Temporary propping at Crossrail Paddington station

Paul Chambers,Sam Reed,Adrian Dobbins,Charles Augarde

doi:10.1680/jgere.15.00009

Paul Chambers, Sam Reed + Show 2 more

Open Access

https://doi.org/10.1680/jgere.15.00009

Copy DOI

Abstract

The construction of Crossrail Paddington station in London (between 2011 and 2018) required a large temporary propping system, which contained one of the most comprehensive monitoring schemes to date. This paper explores the design and operation of this system through the analysis of a data set collected during the construction period and the numerical modelling undertaken at Durham University. The effects of temperature variation on the partially exposed propping system are quantified, as well as the impact of events in the construction sequence including slab casting, adjacent prop removal and excavation. Several lessons were learned during the construction, in terms of prop installation and removal and the management of the monitoring system. These are discussed for the benefit of future projects using temporary propping and monitoring schemes. The findings from this research have led to a greater understanding of the behaviour of propping systems under different environmental conditions, and may therefore lead to more efficient and safer designs in the future.

Highlights

Crossrail is a £14·8 billion underground rail project running from Reading and Heathrow to the west of London to Shenfield and Abbey Wood to the east
This paper records the investigation and analysis of the temporary propping system used in the construction of Crossrail Paddington station while considering the wider industry design of temporary propping systems
The measured temperature variation on the prop surfaces was approximately half of that specified at the design stage, indicating considerable thermal damping in partially exposed systems

Summary

Introduction

Crossrail is a £14·8 billion underground rail project running from Reading and Heathrow to the west of London to Shenfield and Abbey Wood to the east. This was largely attributed to an overestimation of thermal loads These previous studies indicate that design assessments of the effects of temperature, system restraint and construction sequence on propped deep excavations could be overconservative, a finding that is backed up by the data obtained at Paddington. The paper suggests that the bending moments in the walls are mainly dominated by the in situ lateral earth pressure It reports that small variations in stress distributions can cause comparatively large changes in the prop load. Establishing the model All of the props used in the construction of Paddington were preloaded to 70% of their design value This meant that the load data could not show how deflections varied with prestress. The soil parameters chosen for the HS small soil model were mainly derived from the factual geotechnical report

40 Eastbourne Terrace

Findings

Conclusions