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Kato, Fuminori, Yoshio Suwa, Kunihiro Watanabe i Satoshi Hatogai. "MECHANISMS OF COASTAL DIKE FAILURE INDUCED BY THE GREAT EAST JAPAN EARTHQUAKE TSUNAMI". Coastal Engineering Proceedings 1, nr 33 (25.10.2012): 40. http://dx.doi.org/10.9753/icce.v33.structures.40.
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Based on the results of field surveys, coastal dike failures caused by the Great East Japan Earthquake were classified into eight patterns. The results of hydraulic model experiments related to major failure patterns reinforced the proposed failure processes. In addition, the aggregated length of each failure pattern showed that failure from scouring at the landward toe is the dominant failure pattern.
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Lufira, R. D., S. Marsudi, S. Agustien i A. Khosin. "Determining the Depth of Local Scouring in a Downstream Energy Dissipation in the Physical Model Test". IOP Conference Series: Earth and Environmental Science 930, nr 1 (1.12.2021): 012022. http://dx.doi.org/10.1088/1755-1315/930/1/012022.
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Abstract Karangnongko Weir is planned to be located in the Bengawan Solo River (Lower Solo River Basin) about 15 km downstream of the confluence of Bengawan Solo River with the Madiun River in Ngelo Village, Margomulyo Sub-District, Bojonegoro Regency, and Ngrawoh Village in Kradenan Sub-District, Blora Regency. This study aims to determine the Depth and pattern of scouring in downstream energy dissipation through physical model tests based on initial planning. Downstream protection of energy dissipation in the original design model combines 50 m of riprap rocks and 50 m of riprap concrete for a total length of 100 m of protection. The maximum scouring pattern occurred at elevation + 17.64 m, where the scouring was 4.36 m deep, from the planned essential height of Height 00 m. Thus, the downstream protection of energy dissipation was extended to 112 m in riprap concrete blocks for the final design model. Scouring at the end of riprap was 3.04 m, the original elevation of the river bottom of + 22.00 m, down to + 18.96 m. It is concluded that the protection is effective in reducing scouring by up to 30.27%.
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Paramadita, Tifarah Dayansabila, Nadia Azarine, Aburizal Azhar i Didit Puji Riyanto. "Local Scouring Visualization of Bed Channel Surface in Hydraulic Structure Using Surfer". Jurnal Teknik Sipil dan Perencanaan 24, nr 2 (31.10.2022): 140–49. http://dx.doi.org/10.15294/jtsp.v24i2.36499.
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Abstract. Water flowing in the river causes a scouring event that occurs at the bed channel. The existence of scouring will increase along with changes in the geometry of the river and obstacles such as the weir which are followed by local scouring around the weir. Local scouring often occurs downstream end of weir sill which weakens its construction. Scouring measurement was conducted to monitor the pattern of scouring that occurs. By using Surfer software, the scouring visualization through the Data Grid and 3D Surface can be seen. In this research, scour monitoring in the laboratory using open channels (flume) and MDO weir with fine aggregate material as the basis of the channel. The retrieval of scouring data was performed after installing fine aggregate and three times variations of flow discharge, then the data were processed using Surfer. The first flow used water level +3.50 with the material carried at 3.77%. The second flow used water level +4.50 with the material carried at 11.16%. The third flow used water level +5.70 with the material carried at 25.46%. So with the continuous method, the total material carried at 36.27% is equivalent to 12575.77 cm3.
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Gao, Pengcheng, Xianyou Mou i Honglan Ji. "Simulation Study on Local Scour Characteristics of Tandem Bridge Piers in a Straight River under a Changing Environment". Sustainability 15, nr 15 (31.07.2023): 11776. http://dx.doi.org/10.3390/su151511776.
