Compaction Technology: Proceedings of the conference organized by New Civil Engineer and held in London on 29 October 198

179 Pages·1988·12.983 MB·English

by  Thomas Telford

Compaction technology

Compaction technology
Proceedings of the conference organized by
held in London
New Civil Engineer said
on 29 October 1987
\i Thomas Telford, London
Conference sponsored by New Civil Engineer
British Library Cataloguing in Publication data
Compaction technology: Proceedings of the conference organized by New Civil Engineer and held in London on
29 October 1987.
1. Roads. Foundations. Compaction.
625.7'33
ISBN 07277 1338 8
First published 1988
© Thomas Telford Ltd, 1987,1988, unless otherwise stated
All rights, including translation, reserved. Except for fair copying, no part of this publication may be reproduced, stored in a
retrieval system, or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise,
without the prior written permission of the publisher. Requests should be directed to the Publications Manager, Thomas
Telford Ltd, Telford House, 1 Heron Quay, London E149XF.
Papers or other contributions and the statements made or opinions expressed therein are published on the understanding
that the author of the contribution is solely responsible for the opinions expressed in it and that its publication does not
necessarily imply that such statements and or opinions are or reflect the views or opinions of the Thomas Telford Board or
Thomas Telford committees.
Published by Thomas Telford Ltd, Telford House, 1 Heron Quay, London E149XF.
Printed and bound in Great Britain by Robert Hartnoll (1985) Ltd, Bodmin, Cornwall.
Contents
1. Compaction and the new specification for highway works.
P.E.NUTT
2. Compaction and performance of dense roadbase macadam.
W. D. POWELL and D. LEECH
3. A study of the relationship between compaction, mix
composition and performance of dense bituminous macadam
wearing courses in Northern Ireland A R WOODS1DE and
D. M. McKIBBIN
4. End result compaction and the blacktop contractor.
C.ALOVEDAY
5. Errors in compaction site control. A. G. WEEKS and R J. PARKER
6. Review of plant. A J.FERRIS
7. The moisture condition value and compaction of stony clays.
G. E. BARNES
8. Assessment of embankment suitability. R. G. V. GREEN
and A B.HAWKINS
9. A new approach to the execution and control of dynamic
compaction. A HOLEYMAN and G. VANNESTE
10. Shear surfaces induced in clay fills by compaction plant.
I. L. WHYTE and I. G. VAKALIS
11. Reclaimed PFA—field trials to determine compaction
characteristics and a performance specification. D. ATHERTON
12. Aspects of opencast mine backfill compaction. S. M. REED,
A McLEAN and R N. SINGH

