Numerical modelling of unsaturated tropical slopes

PhD ThesisAdapting to climate change is one of the greatest challenges facing engineers. Many studies have been conducted since the 1900s directed at predicting extreme weather events. Changes in global weather patterns, such as temperature and rainfall distributions, can have major economic and societal impacts. One example, addressed in this thesis, is the stability of natural slopes. In Southeast Asia, landslides are common due to the effect of abundant rainfall during the wet monsoon. The local climate in the region is characterised by annual wet and dry seasons, in which the cycle forms an unsaturated zone at the surface of the slopes. However, as a result of climate change, prolonged drying and heavy rainfall are observed that may exacerbate slope failure particularly in unsaturated soils. The prediction and mitigation of slope failures are consequently major challenges due to the complexity of the unsaturated behaviour of tropical soils subjected to irregular weather changes. This thesis develops a methodology to model unsaturated slope behaviour taking into account the effects of climate change. The approach includes groundwater flow, soil deformation and stability analyses using a finite element method and climate change predictions to incorporate future weather scenarios. The method was established by validating the groundwater flow analysis by involving a case study in Zaoyang, China. Subsequently, a more complex case study of a tropical unsaturated slope in Bukit Timah, Singapore was also considered to calibrate the soil-water characteristic curves (SWCC), a major controlling factor in unsaturated soils mechanics. The coupled flow-deformation analysis was undertaken on the validated case studies to predict soil displacement. In addition, a parametric study was conducted to critically analyse the effects of void ratio, saturated permeability, hysteretic SWCC, soil elasticity and rainfall intensity regarding slope behaviour. Finally, statistical analysis was performed to predict the impact of climate change on the rainfall distribution in Singapore up to the year 2100 by using the historical data from 1980 to 2010. Frequency analysis was adopted to estimate the rainfall return period. The results of the future extreme rainfall were compared to predictions by the Met Office in Singapore and the United Kingdom. The effects of climate change on slope behaviour was assessed by applying the predicted climate in the slope models. The outcomes reveal that the modelling approach is able to capture groundwater flow, slope deformation and safety factor accurately under extreme weather scenarios.Government of Malaysi

Perbandingan pendekatan pengurusan tanah perkuburan lama dan baharu: satu analisis tinjauan literatur sistematik

Masalah berkaitan tanah perkuburan lama sedia ada memerlukan penambahbaikan dan cara mengatasinya sekiranya pemilihan tanah perkuburan baharu hendak diwujudkan. Kekurangan tanah untuk pengebumian adalah masalah utama yang kerap timbul terutama di bandar-bandar besar termasuk Malaysia, adalah antara perkara yang perlu diatasi tetapi ianya memerlukan spesifikasi yang memenuhi semua kehendak termasuk kesihatan dan lokasi berkenaan. Objektif kajian bertujuan untuk menganalisis literatur sedia ada berkaitan signifikan kajian terhadap tanah perkuburan sedia ada dan kaedah yang telah digunakan untuk mendapatkan tanah perkuburan baharu. Metodologi kajian yang merupakan kajian SLR adalah berasaskan model PRISMA. Sebanyak 74 rujukan terkini berjaya untuk dianalisis dengan sistematik hasil dari carian melalui Web of science, Scopus, dan Google Scholar serta sumber tambahan lain yang dicari secara manual. Artikel ini telah dipilih berdasarkan kesesuaian bagi menjawab objektif kajian. Dari kajian ini, dapat dikenal pasti bahawa setiap tanah perkuburan lama hampir mempunyai masalah yang sama kecuali beberapa perkara yang berkaitan cara pengebumian yang menggunakan bahan tertentu dan secara tidak langsung memberi kesan kepada alam sekitar. Penggunaan GIS mampu memudahkan kerja-kerja analisis mendapatkan tanah perkuburan baharu termasuklah pengurusan serta pentadbirannya. Selaras dengan perkembangan bidang GIS, aplikasi ini dilihat mampu dikembangkan kepada aplikasi yang lebih bersepadu dalam teknologi internet of things (IoT) dalam ruang penggunaan berasaskan web dan menghubungkan tanah perkuburan secara keseluruhannya. Secara kesimpulannya, kajian untuk mendapatkan lokasi tanah perkuburan baharu yang sesuai perlu memahami kriteria yang perlu diberi keutamaan hasil dari masalah yang timbul dari perkuburan sedia ada

