Artículo rocas 2

Engineering Geology 117 (2011) 159–169

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Engineering Geology
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / e n g g e o

Re-evaluation of rock core logging for the prediction of preferred orientations of karst
in the Kuala Lumpur Limestone Formation
Hareyani Zabidi a,⁎, Michael Henry De Freitas b
a
School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia
b
Department of Civil and Environmental Engineering, Skempton Building, Imperial College, SW7 2AZ, London, United Kingdom

a r t i c l e i n f o a b s t r a c t

Article history: Based on the relationship between the geological structures and river patterns, the preliminary prediction of
Received 17 December 2009 the karstic features in the Kuala Lumpur Limestone Formation, based on the existing geological, map appears
Received in revised form 9 August 2010 to be directed between N030° to 070° and N120° to 150°. The factual evidence of this occurrence is obtained
Accepted 9 October 2010
from investigation in the field: first, using the two sites exposed for construction of the SMART tunnel under
Available online 16 October 2010
Kuala Lumpur and second, based on the SMART tunnel project rock cores recovery. A much detailed prediction
Keywords:
was made by re-evaluating the TCR, RQD and SCR values. The reassessment of these values enables the drilled
Limestone ground to be classified into four different qualities of rock mass: good quality limestone; moderate quality
Karst limestone; weathered limestone; and fully developed void-like karst. According to this new classification
RQD system, the tunnel appears to align generally in the heavily karstified limestone in the northern section and
SMART tunnel massive good quality limestone in the southern section of the study area; which is represented as rose
Rose diagram diagrams. The evidence for this analysis is given and the methods used for these studies are explained.
Kuala Lumpur © 2010 Elsevier B.V. All rights reserved.

1. Introduction formation developed in the area. Buried karst occurs as a bedrock and
dominates the sub-surface of Kuala Lumpur Valley. According to
In Malaysia, limestone caves extensively outcrop in the northern Waltham and Fookes (2003), the highly irregular topography of
half of the Peninsular Malaysia, such as in Langkawi Islands, northern limestone formation, which is classified as extreme karst (kV), was
Perlis, Kinta Valley in Perak and Klang Valley in Kuala Lumpur. first discovered buried beneath the alluvium layer. This happened
Although these limestone formations vary considerably in geological when they were exposed to the air between 1970's and mid 1980's in
age and tectonic setting, they are very similar in chemical composi- the tin mines that were found scattered around Ipoh and Kuala
tion; being dense, recrystallised, and massive with little impurities; Lumpur, and for the first time, were presented as highly irregular sub-
and, by having these properties, the formations are more likely to surface rockhead and fractured rock mass of buried karst (Fig. 1) (Tan,
develop karst landscape and large caverns within them (Gobbett, 1985; Yeap, 1985). Deep borehole records from construction sites in
1965). The features can be seen well developed in limestone the city confirm its occurrences (Mitchell, 1985; Tan et al., 1985).
formation at many of the previously exposed open hydraulic tin Upon the discovery of highly variable karst formation from the tin
mines in Perak and Kuala Lumpur (Yeap, 1987). mining activities, extensive studies were carried out, with most of
In contrast to any other karst formations in the country, karst effort looking specifically at the process and the time-scale at which
terrain in Kuala Lumpur is a home for many big foundations of high karst had developed. Yeap (1985) attempted to classify the karstic
and heavy buildings, thus, it is so important to understand its features into 5 significant groups based on the physical and
existence (Pollalis, 2002). Karst in Kuala Lumpur could simply be morphological characterization. This classification is also in good
divided into two groups based on its morphology. The first group is agreement with the 5 stages of karst evolution proposed by Yeap
surface karst and the second is buried karst where the latter group is (1987). Based on the observations carried out by Yeap (1985, 1987,
the dominant type of karst that occurs in Kuala Lumpur (Yeap, 1985). 1993) at the previously open tin mines around the Kuala Lumpur area,
Batu Caves at the northern part of Kuala Lumpur represents the it was believed that the karstification process occurred beneath a
surface karst, and towers vertically above a flat alluvial plain of Klang permeable layer of sediment that was later eroded to expose the
Valley. However, Batu Caves represents only 1% of the whole karst karstic formations to the air before later being buried once again
under alluvium. This is verified by Tan (1986a,b, 1987) in more
specific study areas, where he pointed out the presence of a very soft
⁎ Corresponding author. Tel.: + 60 135016293; fax: + 60 45941011. soil zone, where the SPT value is 0, located immediately above the
E-mail address: srhareyani.zabidi@eng.usm.my (H. Zabidi). limestone bedrock below the much younger formation; the Kenny Hill

0013-7952/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.enggeo.2010.10.006

160 H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169

Fig. 1. (a) Sungai Way Mine, Kuala Lumpur (picture from Yeap, 1985). The irregular top surfaces of the Kuala Lumpur Formation were revealed during the tin mining exploration;
(b) high pinnacles of the limestone rock surface in Kuala Lumpur (picture from Tan, 1985).

