Institution of Civil Engineers International conference on Ground Anchorages and Anchored Structures in Service 2007 Proceedings of the two day international conference organised by the Institution of Civil Engineers and held in London on 26 and 27 November 2007 Edited by Stuart Littlejohn Sponsored by: DSI ©GfTlGE ^ritchies KELLER (S|) BACHY SOLETANCHE ^^ JAPAN ANCHOR ASSOCIATION I ^ SAMWOO-AnchorTec Co-sponsored by: The British Dam Society Engineering Group of the Geological Society of London Organising committee: Stuart Littlejohn, University of Bradford (Chairman) Raymond Coe, Black and Veatch Ltd Mike Crilly, British Geotechnical Association John Graham, Keller Ground Engineering Ltd Roger Margerison, AMEC Group Ltd Caesar Merrifield, Coffey Geotechnics Devon Mothersille, Geoserve Global Ltd Overseas advisory committee: Stuart Littlejohn, University of Bradford (Chairman) Tony Barley, SBMA Ltd Donald Bruce, Geosystems L.P. John Finnis, Dywidag Systems International Gareth John, CAPCIS Ltd Hiroaki Kubo, Japan Anchor Association Ursula Lawrence, Engineering Group of the Geological Society of London Yves Legendre, Bachy Soletanche Paul McBarron, Austress Menard Published for the Organising Committee by Thomas Telford Publishing, Thomas Telford Ltd, 1 Heron Quay, London E14 4JD. www.thomastelford.com Distributors for Thomas Telford books are USA: ASCE Press, 1801 Alexander Bell Drive, Reston, VA 20191-4400, USA Japan: Maruzen Co. Ltd, Book Department, 3-10 Nihonbashi 2-chome, Chuo-ku, Tokyo 103 Australia: DA Books and Journals, 648 Whitehorse Road, Mitcham 3132, Victoria First Published 2007 A catalogue record for this book is available from the British Library ISBN 978-07277-3561-4 © Institution of Civil Engineers 2007 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 or otherwise, without the prior written permission of the Books Publisher, Thomas Telford Publishing, Thomas Telford Ltd, 1 Heron Quay, London E14 4JD. This book is published on the understanding that the authors are solely responsible for the statements made and 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 publishers or of the Institution of Civil Engineers. Flash drive manufactured by Gold Products Ltd, Telford, Shropshire Printed and bound in Great Britain by Lightning Source, Milton Keynes Foreword Millions of ground anchorages have been installed over the past 80 years with relatively few recorded failures. However, as permanent anchorages in service become older, the subject is of growing importance, particularly for anchorages installed over 30 years ago: many of which have been designed with corrosion protection considered inadequate by today's standards. Water levels reached 150-year highs in 2002 with associated flooding across Central and Eastern Europe, so the importance of anchored river and seawalls cannot be overemphasised. Winter storms are now judged by the insurance industry to represent the largest potential event loss in Europe. Elsewhere in the world, the highest potential losses are associated with earthquakes and typhoons, where anchored slopes are vital in resisting landslides and rock avalanches. Routine programmes of inspection and monitoring can extend the service life of the anchored structures that represent key elements of a country's infrastructure. Where inspection highlights unacceptable tendon corrosion or over-stressing, the results provide early warning of the need for precautionary or remedial measures, in order to safeguard the integrity of the anchored structure. In spite of these benefits, sufficient attention is not currently paid to routine maintenance inspection and service behaviour monitoring. As a consequence, papers selected for this conference are designed to illustrate the performance of anchorages in practice, provide guidance on monitoring and maintenance procedures, introduce recent developments in non-destructive testing and describe appropriate corrosion monitoring and corrosion protection systems. It is hoped that delegates will enjoy these proceedings and benefit from the knowledge and experience of the authors. Importantly, delegates are encouraged to participate in the Session discussions, in order to debate the current issues and future challenges relating to the service behaviour of ground