A case history of repair works of major road embankment failure along Genting Highlands to Bukit Cincin, Pahang is presented. Failures at 10 locations along Genting Highlands to Bukit Cincin road occurred on 30th October 1997 during the monsoon seasons. The repair works at Location 1 using reinforced earth wall was considered since there was enough space available at the downslope section and also the soil at the downslope section of the failed embankment was strong enough to construct the wall safely. This paper fully explained the details remedial works using reinforced earth wall at Location 1

Ahmad, Mohd Farid

Jamalludin, Damanhuri

Md. Issa, Ahmad Kamal

Mohd Salleh, Samsuri

English

Universiti Teknologi MARA Institutional Repository

  
Repair of Major Road Embankment Failure Using Reinforced Earth (re) wall 
 
Assoc. Prof. Ir. Damanhuri Jamalludin 
 Ir. Dr. Mohd Farid Ahmad
 
Samsuri Mohd Salleh
 
Ahmad Kamal Md. Issa
 
  
Abstract 
 
A case history of repair works of major road embankment failure along Genting 
Highlands to Bukit Cincin, Pahang is presented. Failures at 10 locations along Genting 
Highlands to Bukit Cincin road occurred on 30th October 1997 during the monsoon 
seasons. The repair works at Location 1 using reinforced earth wall was considered since 
there was enough space available at the downslope section and also the soil at the 
downslope section of the failed embankment was strong enough to construct the wall 
safely. This paper fully explained the details remedial works using reinforced earth wall 
at Location 1. 
 
Introduction 
 
In Malaysia, like in many other tropical and subtropical countries, rocks are weathered at 
great depth as a result of warm and wet climatic conditions. Othman (1990) explained 
that deep cuttings into residual soils suffer severe instability problems particularly during 
the wet seasons between October and February. 
As mentioned by Neoh (1997) and Omar at al. (1997), the roads in mountainous 
terrains of tropical regions are characterized by steep and deep weathered rocks which are 
prone to landslide and slope failures during prolong intense rainfall. Rain induced 
landslide and slope instability are really a costly recurring problem faced by many 
tropical countries like Malaysia. Millions of ringgits are spent in slope repairs. Slope 
stability depends on the complex interplay between slope gradient, geological conditions, 
soil properties and ground water condition of which they are all of dynamic in nature. It 
is also influence by the road design, its construction and maintenance. This paper 
presents the detail remedial works to repair a major road embankment failure. 
 
Background Of The Road 
 
The Genting Highlands to Bukit Cincin road is a road linking the Genting Highlands and 
the Department of Civil Aviation (DCA) Radar station.  Figure 1 shows the location plan 
of the road while Figure 2 shows the location of the road failure. The total length of this 
hilly and winding road was about 2 km and it was 3.5m wide. It was constructed 1975. 
On 30th October 1997, 10 locations of road instability or failure had occurred during the 
monsoon season. Of the 10 repaired locations, the repair works at Location 1 is fully 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
described in detail. The total cost of the repair works was RM 3.7 million and was 
repaired on design and construct basis. The site possession was on 10 May 1999 and was 
completed on 15 May 2000.  
          
Causes Of The Failure  
 
The road embankment was totally collapsed and was impassable to vehicles. The existing 
pavement, drains as well as gabion stabilizing and supporting the embankment at its toe 
also collapsed. Temporary access was carried out by Genting Berhad by dumping soil on 
the failed embankment so that vehicles can pass through the failed road. 
The causes of failure for this embankment were predominantly due to (a) soil erosion 
since roadside drains were not connected to cascading drain to lead rain water and surface 
runoff to the toe of slope and (b) improper compaction of the fill material resulting in 
critical battering of the slope. Erosion caused the toe of slope to progressively fail. Figure 
3 shows erosion causing the major road failure while Figure 4 shows the failure at 
Location 1.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
  
W. P. KUALA 
LUMPUR 
Genting 
Highlands  
Town 
PAHANG 
SELANGOR 
KL – Karak 
Highway 
Location 1 
Genting Highlands 
Town 
Bukit Cincin 
Radar Station 
 
 
Roadside 
drains 
stopped here Embankment 
failure 
Lowest point 
Directions of surface 
runoff 
Road 
Fig. 3 : No cascading drains causing 
erosion which lead to embankment failure.  
Road 
 
Fig. 4 : Road embankment failure 
at Location 1. 
To Bukit 
Cincin radar 
station 
Embankment 
failure 
955 
950 
945 
Road 
Fig. 1 : Location plan of the failed  
Road near Genting Highlands town. 
Fig. 2 : Location of road failure at  
Location 1 
  
The shallow slips retrogressively moved towards the crest of the embankment created 
instability to the embankment. As this phenomena proceed, slumping of soil mass 
occurred and forming a vertical scarp at the crest of the embankment as described by 
Bumi Hiway (1998). Figures 5 and 6 show the road embankment failure. 
 
