An Overview of Sinkhole Geohazard Incidence Recorded in The Kinta Valley Area, Perak

This paper is prepared to provide an overview of the sinkholes geohazards that occurs quite often in the Kinta Valley area. By fact, the phenomenon of the sinkhole is a common in Kinta Valley as its compound in karsts environment with limestone bedrock underlain about 80% of the area. The occurrences of sinkholes always affected badly on urban development and caused economic loses to the owner or landlord. The record regarding the sinkholes in pass days was started informally through shorthand in the log book and personal diaries. Since the cases arose, Minerals and Geoscience Department of Malaysia (JMG-Malaysia) started proper documentation in year 1970s and until February 2012 there were 161 incidents and 288 sinkholes were recorded surrounding Kinta Valley. Preliminary interpretation shows that the development of sinkhole associated to the factors of subsurface geology, historic of site activities which related to mining, current land used status, also seasonal drastic change between dry and wet spell in local climate

Peak friction angle estimation from joint roughness coefficient of discontinuities of limestone in Peninsular Malaysia

The peak friction angle (φpeak) roughness of discontinuity surfaces is a value that is fundamental to the understanding of shear strength of geological discontinuities, considering its importance in determining the mechanical properties of the discontinuity surface. It is however, both time and cost demanding to determine the peak friction angle as it requires an extensive series of laboratory tests. This paper presents an approach in the form of an experimentally determined polynomial equation to estimate peak friction angle of limestone discontinuity surfaces by measuring the Joint Roughness Coefficient (JRC) values in a field survey study, and applying the fore mentioned empirical correlation. A total of 1967 tilt tests and JRC measurements were conducted in the laboratory to determine the peak friction angles of rough limestone discontinuity surfaces. The experimental results were analyzed and correlated to establish a polynomial equation of φpeak = -0.0635JRC2 + 3.95JRC + 25.2 with coefficient of determination (R2) of 0.99. The laboratory results were also compared with theoretical results calculated from Barton’s linear equation. The results shown that estimation of peak friction angles were more accurate using the newly proposed polynomial equation since the percentage differences between measured and calculated peak friction angles is less than 6% compared to estimation from Barton’s linear equation where the percentage of differences is less than 11%. The proposed correlation offers a practical method for estimation of peak friction angles of discontinuity surfaces of limestone from measurement of JRC in the field

A systematic approach of rock slope stability assessment: a case study at Gunung Kandu, Gopeng, Perak, Malaysia

The stability of the limestone cliff at Gunung Kandu, Gopeng, Perak, Malaysia was assessed based on the Slope Mass Rating (SMR) system on 53 cross sections of the Gunung Kandu hill slopes. The slopes of Gunung Kandu were identified as class I (very good) to IV (poor). The kinematic analysis showed that 12 out of 53 hill slopes of Gunung Kandu were identified as having potential wedge, planar and toppling failures. The assessment showed that the stability of the western flanks can be classified as stable to unstable with the probability of failure from 0.2 to 0.6. The stability of the eastern and southern flanks range from very stable to partially stable with the probability of failure from 0.0 to 0.4. While the stability of northern flanks are from very stable to stable with the probability of failure of 0.0 - 0.2. This systematic approach offers a practical method especially for large area of rock slope stability assessment and the results from probability of failure values will help engineers to design adequate mitigation measures

ROCK SLOPE STABILITY ASSESSMENT OF LIMESTONE HILLS, SOUTHERN KINTA VALLEY, IPOH, PERAK, MALAYSIA

The uniqueness of the karst topography of Kinta Valley is the result of the spectacular shaped steep-sided limestone towers. The instability of these hillslopes however, may affect the vulnerability of the surrounding area. This paper presents the results of slope stability assessment by using kinematic analysis to investigate the possible failure modes of 7 slopes in Gua Naga Mas (GNM1, GNM2 and GNM3), Gua Kandu (GK1, GK2 and GK3) and Gua Tempurung (GT) located in the southern part of the Kinta Valley, Ipoh, Perak. From the results of the slope stability assessment, it was determined that planar failure and wedge failure were the main failure modes. The GNM1 slope of Gua Naga Mas consist of four wedge failures and a planar failure with dip directions/dip angles of 005⁰/54⁰, 354⁰/59⁰, 124⁰/52⁰, 360⁰/50⁰ and 063⁰/70⁰ respectively. The GNM2 slope consists of a wedge failure with the dip direction/dip angle of 021⁰/64⁰. Two wedge failures and a planar failure were identified on slope GNM3 with the respective dip directions/dip angles of 336⁰/49⁰, 301⁰/68⁰ and 270⁰/71⁰. The GK1 slope for Gua Kandu consists of wedge and planar failures with dip directions/dip angles of 231⁰/49⁰ and 217⁰/49⁰ respectively. The mode of failure at GK2 slope was identified as wedge failure with the dip direction/dip angle of 154⁰/44⁰. No mode of failure was identified on slope of GK3. Slope GT of Gua Tempurung was identified to have two wedge failures with dip directions/dip angles of 011⁰/49⁰ and 321⁰/48⁰ respectively