anchorages and anchored structures. Stuart Littlejohn (Chairman of the organising committee) University of Bradford Contents Keynote presentation Maintenance testing and service behaviour monitoring of permanent ground anchorages Stuart Littlejohn and Devon Mothersille i Session one: Inspection procedures and physical conditions recorded in service A case study of inspection, integrity investigation and repair of anchors used to stabilise slopes around dam lake Minoru Okuno and Takahiro Takemata 1 Inspection of anchorages supporting waterside structures Devon Mothersille and Tony Barley 12 Inspection, integrity investigation and repair of 30-year-old anchors Yukio Fuseya and Hiroyuki Takeda 23 Performance and condition assessment of 30-year-old anchorages, River Clyde, Glasgow Devon Mothersille, Stuart Jackman and Jim Ferrier 33 Some examples of the poor installation of electrically isolated prestressed ground anchors in Slovenia Iztok Klemenc and Viljem Kuhar 43 Maintenance control of ground anchors constructed in Japanese Expressways Masahiro Yoshimura, Masaru Takemoto and Kiyoyuki Amano 53 Session two: Service behaviour monitoring procedures and performance in service Long term monitoring and routine maintenance of ground anchorages at Devonport Royal Dockyard, Plymouth UK Michael Whitworth and Steve Parrish 63 The long-term performance of permanent ground anchors forming part of the Thames Barrier project Mike Turner and David Richards 72 25 years of monitoring of rock anchors installed for landslide stabilisation at Nantgarw, South Wales Hugo Wood and Peter Martin 82 Anchored slope monitoring and test for periodic inspection in Japanese Expressways Katsumi Okubo, Masaru Takemoto and Hiroshi Yamada 92 Monitoring of multi-strand ground anchors at the City of Manchester stadium Lee Jordan 92 Repeated lift-off testing of single bore multiple anchors for dam retaining wall over a 5-year period Mary Ellen Bruce, Jesus Gomez and Robert Traylor 111 Session three: North American Dam rehabilitation Rock anchors for North American dams: the national research program bibliography and database Donald Bruce and John Wolfhope 121 Post-tensioned rehabilitation applied to hydropower dams: continuously improving on an anchor program John Wolfhope, Donald Bruce, Gregor Forbes and Leslie Boyd 132 Case histories of high capacity anchors for two dams in Canada involving long term monitoring Horst Aschenbroich 144 The stabilization of Gilboa Dam, New York using high capacity rock anchors: addressing service performance issues Kessi Zicko, Donald Bruce and Robert Kline 155 The performance of Pacoima Dam in two major earthquakes, with and without post-tensioned anchors Mark Schultz, Shawn Jones and Jeff Howard 166 Session four: Rock bolts in tunnels and mines A review of glass reinforced polymer (GFRP) tendon for rock bolting in tunnels Alison Littlejohn 177 Design and construction of large rock caverns supported by ground anchorages Kenji Aoki 188 Monitoring and testing of mine anchor systems: cases studies and applications to the civil industry Peter Altounyan, David Bigby and Lorraine Kent 199 Session five: Non-destructive integrity testing Common anchorage issues addressed by numerical modelling Ana Ivanovic, Richard Neilson, Andrew Starkey and Albert Rodger 209 Non-destructive testing of deep mine anchorages Andrew Starkey, Richard Neilson, Ana Ivanovic and Albert Rodger 220 Ultrasonic technique for rock bolt and rock mass bond quality control Takayuki Mori, Makoto Nakajima and Tohru Tsutsui 231 The development of the method of detecting the anchor tensile force to impact elastic wave Kuniyasu Tanaka, Hidenobu Okada and Masayasu Izakura 238 Development of loading apparatus and test procedure of rapid load test for ground anchors Tatsuro Sueyoshi and Kazuo Tani 250 Session six: Corrosion monitoring and corrosion protection systems Durability of buried and encased ground anchorages and structural components; requirements for corrosivity assessment and protection to ensure service life Gareth John and Stuart Littlejohn 263 Application of linear polarisation resistance measurements and system modelling for corrosion assessment of high strength rock anchorages Gareth John and Petra Ernst 273 Corrosion protection options for permanent anchorages Chris Irvin