160 H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169Fig. 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 thelimestone 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 themuch 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 theform of a hazard map is a useful tool in urban planning, particularly structural geology, topography, mineralogy, sedimentology andin a highly developed karstic area, as in Kuala Lumpur. Currently palaeoclimate. Parts of these relationships and observations havepractice of depending heavily on borehole drilling to study the been well written by many researchers in Malaysia, for example, theycomplexity of the ground in Kuala Lumpur is risky and incorrect, as attempted to link the close relationship of karst formation with themuch of the commercial centre of Kuala Lumpur is founded on the geological structures and drainage patterns, by which the predictionheavily karstiﬁed limestone of the Kuala Lumpur Limestone of karst can be made by analysing the stream trellis form in the groundFormation and boreholes give no guarantee of ﬁnding all the (Tjia, 1970, 1996). However, many authors did not consider thekarst; and, this has always been a challenge for engineers working in possibility of quantitatively studying the karst formation and ratherKuala 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 alonemapping, geophysical survey and borehole drilling, have been detected by borehole drillings. Hence, the main objective of this paperconducted to understand and further predict the extremely complex is to do the methodology self-checked analysis by quantitativelysystem of the underground cavities (Epting et al., 2009). Current identifying the distribution of the karst cavity formed in the Kualastudies on the underground karst were largely based on the cave Lumpur Limestone Formation using the so obtained borehole logs ofresearch and expose outcrops seen at road cuts, mines or quarries the SMART tunnel project. In this study, the geometry of the karstwith 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 installedareas of interest (Gao et al., 2005; Brinkman et al., 2008; Bruno et al., piezometer readings. This is the second phase of analysis following2008; Guerrero et al., 2008). Nonetheless, in the recent years, many the ﬁrst paper written by Zabidi and deFreitas (2006), where theavailable logged boreholes were recovered from karst terrain as prediction of karst orientations in Kuala Lumpur were deduced frommore engineering structures in the urban area are in demand. The the map study and later veriﬁed by ﬁeld observations carried out atanalysed 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 theand other karst features (Manda and Gross, 2005; Papadimitriou construction of the Stormwater Management and Road Tunnelet 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 proposedpattern of distribution to form spatial coexistence between two the construction of the SMART project on account of the frequency ofboreholes logs, and this should be taken into consideration in ﬂooding in Kuala Lumpur over the past three years; the cityinterpreting karst (Urban and Rzonca, 2009). Commonly conducted experiences frequent ﬂash ﬂoods from the Klang River during thein the geotechnical study, borehole logs are mainly used to deduce the monsoon season because it is situated at the conﬂuence of the Klangvertical 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). Thisunderground cavities commonly utilises several techniques of innovative solution involves a dual-purpose tunnel, which will notgeophysical survey which provides much comprehensive and thor- just be used to control the volume of ﬂood water coming into the cityoughly information on the characteristics of the underground karst centre during the rainy season but will also be used as an automobileterrain compared to drilling alone. Boreholes are commonly used for corridor to reduce trafﬁc congestion at the southern gateway of Kualaground 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 tostudied 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, estimatedkarst 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 affectedplain within the broad valley of the Klang River, bounded by high hills all the formations, including the granite. The fault zones of the Ampangpredominantly of granitic rock to the west and east. The main river of Fault, trending at N285°, and the Gombak Fault, at N200°, have markedlythe study area is the Klang River that drains a catchment area of displaced the Kuala Lumpur Limestone Formation and can be expectedapproximately 1288 km2, and traverses a distance of nearly 120 km. to have affected its hydraulic conductivity. Paton (1964) believed thatGenerally, 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 theair streams which sweep across the Peninsular Malaysia twice a year, Quaternary, although it is possible that considerable dissolution alsoblowing from the southeast and the northeast direction, and responsible occurred prior to the deposition of the