A Case Study at KEK Look Tong Cave, Perak

International Journal of Advanced Science and Technology Vol. 29, No. 1, (2020), pp. 1435- 1454 Cave Stability and Sustainable Development: A Case Study At KEK Look Tong Cave, Perak 1Ailie Sofyiana Serasa, 2Goh Thian Lai, 2Nur Amanina Mazlan 1School of Engineering, Asia Pacific University of Technology & Innovation, 57000 Bukit Jalil, Kuala Lumpur, Malaysia 2Geology Program, Center of Earth Science and Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor

Abstract

The beauty of karst terrains of limestone caves attracts many tourists due to its unique architecture. In Malaysia, some of the caves have been converted into religion caverns. However there is no systematic guideline to evaluate the stability and sustainability of the cave and cave wall. This research paper presents a systematic approach for the assessment of limestone cave stability using Q system and Slope Mass Rating (SMR) at Kek Look Tong, Perak. Based on the assessment of Slope Mass Rating (SMR), the entire cave walls were classified from class II to IV. The cave walls without potential failure were classified into class II. 10 out of 33 cave walls were identified to have potential wedge and planar failure with the SMR score from 36 to 78.5. The cave wall of GR2-1 and GR2-2 were classified as class II to III (stable to partially stable) and class II (stable) respectively. The cave wall of GR4-2, GR4-6, GR4-8 and GR4-9 were classified as class II (stable). The cave wall GR4-4 was classified as class III (partially stable). Cave wall of GR4-1 was classified as class IV (unstable). The Q- value for both section A and Section B of the cave were 4. The stability assessment based on relationship between Q- value and the cave width shows that all sections of the cave were categorized into the support field zones according to the guidelines for the Norwegian Tunnelling Method. Keywords: Cave stability, cave sustainability, engineering geology, SMR

INTRODUCTION Karst morphology in limestone hills are characterized by the presence of caves resulting from the dissolution process. The uniqueness of cave features has become the attraction of tourists and worshippers. Caves represent the ground conditions where the engineering strength and bearing capacity are significantly reduced (Waltham, 2002). Two reports of cave collapsed involving one death in Perak Tong can be obtained in presentations of Tuan Rusli Mohamed &

1435 ISSN: 2005-4238 IJAST Copyright ⓒ 2019 SERSC International Journal of Advanced Science and Technology Vol. 29, No. 1, (2020), pp. 1435- 1454 Ahmad Khairut Termizi (2012) and Ros Fatiha & Yeap (2000). The catastrophic hazard event of limestone hill failure at Bukit Tunggal (1919), Gunung Cheroh (1973), GunungRapat (1975), Gunung Karang Besar (1980, 2008), GunungTasek (1984), Gunung Tunggal (1987), Gunung Karang Kecil (1990), Gunung Lang (1993), Gunung Bercham (2004) and Gunung Lang (2012) have caused the loss of 54 lives. One of the tourist attraction cave, Gua Tempurung was closed in 2015 due to the collapse of a cavewall. The hazard is likely to recur in the large cave at shallow depth that disturbed the integrity of foundation (Waltham & Fookes, 2003). The literature study revealed that most of the study regarding cave stability were conducted based on scientific qualitative observations without using quantitative standardised methods. Waltham & Park (2002) assessed the stability based on the density and the pattern of exposed joints inside the cave. Spiteri & Sinreich(2003) considered the influence of gravity, tectonic stress and underground vibration on the natural stability of the cave. Szunyogh (2010) developed a regional cave risk map which takes into account the overall joint patterns through the preparation of joints element map. A few researchers conducted the cave stability assessment by analytical approaches as in Tharp (1995), Kesseru (1997), Siegel et. al (2001) and Kortnik dan Sustersic (2002). Waltham (2002) and Waltham & Fookes (2003) consider the dimension of the cave as the cave is stable if the thickness of rock is equal to or greater than its width. Besides, less research on the cave stability assessment of limestone hills has been carried out by local researchers, where most of the research were focused in rock material strength (Goh et al. 2015a, 2015b, 2016a). However, Goh et al. (2016b) assessed the rock mass of limestone using slope mass rating (SMR) method at Gunung Lang, Ipoh, Perak, Malaysia. This research paper presents a systematic approach for the assessment of limestone cave stability using Q value and Slope Mass Rating (SMR). Thus the significance of this research is to develop cave stability guidelines for limestone caves in Malaysia and to ensure no risk is encountered by tourists. The study area is located within the Kinta Valley limestone area. The assessment was carried out at Kek Look Tong, Gunung Rapat, Kinta Valley, Ipoh, Perak (Figure 1).

