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 1437 ISSN: 2005-4238 IJAST Copyright ⓒ 2019 SERSC International Journal of Advanced Science and Technology Vol. 29, No. 1, (2020), pp. 1435- 1454 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: 1438 ISSN: 2005-4238 IJAST Copyright ⓒ 2019 SERSC International Journal of Advanced Science and Technology Vol. 29, No. 1, (2020), pp. 1435- 1454 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). 1440 ISSN: 2005-4238 IJAST Copyright ⓒ 2019 SERSC International Journal of Advanced Science and Technology Vol. 29, No. 1, (2020), pp. 1435- 1454 Figure 4. Stereographs for slopes GR1, GR2, GR3 and GR4 accordingly 1441 ISSN: 2005-4238 IJAST Copyright ⓒ 2019 SERSC International Journal of Advanced Science and Technology Vol.