Penilaian cerun bagi meramalkan potensi tanah runtuh menggunakan kaedah sistem penilaian cerun model-B di Empangan Sultan Mahmud, Tasik Kenyir, Kuala Berang, Terengganu, Semenanjung Malaysia

Penilaian geobahaya cerun telah dijalankan di Empangan Sultan Mahmud, Tasik Kenyir, Kuala Berang, Terengganu menggunakan kaedah Sistem Penilaian Cerun Model-B bertujuan untuk meramalkan potensi cerun mengalami tanah runtuh dengan nilai skor geobahaya. Kajian juga bertujuan untuk menilai ketepatan terhadap jenis cerun yang berbeza di ketiga-tiga kawasan kajian. Cerun di dalam kawasan kajian ini melibatkan cerun jenis potongan batuan, cerun potongan tanah dan cerun potongan batuan bercampur tanah. Terdapat 9 parameter yang diambil kira di dalam penilaian geobahaya iaitu sudut cerun, keluasan fitur, jarak dari permatang, bentuk cerun, peratusan fitur tak tertutup, kehadiran batuan terdedah, kehadiran saliran bertangga, kehadiran saliran mendatar dan kehadiran hakisan. Penilaian dijalankan di dalam batuan granit di kawasan berbukit iaitu di tiga tapak kajian iaitu tapak kajian 1, 2 dan 3 yang merangkumi keluasan 129 hektar. Hasil kajian di tapak kajian 1 mendapati skor geobahaya cerun batuan ini dikelaskan sebagai sangat tinggi dan tinggi. Faktor utama yang mempengaruhi skor geobahaya yang sangat tinggi dan tinggi adalah disebabkan sudut kecerunan yang tinggi dan keadaan batuan yang terdedah. Hasil kajian di tapak kajian 2 mengelaskan skor geobahaya adalah tinggi sahaja. Ini disebabkan oleh kecerunan yang tinggi, bentuk cerun, kewujudan hakisan dan tumbuhan tutup bumi. Manakala, hasil kajian di tapak 3 mendapati skor geobahaya adalah sederhana. Faktor utama yang menyebabkan skor geobahaya sederhana adalah kerana sebahagian merupakan cerun semula jadi, sudut kecerunan yang rendah, litupan tumbuhan pada cerun dan kehadiran hakisan yang rendah. Kesimpulan daripada kajian ini menunjukkan kaedah Sistem Penilaian Cerun Model-B (SPCM-B) adalah bersesuaian untuk digunakan dalam memetakan skor geobahaya bagi cerun jenis tanah potongan kejuruteraan

Pemetaan geobahaya berdasarkan kaedah Faktor Penilaian Tanah Runtuh (LHEF) di Empangan Sultan Mahmud, Tasik Kenyir, Kuala Berang, Terengganu

Kajian pemetaan potensi tanah runtuh telah dilakukan dengan menggunakan kaedah Faktor Penilaian Tanah Runtuh (LHEF) di Empangan Sultan Mahmud, Tasik Kenyir yang melibatkan kawasan tanah tinggi dengan litologi batuan granit, cerun potong kejuruteraan dan cerun semula jadi. Kaedah pemetaan LHEF sangat berguna kepada perancang bandar bagi tujuan pembangunan kawasan untuk memastikan secara relatif kawasan tersebut selamat. Permasalahan dalam kajian ini adalah kawasan kajian yang berbukit dan berbatu yang curam yang mana agak sukar untuk memperoleh data. Sebanyak enam (6) parameter dipertimbangkan dalam penilaian geobahaya cerun iaitu litologi, struktur geologi, morfometri cerun, penurunan relatif, guna tanah dan tutupan tanah serta keadaan hidrogeologi. Hasil daripada penilaian yang dijalankan diplotkan di dalam peta geobahaya potensi tanah runtuh. Penentuan kaedah pemetaan geobahaya sesuatu kawasan perlu mengambil kira keadaan sesuatu bagi memastikan pemetaan geobahaya yang dijalankan menghasilkan keputusan yang tepat. Sebanyak 858 cerun telah dinilai di dalam kajian ini yang merangkumi kawasan kajian 1, 2 dan 3. Didapati 699 cerun dizonkan sebagai geobahaya sederhana, 87 cerun dizonkan sebagai geobahaya tinggi dan hanya 72 cerun dizonkan sebagai geobahaya rendah. Secara asasnya ciri cerun yang dikategori sebagai geobahaya rendah adalah landai, tiada hakisan dan tiada struktur geodinamik. Zon geobahaya cerun sederhana pula adalah cerun yang mempunyai kecerunan sederhana curam, hakisan alur dan galur. Cerun yang dikategori sebagai geobahaya tinggi mempunyai struktur geodinamik seperti tegangan, rekahan, kecerunan melebihi 45 darjah, batu tongkol yang longgar, runtuhan lama, hakisan dan ketakselanjaran yang recam

Assessment of ultimate bearing capacity based on the Hoek-Brown failure criterion