Permo-Carboniferous Kenny Hillfor two interchangeable seasons each year: monsoonal and trans- Formation; this paleo-landscape has been buried by alluvium to formmonsoonal 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 tunnelalignment between Ampang at the northern section and Taman Desa 3. Method of analysisat the southern end of Kuala Lumpur. The bedrock geology of thestudy area consists of sediments ranging in age from Middle In this study, an almost continuous proﬁle of the Kuala LumpurOrdovician to possibly Permian, and a granitic body intruded during Limestone Formation along the 9.7 km tunnel is provided by thethe Late Triassic. The oldest of the sequence is the Hawthornden records of boreholes drilled during the site investigation for theFormation (Middle Ordovician to Middle Silurian), a mixture of quartz – SMART project, thus offers a good opportunity to study the groundmica amphibolites and carbonaceous schists, phyllites and quartzites – condition of karst features along the line (T&T, 2005). Due to theseoverlain by the Kuala Lumpur Limestone Formation (Middle Silurian to demanding ground conditions, extensive site investigation along theLower-Middle Devonian) (Gobbett, 1964). The overlying Kuala Lumpur tunnel alignment was necessary, comprising around 500 drillings ofLimestone Formation is composed of ﬁne to coarse grained, white to deep sub-surface investigations with drilling up to a maximum depthgrey, predominantly recrystallised limestones, with local developments of 50 m below ground level (BGL), in addition to a resistivity surveyof dolomitic limestone and dolomites, all with few impurities. These was carried out before and during the construction of the tunnel. TheLower Palaeozoic formations experienced their ﬁrst phase of folding collection of borehole records used in this study was largely based onduring the Devonian to form east–west fold axes. An extensive period of the drilling and logging carried out by several private geotechnicaluplift, weathering and erosion followed during which karst developed companies in Kuala Lumpur, appointed by the Malaysians 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 werethe shales, mudstones and sandstones of the Kenny Hill Formation, reanalysed during this study to re-assess the Solid Core Recoverywhich 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 beorogeny during the Late Triassic. This strongly deformed the Lower determined. Using the values so obtained, the ground is re-classiﬁedPalaeozoic rocks to produce the metamorphic grades now seen and into four different qualities of rock mass, ranging from very good tofolded strata to follow a north–south trend. The Lower Palaeozoic very poor. Based on this classiﬁcation and the position of thesequence has bedding dips that are commonly steep and overturned, boreholes, a percentage of karst per unit area seen in plans, couldcontrasting with the more gentle dips of the Kenny Hill Formation which be calculated, which was then presented as rose diagrams.
162 H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169Fig. 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 LimestoneFormation, 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 rockrepresented as small values on a rose diagram, whereas poor quality below the alluvium, varying in elevation by tens of meters over tens ofground, which is thus expected to contain much karst, is represented by meters and containing numerous voids, many of which have collapsedlarge values. However, as the boreholes were drilled at different and are partially ﬁlled, and a Karst Scale 2 (K2) which is much smallerspacings and at different depths, a further analysis is required to and concentrated on fractures which have developed an opennessproduce a representative value per unit area seen in plan. Thus, an area (measured in centimeters) and freshness that suggest that it is stillanalysis was carried out, using the three nearest borehole method of actively developing. The existence of two different groups of karst incalculation; a modiﬁed version of the Thiessen Polygon method; this is the area was recorded from the mapping of two localities exposedpresented in the second part of the paper. In this analysis, the percentage during the construction of the SMART tunnel: the North Junction Boxof karst was deﬁned in any area by the three closest boreholes. The in Kampung Pandan Roundabout and the South Junction Box in Sungaiboreholes 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 aKampung Pandan Roundabout section; the South Bound section and the detailed study of such karst to be conducted, since the Kuala LumpurTaman Desa section; each of the sections contains different clusters of Limestone Formation is the predominant geological formation at theboreholes which can be used to form several different triangles, each tunnel level throughout the route. Nonetheless, this data is muchjoined 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 carriedplotted 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 outarea 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), inin a volume of the ground, where the vertical variable was studied. In addition to description of the rock and the fractures according to BSthis 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 recoveryagainst the volume of the ground. The Northbound and the Southbound section of the tunnel were4. 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 heavilyLumpur 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