 
 
 
 
 
 
 
 
SITE INVESTIGATION WORKS  
Borehole 1 was carried out at this location. Loose SAND was found between 0m to 4.5m 
and medium dense SAND was at depth between 4.5m and 13.5m. Very stiff sandy SILT 
was between 13.5m and 16.0m while very dense SAND was found beyond the depth of 
16.0m. It can be observed that the soil strength increased with depth. The fill mass 
forming the embankment slope was about 4m to 5m depth. Water table was found at the 
depth of  6.5m. The detail results of Borehole 1 are shown in Figure 8. 
 
REPAIR WORKS 
Reinforced earth wall was suitable and used as the repair works for the failed 
embankment since the soil to place the wall was strong and also enough space was 
available to place the wall safely as recommended by Neoh et al. (1997). The base of the 
wall was decided at 9.5m below the existing road level. From BH/1, at this level, the soil 
type was medium dense clayey SAND with SPT N value of 9.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
 
Fig. 5 : Major road embankment 
failure.  
  
Fig. 6 : Another view of the road  
embankment failure. The road was  
totally impassable to vehicles. 
 
 
Stone filled gabion mattress 
 Cascading drain 
BH/1 
 Roadside drain 
1 : 2  slope sprayed 
with hydroseeding 
and planted with 
vertiver grass at   
1m spacing  
RE 
wall 
Repaired road 
To Bukit Cincin 
radar station 
Fig. 8 :  Typical cross section of the repair 
works and the results of BH/1.  
Fig. 7 : The plan view of the repaired zone 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The wall height was 5.5m by 5.9m wide and about 29m long.  Figure 7 shows the plan 
view of the repaired zone while the typical cross section of the repair works and the 
results of BH/1 are shown in Figure 8. 
A minimum horizontal distance of 2m was provided between the toe of the 
reinforced earth wall and top edge of down slope. Weak and failed materials were 
removed and the base was placed on firm ground. JKR probe tests were carried out to 
confirm the allowable bearing capacity of the base. Figure 9 shows JKR probe test is in 
the progress of being carried out.  
A vertical drainage blanket 500mm thick was constructed between the reinforced 
earth wall and the existing embankment. It consisted of gravel wrapped with filter 
geotextile material. Rock fill 300mm by 600mm wrapped with geotextile TS20 was 
placed at the front toe of the reinforced earth wall as shown in Figures 10 and 11. 
Horizontal PVC drains 150mm diameter with spacing of 6000mm were placed almost at 
the base of the reinforced earth wall to drain groundwater collected in the vertical 
drainage blanket to the rock fill. Good external and internal drainage must be provided as 
recommended by Jones (1985) since large catchment area and also water table was found 
at 6.5m below road level. Drainage was provided by rock fill at toe, berm drain and 
shoulder drain in which all were connected to a cascading drain. Stone filled gabion 
mattress was constructed at the toe of the cascading drain to prevent toe erosion as shown 
in Figure 7.  
The reinforced earth wall consisted of hexagonal shaped precast concrete panel 
connected to hot dipped galvanised reinforcing tendons as shown in Figures 12 and 13. 
 
  
50 
 RE 
wall 
1 : 2  fill slope with hydroseeding 
and vertiver grass at 1m spacing   
Well compacted 
granular material 
500mm thick  
vertical drainage 
blanket 
Rock fill 
Loose 
SAND 
9.5m 
Medium 
dense   
SAND 
V. Stiff 
SILT 
Reinforcement 
tendons 
Water 
Table 
Horizontal 
drains 
Berm 
drain 
Failed 
profile 
5.5m 
SPT N value 
 
  
Precast anchor blocks were placed at the end of the reinforcing tendons to provide an 
additional anchoring capacity to the system. Concrete levelling pad of size 150mm by 
350mm was placed as the base of the panel wall. Well-compacted granular fill was used  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 9 : C nducting JKR probe at the
base level. 
Fig. 10 : Trench is excavated at the 
toe of RE Wall to construct the 
Rock Fill. 
 
