments

SandstoneGlacial Till Plastic 100 0.3

Young's Modulus Poisson's RatioPlastic 0.01

Plastic 10000 0.2

Mohr-Coloumb 0 0.01Mohr-Coloumb 0 0.01

Tensiles Strength (MPa)

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 88

TBM AdvancementTBM AdvancementSettlement Progression ProfileSettlement Progression Profile

100%

50%

10%

3D 0%

D

D

D

28%

TBM STANDARD

MODELLED

EPBM (IDEAL)

SOIL DILATIONPRIOR TO CONCRETEINSTALLATION

6D3D

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 99

PhasePhase22 AnalysisAnalysisModel Section 3Model Section 3

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 1010

PhasePhase22 AnalysisAnalysisModel Section 3Model Section 3

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 1111

Sensitivity AnalysisSensitivity Analysis

0.0002

0.00021

0.00022

0.00023

0.00024

0.00025

0.00026

0.00027

0.00028

0.00029

-30% -15% 0% +15% +30%

Variance of Parameters

Tota

l Disp

lace

men

t (m

)

Unit Weight of Sandstone Unit Weight of Marine Sediments (and Fill)

Unit Weight of Till Young's Modulus of Sandstone

Young's Modulus of Marine Sediments (and Fill) Young's Modulus of Till

Lateral Earth Pressure, K

Vortech Engineering Ltd.Vortech Engineering Ltd. EOSC 433 EOSC 433 -- Term Project Term Project 1212

ConclusionsConclusions

Recommend additional drilling to further investigate presence ofRecommend additional drilling to further investigate presence of faults and faults and discontinuities, including orientation relative to tunnel axis discontinuities, including orientation relative to tunnel axis (unable to (unable to determine strike and dip from current borehole data)determine strike and dip from current borehole data)

10.5210.52440.3310.331330.2980.298224.4794.47911

Total Displacement (mm)Total Displacement (mm)Model SectionModel Section

Based on this preliminary assessment, tunnel stability should noBased on this preliminary assessment, tunnel stability should not be a major t be a major issue assuming proper support guidelines are followed.issue assuming proper support guidelines are followed.

The possible presence of one or more shear or fault zones crossiThe possible presence of one or more shear or fault zones crossing the ng the tunnel alignment may be a cause for concern.tunnel alignment may be a cause for concern.

Minimum Pillar Width Minimum Pillar Width Between Twin Bored Tunnels Between Twin Bored Tunnels

along Granville St.along Granville St.

International Solutions Ltd.Veronica Lau, Murthy Pathi, Roald Strand, Daniela Welkner & Marcia Wilson

Introduction

•• Downtown Granville Downtown Granville St.St.

•• From Nelson to W. From Nelson to W. CordovaCordova

•• Twin sideTwin side--byby--side side tunnel section using tunnel section using TBMTBM

Information Provided•• Tunnel DiameterTunnel Diameter•• Depth to Top of TunnelDepth to Top of Tunnel•• Types of Soil/Rock to be encounteredTypes of Soil/Rock to be encountered

Assumptions Required•• Rock/soil parametersRock/soil parameters•• Building loads and positionBuilding loads and position•• Water table elevationWater table elevation

•• StratigraphyStratigraphy•• Constant tunnel depthConstant tunnel depth•• Tunnel supportTunnel support

Analysis

•• Numerical modelling using Phase2Numerical modelling using Phase2•• Several different scenarios Several different scenarios

•• Varying rock and soil interfaces Varying rock and soil interfaces •• Excavation sequencingExcavation sequencing•• Building excavation optionBuilding excavation option

•• Strength factorStrength factor

Water table 20m deep

Scenario 1 – Twin Bored Tunnels

Water table at surface

Scenario 2 – Influence of Existing Buildings

Stage 1

Stage 2 Stage 3

Pre-Tunnel Conditions

Scenario 3 – Impact of Future Building

Stage 1 Stage 2

Stage 3 Stage 4

Till

Sandstone

Scenario 4 – Future Building & Thicker Soil Cover

Stage 1 Stage 2

Stage 3 Stage 4

Till

Sandstone

Summary & Conclusions•• Potential failures (assuming a twinPotential failures (assuming a twin--tunnel tunnel

spacing of 11.4m) when tunnels driven in poor spacing of 11.4m) when tunnels driven in poor till or sand, successes when driven in poor to till or sand, successes when driven in poor to good sandstones good sandstones –– geology plays a significant geology plays a significant role in determining pillar widthrole in determining pillar width

•• Found that sequence of construction is relevant, Found that sequence of construction is relevant, especially with respect to future developments in especially with respect to future developments in VancouverVancouver’’s downtown core (i.e. interactions s downtown core (i.e. interactions between new building foundations and existing between new building foundations and existing Canada Line tunnels) Canada Line tunnels)

11.4m

2 tunnel diameters

only with proper soil improvement or tunnel support

Tunnel SpacingTunnel Spacing