and Devon Mothersille 283 Replenishment of underhead protection (below bearing plate) Kouichi Suga, Akira Yonemura and Yoshio Iwaida 293 Durability of ground anchors and other geotechnical stabilization applications in concrete reinforcement steel quality subject to new European regulations Dieter Jungwirth and Susanne Adler 302 A case study on corrosion protection effect of using field- mixed resin as tie-back anchors' grout material for retaining wall and its inspection method Chihping Kuo and Hung-Jiun Liao 312 Advancements in ground anchors: carbon fibre reinforced polymer (CFRP) strands Matthew Sentry, Abdelmalek Bouazza, Riadh Al-Mahaidi, Darren Loidl, Chris Bluff and Len Carrigan 321 Ground anchor tendons in carbon fibre-reinforced polymers Tony Barley and John Hartley 331 Ground anchor made of new materials applicable for highly corrosive environments Tsuyoshi Enomoto, Toshio Sugisaki, Kouichi Suga and Tatsuro Sueyoshi 341 New development of low relaxation epoxy coated strand Tiger Kido, Takayuki Yamagiwa, Toshihiko Niki and Yoshihiko Touda 351 Session seven: Case histories of satisfactory performance, shortcomings and failures in service Assessment of cement grout cover as sole protection of permanent tensioned steel tendons Stuart Littlejohn 357 The failure of anchorage B160 at Devonport Royal Dockyard, Plymouth; reasons for failure and lessons learnt Michael Whitworth and Steve Parrish 368 Service performance of multiple anchors in difficult ground conditions for both permanent anchors and temporary removable anchor usage Tony Barley and Mark Edwards 380 Investigation of the failure of permanent anchorages adjacent to a tidal surge barrier Tony Barley, Devon Mothersille and Peter Chamley 387 Reliability-based failure probability and resistance factor for flush-drilled anchors in Taipei Basin Hung-Jiun Liao, Jianye Ching and Chia-Wei Sue 397 Field surveys of anchored slopes after 2004 Niigataken Chuetsu earthquake Jiro Takemura, Hiroaki Kubo and Junichi Yamazaki 407 Rehabilitation of a failing anchored retaining wall Thomas Richards and Daniel Thome 417 Predicted and observed performance of an anchored retaining wall in granite Abid Adekunte, Douglas Madsen, Neil Margetson and Liam Quinn 427 The design, installation & monitoring of high capacity antiflotation bar anchors to restrain deep basements in Dublin Jim Martin, Philip Daynes, Cathal McDonnell and Martin Pedley 438 Session eight: Recommendations and standards for inspection, monitoring and repair A new manual for ground anchor inspection, integrity investigation and remedial measures Hiroaki Miyatake, Takeshi Oshita, Hiroaki Kubo and Mitsunari Takeyama 451 Structural integrity and durability of ground anchors - general programme of research in Japan Junichi Yamazaki, Tatsuro Sueyoshi and Nobuyuki Urakawa 461 Engineering assessment of the grease-filled annulus of sheathed prestressing strand for use in permanent ground anchorages Tony Barley and Devon Mothersille 471 Rock anchors for North America dams: the development of the national recommendations (1974-2004) Donald Bruce and John Wolfhope 481 Author index 493 KEYNOTE PRESENTATION MAINTENANCE TESTING AND SERVICE BEHAVIOUR MONITORING OF PERMANENT GROUND ANCHORAGES Stuart Littlejohn, University of Bradford, UK Devon Mothersille, Geoserve Global Ltd, UK Abstract Maintenance and monitoring of permanent anchorages are important, particularly for those installed over 30 years ago that may have been designed with inferior or inadequate corrosion protection. Following a review of tendon corrosion failures and observed anchor head conditions after 28 to 33 years of service in aggressive environments, guidelines on good practice for inspection, testing, maintenance and service behaviour monitoring are presented. Topics include designer responsibility, anchor head inspection, component and material testing, load monitoring, extent and frequency of inspections, and associated records. Current national, European and international recommendations are summarised. Case histories of permanent anchorage corrosion are reported, where the conditions of the ground or groundwater and anchorage components are quantified. These cases illustrate the value of detailed metallurgical examination and testing to investigate the nature, intensity