The ultimate bearing capacity is an essential requirement in design quantification for shallow foundations especially for structures built on large rock masses. In many engineering projects, structures built on foundation of heavily jointed rock masses may face issues such as instability and sudden catastrophic rock slope failure. Determination of the ultimate bearing capacity (Qult) of foundations resting on rock mass has traditionally been determined by employing several strength criterions. One of the accepted and widely implemented methods is to use the Hoek-Brown failure criterion 2002, where the required parameters are determined from a rock mass classification system, Geological Strength Index (GSI). This paper defines an assessment for ultimate bearing capacity (Qult) based on the Hoek-Brown failure criterion 2002 for a granitic rock slope beneath a 20 m diameter concrete water tank at Bandar Mahkota Cheras, Kajang, Selangor. Based on the Hoek-Brown failure criterion 2002, the ultimate bearing capacity (Qult) of rock mass was 7.91 MPa. The actual stress acting on the rock mass was 0.32 MPa. The assessment showed that the rock mass is safe since the ultimate bearing capacity (Qult) is 24.7 times higher than the actual stress acting on the rock mass

Application of a Comprehensive Rock Slope Stability Assessment Approach for Selected Malaysian Granitic Rock Slopes (Pengaplikasian Pendekatan Penilaian Kestabilan Cerun Batu Komprehensif untuk Cerun Batu Granit Malaysia yang Terpilih)

In Malaysia, rock slope stability analysis has been largely confined to kinematic analysis with rock mass rating systems as assessment tools for stability analysis. While this method addresses the fundamental issues of rock slope stability including identifying potential failure modes, an information gap still exists between geologists and engineers in designing proper mitigation measures for rock slopes. This paper aims to address this issue by incorporating several methodologies, including kinematic analysis, slope mass rating and the Barton-Bandis criterion for the limit equilibrium method. Four rock slopes with potential instabilities namely KSA, KSB, LHA, and LHB were studied. KSA and KSB were located near Kajang, Selangor while LHA and LHB were located near Rawang, Selangor. Each slope exhibits multiple potential failures, with attention given on sliding-type failures in planar or wedge form. A slope mass rating value was assigned to each potential failure based on rock mass ratingbasic and the slope mass rating based on readjustments for discontinuity orientation and excavation method. Factor of safety from limit equilibrium method show potentially unstable blocks and failed blocks (Factor of Safety <1.00) with confirmation on site. Water filling of discontinuity apertures plays an important role in destabilizing rock blocks, especially in wet conditions experienced in Malaysia’s tropical climate. Several geometries are identified as potentially unstable due to low slope mass rating (Class V) and factor of safety of <1.2, such as planar J5 and wedge J2*J5 at KSA, wedge forming with sets J3, J4 and fault plane at KSB, planar J2 at LHA, and wedge J3*J4 at LHB. Stabilization structures such as rock bolts can be better designed with the determined factor of safety values coupled with relevant geological and geotechnical inputs. In this comprehensive rock slope stability assessment approach, limit equilibrium method serves as a useful method in analyzing rock slope stability to complement kinematic analysis and stability ratings often used in Malaysia

Application of a comprehensive rock slope stability assessment approach for selected Malaysian granitic rock slopes

In Malaysia, rock slope stability analysis has been largely confined to kinematic analysis with rock mass rating systems as assessment tools for stability analysis. While this method addresses the fundamental issues of rock slope stability including identifying potential failure modes, an information gap still exists between geologists and engineers in designing proper mitigation measures for rock slopes. This paper aims to address this issue by incorporating several methodologies, including kinematic analysis, slope mass rating and the Barton-Bandis criterion for the limit equilibrium method. Four rock slopes with potential instabilities namely KSA, KSB, LHA, and LHB were studied. KSA and KSB were located near Kajang, Selangor while LHA and LHB were located near Rawang, Selangor. Each slope exhibits multiple potential failures, with attention given on sliding-type failures in planar or wedge form. A slope mass rating value was assigned to each potential failure based on rock mass ratingbasic and the slope mass rating based on readjustments for discontinuity orientation and excavation method. Factor of safety from limit equilibrium method show potentially unstable blocks and failed blocks (Factor of Safety <1.00) with confirmation on site. Water filling of discontinuity apertures plays an important role in destabilizing rock blocks, especially in wet conditions experienced in Malaysia’s tropical climate. Several geometries are identified as potentially unstable due to low slope mass rating (Class V) and factor of safety of <1.2, such as planar J5 and wedge J2*J5 at KSA, wedge forming with sets J3, J4 and fault plane at KSB, planar J2 at LHA, and wedge J3*J4 at LHB. Stabilization structures such as rock bolts can be better designed with the determined factor of safety values coupled with relevant geological and geotechnical inputs. In this comprehensive rock slope stability assessment approach, limit equilibrium method serves as a useful method in analyzing rock slope stability to complement kinematic analysis and stability ratings often used in Malaysia