H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169 163 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 TCRand in the Jalan Kampung Pandan, at the North Junction Box site. In were chosen to independently describe the quality of the groundthe Kampung Berembang site, 12 boreholes, with a horizontal drilled along the alignment and further used to calculate thedistance between them less than 10 m, revealed a very poor recovery, percentage of existing sub-surface karst, where the drilled rock corelots of cavities and broken material. The ground condition becomes was classiﬁed into four different qualities of rock mass: good qualityextremely unpredictable as the rock mass change over a short limestone; moderate quality limestone; weathered limestone anddistance between much karstiﬁed grounds to solid massive rock. fully developed void-like karst. For every closely spaced cluster ofFurther down to the south, close to the Kampung Pandan Roundabout, boreholes, the percentage of karst per unit area was measuredon the discovery of the poor ground conditions from the ﬁrst stage between two boreholes in any given direction; the percentage of karstdrilling 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 morethan 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 deﬁnedfrom 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 RecoveryReservoir Pond, where the rock cores are heavily weathered and (SCR) is referred to as the percentage ratio of the solid core recoveredfractured. Other than those two locations, the boreholes consistently to the total length of each core run, whereas the Rock Qualityrevealed cores that have percentages more than 90% of TCR, SCR and Designation (RQD) is deﬁned as the ratio of the total length of theRQD values. The drilled limestones were massive, dense and show few solid core (the SCR deﬁnition) pieces each greater than 100 mmfractures in comparison to the limestones drilled from the North between natural (not drilling induced) discontinuities, to the lengthBound tunnel section; and this proﬁle of core logs was in good of core run. For the purpose of this study, the BS 5930:, 1999agreement with the exposed rock sections mapped in the South classiﬁcation of TCR, SCR and RQD is neither detailed nor speciﬁcJunction 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 theborehole logs obtained from the rock core drilling carried out for the borehole logs quantitatively a further classiﬁcation and practicalSMART tunnel; leaving out biased data. This was done by having left deﬁnition on the quality of the limestone rock has been made in orderout 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
164 H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169was largely based on the Solid Core Recovery (SCR), the Rock Quality broken pieces of rock. Hence, these two have been used to grade theDesignation (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 andcarried out. In this classiﬁcation system, the range of percentages for hence represented areas of the ground having great potential toeach group was chosen after checking and re-assessing all the contain well developed small scale karst. In this class, a muchrecorded 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 ofmodern karst in the recovered limestone was deﬁned as karst and was solid rock, but frequently as a non-intact mass; broken pieces ofanalysed 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 developeddetected by TCR and had shown much consistence values of high void-like karst; which revealed little recovery of the solid core withpercentages 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, betweendrillings and largely used to assess the overall proﬁle of the ground; 69% and 50%, but different classes of RQD was used to differentiate thethe 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 ofdeﬁned in BS 5930:, 1999. Within the recovered core there could be rock whilst 34%–0% in the weathered group of rock. In contrast to thissmall scale karst (K2); this would be reﬂected in SCR and RQD. This presentation, different classes of SCR percentages in combination withmuch 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 groundconsidered the solid or hard rock materials and the RQD represents (Table 1). This was basically based on the observation of recovered rockthe quality of the recovered hard rock; either as an intact mass or cores at sites, structural mapping carried out on the excavated rock facesTable 1New 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 SCRand RQD (after BS 5930:, 1999).