Formation. This soft soil zone was interpreted as a weathered into the studied engineering structures and hence, characterizing the
limestone formation which was possibly weakened by dissolution hydraulic properties of the ground.
after being covered by the Kenny Hill Formation, and overlain by Research conducted for the last 50 years had shown that the
much harder or stiffer layer of soils from the Kenny Hill Formation development of a dissolution cavity is more likely to follow some
(SPT = 30–50 or even greater). preferred orientations and patterns. These variations were observed
A systematic presentation of engineering geological data in the to follow the significant patterns of variables involved, such as the
form of a hazard map is a useful tool in urban planning, particularly structural geology, topography, mineralogy, sedimentology and
in a highly developed karstic area, as in Kuala Lumpur. Currently palaeoclimate. Parts of these relationships and observations have
practice of depending heavily on borehole drilling to study the been well written by many researchers in Malaysia, for example, they
complexity of the ground in Kuala Lumpur is risky and incorrect, as attempted to link the close relationship of karst formation with the
much of the commercial centre of Kuala Lumpur is founded on the geological structures and drainage patterns, by which the prediction
heavily karstified limestone of the Kuala Lumpur Limestone of karst can be made by analysing the stream trellis form in the ground
Formation and boreholes give no guarantee of finding all the (Tjia, 1970, 1996). However, many authors did not consider the
karst; and, this has always been a challenge for engineers working in possibility of quantitatively studying the karst formation and rather
Kuala Lumpur (Mitchell, 1985; Gue and Tan, 2001; Abdullah, likely to make a straight forward depiction of the studied rock mass,
2004a). Around the world, various studies, ranging from cave leaving the currently available method of karst prediction to be alone
mapping, geophysical survey and borehole drilling, have been detected by borehole drillings. Hence, the main objective of this paper
conducted to understand and further predict the extremely complex is to do the methodology self-checked analysis by quantitatively
system of the underground cavities (Epting et al., 2009). Current identifying the distribution of the karst cavity formed in the Kuala
studies on the underground karst were largely based on the cave Lumpur Limestone Formation using the so obtained borehole logs of
research and expose outcrops seen at road cuts, mines or quarries the SMART tunnel project. In this study, the geometry of the karst
with most of the studies looking at the known distributions of system was directly observed from the quality of recovered cores,
sinkholes in predicting the future occurrences of sinkholes in the whereas the hydraulic properties were analysed from the installed
areas of interest (Gao et al., 2005; Brinkman et al., 2008; Bruno et al., piezometer readings. This is the second phase of analysis following
2008; Guerrero et al., 2008). Nonetheless, in the recent years, many the first paper written by Zabidi and deFreitas (2006), where the
available logged boreholes were recovered from karst terrain as prediction of karst orientations in Kuala Lumpur were deduced from
more engineering structures in the urban area are in demand. The the map study and later verified by field observations carried out at
analysed data is improved by advanced technology that has created the two previously exposed sites for the SMART construction.
borehole imagery to study the solution conduits in karst aquifers In this study, a high density of logged boreholes, drilled for the
and other karst features (Manda and Gross, 2005; Papadimitriou construction of the Stormwater Management and Road Tunnel
et al., 2008). (SMART), provides a great opportunity to quantitatively analyse the
However, boreholes are commonly drilled in a less systematic sub-surface cavity karst (Fig. 2). The Malaysian Government proposed
pattern of distribution to form spatial coexistence between two the construction of the SMART project on account of the frequency of
boreholes logs, and this should be taken into consideration in flooding in Kuala Lumpur over the past three years; the city
interpreting karst (Urban and Rzonca, 2009). Commonly conducted experiences frequent flash floods from the Klang River during the
in the geotechnical study, borehole logs are mainly used to deduce the monsoon season because it is situated at the confluence of the Klang
vertical profile and the distribution of strata in studied area underlain River and the Gombak River (Abdullah, 2004b; Klados and Yeoh,
by bedded sequences of rocks. In the karst study, mapping of the 2004; Krause et al., 2004; Tunnel and Tunnelling, 2005). This
underground cavities commonly utilises several techniques of innovative solution involves a dual-purpose tunnel, which will not
geophysical survey which provides much comprehensive and thor- just be used to control the volume of flood water coming into the city
oughly information on the characteristics of the underground karst centre during the rainy season but will also be used as an automobile
terrain compared to drilling alone. Boreholes are commonly used for corridor to reduce traffic congestion at the southern gateway of Kuala
ground validating purposes and hydrogeological observations (Sudha Lumpur during the dry season. The tunnel has a total length of 9.7 km;
et al., 2009). Pesendorfer and Loew (2009) and Filipponi et al. (2009) the central 3 km section of the tunnel doubles up as a two-deck to
studied the groundwater networks, looking into the potential inflows alleviate traffic congestion in central Kuala Lumpur.

