OVERVIEW OF THE REINFORCED EARTH STRUCTURES FOR …

OVERVIEW OF THE REINFORCED EARTH STRUCTURES FOR BERMONDSEY DIVE UNDERIGS UK Symposium: Use of Geosynthetics in Rail: Towards 2025

BERMONDSEY DIVE UNDER

National Rail map

• North-South between Bedford and Brighton

• Serving Gatwick and Luton airports

• 12 car capacity and 24 train paths per hour through the “Central Core”.

Bermondsey

THAMESLINK

BERMONDSEY DIVE UNDERA KEY COMPONENT OF THE FINAL STAGE OF THE THAMESLINK PROGRAMME AND THE REBUILDING OF LONDON BRIDGE STATION.

Untangling of the existing tracks over a 1.4 km section through Bermondsey


THE ORIGINAL RAILWAY

BOLINA ROAD BEFORE CONSTRUCTION


JANUARY 2017

BERMONDSEY DIVE UNDER GROUND ENGINEERING AWARDS 2017

LAYOUT OF THE STRUCTURES

Western Flyover Ramp

Western Dive Under Ramp Pre-cast Arches supported on existing arch foundations

Western Dive Under Ramp Reinforced Earth Walls

Dive Under Box and Earthworks

Bolina Road Structures


JANUARY 2017

BERMONDSEY DIVE UNDER GROUND ENGINEERING AWARDS 2017

LAYOUT OF THE STRUCTURES

Eastern Ramp Reinforced Earth

Eastern Ramp Pre-cast Arches

Steel Composite Structure

Embankment


BERMONDSEY DIVE UNDERGRIP 4 DESIGN OF THE REINFORCED EARTH STRUCTURES

BERMONDSEY DIVE UNDERGRIP 4 DESIGN OF THE REINFORCED EARTH STRUCTURES

The main concept was for a

reinforced earth wall

supported on a piled load

transfer platform


Area to be filled within the Box

GRIP 4 DESIGN OF THE REINFORCED EARTH STRUCTURES

“Bridge” Pier

GRIP 4 DESIGN OF THE REINFORCED EARTH STRUCTURES



GRIP 5 REINFORCED EARTH WALL DESIGN

GRIP STAGE 5 DESIGNBERMONDSEY DIVE UNDERGEOTECHNICAL AND DESIGN RISKS

• Validating the re-use of the arch foundation.

• Validating and material quality of the crushed brick

• Use of restricted access piling

• Protecting the Chalk Aquifer

• Settlement of the approach embankments

� Made Ground

� Alluvium

� River Terrace Deposits

� Chalk

GRIP STAGE 5 DESIGNBERMONDSEY DIVE UNDERGRIP 5 REINFORCED EARTH WALL DESIGN

BERMONDSEY DIVE UNDERGRIP 5 REINFORCED EARTH WALL DESIGN

Geo-grid Reinforcement

Modular Block Reinforced Wall

Derailment Wall

Drainage

Derailment Wall

Modular Block Reinforced Wall

DrainageRC deck near above existing ground level


Method of analysis:

• Ultimate Limit State Design – BS8006:2010

• Serviceability Limit State – Plaxis 2D FE

Typical Loading Conditions:

• Rail Live Load – 50 kPa

• Walkways – 5 kPa

• Abnormal Rail Loading - KIROW KRC1200 UK rail mounted crane operating as a crane


Plaxis Models:

Model 1 – Reinforced earth ‘back to back’ wall system

Model 2 – Typical embankment with good granular fill material (same properties as reinforced earth)

Model 3 – Typical embankment with poor granular fill material


Layer Unit Weight, γ

(kN/m3)

Cohesion, c

(kN/m2)

Angle of Internal Friction, φ

(degrees)

Young’s Modulus, E

(kN/m2)

Ballast 21 0.1 35 60000

Reinforced Earth Fill 20 0.1 35 50000

Good granular Fill 20 0.1 35 50000

Embankment Fill 20 0.1 30 25000

Analysis Assumptions:• All wall elements are fixed connections• The base of the reinforced earth wall facing is fixed to the reinforced concrete

slab at the base of the model therefore there is no lateral or rotational movement at this point

• The parameters of the crushed brick fill for the reinforced earth are the same as those from the Bermondsey Dive Under structure Form A documents

• Fill material properties





Model Maximum Lateral Movement of Wall

Element or within Embankment (mm)

Maximum Vertical

Displacement (mm)

Model 1 0.6 (wall) 3.2

Model 2 0.9 (embankment) 4.4

Model 3 1.5 (embankment) 5.6

Summary of the Plaxis results


USE OF THE DEMOLISHED BRICK FROM THE ARCHES

GRIP STAGE 5 DESIGNBERMONDSEY DIVE UNDERUSE OF THE DEMOLISHED BRICK FROM THE ARCHES

Risks

• Crushing of the bricks not providing a Class 6I/6J fill

• Long-term durability

Mitigation

• Materials Management Plan• Materials Engineer on site• Use as an alternative material

where not compliant as a 6I/6J fill e.g. working platforms

GRIP STAGE 5 DESIGNBERMONDSEY DIVE UNDERUSE OF THE DEMOLISHED BRICK FROM THE ARCHES

Preliminary Testing of the Crushed Brick

• Crushing of the bricks not providing a Class 6I/6J fill

• Long-term durability

Mitigation

• Materials Management Plan• Materials Engineer on site• Use as an alternative material

where not compliant as a 6I/6J fill e.g. working platforms

BERMONDSEY DIVE UNDERSUSTAINABLE INFRASTRUCTURE DELIVERY

Environmental Benefits • Reduced impact on local

traffic• Reduced consumption of

steel and concrete• Reduced carbon emissions• Reduced risk to the

contaminating groundwater

• Reduced waste by using

off-site pre-cast concrete• Reduced programme time

and delays to passengers

Economic Efficiencies • Removed around 40% of the

piles from the scheme • Reduced pile lengths through

preliminary pile testing• Reduced excavations and

material disposal• Limit the amount of material for

and re-use of working platform materials

• Re-use of the brick from the demolished arches and other recycled materials where possible

• Reduced programme

SocialBenefits • Structures sympathetic to the

existing viaducts which are some of the oldest in London

• Enhancement of the existing arches and allow Network Rail to rent them out for business use

• Will improve the experience of rail travel across the capital for thousands of people every day.

• Enables increased passenger capacity

• The site has now been cleaned up and rejuvenated to provide a vastly improved environment for local residents to enjoyEconomic Environmental

Social

BERMONDSEY DIVE UNDERSUSTAINABLE INFRASTRUCTURE DELIVERY

BOLINA ROAD AFTER CONSTRUCTION

THANK YOU

Documents

OVERVIEW OF THE REINFORCED EARTH STRUCTURES FOR …