H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169 165and core photos from the SI report, where a signiﬁcant drop of rock rockhead is located deeper down than the rest of the rock in thequality, 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 asvalue is within 34%–0%. This was basically looking at the signiﬁcant 100% karst as the revealed rock core contains very low values ofdifferences the ground made by just considering the classiﬁcation alone SCR and RQD. The core was drilled at a depth of 28.00 m BGL, theand 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 ofclose 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 thephotos taken at sites. Therefore, to calculate the percentage of karst 5.2. The percentage of karst between two aligned boreholesdeveloped along the general alignment of the tunnel, the last group ofkarst, the SCR 49% to 0% and RQD 34% to 0% was used. This range of Following this classiﬁcation system, the original SCR and the RQDpercentages is assigned to represent the voids given to the poor core values between aligned boreholes were re-evaluated for everyrecoveries, containing most of soft fragment of rock and soils. These borehole location where closely spaced clusters of boreholes existedmaterials are believed to be the in-ﬁlling materials of voids or cavities (boreholes space at distances of between 10 m to 20 m) so thatoriginated from the heavily fractured and deformed limestone comparisons in different directions could be made, in order toformation. It is assumed that these hard materials were slowly softened produce a percentage of dissolution in given directions. The ﬁnalby the process of weathering that ﬁnally changed it into the soft soils. values of SCR and RQD were then plotted as rose diagrams of likelyValidation of these percentages has been made through the mapping karst. Directions with small values in these diagrams reﬂect highcarried out at the Kampung Pandan Roundabout or Northbound box values of SCR and RQD and are assumed to represent a reasonablywhere karst is seen to develop at the intersection zone between two good quality of limestone in which little dissolution might bevery 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. Toquality 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 Jalanone borehole. Kampung Pandan was taken here as an example for the calculation used to present the percentages of karst between two boreholes in any given1. 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% karst2. 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 karst3. 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 twoFig. 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, afterhaving quantiﬁed using the new classiﬁcation system of RQD and SCR values. Elevations are in meters above sea level.
166 H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169Fig. 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 therock 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 intodirection 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 boreholesdiagram, shown in Fig. 7 (rose diagram); and, based on the rose drilled out from the North Bound (NB-A) and another twodiagram, karst in this area is predicted to have mainly developed in groups of boreholes drilled in between of Jalan U Thant andthe 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 wereof karst for every closely spaced cluster of boreholes drilled along the drilled near the Klang Holding Basin site, at a distance less than9.7 km tunnel alignment. In total, 36 clusters of boreholes were selected 10 m between each of the boreholes; here, the quality of thefor this analysis leaving out all the boreholes drilled in a single line as the recovered core log is being reﬂected by the major directions ofdata is biased to the directions of the line of boreholes. Even so, the the rose diagram, which means high percentage of dissolutioninterpretation carried out is still strongly biased by the obtained data, features in approximately every direction of the ground. Thethe drilled boreholes; so, the absence of directions in the rose diagram other two groups (NB-B and NB-C) show less intensity of karstcould 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-A6. 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 highprovide an overview of the karst condition beneath the proposed percentage of karst, as presented in the major direction of roseFig. 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 alignedboreholes 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 rosediagram 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 arebelieved to represent a good quality of limestone.
H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169 167Fig. 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 diagramanalysis. 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
168 H. Zabidi, M.H. De Freitas / Engineering Geology 117 (2011) 159–169Fig. 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 diagramanalysis.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 threeanalysing 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: theKuala Lumpur now buried beneath the alluvium layer, makes it quality of the ground was deﬁned by the percentage of karst, so theimpossible to do a direct comparison. But, data obtained from direction with a small karst percentage value has good quality groundborehole log analysis should also represent some limitations as the and the direction with a large value has poor quality ground. Roseinterpretation is the result of random sampling over a large volume of diagrams reﬂecting good quality ground could be seen formed in thea karstic terrain and this gives no guarantee of ﬁnding the karst cavity. southern section of the tunnel, whilst rose diagrams for the northernHence, 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 karstborehole logs that could be used to develop much representative surfaces observed at the two sites previously exposed during theanalysis 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 berock core recoveries, a further classiﬁcation system is needed to seen between the grounds exposed in the two areas. In the North, theproperly log the rock cores. The currently used classiﬁcation and ground is heavily fractured, strongly deformed and varied greatly indescription of the rock core, based on the RDQ percentage is too the pattern of fracturing over a short distance. Frequently found at thegeneral and not speciﬁc enough to deﬁne the characters of karst site, mainly in the North Junction Box, is a wet yellow colouredobserved, and thus to predict the location and the dimension of karst slickensided surface believed to have formed as a result of shearin the ground. Therefore, in this study, the logged boreholes were re- displacement and the continuous ﬂow of running water. The studiedevaluated with the modiﬁed classiﬁcation system. This modiﬁed rockmass is heavily weathered to form variable features of karst
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