MATERIALS AND METHODOLOGY. GEOLOGICAL SETTING

1436 ISSN: 2005-4238 IJAST Copyright ⓒ 2019 SERSC International Journal of Advanced Science and Technology Vol. 29, No. 1, (2020), pp. 1435- 1454 Kinta valley forms steep limestone towers that bulge outwards to the alluvial plain, (RosFatihah Muhammad & Ibrahim Komoo, 2003). The limestone towers were formed as the result of unequal denudation process of heavily jointed limestones that lie uncomformably above older limestones and sheared schist, (Cameron, 1925). Many researchers believe that the age of the limestone body is Carboniferous, (Rastal 1927), and older than phyllites and quartzites, (Srivenor, 1913). It is interbedded with argillaceous strata, (Ingham & Bradford, 1960). The limestone body was intruded by granite in Late Triassic to Early Jurassic forming four granitoid bodies that encircle the limestone hills;(i) Main Range on the east flank of Kinta Valley, (ii) Kledang Range on the west flank, (iii) Bujang Melaka granitoid on east-south of the valley and (iv) Tanjong Tualang granitoid on west south of the valley (Rajah, 1979). Figure 2 is the geological map of Kinta Valley showing the limestone bounded by igneous intrusion.

Figure 1. Location of study area at Kek Look Tong Cave, Ipoh

Figure 2. The geological map of Kinta Valley showing the limestone bounded by igneous intrusion ASSESSMENT OF CAVE WALL : SLOPE MASS RATING METHOD (SMR)

The slope mass rating method published by Romana (1985) was used to assess the stability of cave wall in the cave. Seven components that are used in SMR are: (a) Uniaxial Compressive Strength (UCS) (b) Rock Quality Designation (RQD) (c) Discontinuities spacing (d) Conditions of discontinuities (e) Ground water condition (f) Adjusting factors for joints (F1, F2, F3) (g) Adjusting factor for excavation (F4). The values of the respective components of rock quality designation (RQD), discontinuities spacing, conditions of discontinuities and ground water condition were determined from scan line discontinuities survey, following suggestions of ISRM (1981).F1 was the rating for considering the difference of dip direction between joints and slope face. F2 was the rating of dip angle of the respective joint. F3 was the rating of considering the difference of dip angle between joints and slope face. The total rating, RMRb was determined as:

RMRb= Rating(a) + Rating(b) + Rating(c) + Rating(d) + Rating(e) (1) The rating for SMR was determined based on the following equation suggested by Romana (1985):

SMR = RMRb + (F1 x F2 x F3) +F4 (2) ASSESSMENT OF CAVE WALL : Q-SYSTEM AND CAVE WIDTH The Q value is calculated from Rock Mass Rating (RMR) (Bieniawski, 1984), as suggested by Barton (1995) using the formula (3): RMR = 15 log Q + 50 (3)

The stability of limestone cave was classified based on recommendations of Waltham (2002) and Waltham and Fookes (2003). The Q value and limestone cave width were used to assess the stability (Figure 3).