Foreword
The Department of Transport's sixth edition of 'Specification
for highway works1, together with the companion 'Notes for
guidance', represents the most significant development in
compaction technology over the past decade. It forms the
basis of the British Government's expenditure on UK roads -
annually worth about £1000 million to the construction
industry.
The original specification was first published in the 1950s
and last revised in 1976; it is known throughout the industry
as 'The blue book'. However, the latest edition, known as
'The brown book', announced by Minister of Roads and Traffic
Peter Bottomley in October 1986, now forms the basis for
drawing up contract documents for all future road schemes.
All local authorities, consultants, contractors, specialist
subcontractors and plant and materials' suppliers engaged in
earthworks and road pavement compaction are affected by it.
The papers presented at this Conference introduce and
explain the new specification and its implications. They
include a major contribution from the Department of
Transport, which reviews and describes the new
specification's requirements for compaction of materials
contained in the earthworks and road pavements series'
clauses, the compaction and performance of dense bitumen
macadam by the Transport and Road Research Laboratory,
contractor's compaction experiences, case histories of
compaction problems, compaction plant developments through to
the compaction of PFA and opencast backfill materials.
Major changes incorporated in 'The brown book' include an
increase in layer thickness of up to a minimum of 90 mm, the
acceptance of vibratory rollers and the adoption of a
percentage refusal density performance specification for road
base and base course macadams.
The previous method specification dictated contractors to
use 8 t and 10 t deadweight rollers for a specific number of
passes over a particular mat. These constrictions stifled
roller development to the extent that the design of the
latest diesel-driven deadweights has changed little from the
initial steam-driven versions. However, the latest shift
towards a performance specification has given contractors
considerably more latitude in the method of compaction and
the type of plant that can be used, so long as the required
density is attained. The move has also given compaction
equipment manufacturers the incentive to invest large sums in
the research and development of new vibratory compacting
rollers, which are considerably more efficient than the old
deadweight rollers.
Compaction technology. Thomas Telford, London, 1988
COMPACTION TECHNOLOGY
Vibratory compacting rollers of just 2 t have been shown in
independent trials by the TRRL and some local authorities to
be capable of producing a denser mat and more uniform
compaction than standard 8 t deadweights. However,
contractors opting to use vibratory rollers under the new
specification must prove to resident engineers that the
performance of the chosen equipment is equivalent to that of
a deadweight roller. Vibratory rollers must also be equipped
with suitable display units, which can be read easily by the
resident engineer, indicating vibration frequency and the
machined travel speed.
The Department of Transport first agreed to try vibratory
rollers under contract conditions in 1980 on an M6
reconstruction job in the Midlands, where contractor R. M.
Douglas conducted trials of various makes of vibratory
compacting roller on bituminous materials. Since then the
Department of Transport and some local authorities have been
using vibratory compactors on some projects although they
have not strictly conformed to the fifth edition of the
Department's specification.
The sixth edition has effectively legitimized the use of
vibratory compactors, but the inclusion of percentage refusal
density as a measure of compaction is bound to cause
controversy, particularly on lane rental contracts where
speed and quality control are essential. Core samples must
be taken from the compacted layer to ascertain that a mean
93% of the refusal density has been achieved. The material
being tested could be overlaid by the time laboratory results
are available.
Fortunately the 'Notes for guidance1 allow other means of
monitoring compaction, which reduce the amount of percentage
refusal density testing required. Nuclear density (isotopic)
gauges may be used after a gauge reading has been established
to correspond to a 93 PRD level of compaction obtained from
core sampling. Such gauges allow much faster testing of the
