Crossrail C336 Paddington New Yard

Bored Piling

LONDON , U.K.

Scope of Works

162no. CSP secant piles, 106 no.Batching Plant LDA piles, 122no. Derailment LDA piles, 74no. SolThread piles, 77no. Restricted LDA piles and 51no. restricted access mini-piles.

Introduction

Adjacent to Paddington Station, the redevelopment of

Crossrail’s Western Gateway, Paddington New Yard, is a

site that is steeped with historical interest. On this site the

team uncovered the foundations of Brunel’s’ engine shed

and two brick turntables dating to the 1800s – findings,

which in conjunction with a logistically challenging site,

have led to a complex ground engineering solution being

sought for the project.

Tasked with delivering specialist ground-engineering work

for the construction of derailment walls, bus depot and

batching plant, Crossrail and Costain appointed Bachy

Soletanche to the intricate project to deliver a unique piling

technique following a period of initial testing period.

Working alongside contractor Costain, Bachy installed162

CSP secant piles, 106 Batching Plant LDA piles, 122

Derailment LDA piles, 77 low headroom LDA piles, 74

SolThread piles and 51 restricted access minipiles,

operating in a head room of 5m. The low headroom Soiltek

rig operated in LDA rotary mode and had its mast reduced

to 9.3m to enable it to work safely under the A40 West Way

viaduct with, in places, a height restriction of only 10.36m.

The site team were keen to offer a more sustainable piling

solution, and so their design team proposed an innovative

technique to the project; following ten years of development

SolThread was delivered as a sustainable alternative to

conventional piles. Due to its threaded shape and design

SolThread requires less concrete to build the piles, and

less muck away lorries to remove pile spoil.

Rotary Bored Sol Thread Piles

A648

Secant piling, Rotary Bored piles, Low Headroom piles, Mini-piles, and SolThread piles

CLIENT: Crossrail

MAIN CONTRACTOR: Costain

CONSULTING ENGINEER: Capita

DURATION OF WORKS:

www.bacsol.co.uk

Sustainability Innovations

√ 1 Concrete savings using SolThread threaded piles

√ 2 Reduced pile spoil and lorry movements

A648

“

The SolThread technique also offers financial and

environmental savings, in addition to a reduction in

site traffic and an associated improvement in safety

for road users. The aim of the development of this

innovative technique was the reduction of material

use and lorry movements compared to conventional

rotary piles through the creation of a threaded rotary

bored pile.

The process is based upon standard pile construc-

tion techniques with the addition of a stage to create

the thread on the pile bore. Remote access inspec-

tion techniques, based upon those for inspection of

under ream piles, are used to demonstrate the effec-

tiveness of the threading process, combined with

static load tests to validate the design assumptions.

Specially developed on-board electronic systems en-

able the operator to monitor thread formation and

provide as built record information.

www.bacsol.co.uk

Cased CFA Secant Piled Wall

This patented pile consists of a central core, with a

helical thread formed around this - increasing the

effective geotechnical diameter of the pile by

150mm. A pile with a threaded shaft also offered

increased skin friction compared with an unthread-

ed shaft and therefore increased pile capacity by

40% for the project. These piles form the basis of

the site’s facilities, which on completion will be

home to a concrete batching plant owner, a bus

depot, Crossrail running lines & turn backs, plus

sidings for freight rail operators, DB Schenker.

Low Headroom Rotary Piling under A40

The final phase of our works involved re-stricted access minipiling. This involved 51no., 600mm diameter piles up to 20m long and with a working height of only 5m, underneath a elevated section of the A40 roadway. Some of these piles also includ-ed I-beams, positioned to a tight verticality and positional tolerance, for use as King Posts retaining walls. Remote inspection of pile threads

Restricted Access Minipiles