Rock Slope Stability Assessment of Limestone Hills in Northern Kinta Valley, Ipoh, Perak, Malaysia

The uniqueness of karsttopography in Kinta Valley lies with the spectacular shape of the steep-sided limestone towers. However, theinstability ofthese hillslopes may affect the vulnerability of the surrounding area. Thus, this study was conducted with the objective to investigate the failure modes of 9 slopes in the vicinity ofnorthernKinta Valley, Ipoh, Perak. There were two types of failure modes identified in the study area,which are planar and wedge failures. Planar failures were identified on slope GL3of Gunung Lang and slope GR3of Gunung Rapat with the dip direction and dip angle of 280⁰/79⁰ and 004⁰/ 64⁰ respectively. Two wedge failures were identified on slope QXL1of Qing Xing Ling, Taman Saikat with dip direction and dip angle of 252⁰/82⁰ and 302⁰/74⁰ respectively. A wedge failure was identified on slope GL3 for Gunung Lang, slope GR1, slope GR3 for Gunung Rapat and slope QXL2 for Qing Xing Ling,Taman Saikat. The dip direction and dip angle for the respective wedges failure were 345⁰/65⁰, 036⁰/ 49⁰, 006⁰/ 64⁰ and 025⁰/60⁰. No failure was identified on slope GL1, and slope GL2,forGunung Lang and slope GR2, and slope GR4forGunungRapat

Stability assessment of limestone cave: Batu Caves, Selangor, Malaysia

The limestone hill of Batu Caves is slowly being turned into a recreation park for slope climbing, base jumping and cave exploring. Quantitative assessment on the stability of the cave is essential to ensure the safety of tourists and visitors. The aim of this study was to quantitatively assess the stability of Gua Damai, Batu Caves, Selangor, Malaysia by using the Q system for rock mass classification, together with other factors such as cave width and thickness of the cave roof. The stability of the limestone cave wall was evaluated using Slope Mass Rating (SMR). A discontinuity survey conducted along the slopes beneath the opening of the cave showed that the rock mass comprised of four major joint sets labeled as J1, J2, J3, and J4 with the dip directions and angles of 110˚/73˚, 325˚/87˚, 243˚/39˚ and 054˚/30˚, respectively. The result of kinematic analysis showed that the dip direction/dip angle of a potential wedge failure was 051˚/59˚. By referring to the ratio of cave roof thickness with cave width, the results showed that the cave is stable. Based on the relationship between Q system and the cave width, the stabilities of Section 4 of Gua Damai is stable while Section 1, 2, 3, 5, 6, 7 and 8 require supports. Based on SMR, the cave walls stability at Portion c, d, and f were not stable while Portion a, b, e and g were stable. Overall, the most stable part of the cave is Section 4 followed by Sections 5 and 2. Sections 1, 3 and 8 are moderately stable while Sections 6 and 7 have poor stability

Integrated cave stability assessment: a case study at Naga Mas Cave, Mount Pua, Kinta Valley, Ipoh, Perak, Malaysia

Naga Mas Cave, a natural cave which also houses a temple is becoming one of the popular places of worship for Buddhist community in Ipoh, Perak. With the increasing number of worshippers entering the cave, the stability of this cave becomes important. With that in mind, an assessment on natural cave stability was conducted in the interest of public safety. Slope Mass Rating (SMR), Q rock mass classification system and cave roof thickness-width ratio of cave were employed in this assessment. The lithology of study area consists of dolomitic limestone. Discontinuity surveys were conducted at two slopes, labeled C1 and C2. For slope C1, three (3) joint sets J1, J2 and J3 with the dip direction and angles of 332º/49º, 154º/37º and 049º/80º, respectively, were identified. While slope C2 has four (4) sets of joints J1, J2, J3 and J4 with the dip direction and angles of 323º/44º, 125º/57º, 42º/76º, 263º/67º, respectively. The relationship between the rock quality, Q values and cave width shows that all parts inside the cave need support except for the cave chamber at the northern part. As for the cave wall stability, the northern part of the south east wall, south eastern and southern part as well as the north western wall and south western corner were classified as poor slope class due to the unfavorable orientation of the cave wall. Ratio of cave roof thickness and cave width shows that the cave is stable. From the results, a mitigation plan is proposed to highlight the cave safety zone to ensure the safety of worshippers and public visiting the cave