H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169 161

Fig. 2. SMART alignment, crossing between Ampang at the northern section and Taman Desa at the southern section of Kuala Lumpur.

2. Geology of Kuala Lumpur and its relationship with lies over them. The country rock was then intruded by granite, estimated
karst formation to be either broadly contemporaneous with or younger than the second
phase of folding, occurring towards the Late Triassic. The last period of
Kuala Lumpur is located in Peninsular Malaysia, lies on a flat alluvial deformation is NE–SW and NW–SE trending faulting, which has affected
plain within the broad valley of the Klang River, bounded by high hills all the formations, including the granite. The fault zones of the Ampang
predominantly of granitic rock to the west and east. The main river of Fault, trending at N285°, and the Gombak Fault, at N200°, have markedly
the study area is the Klang River that drains a catchment area of displaced the Kuala Lumpur Limestone Formation and can be expected
approximately 1288 km2, and traverses a distance of nearly 120 km. to have affected its hydraulic conductivity. Paton (1964) believed that
Generally, Kuala Lumpur has a uniformly high air temperature the presence of mature karstic features, as distinct from the palaeo-
throughout the year, averaging between 25 °C and 28 °C with 80% karst, in this area is the result of climate in the present and recent past.
humidity. The climate is strongly affected by the speed and direction of The rock head karst is generally believed to have developed during the
air streams which sweep across the Peninsular Malaysia twice a year, Quaternary, although it is possible that considerable dissolution also
blowing from the southeast and the northeast direction, and responsible occurred prior to the deposition of the Permo-Carboniferous Kenny Hill
for two interchangeable seasons each year: monsoonal and trans- Formation; this paleo-landscape has been buried by alluvium to form
monsoonal that carry with them strong wind and heavy rainfall. the current landscape of Kuala Lumpur (Chan and Hong, 1985).
Fig. 3 shows the location and geologic setting of the SMART tunnel
alignment between Ampang at the northern section and Taman Desa 3. Method of analysis
at the southern end of Kuala Lumpur. The bedrock geology of the
study area consists of sediments ranging in age from Middle In this study, an almost continuous profile of the Kuala Lumpur
Ordovician to possibly Permian, and a granitic body intruded during Limestone Formation along the 9.7 km tunnel is provided by the
the Late Triassic. The oldest of the sequence is the Hawthornden records of boreholes drilled during the site investigation for the
Formation (Middle Ordovician to Middle Silurian), a mixture of quartz – SMART project, thus offers a good opportunity to study the ground
mica amphibolites and carbonaceous schists, phyllites and quartzites – condition of karst features along the line (T&T, 2005). Due to these
overlain by the Kuala Lumpur Limestone Formation (Middle Silurian to demanding ground conditions, extensive site investigation along the
Lower-Middle Devonian) (Gobbett, 1964). The overlying Kuala Lumpur tunnel alignment was necessary, comprising around 500 drillings of
Limestone Formation is composed of fine to coarse grained, white to deep sub-surface investigations with drilling up to a maximum depth
grey, predominantly recrystallised limestones, with local developments of 50 m below ground level (BGL), in addition to a resistivity survey
of dolomitic limestone and dolomites, all with few impurities. These was carried out before and during the construction of the tunnel. The
Lower Palaeozoic formations experienced their first phase of folding collection of borehole records used in this study was largely based on
during the Devonian to form east–west fold axes. An extensive period of the drilling and logging carried out by several private geotechnical
uplift, weathering and erosion followed during which karst developed companies in Kuala Lumpur, appointed by the Malaysian's govern-
in the Kuala Lumpur Limestone Formation. ment and also a company joint-venture pact between Gamuda Berhad
These Lower Palaeozoic formations are overlain unconformably by and Malaysia Mining Corporation Berhad (MMC). These logs were
the shales, mudstones and sandstones of the Kenny Hill Formation, reanalysed during this study to re-assess the Solid Core Recovery
which accumulated towards the end of the Carboniferous and the start (SCR), Total Core Recovery (TCR) and Rock Quality Designation (RQD)
of the Permian. These sediments were folded by a second tectonic so that a quantitative measure of the quality of the ground can be
orogeny during the Late Triassic. This strongly deformed the Lower determined. Using the values so obtained, the ground is re-classified
Palaeozoic rocks to produce the metamorphic grades now seen and into four different qualities of rock mass, ranging from very good to
folded strata to follow a north–south trend. The Lower Palaeozoic very poor. Based on this classification and the position of the
sequence has bedding dips that are commonly steep and overturned, boreholes, a percentage of karst per unit area seen in plans, could
contrasting with the more gentle dips of the Kenny Hill Formation which be calculated, which was then presented as rose diagrams.


