Kajian ketumpatan lineamen dalam penilaian potensi jatuhan batuan di kawasan Lembah Kinta

Perbukitan batu kapur di Lembah Kinta membentuk landskap muka bumi yang unik dan indah hasil daripada proses pelarutan batuan karbonat. Namun begitu, bergantung kepada kawasan perbukitan batu kapur tersebut, kehadiran pelbagai struktur geologi seperti struktur retakan dan kekar yang ekstensif mampu memberi ancaman kepada manusia dan harta benda. Kajian ini bertujuan melihat hubungan antara ketumpatan lineamen dan tahap kestabilan tujuh cerun gunung batu kapur di Lembah Kinta, Malaysia. Kajian ini terbahagi kepada dua peringkat, iaitu pemetaan ketumpatan lineamen dan penilaian kestabilan cerun dengan menggunakan kaedah Kekuatan Jasad Batuan (RMS). Sebanyak 599 lineamen rantau dikenal pasti dengan panjang keseluruhan lineamen mencapai 317 km. Seterusnya, peta ketumpatan lineamen yang dihasilkan dikelaskan kepada tiga kelas: Rendah (137.0-84.23) m, sederhana (84.22-46.83) m dan tinggi (46.82-0.0) m. Kaedah RMS yang dijalankan di lapangan pula adalah bertujuan bagi mengesahkan peta ketumpatan lineamen yang dihasilkan. Sebanyak dua belas stesen dinilai dengan tujuh parameter RMS iaitu kekuatan bahan batuan, tahap luluhawa, bukaan kekar, orientasi kekar, kelebaran kekar, ketakselanjaran dan aliran air bawah tanah. Setiap cerun yang dinilai dikelaskan kepada lima kumpulan daripada sangat lemah hingga sangat kuat. Skor RMS berdasarkan jumlah akhir setiap parameter yang dinilai. Hampir kesemua stesen yang dicerap berada pada kelas sederhana (Gunung Rapat, Datok, Kandu, Panjang, A, Tempurung) manakala hanya satu stesen (Gunung Lang) berada pada kelas lemah. Korelasi antara peta ketumpatan lineamen dan skor RMS menunjukkan korelasi yang baik dengan 73% ketepatan. Ini menunjukkan bahawa kestabilan cerun di Lembah Kinta dipengaruhi secara langsung oleh ketumpatan lineamen rantau

Representing landslides as polygon (areal) or points? How different data types influence the accuracy of landslide susceptibility maps

In the literatures, discussions on the accuracy of different models for landslide analysis have been discussed widely. However, to date, arguments on the type of input data (landslides in the form of point or polygon) and how they affect the accuracy of these models can hardly be found. This study assesses how different types of data (point or polygon) applied to the same model influence the accuracy of the model in determining areas susceptible to landsliding. A total of 137 landslides was digitised as polygon (areal) units and then transformed into points; forming two separate datasets both representing the same landslides within the study area. These datasets were later separated into training and validation datasets. The polygon unit dataset uses the area density technique reported as percentage, while the point data uses the landslide density technique, as means of assigning weighting to landslide factor maps to generate the landslide susceptibility map that is based on the analytical hierarchy process (AHP) model. Both data groups show striking differences in terms of mapping accuracy for both training and validation datasets. The final landslide susceptibility map using area density (polygon) as input only has 48% (training) and 35% (validation) accuracy. The accuracy for the susceptibility map using the landslide density as input data achieved 89% and 82% for both training and validation datasets, respectively. This result showed that the selection of the type of data for landslide analysis can be critical in producing an acceptable level of accuracy for the landslide susceptibility map. The authors hope that the finding of this research will assist landslide investigators to determine the appropriateness of the type of landslide data because it will influence the accuracy of the final landslide potential map

Pencirian geomekanik jasad batuan dan analisis kestabilan cerun di Laman Granview, Saujana Puchong, Selangor, Malaysia