Influence of initial conditions on unsaturated groundwater flow models

Slope failure in unsaturated soils is common in tropical countries due to the seasonal pattern of abundant rainfall preceding a period of prolonged drying. Much research has been undertaken to understand the behaviour of unsaturated slopes and reduce the number of catastrophic failures. The initial conditions are important factors in numerical modelling of the groundwater flow yet rarely considered in detail in the literature. This paper presents a parametric study of the initial conditions at a slope in Bukit Timah, Singapore. The intensity and duration of rainfall are varied to assess the effect on the pore-water pressure in the slope. The generated pore-water pressure profile is compared with field measurements and previous numerical studies. It is discovered that a low rainfall, with an intensity of 1x10-7 m/s over a period of 62 days, results in initial pore-water pressure which is consistent with data recorded at the field. Unlike the duration, changes in the rainfall intensity are shown to have a significant effect on the pore-water pressure in the slope. This study, therefore, demonstrates the importance of determining appropriate initial conditions in unsaturated groundwater flow analysis

Bioconversion of coconut-residue to soluble protein by Aspergillus awamori

Protein is the most expensive and important nutrient component in feed formulation. An alternative protein source should be employed to reduce the dependency on fish meal. Limited reports are available regarding the bioconversion of coconutresidue derived-carbohydrate to soluble protein. The objective of this study was to determine the soluble protein and amino acid contents of coconut-residue after solid-state-fermentation by Aspergillus awamori. The complete randomised design (CRD) with three parameters; the inoculum-size (10%, 20%, and 30%), incubation temperature (30°C, 35°C and 40°C) and salt concentration (1x, 2x, 3x) were tested. Response surface method (RSM) was used to optimise the fermentation conditions. As a result, fermentation was increased and showed that the soluble protein content of the coconut-residue, to be 1.13-folds higher than the control. RSM analysis displayed that the best fermentation conditions comprised of 21.29% of inoculum size, 34.39°C of incubation temperature and 2.7-times of salt concentration after nine days of fermentation. Essential amino acids namely; histidine, valine, methionine, isoleucine, as well as three non-essential amino acids like the aspartic acid, serine and proline were significantly improved in the fermented coconut-residue. The current findings suggested that fermented coconutresidue is a feasible source of protein and amino acids in feed formulation

Bioconversion of coconut-residue to soluble protein by Aspergillus awamori

Protein is the most expensive and important nutrient component in feed formulation. An alternative protein source should be employed to reduce the dependency on fish meal. Limited reports are available regarding the bioconversion of coconutresidue derived-carbohydrate to soluble protein. The objective of this study was to determine the soluble protein and amino acid contents of coconut-residue after solid-state-fermentation by Aspergillus awamori. The complete randomised design (CRD) with three parameters; the inoculum-size (10%, 20%, and 30%), incubation temperature (30°C, 35°C and 40°C) and salt concentration (1x, 2x, 3x) were tested. Response surface method (RSM) was used to optimise the fermentation conditions. As a result, fermentation was increased and showed that the soluble protein content of the coconut-residue, to be 1.13-folds higher than the control. RSM analysis displayed that the best fermentation conditions comprised of 21.29% of inoculum size, 34.39°C of incubation temperature and 2.7-times of salt concentration after nine days of fermentation. Essential amino acids namely; histidine, valine, methionine, isoleucine, as well as three non-essential amino acids like the aspartic acid, serine and proline were significantly improved in the fermented coconut-residue. The current findings suggested that fermented coconutresidue is a feasible source of protein and amino acids in feed formulation