Fig. 3. A simplified version of the geological map of Selangor, Sheet 94 (Yin, 1967). The valley area is composed of the Hawthornden Formation, the Kuala Lumpur Limestone
Formation, the Kenny Hill Formation and granitic body.

In the two aligned borehole analysis, good quality of the ground is (K1) which is well developed creating a highly irregular level of rock
represented as small values on a rose diagram, whereas poor quality below the alluvium, varying in elevation by tens of meters over tens of
ground, which is thus expected to contain much karst, is represented by meters and containing numerous voids, many of which have collapsed
large values. However, as the boreholes were drilled at different and are partially filled, and a Karst Scale 2 (K2) which is much smaller
spacings and at different depths, a further analysis is required to and concentrated on fractures which have developed an openness
produce a representative value per unit area seen in plan. Thus, an area (measured in centimeters) and freshness that suggest that it is still
analysis was carried out, using the three nearest borehole method of actively developing. The existence of two different groups of karst in
calculation; a modified version of the Thiessen Polygon method; this is the area was recorded from the mapping of two localities exposed
presented in the second part of the paper. In this analysis, the percentage during the construction of the SMART tunnel: the North Junction Box
of karst was defined in any area by the three closest boreholes. The in Kampung Pandan Roundabout and the South Junction Box in Sungai
boreholes along the alignment were grouped into five different sections: Besi (Zabidi, 2008).
the North Bound section; the Jalan Kampung Pandan section; the The construction extends the existing borehole data and permits a
Kampung Pandan Roundabout section; the South Bound section and the detailed study of such karst to be conducted, since the Kuala Lumpur
Taman Desa section; each of the sections contains different clusters of Limestone Formation is the predominant geological formation at the
boreholes which can be used to form several different triangles, each tunnel level throughout the route. Nonetheless, this data is much
joined by the three nearest boreholes, as mentioned above. better in some places than in others. The drilling was done in
The calculated karst percentage obtained from the analysis was accordance with BS 5930, 1981, whereas the core logging was carried
plotted against per unit area to give a profile of the ground in terms of out with reference to BS 5930:, 1999. The quality of rock drilled out
area along the alignment. Having considered the horizontal variable from the ground was measured by the Total Core Recovery (TCR),
towards the karstification, the next step was the assessment of karst Solid Core Recovery (SCR) and Rock Quality Designation (RQD), in
in a volume of the ground, where the vertical variable was studied. In addition to description of the rock and the fractures according to BS
this analysis, the same triangles were used to check the volume of 5930:, 1999.
karst developed as were used to calculate its presence per unit area;
the results obtained were presented as the fraction of karst plotted 5. SMART tunnel rock core recovery
against the volume of the ground.
The Northbound and the Southbound section of the tunnel were
4. Factual data from the SMART tunnel project named in reference to the advancement of TBM to the north and south
of the Kampung Pandan Roundabout (Fig. 4). The cores drilled from
From field observation, the buried karst landscape of the Kuala the Northbound tunnel section can generally be classified as heavily
Lumpur Limestone Formation can be further grouped into two classes karstified; this is largely based on the quality of the recovered core.
in accordance to its dimensions and characteristics: a Karst Scale 1 Poor recovery was often encountered, especially in the Kampung


Fig. 4. A general map of the SMART tunnel alignment. The location of boreholes is shown in different clusters of boreholes.

