National Geoscience Conference 2011 - Department Of Geology ...

NATIONAL GEOSCIENCE CONFERENCE 2011
11 – 12 June 2011 • The Puteri Pacific Johor Bahru, Johor, Malaysia
Paper A10
A Tale of Two Airports: the New LCCT, Sepang, and the Senai Airport
Tan Boon Kong
Consultant Engineering Geologist, Petaling Jaya
Email address: tanboonkong@gmail.com
Owing to severe congestion problems in the present Low Cost Carrier Terminal (LCCT) in Sepang, a new LCCT
has been planned and is currently under construction. The new LCCT is located adjacent to the Kuala Lumpur
International Airport (KLIA) in Sepang, and has been re-designated as KLIA2. The terminal or project area is
underlain by thick deposits of Quaternary sediments and peat, with Kenny Hill formation as the underlying bedrock.
The soil profile typically consists of three layers, namely (from top to bottom): Quaternary Sediments/Peat, Residual
Soils (of Kenny Hill formation), and Bedrock (Kenny Hill formation).
The main concern with the construction of the terminal and runway is the settlement or differential settlement
problems arising from the thick Quaternary deposits and peat. Thus, the determination of the spatial distribution and
thickness of these deposits is crucial, and this has been done via a series of boreholes. Borehole data shows that the
thickness of the soft deposits in general increases towards the seaward side, with a maximum thickness of about 30
m been recorded from the boreholes. Figure 1 shows an isopach map of the Quaternary sediments/peat. The soil
settlement problem is tackled during construction with the use of pre-loading/surcharging and incorporating vertical
drains to accelerate the consolidation of the soft soils.
The Senai airport (Sultan Ismail International Airport) in Johor was recently re-developed, with the runway
extended. In contrast to the KLIA2 area, the underlying geology in the Senai airport area comprises stiff to hard
granitic residual soils underlain by granite bedrock. Detailed soil profiles and soil properties were again determined
via boreholes and laboratory tests. The granitic residual soils typically consist of stiff to hard yellow-brown-red
sandy SILT and sandy CLAY. Standard Penetration Test (S.P.T.) N values increase with depth, as is the case in
general for residual soils. The granite “bedrock” occurs at depths of 11.5 – 39.0m, i.e. a large variation in depth.
It could also mean that some of the shallower (say < 20 m) “bedrock” were in fact core boulders. Some boreholes
did not encounter rock and were terminated at S.P.T. N > 50 (for 6 consecutive N>50 values). The granite rock is
described as a light grey, medium to coarse-grained, slightly fractured weathered granite (grade III), strong rock.
Groundwater depth ranges from 1.0 to 7.5m, but is mostly at shallow depths of < 3m. One borehole encountered
GABBRO, described as grey-brown fine-grained, highly fractured, moderately weathered (grade III), very weak
rock. The topography of the project site consists of low-lying, undulating hills/hillocks, of contours ranging from
40-50m. Many of the low hills/hillocks were excavated as borrow pits. The highest borrow pit of 50m contour is
located near the runway extension just south or southeast of the present runway. Earthworks cut-and-fill operations
have resulted in most of the low-lying small streams/valleys being backfilled to attain the various platform levels
required for the development.
As the original topography was low-lying and consist of
small hills/hillocks of 40-50 m contours, there are no major
concerns with slopes or slope stability problems to begin
with. Furthermore, the current development involving cutand-fill
operations would effectively “flatten” the entire
project sites, and hence, no slope problem to be concerned
about. Granitic residual soils are generally of high strengths,
and stability of cut slopes would generally not be a problem.
The cut-and-fill operations involve compaction of the fill
materials borrowed from the various hillocks/borrow
pits. Granitic residual soils provide good fill materials for
compaction, partly due to the well-graded nature of the soils
(sandy CLAY, sandy SILT). The laboratory compaction test
results show:
– maximum dry density = 1.44–1.61 Mg/m 3 , i.e. high mdd,
– optimum moisture content = 12.0–20.5 %., i.e. low omc.
(compaction by 4.5Kg rammer, 5 layers, with 15 blows/
layer).
Hence, engineering wise, this second project is less
problematic compared to KLIA2.
Figure 1: Isopach map of Quaternary Sediments/Peat in the
new LCCT area, Sepang (contours in meter).
18