Physical, chemical and morphological properties of laterite soil in Bandar Baharu District

The Bandar Baharu District in southern of Kedah, Malaysia is extremely rich in laterite soil. The district is distinguished by the widespread presence of laterite soil, making it critical to thoroughly explore its physical, chemical, and morphological properties. Understanding these properties is essential for determining the acceptability and behaviour of laterite soil in a variety of engineering and building applications. Thus, the objective of this study is to analyze and evaluate the physical, chemical, and morphological properties of the selected laterite soil. Three sources of laterite soils have been identified in Sungai Kechil, Bandar Baharu, and Relau. The samples are labeled as SS-A, SS-B, and SS-C. The soils are categorized as SM, SC and MH respectively according to classification by Unified Soil Classification System (USCS). Since the pH values were less than 6, all of the soils were acidic. The X-ray fluorescence (XRF) characterization shows that the three soil samples have three main chemical components, namely silicon dioxide (SiO2), aluminium oxide (Al2O3) and iron oxide (Fe2O3). According to the X-Ray diffraction analysis (XRD) results, the minerals discovered in the laterite soils were gibbsite, quartz, kaolinite, and magnetite. Based on the scanning electron microscope (SEM) image, the sample with the highest fine particle content, which is 55.7% for the SS-C sample, shows the smallest pore siz

Behaviour of prestressed box beam strengthened with CFRP under effect of strand snapping

U radu se analizira ponašanje prednapete sandučaste grede ojačane polimerom s ugljičnim vlaknima (CFRP) za slučaj pucanja prednapetih užadi. Tri vanjske prednapete sandučaste grede ispitane su do sloma. Analiza je provedena s naglaskom na nosivost, širinu i obrazac širenja pukotina, te na torzijsku čvrstoću grede. Rezultati pokazuju da primjena CFRP-a dovodi do znatnog smanjenja progiba i do povećanja nosivosti u slučaju pucanja užadi. Pukotine se ne pojavljuju na dnu grede na koju je postavljen CFRP, a bitno je povećana i krutost grede na torziju.The study aims to evaluate behaviour of a prestressed box beam strengthened with the Carbon Fibre Reinforced Polymer (CFRP) under the snapping of prestressed strands. Three external prestressed box beams are tested until failure. The evaluation focuses on the load carrying capacity, cracks pattern and width, and torsional capacity of the beam. The results show that the use of CFRP causes significant reduction of beam deflection and an increase of its loading capacity under snapping effects. The cracks do not appear at the bottom of the beam where the CFRP is placed, and the torsion stiffness of the beam increases considerably

The stability of diaphragm wall for deep excavation

Rapid urbanisation and the increase in population has led to massive use of underground spaces, especially in the city. Before an underground structure is built, the use of retaining structure is crucial in order to prevent the excavation from failure. Diaphragm wall is a widely used retaining structure, particularly for deep excavation. A holistic understanding of the performance and its behaviour is essential to provide stability of the soil retained. A parametric study by using Plaxis2D has been conducted to determine the factors affecting the stability of diaphragm wall and the excavation sites in underground Mass Rapid Transit station of Hospital Kuala Lumpur (HKLX). The objectives of this study are to determine the effect of diaphragm wall stiffness, groundwater drawdown and the depth of wall for deep excavation. The stability is captured based on the lateral deflection of wall, bending moment, safety factor and ground movement near the diaphragm wall. From the study, it is found that the diaphragm wall with high stiffness can reduce wall deflection up to 20% with the addition of 49% bending moment and achieve a high factor of safety. Furthermore, groundwater drawdown is seen reducing lateral deflection of the wall up to 1.08% as well as increasing the factor of safety. Finally, decreasing wall depth reduces the wall deflection by 0.38% and also the basal heaving