Berembang area, near to the Klang Holding Pond construction site, directions of the line of boreholes. The values of RQD, SCR and TCR
and in the Jalan Kampung Pandan, at the North Junction Box site. In were chosen to independently describe the quality of the ground
the Kampung Berembang site, 12 boreholes, with a horizontal drilled along the alignment and further used to calculate the
distance between them less than 10 m, revealed a very poor recovery, percentage of existing sub-surface karst, where the drilled rock core
lots of cavities and broken material. The ground condition becomes was classified into four different qualities of rock mass: good quality
extremely unpredictable as the rock mass change over a short limestone; moderate quality limestone; weathered limestone and
distance between much karstified grounds to solid massive rock. fully developed void-like karst. For every closely spaced cluster of
Further down to the south, close to the Kampung Pandan Roundabout, boreholes, the percentage of karst per unit area was measured
on the discovery of the poor ground conditions from the first stage between two boreholes in any given direction; the percentage of karst
drilling carried out in the area, further deep drilling, consisting of was represented as rose diagrams.
closely spaced probes at a distance less than 10 m and at depth more
than 40 m BGL was carried out during the construction of the tunnel 5.1. The SCR, RQD and TCR values
(Zabidi, 2008).
In contrast, a much better quality rock mass was recovered out Following BS 5930:, 1999, the Total Core Recovery (TCR) is defined
from the South Bound tunnel section with one or two exceptional as the percentage ratio of the core recovered (either solid or non-
locations, e.g. the Sungai Besi Junction Box and the Taman Desa intact) to the total length of each core run. The Solid Core Recovery
Reservoir Pond, where the rock cores are heavily weathered and (SCR) is referred to as the percentage ratio of the solid core recovered
fractured. Other than those two locations, the boreholes consistently to the total length of each core run, whereas the Rock Quality
revealed cores that have percentages more than 90% of TCR, SCR and Designation (RQD) is defined as the ratio of the total length of the
RQD values. The drilled limestones were massive, dense and show few solid core (the SCR definition) pieces each greater than 100 mm
fractures in comparison to the limestones drilled from the North between natural (not drilling induced) discontinuities, to the length
Bound tunnel section; and this profile of core logs was in good of core run. For the purpose of this study, the BS 5930:, 1999
agreement with the exposed rock sections mapped in the South classification of TCR, SCR and RQD is neither detailed nor specific
Junction Box located in Sungai Besi. enough in definition to explain the complex nature of the karstic
The analysis started with a comprehensive study of almost all landscape of the Kuala Lumpur Limestone Formation. To analyse the
borehole logs obtained from the rock core drilling carried out for the borehole logs quantitatively a further classification and practical
SMART tunnel; leaving out biased data. This was done by having left definition on the quality of the limestone rock has been made in order
out all the boreholes drilled in a single line as the data is biased to the to define the presence or absence of such smaller scale (K2) karst; this


