2977
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1
Instrumented Trial Embankment on Soft Ground at Tokai, State of Kedah, Malaysia
Embankment essai instrumenté sur un sol mou à Tokai, État de Kedah, en Malaisie
TAN Yean-Chin, LEE Peir-Tien & KOO Kuan-Seng
G&P Geotechnics Sdn Bhd, Malaysia.
ABSTRACT: The geometrical tolerance of railway tracks at high operating speed is generally very stringent. Hence, when long
stretches of the railway embankment traversing through soft alluvium deposits, cost effective designs meeting the design performance
and construction schedule are required. A cost effective treatment such as prefabricated vertical drain (PVD) with temporary
surcharging was designed to meet the stringent performance requirements. In addition, basal reinforcement was adopted to allow
higher embankments to be built without compromising on the embankment stability during construction and to meet the tight
construction schedule. Therefore, a fully instrumented trial embankment was carried out at Tokai, State of Kedah, Malaysia to verify
the design philosophy of the ground treatment method adopted. This paper presents the consolidation settlement behavior and excess
pore water pressure responses of the trial embankment during construction and surcharge waiting period. Back analyses using Finite
Element Modeling (FEM) was performed to evaluate the performance of the ground treatment and to verify the subsoil parameters
used in the design.
RÉSUMÉ :
La tolérance géométrique des voies ferrées à grande vitesse de fonctionnement élevée est généralement très strictes. Ainsi,
lorsque de longues étendues de la voie ferrée traversant remblai par des dépôts d'alluvions souples, efficaces coûtent conceptions
répondant à la performance de la conception et du calendrier de construction sont nécessaires. Un traitement rentable telles que
vidange verticaux préfabriqués (PVD) avec surcharge temporaire a été conçu pour répondre aux exigences de performance
rigoureuses. En outre, le renforcement de base a été adopté pour permettre aux plus digues pour se construire sans compromettre la
stabilité de remblai lors de la construction afin de respecter le calendrier de construction serré. Par conséquent, un remblai d'essai
entièrement instrumenté a été effectuée à Tokai, État de Kedah, en Malaisie afin de vérifier la philosophie de conception de la
méthode de traitement des sols adopté. Cet article présente le comportement tassement de consolidation et de l'excès de pression d'eau
interstitielle des réponses du remblai d'essai pendant la construction et la période d'attente. Retour à l'aide des analyses de
modélisation par éléments finis (FEM) a été réalisée afin d'évaluer la performance du traitement des sols et de vérifier les paramètres
du sous-sol utilisés dans la conception
KEYWORDS: Instrumented trial embankment, soft ground, consolidation settlement .
1 INTRODUCTION
The construction of the electrified double track project in
northern part of Peninsular Malaysia commenced in year 2007.
As most of the embankments are founded on soft alluvium
deposit, cost effective ground treatment such as PVD with
temporary surcharging was widely adopted to meet the stringent
settlement requirements and tight construction schedule. In view
of this, a fully instrumented trial embankment was constructed
at Tokai, State of Kedah as shown in Figure 1 to verify the
design philosophy of the ground treatment method adopted.
This is to study the consolidation settlement behavior, excess
pore water pressure response and lateral displacement at the toe
of embankment as indicator of consolidation process and
embankment stability during construction filling and rest
period.
This paper presents the settlement behaviour and excess
pore water pressure response of the trial embankment. Back
analyses using Finite Element Modelling (FEM) was also
performed to evaluate the performance of the ground treatment
and to verify the subsoil parameters adopted in the design.
2 SUBSOIL CONDITION
The subsoil is relatively homogenous consisting of very soft to
soft CLAY (15m thick) overlying dense silty sand to sand from
depth of 15m to 24m. Hard layer with SPT
‘
N
’
value of more
than 50 was found below 24m. The general subsoil properties
including bulk density, compression ratio (CR), re-compression
ratio (RR), over consolidation ratio (OCR), pre-consolidation
pressure (Pc), undrained shear strength (s
u
) and Atterberg limit
are plotted in Figure 2. The interpreted subsoil parameters based
on the field and laboratory tests are summarized in Table 1.
3 GROUND TREATMENT AND INSTRUMENTATION
The general ground treatment details for trial embankment are
summarised in Table 2. The instrumentation scheme includes
settlement gauges, extensometers, inclinometers, ground
displacement markers, vibrating wire piezometers, standpipe
and surface settlement markers as shown in Figure 3. Settlement
at centre of embankment was measured by settlement gauges
SG2, SG5 and SG8. Whilst, settlements at edge of embankment
were measured by settlement gauges SG1, SG3, SG4, SG6, SG7
and SG9. Settlements at various depths were measured by
extensometers EXT1, EXT2 and EXT3. The multistage
construction with higher height of up to 7.6m was carried out
due to site condition and problems such as delay in view of wet
monsoon season, no borrow source, etc. The original intent is to
construct the trial embankment in single stage loading of up to
5.9m
4 BACK ANALYSIS BY FEM MODELLING
Back analyses were carried out by using finite element
modelling (FEM) software (Plaxis). Soft Soil Model (SSM) was
Tan Y.-C., Lee P.-T., Koo K.-S.
