St James’s Market Service Tunnel

Damien Brennan Design Engineer Barhale plc

GE Basements and Underground Structures Conference

Presentation overview

Developing a Temporary Works solution to construct and support a permanent service

tunnel between basements

Presentation Content • Clients Brief

• Design Considerations

• Selection of Temporary Works Solution

• Design change

• Outline of design

• Design loading

• Technical Features

• Installation Sequence

• Construction Obstacles

• Installation Progression

• Construction Benefits

Clients Brief

• Provide an underground service corridor between two eight-

storey retail and commercial blocks basements between 1 St

James’s Market (1 SJM) and 2 St James’s Market (2 SJM).

• Corridor to consist of underground reinforced concrete finish,

8m deep

• Temporary corridor/tunnel support system that is:

• Cost-effective,

• Fully designed,

• Adaptable solution that could be delivered and

• Installed safely

Clients Brief

Clients Brief

Design Considerations

• Ground conditions: Stiff London CLAY

formation beneath 3m of soft slightly gravelly

CLAY

• Ground water was recorded below proposed

invert level of construction.

Design Considerations • Site access and compound size

restrictions due to the on-going

redevelopment works for the

adjoining building on each side of

corridor.

• Ground level above tunnel profile to

be used as a storage area

Design Considerations

• Design to be adaptable to change during

construction if any obstacle/unknown objects

or adverse ground conditions are encountered.

• Design to be constructible in terms of

components that can be man-handable,

delivery of installation sequence and access to

works areas

Two options considered for Temporary Works Solution tunnel construction:

• Pipe Roof Method

• Timber Heading construction

Selection of Temporary Works Solution

Typical Pipe Roof Method Typical Timber Heading

Pipe Roof Method • Generally shaft sunk on each end (from each basement)

• Microtunnel from centre top, proceeding in both direction if required

• Pipes to be braced/supported during excavation of soil

• Pipes fill with concrete

• Internal lined with concrete lining

• Lifting required for TBM and pipes

• Launch/reception frame required on each side for each Microtunnel launch

Timber Heading Construction • Drive length up to 25m

• Timber side & head boards

• Steel or timber head & side Trees

• Head boards driven and cell hand excavated and support by each setting

• Each cell connected on all sides

• Working platform required on each side on each level

• Drive direction can be changed

Heading Option Selected

Key Reasons

• Drive direction can change if unknown obstacles

are encountered

• Conditions can be monitored and design changed

during construction

• No plant required all hand dig

• All structural elements fabricated off-site

• All structural elements are man-handable

• No constraints in terms of tunnel dimensional

change

Design Change

Design Outline

Design Outline

Design Outline

Design Outline

Design Loading

Technical Features • Corridor/Tunnel 8m deep to invert level

• Total drive length 7.5m

• Internal Tunnel opening at 6.7m wide x 3.2m high & 2.2m high

• Main steel Headtrees, Sidetrees and Cills 152x23UC

• Maximum spacing of primary supports (Headtrees) 1.45m

• Internal heading dimensions 1.4m x 1.45m

• Total number of heading set per row 8

• Circa 350 Tonnes of hand dig soil removed during construction

• Thickness of permanent reinforced concrete skin wall of tunnel lining

350mm thick

Installation Sequence

Installation Sequence

Installation Sequence

Construction Obstacles

Construction Obstacles

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Installation Progression

Construction Benefits

• Adaptable to change –drive direction change

• Conditions can be monitored and design changed

during construction

• No plant required all hand dig

• All structural elements fabricated off-site

• All structural elements are man-handable

• No constraints in terms of tunnel dimensional

change

Questions?