was largely based on the Solid Core Recovery (SCR), the Rock Quality broken pieces of rock. Hence, these two have been used to grade the
Designation (RQD) and the Total Core Recovery (TCR), as the limestone into 4 types; Table 1 illustrates the re-classification.
classification is the most practical and available system to date for
1. SCR 100% to 70%: RQD 100% to 35%. Good quality rock.
interpreting the quality of rock mass drilled from the ground.
2. SCR 69%–50%: RQD 100%–35%. Moderate quality rock.
Additional input can also be obtained by the core photos taken from
3. SCR 69% to 50%: RQD 34% to 0%. This is taken as “weathered”
the sites, and this may allow for the re-checking of the core log to be
limestone, where weathering has opened discontinuities and
carried out. In this classification system, the range of percentages for
hence represented areas of the ground having great potential to
each group was chosen after checking and re-assessing all the
contain well developed small scale karst. In this class, a much
recorded boreholes by comparing their core logs with their photos.
higher percentage of SCR was used in comparison to the RQD given
In this analysis, the presence of what might be palaeokarst and
that the recovered core within this value shows good recovery of
modern karst in the recovered limestone was defined as karst and was
solid rock, but frequently as a non-intact mass; broken pieces of
analysed every 1.5 m length of the core. The problem here was
rock less than 100 mm long result to the lowering of the RQD value.
detecting small scale karst (K2). Large scale karst (K1) was mainly
4. SCR 49% to 0% and RQD 34% to 0%. This was taken as fully developed
detected by TCR and had shown much consistence values of high
void-like karst; which revealed little recovery of the solid core with
percentages of recovery throughout the exercise; detection of small
the occurrence of soft fragments of rock or no recovery of the core.
scale karst cavity was less significant to compare to this percentage.
The TCR value was analysed by measuring up the total depth of Using this approach, the same range of SCR percentages, between
drillings and largely used to assess the overall profile of the ground; 69% and 50%, but different classes of RQD was used to differentiate the
the value is a combination of soft soil and hard rock materials, as quality of the ground; the RQD is 100%–35% in the moderate quality of
defined in BS 5930:, 1999. Within the recovered core there could be rock whilst 34%–0% in the weathered group of rock. In contrast to this
small scale karst (K2); this would be reflected in SCR and RQD. This presentation, different classes of SCR percentages in combination with
much smaller scale of karst concentrated on fractures can directly be the same range of RQD values gave another set of ground qualities;
interpreted from these two percentages as the SCR has only ranges from good to moderate and from weathered to void karst ground
considered the solid or hard rock materials and the RQD represents (Table 1). This was basically based on the observation of recovered rock
the quality of the recovered hard rock; either as an intact mass or cores at sites, structural mapping carried out on the excavated rock faces

Table 1
New classification system of quantifying the borehole log, using the SCR and RDQ values. The quality of recovered cores is classified into four groups according to the values of SCR
and RQD (after BS 5930:, 1999).


and core photos from the SI report, where a significant drop of rock rockhead is located deeper down than the rest of the rock in the
quality, which is heavily weathered and broken pieces of rock cores, can area and in this case, the core was labelled as 100% karst.
be seen when the SCR value is in between 69% and 50% and the RQD 4. In the fourth borehole of Bh3650R, the core was also classified as
value is within 34%–0%. This was basically looking at the significant 100% karst as the revealed rock core contains very low values of
differences the ground made by just considering the classification alone SCR and RQD. The core was drilled at a depth of 28.00 m BGL, the
and the value was not so good when the TCR was small or the core was rockhead was discovered at 10.80 m BGL to leave the 17.20 m of
close to a cavity; in this case the SCR and the RQD values appeared to be the rock core with very low values of SCR and RQD.
higher but the core was poor. This had been cross-checked with the
photos taken at sites. Therefore, to calculate the percentage of karst 5.2. The percentage of karst between two aligned boreholes
developed along the general alignment of the tunnel, the last group of
karst, the SCR 49% to 0% and RQD 34% to 0% was used. This range of Following this classification system, the original SCR and the RQD
percentages is assigned to represent the voids given to the poor core values between aligned boreholes were re-evaluated for every
recoveries, containing most of soft fragment of rock and soils. These borehole location where closely spaced clusters of boreholes existed
materials are believed to be the in-filling materials of voids or cavities (boreholes space at distances of between 10 m to 20 m) so that
originated from the heavily fractured and deformed limestone comparisons in different directions could be made, in order to
formation. It is assumed that these hard materials were slowly softened produce a percentage of dissolution in given directions. The final
by the process of weathering that finally changed it into the soft soils. values of SCR and RQD were then plotted as rose diagrams of likely
Validation of these percentages has been made through the mapping karst. Directions with small values in these diagrams reflect high
carried out at the Kampung Pandan Roundabout or Northbound box values of SCR and RQD and are assumed to represent a reasonably
where karst is seen to develop at the intersection zone between two good quality of limestone in which little dissolution might be
very prominent fracturing systems in the limestone formation. expected, whereas directions with large values are expected to be
In Fig. 5, four different rock cores which represent four different more likely to contain dissolution that has been better developed. To
quality of rock mass, are presented, namely here as CP4-4, BH-NVS2, the civil and tunnel engineers all such dissolution is viewed as “karst”.
BH2 and Bh3650R. These boreholes are illustrated here as an example A cluster of closely spaced boreholes (named as BhA1, Bh-V6, Bh-V5,
of the calculation used to quantify the percentage of karst formed in Bh4053R, Bh4053CL, and Bh4053L) located at Ch4000, near Jalan
one borehole. Kampung Pandan was taken here as an example for the calculation used
to present the percentages of karst between two boreholes in any given
1. In the first borehole of CP4-4, the core was drilled to 27 m BGL with direction. All the measurements are shown in Fig. 6; according to the
the rockhead at 2.80 m BGL, to leave 24.80 m rock core with high new system, the six drilled boreholes were classified as follows:
values of TCR, SCR and RQD; it has 0% of karst and thus to be classed Borehole BhA1 was measured to have 37.77% karst content;
as good quality of rock mass. borehole Bh-V5 is classed as good quality limestone with 0% karst
2. In the second borehole of BH-NVS2, the total length of the core is content; borehole Bh-V6 contained 19.26% karst; borehole Bh4053R
30.00 m with 4.60 m of soft soil cover and 25.40 m of rock core. A contained the most percentages of karst in the group with 66.31%
total of 2.40 m length of the low percentage in SCR and RQD has karst; borehole Bh4053CL also has 0% karst as it was drilled at only
resulted to the 9.44% of karst within this one borehole. 10.40 m BGL and Bh4053L had 53.84% karst. The percentage of karst
3. In borehole BH2, the core was drilled much deeper, down to between two aligned boreholes for every borehole in the group was
44.00 m BGL, but failed to encounter bedrock; this means that the calculated by taking the average percentage of karst within the two