Figure 3. Cave stability assessment based on Q-value and cave width. Source: Waltham (2002) and Waltham and Fookes (2003)

RESULT AND CONCLUSION Discontinuity surveys were carried out at hill slopes on both sides of the entrance and the exit of Kek Look Tong. The slopes were labelled as GR1 and GR2 for the hill slopes at the cave entrance, and GR3 and GR4 for the hill slopes at the cave exit. The major joint sets of slopes GR1, GR2, GR3 and GR4 at Kek Look Tong were assessed using stereographs. Figure 4 shows the stereograph of main joint sets for GR1, GR2, GR3 and GR4. The respective slopes GR1, GR2 and GR3 are composed of four main joint sets. Slope GR4 is composed of three main joint sets. The kinematic analysis (Figure 5) shows the stereoplot without the orientation of slope face

1439 ISSN: 2005-4238 IJAST Copyright ⓒ 2019 SERSC International Journal of Advanced Science and Technology Vol. 29, No. 1, (2020), pp. 1435- 1454 cave walls. The respective results of stereographs for GR1, GR2, GR3 and GR4 were utilized in the kinematic analysis for cave walls of GR1-1 to GR1-10, GR2-1 to GR2-5, GR3-1 to GR3-8 and GR4-1 to GR4-9 (Figure 6). The kinematic analysis were conducted based on respective orientation of slope face of cave walls and the potential mode of failure of respective cave walls were identified. The peak friction angles for slope GR1, GR2, GR3 and GR4 were 47˚, 33˚, 41˚ and 29˚ respectively. The peak friction angles were determined based on the recommendation of Abdul Ghani & Goh (2012).

Figure 4. Stereographs for slopes GR1, GR2, GR3 and GR4 accordingly

Figure 5. Stereoplots for slopes GR1, GR2, GR3 and GR4 respectively. The peak firction angles were taken as 47°, 33°, 41° and 29°, respectively

The respective Rock Mass Ratingbasic (RMRb) for slope GR1, GR2, GR3 and GR4 were 73, 71, 69 and 71. The description for the parameters of Rock Mass Rating of slopes GR1, GR2,

GR3 and GR4 are shown in Tables 1,2,3 and 4 respectively. Based on the results of RMRb, a total of 33 cave walls were assessed using Slope Mass Rating (SMR) classification system and the entire cave walls were classified from class II to IV. The Slope Mass Rating (SMR) results for the respective cave walls are shown in Table 5 and Figure 6. 10 cave walls were identified to have potential wedge and planar failures. No mode of failure were identified at cave walls of GR1-1 to GR-10, GR2-2 to GR2-5, GR3-1 to GR3-8, GR4-3, GR4-5 and GR4-7. The stability of cave walls of GR1-1 to GR1-10 were classified as stable (class II) with Slope Mass Rating scores of 73. The cave walls stability of GR2-1 to GR2-5 were classified stable to partially stable (class II to Class III) with the SMR scores of 61 to 78.5. The cave wall GR2-1 with the potential wedge and planar failure was classified as class II to III (stability of stable to partially stable) with SMR scores of 61 to 78.5. The cave wall of GR2-2 with the potential wedge failure was classified as class II (stable) with SMR results of 78.5. The cave walls of GR2-3 to GR2-5 with no potential failure were classified as class II (stable) with the SMR scores of 71. The Slope Mass Rating (SMR) results for cave walls of GR3-1 to GR3-8 with no potential failure were classified as class II (stable) with the SMR scores of 76. The SMR results for cave walls of GR4-3, GR4-5 and GR4-7 with no potential failure were classified as class II (stable) with the SMR scores of 71. The mode of failure for the cave wall of GR4-1, GR4-2, GR4-4, GR4-6, GR4-8 and GR4-9 were wedge failure and planar failure. The results of Slope Mass Rating (SMR) for cave wall GR4-1 was 36 and was classified as class IV which is unstable stability. The cave wall of GR4-2, GR4-6, GR4-8 and GR4-9 were classified as class II with the SMR scores of 66 to 78.5. The stability of cave wall GR4-4 was classified as class III (partially stable) with the SMR results of 51. TABLE I. RESULTS OF ASSESSMENT OF RMRB AT GR1 Parameter Value Rating Uniaxial compressive 70Mpa 7 strength, UCS Rock Quality designation, 99.36 % 20 RQD