Slope stability of landfill with waste degradation

Nowadays, a large amount of municipal solid waste (MSW) is generated due to the rapid urbanisation in developing countries leads to the demand for larger and higher capacity landfills. Bioreactor landfill technology has been introduced to accelerate the stability of landfill and to solve the issue of limited landfill area. However, the accelerated degradation of the refuse in bioreactor landfills also considerably changes the geotechnical characteristics of the waste in the landfill and thereby increases the concern for waste stability. Hence, this study aims to analyse the stability of both conventional and bioreactor landfill slope with the effects of waste degradation. Finite element method has been used in the slope stability analysis and the stability is presented by the factor of safety. The objectives of this study are i) to determine and assess the main parameter which influences the stability of the waste slope, ii) to determine the effects of waste degradation to the waste properties and iii) to obtain the factor of safety of the landfill slope using numerical analysis by finite element method. From the literature review, it is found that slope stability of a landfill mainly depends on the geotechnical properties of waste, such as moisture content, unit weight, shear strength parameters and hydraulic conductivity of waste. After the degradation process, engineering properties of field refuse are affected which includes the increased pore-water pressure and unit weight, decreased strength and lower hydraulic conductivity. Based on the analysis of conventional landfill slope stability by using Plaxis software, slope ratio of 1:3, 1:4 and 1:5 calculated safe with 1.69, 2.3 and 2.8 whereas the analysis of bioreactor landfill slope stability calculated safe only for slope ratio of 1:4 and 1:5 with 1.60 and 1.97. Moreover, the factor of safety for steeper slopes is lower and vice versa. From the parametric analysis, it is found that the full height of slope and unit weight of waste input affect the result analysis. This study is significant to evaluate the landfill slope stability with the effects of waste degradation and to ensure both conventional and bioreactor landfill slope stability for long periods. © BEIESP

Keberkesanan kaedah pembelajaran berasaskan masalah dalam meningkatkan kemahiran berfikir aras tinggi dan menyelesaikan masalah dalam kalangan pelajar

Aspirasi negara yang diilhamkan dalam Wawasan 2020 ialah mencapai taraf negara maju. Hal ini telah meletakkan kepentingan yang sangat tinggi terhadap pendidikan sebagai pemacu untuk mencapai matlamat menjadi sebuah negara maju yang mampu mendepani cabaran dan permintaan ekonomi yang dipacu oleh sains dan teknologi, seperti yang telah digariskan dalam Pelan Pembangunan Pendidikan Malaysia. Pembelajaran Berasaskan Masalah (PBM) adalah satu pendekatan pengajaran berasaskan masalah sebenar, yang melibatkan penggunaan pelbagai kemahiran untuk menyelesaikannya. Kajian kuasi-eksperimental ini bertujuan mengkaji keberkesanan kaedah PBM dalam meningkatkan Kemahiran Berfikir Aras Tinggi (KBAT) dan kemahiran menyelesaikan masalah pelajar. Kajian ini mengambil masa selama lapan minggu. Instrumen yang digunakan dalam kajian ini ialah soalan ujian pra-pasca, senarai semak dan soal selidik. Kajian ini melibatkan 71 orang responden dari Sekolah Menengah Kebangsaan Tun Ismail yang terbahagi kepada dua kumpulan, iaitu kumpulan rawatan dan kumpulan kawalan. Kesemua responden ini ialah kumpulan pelajar yang mengambil mata pelajaran sains tingkatan empat. Data yang diperoleh dianalisis secara deskriptif dan inferensi menggunakan perisian Statistical packages for Social Science Version 21.0 (SPSS). Hasil dapatan kajian ini membuktikan kaedah PBM berjaya meningkatkan Kemahiran Berfikir Aras Tinggi (KBAT) dan kemahiran menyelesaikan masalah pelajar. Pelajar juga menunjukkan persepsi positif terhadap kaedah PBM ini. Dapatan kajian ini menggambarkan teknik pengajaran dan pembelajaran yang berbeza, menarik serta berkesan dari kaedah tradisional mampu meningkatkan kemahiran pelajar