Fig. 5. Details of four different rock cores, drilled out from four different areas along the tunnel alignment. Each of the boreholes represents a different quality of the rock core, after
having quantified using the new classification system of RQD and SCR values. Elevations are in meters above sea level.


Fig. 6. Six boreholes from a cluster of closely drilled borehole from the Kampung Pandan Roundabout, the location of boreholes are presented in the above map. The quality of the
rock core is valued in karst percentage, quantified using the new quantitative system. Elevations are in meters above sea level.

boreholes in the given direction (Fig. 7, map 1); where each of the alignment (Fig. 8 and 9). These groups of boreholes were divided into
direction is aligned between two drilled boreholes. This six boreholes 5 different sections in accordance to the area of drilling as follows:
had produced 15 different directions of predicted karst percentages,
presented in Table 2 (Fig. 7), which were later plotted as a rose (1) First was the North Bound (NB) section, consisting of boreholes
diagram, shown in Fig. 7 (rose diagram); and, based on the rose drilled out from the North Bound (NB-A) and another two
diagram, karst in this area is predicted to have mainly developed in groups of boreholes drilled in between of Jalan U Thant and
the N310° and N360° directions. Jalan Kampung Pandan (NB-B and NB-C). All three clusters are
A similar method of calculation was used to measure the percentage presented in Fig. 8. In the first group (NB-A), 12 holes were
of karst for every closely spaced cluster of boreholes drilled along the drilled near the Klang Holding Basin site, at a distance less than
9.7 km tunnel alignment. In total, 36 clusters of boreholes were selected 10 m between each of the boreholes; here, the quality of the
for this analysis leaving out all the boreholes drilled in a single line as the recovered core log is being reflected by the major directions of
data is biased to the directions of the line of boreholes. Even so, the the rose diagram, which means high percentage of dissolution
interpretation carried out is still strongly biased by the obtained data, features in approximately every direction of the ground. The
the drilled boreholes; so, the absence of directions in the rose diagram other two groups (NB-B and NB-C) show less intensity of karst
could represent the absence of data rather than the absence of karst: development in comparison to NB-A.
with more data it would be possible to resolve the unknown. (2) Second is the Jalan Kampung Pandan (JKP) section consisting of
seven very closely drilled borehole groups (named here as JKP-A
6. Discussion to JKP-F). The poor recovery of rock cores is presented in rose
diagrams as shown in Fig. 8. Here, the drilling of cores was carried
The analysed rose diagrams were drawn along the alignment to out at a distance less than 10 m apart to reveal a very high
provide an overview of the karst condition beneath the proposed percentage of karst, as presented in the major direction of rose

Fig. 7. The quality of each of the rock core is valued in percentage, as karst percentage, having quantified using the new quantitative system. 15 different directions of two aligned
boreholes are shown in map 1; the percentage of karst and the direction of the two aligned boreholes are presented in Table 2. All the measurement are later drawn into a rose
diagram to give the more likely directions of the developed karst; major directions are assumed to represent the major dissolution karst features, whereas the minor directions are
believed to represent a good quality of limestone.