Satu kajian pencirian geomekanik jasad batuan dan analisis kestabilan dua cerun terletak di tapak pembinaan Laman Granview di Saujana Puchong, Selangor telah dijalankan. Kawasan kajian merupakan sebahagian Formasi Bukit Kenny. Kajian telah dijalankan pada dua buah cerun potongan di tapak binaan adalah survei ketakselanjaran dan pencirian mekanik batuan. Kuarzit adalah litologi yang dominan di kawasan ini dengan sedikit filit. Ujian mekanik batuan berikut dijalankan: Ujian kekuatan mampatan sepaksi, ujian indeks beban titik dan ujian kekuatan regangan Brazil, ujian pantulan tukul Schmidt dan ujian Skleroskop Shore. Ujian kemiringan untuk penentuan kekasaran permukaan satah ketakselanjaran dijalankan pada sampel bongkah batuan. Hasil survei ketakselanjaran menunjukkan terdapat empat set ketakselanjaran yang utama di cerun L1 dengan nilai arah kemiringan/sudut kemiringan 62°/42°, 261°/79°, 281°/59° dan 237°/71°. Di cerun L2, terdapat tiga set ketakselanjaran utama iaitu dengan nilai arah kemiringan/sudut kemiringan 81°/41°, 171°/71° dan 198°/60°. Untuk ujian kemiringan, nilai purata sudut geseran puncak (fp) permukaan satah ketakselanjaran batu kuarzit dengan Pekali Kekasaran Kekar (PKK) 8-10 adalah 61°. Ketakselanjaran batuan kuarzit dengan nilai PKK 10-12 pula mempunyai purata sudut geseran puncak (fp) sebanyak 73°. Manakala, nilai purata sudut geseran puncak (fp) batuan filit dengan PKK 4-6 ialah 56°. Berdasarkan analisis kinematik, cerun L1 adalah stabil. Ragam kegagalan cerun L2 pula adalah kegagalan satah tetapi nilai sudut geseran permukaan satah yang tinggi akan menghalang kegagalan berlaku. Nilai perkadaran jasad batuan (RMR) bagi batuan kuarzit ialah 77 dan batuan filit ialah 66 dengan kedua-dua tergolong dalam batuan yang baik dalam kelas II

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

In Situ Determination Of Layer Thickness And Elastic Moduli Of Asphalt Pavement Systems By Spectral Analysis Of Surface Waves (Sasw) Method

Spectral analysis of surface waves (SASW) is a non-destructive and in situ method for determining the stiffness profile of soil and pavement sites. The method consists of generation, measurement, and processing of dispersive elastic waves in layered systems. The test is performed on the pavement surface at strain level below 0.001%, where the elastic properties are considered independent of strain amplitude. During an SASW test, the surface of the medium under investigation is subject to an impact to generate energy at various frequencies. Two vertical acceleration transducers are set up near the impact source to detect the energy transmitted through the testing media. By recording signals in digitised form using a data acquisition system and processing them, surface wave velocities can be determined by constructing a dispersion curve. Through forward modeling, the shear wave velocities can be obtained, which can be related to the variation of stiffness with depth. This paper presents the results of two case studies for near-surface profiling of two different asphalt pavement sites.

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

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

Lineaments And Their Association With Landslide Occurrences Along The Ranau- Tambunan Road, Sabah

ABSTRACT The purpose of this study is to assess the influence of lineaments on landslide occurrences based on the concept of lineament density. The Ranau-Tambunan districts with a 54 km road stretch from Ranau to Tambunan, crossing the Crocker and Trusmadi Formations is selected as the study area. In total, the study area is 844.7 km 2 . Both formations have similar area with Crocker at 405.5 km 2 and Trusmadi at 425.6 km 2 The rest are either igneous and alluvium (13.6 km 2 ). The lineaments were identified using a 5x5 weighted kernel filter on a -645 -Vol. 19 [2014], Bund. C 646 RADARSAT-1 standard mode image. The lineament density was calculated using a 1 km x 1 km grid on the lineament map and the density for each 1 km 2 grid is represented by the total length of lineaments in a grid. A total of 334 lineaments were identified with the lineament density map classified into three classes of density, resulting low (<318-m), moderate (319-775-m), and high (>775-m) using the natural break classification. The lineament density is more pronounced in the Crocker compared to the Trusmadi Formation. The influence of lineament on landslide occurrences was examined by overlapping the lineament density map with 75 landslides observed from fieldwork to determine the number of landslides in each density class. Out of the 75 landslides, 29 landslides occurred in the Crocker Formation and the other 46 landslides in the Trusmadi Formation. From the overlapped, a total of 47 landslides (63%) were captured into the high density class with 19 and 28 landslides in the Crocker and Trusmadi Formations respectively. These results indicate over half of the landslide occurrences are induced by the presence of lineaments with the highest percentage of landslides occurring in the Crocker Formation. As a conclusion, this study found that using the grid technique is an effective way to determine lineament density and quantify its influence on landslide occurrences

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