Spacing of discontinuities 0.35 m 10 Condition of discontinuities Discontinuities length 1-3 m, separation 0 mm, 24 slightly rough, no infilling, slightly weathered Ground water condition Completely dry 15

RMRb 76

TABLE II. RESULTS OF ASSESSMENT OF RMRB AT GR2 Parameter Value Rating Uniaxial compressive strength, 70Mpa 7 UCS Rock Quality designation, 95 % 20 RQD Spacing of discontinuities 0.4 m 10 Condition of discontinuities Discontinuities length 1 – 3m, separation 1 – 19 5mm, slightly rough, no infilling, slightly weathered Ground water condition Completely dry 15

RMRb 71

TABLE III. RESULTS OF ASSESSMENT OF RMRB AT GR3 Parameter Value Rating Uniaxial compressive strength, 70Mpa 7 UCS Rock Quality designation, RQD 92 % 20 Spacing of discontinuities 0.39 m 10 Condition of discontinuities Discontinuities length 1 – 3m, separation 0 24 mm, slightly rough, no infilling, slighty weathered Ground water condition Completely dry 15

RMRb 76

TABLE IV. RESULTS OF ASSESSMENT OF RMRB AT GR4 Parameter Value Rating Uniaxial compressive strength, 70Mpa 7 UCS

Rock Quality designation, RQD 100 % 20 Spacing of discontinuities 0.1 m 8 Condition of discontinuities Discontinuities length 1 – 3m, separation 1 – 5 21 mm, extremely rough, no infilling, unweathered Ground water condition Completely dry 15

RMRb 71

TABLE V. SLOPE MASS RATING OF CAVE WALLS IN KEK LOOK TONG Cave wall Cave wall (dip Mode of failure RMR SMR Class Stability direction/dip (dip angle) direction/dip angle) GR1-1 220/80 No potential 76 76 II Stable failure GR1-2 280/80 No potential 76 76 II Stable failure GR1-3 223/80 No potential 76 76 II Stable failure GR1-4 263/80 No potential 76 76 II Stable failure GR1-5 204/80 No potential 76 76 II Stable failure GR1-6 248/80 No potential 76 76 II Stable failure GR1-7 346/80 No potential 76 76 II Stable failure GR1-8 255/80 No potential 76 76 II Stable failure GR1-9 315/80 No potential 76 76 II Stable failure GR1-10 263/80 No potential 76 76 II Stable failure GR2-1 005/70 Wedge(006/64) 71 78.5 II Stable Planar(004/64) 71 61 III Partially stable GR2-2 046/70 Wedge (008/63) 71 78.5 II Stable GR2-3 070/70 No potential 71 71 II Stable failure GR2-4 058/70 No potential 71 71 II Stable failure GR2-5 244/90 No potential 71 71 II Stable failure GR3-1 100/70 No potential 76 76 II Stable

failure GR3-2 173/70 No potential 76 76 II Stable failure GR3-3 120/70 No potential 76 76 II Stable failure GR3-4 176/70 No potential 76 76 II Stable failure GR3-5 084/70 No potential 76 76 II Stable failure GR3-6 164/70 No potential 76 76 II Stable failure GR3-7 117/70 No potential 76 76 II Stable failure GR3-8 090/70 No potential 76 76 II Stable failure GR4-1 338/80 Wedge (337/70) 71 36 IV Unstable Planar (348/70) 71 36 IV Unstable GR4-2 314/80 Wedge (337/70) 71 66 II Stable GR4-3 262/80 No potential 71 71 II Stable failure - GR4-4 317/80 Wedge (337/70) 71 51 III Partially stable GR4-5 202/80 No potential 71 71 II Stable failure GR4-6 298/80 Wedge (337/70) 71 78.5 II Stable GR4-7 045/80 No potential 71 71 II Stable failure GR4-8 300.80 Wedge (337/70) 71 78.5 II Stable GR4-9 358/80 Wedge (337/70) 71 66 II Stable

