2012/12/1 1 AN OVERVIEW OF EXCAVATION AND LATERAL SUPPORT (ELS) SYSTEMS December 2012 K.W. LEUNG Outline of the Talk Basic considerations Typical lateral support systems Permanent support Temporary support Statutory requirements for ELS Plan Experience sharing
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2012/12/1
1
AN OVERVIEW OF
EXCAVATION AND LATERAL
SUPPORT (ELS) SYSTEMS
December 2012 K.W. LEUNG
Outline of the Talk
� Basic considerations
� Typical lateral support systems
� Permanent support
� Temporary support
� Statutory requirements for ELS Plan
� Experience sharing
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� Site
characteristics
� Development
proposal
� Construction
� Design
� Performance
Basic
Considerations
CIRIA C580
Typical Section
Struts
Ground surface
Excavation
levelTie-backs (as an
alternative to struts)Seepage
cut-off
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Braced Excavation
Tie-back Excavation
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Bottom-up Construction
� � � �
Top-down Construction
� �
� �
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Permanent Support
� Usually thick and massive
� Suitable for both top-down and
bottom-up construction
� Common types:
� Diaphragm wall
� Bored pile wall
� Caisson wall
Diaphragm Wall
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Bored Pile Wall
Caisson Wall
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Temporary Support
� Generally slim and flexible
� Used with bottom-up construction
� Common types:
� Channel planking
� Sheet pile wall
� Pipe pile wall
� Soldier pile and laggings
� Grouted pile wall
� Soil nailing for open cut
Channel Planking
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Sheet Pile Wall
Pipe Pile Wall
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Soldier Pile Wall
Grouted Pile Wall
Formed by
� PIP (Pakt-in-Place) piles; or
� Jet grouting; or
� Deep mixing
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(a) PIP Piling
(b) Jet Grouting
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(c) Deep Mixing
Soil Nailing for Open Cut
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Statutory Requirements
� B(A)R 8(1)(bc) requires submission of ELS
plans where consequence of failure is serious
� PN for APs, RSEs & RGEs – APP 57
� Submission is required where the excavation is:
• >4.5m deep and > 5m long
• liable to affect any road, structure, slope (>30o),
or water main (≥75mmø) within the 45o line up
from the base of the excavation to the ground
surface
Contents of ELS Plan
� Lateral support system, e.g. sheet piles
� Strutting (or tie-back) layout
� Construction sequence
� Supporting geotechnical documents
� Realistic estimates of ground movements
� Assessment of effects of excavation & dewatering on adjoining structures