and extent of the corrosion, in order to determine the risk of failure and the most appropriate remedial measures. Introduction The purpose of this paper is to provide guidelines on good practice in maintenance testing and service behaviour monitoring of individual ground anchorages. As permanent anchorages in service become older, the subject is of growing importance, particularly for anchorages installed over 30 years ago that may have been designed with corrosion protection considered inferior or inadequate by today's standards, e.g. reliance on cement grout cover alone, where the grout has been injected remotely under pressure or by gravity displacement to encase the tendon in situ. Even more recently installed anchorages are not immune due to the employment of inappropriate protective materials and occasional shortcomings in the quality of workmanship, combined with an absence of rigorous Q A/QC procedures in the field. Routine programmes of inspection and monitoring, where satisfactory condition and service performance are confirmed, can extend the service life of anchored structures, such as post- tensioned dams, dry docks, bridges, sports stadiums and multi-storey buildings, stabilised Ground anchorages and anchored structures in service 2007, Thomas Telford, London ii GROUND ANCHORAGES AND ANCHORED STRUCTURES IN SERVICE slopes, earth-retaining walls, river and seawall coastal defences, reinforced tunnels and underground caverns, that represent key elements of a country's infrastructure. Alternatively, in cases where an inspection highlights unacceptable tendon exposure to corrosion, or service behaviour monitoring confirms tendon over-stressing, the results can provide an early warning of the need to carry out precautionary or remedial measures, in order to safeguard the integrity and performance of the anchored structure. In spite of these benefits, insufficient attention is paid to routine maintenance inspections and service behaviour monitoring in current practice, and the potential consequences should not be ignored. Water levels reached 150-year highs during August 2002 with associated flooding across central and eastern Europe, so the importance of anchored river and seawalls cannot be overemphasised. Winter storms are now judged by the insurance industry to represent the largest potential event loss in Europe (Swiss Re, 2003). The Association of British Insurers has identified that in London alone, 500,000 houses, 200 schools, 16 hospitals and eight power stations are located in floodplains (ABI, 2006). Elsewhere in the UK there are numerous examples of waterside infrastructure incorporating anchored quay and wall structures. These include ports and harbours along the east coast of Scotland and England, the Thames Barrier, structures along the Thames Estuary, ports and harbours along the south coast of England, the Bristol Channel, the Welsh coast and west Scotland. Elsewhere in the world, the highest potential losses are associated with earthquakes and typhoons. Given torrential rainfall, anchored slopes are vital in resisting landslides and rock avalanches. In Japan, for example, where the ground anchorage market is $650 million per annum, 64% of an average of 2277km of anchorages installed each year is devoted to landslide prevention and slope stabilisation (Kubo, 2006). Failures of anchorages in service In the 1980s, the Federation Internationale de la Precontrainte (FIP) carried out a world-wide search of anchorage failures and published a study of 35 case histories of failure, primarily by tendon corrosion, relating to ground anchorages installed over the period 1934 to 1980. The detailed findings and records are published in FIP (1986) and Littlejohn (1987). The findings maybe summarised as follows. • Corrosion is localised and appears irrespective of type of tendon in that 9 incidents involved bar, 19 involved wire and 8 involved strand. • The period of service before failure ranged from a few weeks to many years for each tendon type; short term failures after a few weeks of service were due to stress corrosion cracking or hydrogen embrittlement. • In terms of failure location, 19 incidents occurred at, or within lm of the anchor head, 21 incidents in the free length, and 2 incidents in the fixed length.