Figure 6. Kek Look Tong cave map with Slope Mass Rating (SMR) classes Figure 7 shows the stereograph for main joint sets in Section A and Section B, Kek Look Tong, Gunung Rapat, Kinta Valley, Ipoh, Perak. The stereograph for Section A was built based on discontinuities survey results of GR1 and GR2. The stereograph for Section B was built based on discontinuities survey results of GR3 and GR4. The stereographs and stereoplots for GR1,GR2, GR3 and GR4 were displayed as in Figure 4 and Figure 5 respectively. Both sections are composed of four main joint sets. Table 6 shows the adjustment factors for discontinuities orientation of RMR for main joint sets and the results of Q system classification in Kek Look Tong, Gunung Rapat, Kinta Valley, Ipoh, Perak. Malaysia. Based on equation (3), the Q- value for section A and B were rated as 4. Rock Mass Quality for both sections were classified as fair, Figure 8. This Q-value was in good agreement with the Q-value of typical rock mass of limestone karst, suggested by Waltham & Fookes (2003).The cave stability map with slope Mass

1447 ISSN: 2005-4238 IJAST Copyright ⓒ 2019 SERSC International Journal of Advanced Science and Technology Vol. 29, No. 1, (2020), pp. 1435- 1454 Rating assessment results of cave walls and Q value results for Section A and B is shown in Figure 8.

Figure 7. The stereograph for main join sets in Section A and B respectively Fig 8. Adjustment factor for discontinuities orientation of RMR for main joint set and the Q- System classification in Kek Look Tong cave Section RMRb Influenced Adjustment Rating RMR Q- FinalQ- Rock joint factor value value Mass Quality A 71 J1 (214/18) Fair -5 66 12 4 Fair J2(360/57) Fair -5 66 12

J3(059/48) Very -12 59 4 Unfavourable J4(097/79) Very -12 59 4 Unfavourable B 71 J1(190/84) Fair -5 66 12 4 Fair J2(111/17) Fair -5 66 12 J3(316/28) Favourable -2 69 18 J4(273/78) Very -12 59 4 Unfavourable

Figure 9. Cave stability map with Slope Mass Rating assessment results of cave walls and Q values for Section A and B

1449 ISSN: 2005-4238 IJAST Copyright ⓒ 2019 SERSC International Journal of Advanced Science and Technology Vol. 29, No. 1, (2020), pp. 1435- 1454 Fourteen (14) cross sections with the interval of 5 m distance were measured to get the width of cave (Figure 9). The width for respective cross sections are shown in Table 7. The stability assessment based on the relationship between Q system ratings and the cave width (Waltham, 2002) and (Waltham and Fookes, 2003) is shown in Figure 10. The stability assessment is based on relationship between Q- value and the cave width revealed that all sections of the cave required support.

Figure 10. Visual of each cross section

Figure 11. cave width for respective cross section Q- Cross Section Cave Width (m) Value AA’ 37 BB’ 28 CC’ 34 DD’ 32 EE’ 34 4 FF’ 28 GG’ 27

HH’ 22 II’ 13 JJ’ 19 KK’ 26 LL’ 29 MM’ 25 NN’ 17

Figure 12. The stability assessment based on relationship between Q system ratings and the cave width. The study revealed that the entire cave requires support. Source: Modified from Waltham (2002) and Waltham and Fookes (2003)

CONCLUSION The results of the assessment of slope mass rating (SMR) revealed that the cave walls were classified as class II to class IV. The Q-value of the cave was rated as 4. The rock mass quality was categorised as fair. The relationship between the Q-value and the cave width revealed that the cave required support.

ACKNOWLEDGEMENT The authors wish to thank the lab staff of the Geology Programme, UKM and the Geosciences Department of University Technology PETRONAS, UTP. This work has been supported by the Government of Malaysia under the Fundamental Research Grant Scheme FRGS/1/2017/WAB08/UKM/02/1 and Universiti Kebangsaan Malaysia internal grant GUP- 2016-24. The authors would also like to acknowledge the support of the staff at UKM and UTP as well as the use of facilities at both universities.

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