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Managed remediation of a large Victorian gravity quay wall using the observational
method
Stabilisation d'un grand mur de quai de l’époque Victorienne gérée en utilisant la méthode
observationnelle
Turner M J, Smith N A
Applied Geotechnical Engineering, UK
ABSTRACT: The paper describes on-going work to control the stability of a large gravity quay wall at a port on the western seaboard
of the UK, which has had a history of instability dating back over several decades. In 1999 further ground movements of the wall
were triggered by leakage from a fractured water main in the quayside behind the wall. This caused severe settlement damage to the
quay and associated storage warehouses on the quayside. Monitoring of the affected area of the wall was established in early 2000,
with additional ground investigations and instrumentation to supplement existing data. By the end of September 2000 the worst
affected parts of the wall were moving outwards at a rate of 10mm/day. The movements were initially arrested by groundwater
lowering. Subsequently additional remedial measures consisting of anchors and shear keys were designed and installed to provide
physical restraint. The Owner wished to minimise capital expenditure and instead to use an observational approach (Peck 1969) and to
respond to the information obtained. The work had therefore attained what was regarded as an acceptable steady state, with continued
managed remediation to ensure that the wall’s stability is maintained and the Owner can continue to use the berthing facilities.
RÉSUMÉ:
Le document décrit les travaux en cours pour contrôler la stabilité d'un grand mur de quai dans un port de la côte ouest du
Royaume-Uni, qui avait un historique d'instabilité datant de plusieurs décennies. En 1999, de nouveaux mouvements de terrain et du
mur furent déclenchés par une fuite d'eau due à une rupture de tuyaux d’alimentation en eau du quai qui étaient derrière le mur. Ceci
causa des dommages graves au quai et aux entrepôts de stockage sur le quai. La surveillance de la zone affectée du mur commença au
début de 2000, avec addition d’instruments de mesure supplémentaires et investigations complémentaires du sol pour compléter les
données existantes. À la fin de Septembre 2000, les zones les plus touchées du mur se déplaçaient vers l'extérieur à une vitesse de
10mm/jour. Les mouvements furent arrêtés par l'abaissement des eaux souterraines. Par la suite d'autres mesures correctives
constituées de tirants d’ancrage et de piles pour éviter les glissements furent conçues et installées pour assurer la contention physique
du mur. Le propriétaire souhaitait minimiser l’investissement initial et préférait utiliser une approche observationnelle (Peck 1969) en
réponse aux informations obtenues. Le mur était assez stable pour utiliser le quai en continuant l’application opportune des mesures
correctives pour assurer la contention du mur, et le propriétaire peut continuer à utiliser les installations d'accostage.
KEYWORDS: gravity walls; long-term monitoring; long-term displacements; ground anchors; water pressures; effects of dewatering.
1
INTRODUCTION
A section of harbour wall at a port on the western seaboard
of the UK has a history of instability dating back over more than
thirty years. Measurements taken in the 1980s had indicated
that the maximum total horizontal movement of the wall up to
that date had been more than 400mm. In 1999 further ground
movements of the wall were triggered by leakage from a
fractured water main in the quayside behind the wall. This
caused outward movements along a length of over 80 metres,
and severe settlement damage to the quay and associated
storage warehouses on the quayside.
The harbour works were constructed at the end of the 19
th
Century. The wall is a gravity structure of mass concrete and
masonry with sandstone “plums”. At its top, it is some 17
metres above the harbour bed level; it is about 2 metres wide at
its crest, increasing to almost 9 metres at its base. There is a
large tidal range at the site.
After the 1999 movements, monitoring of the affected area
of the quay wall was established in early 2000, with additional
ground investigations to supplement existing data and to
confirm the wall dimensions and the ground/groundwater
conditions behind the wall. Inclinometers and piezometers were
also installed to monitor water levels and the wall behaviour.
Survey lines were established perpendicular to the wall and
extending back to stable reference markers remote from the
wall, with intermediate reference points to measure lateral and
vertical movements in the ground behind the wall.
By mid-2000 the monitoring data showed a deteriorating
situation, with outward movements of the wall accelerating
from an initial value of around 15 to 20mm per month to as
much as 100mm/month, and increasing. By the end of
September of that year the worst affected parts of the wall were
moving outwards at a rate of 10mm/day, and measures were put
in place to stabilise the wall immediately in the short term,
together with further works to ensure the stability of the quay
wall in the medium term.
This current paper describes these measures and the long
term monitoring of the wall over the past decade.
Figure 1. Outline plan of the site.