Fig. 8. The SMART tunnel alignment, for the north section and its relation to the quality of the ground which might be encountered in one given area, based on the rose diagram
analysis.

diagrams, especially in groups JKP-F and JKP-G, where karst is (5) Fifth is the Taman Desa (TD) section (Fig. 9), consisting of a
assumed to have developed in all directions defined by the good quality of rock cores (TD-A) and a poor quality of rock in
boreholes. In the borehole groups of JKP-A to JKP-D, the drilled the group of TD-B. The rose diagram of TD-A has minor
cores contained minor percentages of karst, less than 50%, and in directions in comparison with the major direction of the rose
the predicted directions of karst obtained from the map study. diagram in TD-B, which is assumed to have developed karst in
(3) Third is the Kampung Pandan Roundabout (KPR) section all directions defined by the location of boreholes.
(Fig. 8), consisting of six clusters of boreholes (KPR-A to KPR-
E). Here, the quality of recovered cores was interpreted as a 7. Conclusions
combination of good and poor ground; these were presented in
the rose diagrams. The less percentage of karst, represented by Karst in Kuala Lumpur exists as a part of the bedrock with most of
the minor direction of the rose diagram, has developed in the identification performed by borehole drillings and assisted by the
groups KPR-D, E and F, whereas the developed major direction indirect method of geophysical investigations. However, in Kuala
could be seen in groups of KPR-B and KPR-C, particularly in Lumpur, the geophysical surveys provided little assistance to the
between N360° and N040°. engineers on site in predicting the location of karst. This was
(4) Fourth is the Sungai Besi (SB) section, consisting of five clusters attributed to a high water table and unavoidable levels of background
of boreholes which revealed a very good quality of rock cores geophysical noise (electrical and acoustic), leaving the borehole logs,
(SB-A to SB-E). This data is shown in the rose diagram, Fig. 9. most of the time, to do the prediction alone. Comparing the analysis
The dominant quality of the rock core is seen in most of the rose carried out in this study with the direct observations in caves or
diagrams; karst has minor values, which are less than 30%, and expose outcrop, as previously carried out by many researchers in
could represent a very good quality of the ground condition in Malaysia, might have led to a much better understanding on the
the southern section of the tunnel. development of karst although the latter approach is a more sensitive


Fig. 9. The SMART tunnel alignment, for the south section and its relation to the quality of the ground which might be encountered in one given area, based on the rose diagram
analysis.

method of analysis compared to recovered rock cores; even by method was achieved by combining the values of RQD, SCR and TCR,
considering that the borehole log is a direct method in locating and where a combination of certain ranges of percentages of those three
analysing the intensity of karstification. But, the karst terrain that was parameters would represent the level of karstification in the ground.
once exposed to the air during the active period of mining activities in The first quantitative analysis was presented in a rose diagram: the
Kuala Lumpur now buried beneath the alluvium layer, makes it quality of the ground was defined by the percentage of karst, so the
impossible to do a direct comparison. But, data obtained from direction with a small karst percentage value has good quality ground
borehole log analysis should also represent some limitations as the and the direction with a large value has poor quality ground. Rose
interpretation is the result of random sampling over a large volume of diagrams reflecting good quality ground could be seen formed in the
a karstic terrain and this gives no guarantee of finding the karst cavity. southern section of the tunnel, whilst rose diagrams for the northern
Hence, this paper presents some methodology that quantitatively section reflect poor quality ground.
analyse the occurrence of the karst cavity using a large collection of This is in good agreement with the orientations of joints and karst
borehole logs that could be used to develop much representative surfaces observed at the two sites previously exposed during the
analysis of the karst cavity in the future. construction of the SMART tunnel, the Kampung Pandan Roundabout
In this study, considering the complex system of the karst terrain or the Northbound box and the Sungai Besi or the Southbound box.
that presently exists in the ground, which was confirmed by the poor The two sites are less than 3 km apart, but a clear division could be
rock core recoveries, a further classification system is needed to seen between the grounds exposed in the two areas. In the North, the
properly log the rock cores. The currently used classification and ground is heavily fractured, strongly deformed and varied greatly in
description of the rock core, based on the RDQ percentage is too the pattern of fracturing over a short distance. Frequently found at the
general and not specific enough to define the characters of karst site, mainly in the North Junction Box, is a wet yellow coloured
observed, and thus to predict the location and the dimension of karst slickensided surface believed to have formed as a result of shear
in the ground. Therefore, in this study, the logged boreholes were re- displacement and the continuous flow of running water. The studied
evaluated with the modified classification system. This modified rockmass is heavily weathered to form variable features of karst


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