  
 
Fig. 11: Gravel wrapped with 
geotextile is placed into the 
excavated trench to form Rock Fill. 
Fig. 12 : Erecting the RE Wall. 
 
Fig. 13 : Laying of the galvanised 
reinforcement tendons. 
Anchor 
blocks 
Reinforcement 
tendons 
  
as the backfill material. Above the reinforced earth wall, slope with gradient of   1 : 2 was 
reconstructed as mentioned by Bumi Hiway (1998). 
Hydroseeding grass was sprayed and vertiver grass at 1m spacing was planted on 
the reconstructed slope while at downslope, 3 rows of vertiver grass at 1m spacing were 
also planted. Berm drain and roadside drain were connected to a cascading drain with 
stone filled gabion mattress at its toe. Figure 15 shows the berm and roadside drains. The 
damaged road was also reconstructed on the pile embankment. Partially completed repair 
works are shown in Figure 14 while the fully completed repair works are shown in Figure 
16. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 14 : Partially completed repair works. 
Fig. 15 : New roadside drain is constructed. 
Road shoulder is turfed. 
Roadside 
drain 
Berm drain 
Vertical drainage 
blanket 
Backfilled 
material 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Conclusions 
 
a) If the space at the downslope is large enough and the soil is strong, reinforced 
earth wall is an option to repair major embankment failure. 
b) If the water table is high, suitable internal drainage systems such as vertical 
drainage blanket, horizontal drains and rock fill at toe of the wall must be 
provided. 
c) Roadside drains, berm drains and cascading drains connected to stone filled 
gabion mattress must be provided to cater for surface runoff. 
 
Acknowledgements 
 
The authors wish to thank Dr. HM Abdul Aziz KM Hanifa (Selangor PWD), En. Uzir 
Alimat (Caw. Jalan, PWD), Pn. Sarojini (Caw. Jalan, PWD) and Ir. Azmi Jamaludin 
(Khairi Consult Sdn Bhd.) for all their assistance in the preparation of this paper. 
 
Referencers 
 
Bumi Hiway (M)  Sdn. Bhd., (1998).  Geotechnical Design Report On Proposed Slope 
Repair At Bukit Cincin, Genting Highlands, Pahang 
 
Jones, C. J.F.P., (1985). Earth Reinforcement and Soil Structures, Butterworths, London  
 
Neoh, C.A., (1997). Lecture On Slope Stability Problems And Solutions, Road Branch, 
PWD Malaysia 
 
Neoh, C.A., Che Zain, B., (1997). Slope Stability Problems For Roads In Hilly Terrains, 
Proceeding Of Institute Of Engineers Malaysia, Kuala Lumpur 
 
 
Fig. 16 : Completed RE wall with berm drain 
and cascading drain. 
Cascading drain 
RE wall 1:2 slope with 
hydroseeding and 
vertiver grass 
Berm drain 
  
Omar, W., & Neoh C.A., (1997). Landslides Problems For Roads In Mountainous 
Terrains – Some Malaysian Experiences - PIARC Seminar On Natural Disaster  
 
Reduction For Roads, New Delhi, India 
 
Othman, M.A., (1990). Highway Cut Slope Instability Problems In Peninsular Malaysia, 
PENEMUAN, IKRAM 
 
 
ASSOC. PROF. IR. DAMANHURI JAMALLUDIN, Faculty Of Civil Engineering, 
UiTM Penang Campus, 13500 Permatang Pauh, Penang 
 
IR. DR. MOHD FARID AHMAD, Faculty Of Civil Engineering, UiTM Penang Campus, 
13500 Permatang Pauh, Penang 
 
SAMSURI MOHD SALLEH, Faculty Of Civil Engineering, UiTM Arau Campus, 02600 
Perlis 
 
AHMAD KAMAL MD. ISSA, Faculty Of Civil Engineering, UiTM Arau Campus, 
02600 Perlis 
 


Repair of major road embankment failure using reinforced earth (re) wall

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Repair of major road embankment failure using reinforced earth (re) wall

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