compacted mat, but the amount of use on site will be at the
discretion of the resident engineer. The gauges are not seen
as an alternative to lengthy core testing and full PRD tests
involving core sampling will still be needed occasionally to
verify the isotopic meters.
These density gauges give only spot readings of compaction,
but research is now well advanced on the production of
isotopic gauges to give continuous read-out of density right
across the mat. Units will be located on the compaction
machinery to give the roller drivers a constant reading of
the density being achieved. They could also be used as a
maintenance aid to check any deviation in a road mat.
This equipment will also give contractors and resident
engineers greater control of compaction, and will inevitably
contribute further to improving the quality, strength and
life of UK roads.
1. Compaction and the new specification for highway
works
P. E. NUTT, BSc, MICE, MIHT, Head of Road Pavements Branch,
Engineering Intelligence Division, Department of Transport
SYNOPSIS. This paper reviews the Sixth Edition
Specification for Highway Works published
recently by the Department of Transport, and
describes the requirements for compaction of
materials contained in the earthworks and road
pavements series clauses.
INTRODUCTION
1. The publication of the Sixth Edition
Specification for Highway Works (Ref.l) was
announced by Peter Bottomley MP, Minister of
Roads and Traffic, on 14 October 1986. The
Specification, and the companion Notes for
Guidance, are the latest in a series first
published in the 1950*s and last revised in 1976,
upon which the Governments expenditure on road
construction is based. It is, therefore, at the
heart of contracts worth over 800m each year to
the construction industry. This paper gives a
brief introduction to the Sixth Edition
Specification for Highway Works (SHW) and the
requirements it contains for the compaction of
earthworks and roadmaking materials, with
particular reference to new or revised
requirements. All references to clause or tables
throughout this paper are to the Sixth Edition
SHW or the Notes for Guidance (NG).
THE SPECIFICATION FOR HIGHWAY WORKS
2. The revision of a document the scale of the
Fifth Edition 'Specification for Road and Bridge
Works1 (SRBW, known as the Blue Book and
Compaction technology. Thomas Telford, London, 1987 1
COMPACTION TECHNOLOGY
PUBLISHED IN 1976), IS NOT TO BE UNDERTAKEN
LIGHTLY, AND THE PREPARATION OF THE SIXTH EDITION
'SPECIFICATION FOR HIGHWAY WORKS1 (THE BROWN
BOOK?) SPANNED 6 YEARS, AND TOOK MANY TIMES THAT
IN MAN-YEARS OF WORK. THE REVISION OF THE
SPECIFICATION HAS KNOCK-ON EFFECTS TO A NUMBER OF
OTHER DOCUMENTS WHICH HAVE ALSO BEEN REVISED,
INCLUDING THE METHOD OF MEASUREMENT, LIBRARY OF
STANDARD ITEM DESCRIPTIONS AND THE HIGHWAY
CONSTRUCTION DETAILS. THE REVISION WAS NECESSARY
TO INCORPORATE DEVELOPMENTS TO MATERIALS AND
WORKING PRACTICES IN NEW CONSTRUCTION, AND TO
ACCOMMODATE THE REQUIREMENTS OF MAJOR MAINTENANCE
- AN AREA OF INCREASING IMPORTANCE AS THE
MOTORWAY AND TRUNK ROAD NETWORK DEVELOPED SINCE
THE LATE 1950FS REACHES MATURITY - SMALL SCHEMES
AND WORK IN URBAN AREAS. BEFORE PUBLICATION,
EXTENSIVE CONSULTATIONS TOOK PLACE WITH USERS ON
ALL SIDES OF THE INDUSTRY.
3. THE NEW FEATURES START WITH THE CHANGE OF
TITLE TO REFLECT THE INCREASED SCOPE OF THE
SPECIFICATION, WHICH NOW COVERS ALL ASPECTS OF
WORK IN THE CONSTRUCTION AND MAINTENANCE OF
NATIONAL HIGHWAYS. THE SIXTH EDITION HAS BEEN
PUBLISHED IN SEVEN PARTS (FIG 1 ), EACH WITH A
COMPANION "NOTES FOR GUIDANCE" TO EXPLAIN HOW THE
SPECIFICATION SHOULD BE USED, AND IN A4 FORMAT.
PUBLICATION IN PARTS WILL ALLOW SPECIALISTS
INTERESTED IN ONLY ONE SERIES TO PURCHASE JUST
THAT PART, AND WILL FACILITATE UPDATING BY PART.
THE MOVE TO A4 RECOGNISES THE SPECIFICATION AS A
WORK OF REFERENCE FOR THE SITE OFFICE OR VEHICLE
RATHER THAN A POCKET HANDBOOK, AND IS IN LINE
WITH HMSO POLICY FOR DOCUMENTS LIKE BRITISH
STANDARDS, BUILDING REGULATIONS, ETC.
4. THERE ARE 2 TYPES OF APPENDICES TO THE
SPECIFICATION; NUMBERED AND LETTERED. NUMBERED
APPENDICES GIVE THE DESIGNER FLEXIBILITY TO DEAL
WITH LOCAL CIRCUMSTANCES WITHOUT ALTERING THE
NATIONAL SPECIFICATION. THE "0" (ZERO) SERIES
CONSISTS OF THE FOLLOWING APPENDICES :
APPENDIX 0/1 - A LIST OF REGIONAL ADDITIONAL
AND SUBSTITUTE CLAUSES (MAJOR
TEXT CHANGES).
0/2 - A LIST OF REGIONAL MINOR
AMENDMENTS (MINOR TEXT CHANGES
BY DELETE AND INSERT METHODS).
0/3 - A LIST OF ALL THE NUMBERED
APPENDICES IN THE CONTRACT.
0/4 - A LIST OF THE CONTRACT DRAWINGS.
0/5 - FOR CONTRACTS IN SCOTLAND, WALES
2