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Hydrodynamics is a common manifestation that causes natural scouring of riverbeds, and it is one of the factors that exacerbate the natural disasters of local scouring of bridge piers, causing sustainability of environmental changes in the water. The evolution pattern and scour characteristics of the bed surface around the submerged structures under different scouring conditions vary greatly. In order to investigate the scour mechanism, the reformed group (RNG) turbulence model in computational fluid dynamics (CFD) simulation software (v11.2) was used to simulate the scour under the clear-water scour and live-bed scour environments, and different scour morphology characteristics around the tandem piers under the clear-water scour and live-bed scour environments were obtained in the final simulation. By capturing the cross-sectional vortex and bed shear stress during the scouring process, the characteristic pattern of scouring topography around the pier and the relationship between the scour hole structure scale were analyzed, and the relationship equation between the development of scour depth and time scale was established. The study shows that: under the clear-water scouring environment, the sediment transport rate lags behind, but the contribution time is superior; under the live-bed scouring environment, by the shading and reinforcement influence of the upstream piers, the extent and development of the downstream pier surrounding the scour hole is small; the development trend of the maximum sediment transport rate of the scour hole and the great value of the shear stress is more synergistic, and the peri-pier eddy is positively correlated with the bed shear stress; through the regression equation to compare the relevant test and simulation results, the two are in good agreement, indicating that the simulated local scour evolution law is consistent with the actual law.
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Марьин, Василий, Vasily Mar'in, Александр Верещагин, Alexander Vereshchagin, Николай Бычин i Nicolay Bychin. "Winter Buckwheat Grain: The Dynamic Pattern of the Mechanical Properties of the Main Fraction". Food Processing: Techniques and Technology 49, nr 1 (26.06.2019): 97–103. http://dx.doi.org/10.21603/2074-9414-2019-1-97-103.
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As quality requirements get lower and lower, the quality of buckwheat grain meant for buckwheat groats is deteriorating. The most typical example is winter buckwheat grain. Buckwheat grain has to be sorted according to various fractions before scouring. Thus, the mechanical properties of these fractions remain a relevant field of study. The research features the dynamic pattern in the mechanical properties of the main fractions of winter buckwheat grain according to fraction before and after storage. The research subject is fractions of buckwheat sorted according to grain size before scouring. The buckwheat grain was harvested in the foothills of the Altai Territory in May 2015; it meets the necessary standards. There were twelve samples: six samples were harvested and sent for recycling (May 2015); other six samples were stored for eight months up to March 2016. The buckwheat did not pass the temperature treatment stage. The smaller fractions revealed a greater deformation before and after storage. That can lead to a higher deformation rate during scouring. Thus, the changes in the mechanical properties of winter buckwheat grain occur differently for each fraction.
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Kolahdouzan, Fereshteh, Hossein Afzalimehr, Seyed Mostafa Siadatmousavi, Asal Jourabloo i Sajjad Ahmad. "The Effect of Pipeline Arrangement on Velocity Field and Scouring Process". Water 15, nr 7 (28.03.2023): 1321. http://dx.doi.org/10.3390/w15071321.
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This experimental study investigates the effect of changes in the arrangement of horizontal pipelines on changes in the velocity pattern in three dimensions and the scouring process around these submarine pipelines. Experiments have been carried out in four cases: single pipe, two pipes with a distance of 0.5 D, two pipes with a distance of D, and three pipes with a distance of 0.5 D (D is the diameter of the pipes). The velocity upstream, downstream, and on the pipes have been measured by the Acoustic Doppler Velocimeter (ADV). The results show that a single pipe’s scouring depth in the first case is more significant than in the other cases. In the second case, the presence of the second pipe at a distance of 0.5 D from the first pipe significantly reduced the scour depth (28.6%) compared to the single pipe condition by changing the velocity pattern around the pipelines. By increasing the number of pipes to 3 with a distance of 0.5 D, this reduction in scouring depth has reached 47.6% compared to the single pipe condition. However, in the case of two pipes with a distance of D, the reduction of scouring depth was 21.4% compared to the case of a single pipe, and compared to the case of two pipes with a distance of 0.5 D, it increased by 10%.
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Boroomand, Mohammad Reza, S. Ali Akbar Salehi Neyshabouri i Kameleh Aghajanloo. "Numerical simulation of sediment transport and scouring by an offset jet". Canadian Journal of Civil Engineering 34, nr 10 (1.10.2007): 1267–75. http://dx.doi.org/10.1139/l07-050.
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In this paper the offset jet entering a domain with a movable bed is simulated by the computer program FLUENT. To achieve this aim, sediment transport is numerically simulated using multiphase systems and the empirical coefficients are studied theoretically. The numerical results are verified by comparing the simulated total load with that obtained using existing formulae and concentration profiles from available measured data. In the final step, the offset jet scouring pattern is modeled qualitatively.Key words: offset jet, numerical simulation, FLUENT, multiphase system, turbulence, sediment, scouring.
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Wisafri. "Gerusan Lokal yang Terjadi di Hilir Bendung dan Upaya Pengendaliannya". Jurnal Ilmiah Poli Rekayasa 9, nr 2 (15.04.2014): 74. http://dx.doi.org/10.30630/jipr.9.2.74.
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Majarity of damages on the dam construction in Indonesia is caused by continuous local scouring at the end side of the dam construction. It grows and reach its lower/bottorm part. It could results in degradation in the dam operation safety. This local scouring was caused by major water flowing passing the dam where there is a high difference level between the top and the end of the dam. Furthermore, it generates inbalancing water flow speed and additional water turbulence. There are different approachs to prevent such damage, and for example by providing one or more additional construction at the end part of the dam. This structure is designed and installed at the bottom part of the dam. Various empirical functions have been developed to design this structure, and one of them is developed by Lacey. The function is reprsented by D = 0.47 * (Q/F)1/2 (D= scouring depth, Q= Discharge, F= the size of the sand particle). However, that function has some limitation. For examples are the local river and dam construction characteristics. Therefore, it is required to be validated by developing a model of dam contructed in a laboratory. Experiments was undertaken by using the model with different characteristics of water flow in order to investigate the scouring pattern, and than method prefentif work
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Hassanzadeh, Yousef, Milad Khosravi i Nazila Kardan. "Numerical investigation on the effect of bluntness factor on scouring mechanism by using lenticular geometry piers". Canadian Journal of Civil Engineering 47, nr 3 (marzec 2020): 279–90. http://dx.doi.org/10.1139/cjce-2017-0658.
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Local scour and flow field around cylinders with lenticular geometry and different bluntness factors under the clear-water state were investigated numerically. To examine the scouring, large eddy simulation with a WMLES-Omega sub-grid model incorporating the sediment transport and morphodynamic model was applied. Streamlined geometry of the pier significantly affected the scour pattern and flow field in the lenticular model with length to width ratio of 5 and bluntness factor of zero. In the mentioned case, a very small scoured region was estimated at the sides of the pier, so it can be concluded that scour depth and scoured region decreases as the length to width ratio increases. Investigation of the scouring process and the flow field revealed that, the flow separation can affect the scour mechanism more in comparison to down-flow.
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Vigdorowitsch, Michael, Valery V. Ostrikov, Alexander N. Pchelintsev i Irina Yu Pchelintseva. "Diffusion Kinetics Theory of Removal of Assemblies’ Surface Deposits with Flushing Oil". Computation 11, nr 8 (20.08.2023): 164. http://dx.doi.org/10.3390/computation11080164.
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The diffusion kinetics theory of cleaning assemblies such as combustion engines with flushing oil has been introduced. Evolution of tar deposits on the engine surfaces and in the lube system has been described through the erosion dynamics. The time-dependent concentration pattern related to hydrodynamic (sub)layers around the tar deposit has been uncovered. Nonlinear equations explaining the experimentally observed dependences for scouring the contaminants off with the oil have been derived and indicate the power law in time. For reference purposes, a similar analysis based on formal chemical kinetics has been accomplished. Factors and scouring parameters for the favor of either mechanism have been discussed. Any preference for either diffusion or chemical kinetics should be based on a careful selection of washing agents in the flushing oil. Future directions of studies are proposed.
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Bal, Dursun, Mahmud Bakırhan, Murat Apakhan, Hakkı Ekem, Ömer Sinan Şahin i Muharrem Hilmi Aksoy. "EFFECT OF SCOURER SCREEN PATTERNS ON THE WHEAT HUSK REMOVAL EFFICIENCY". Advanced Engineering Letters 1, nr 3 (2022): 108–13. http://dx.doi.org/10.46793/adeletters.2022.1.3.5.
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The scourer machines remove wheat husk contaminated with pesticides and other impurities that adversely affect product quality and shelf life. For this purpose, at least one scourer machine is used in each industrial grain flour factory, depending on the capacity. The efficiency of these machines is highly dependent on the surface texture and scourer screen patterns. In this study, the efficiency of the wheat scourer machines with various wall patterns and meshes was investigated experimentally. The investigation employed six distinct types of scourer screens. Type-4 has produced the best results in fractured grain rate, whereas Type-2 has produced the best in ash content. It was revealed that wheat’s scouring efficiency and physical and chemical properties vary depending on the scourer screen pattern.
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Prasetyo Wahono, Endro, Ika Kustiani i Suharno. "Scouring Pattern of Movable-Bed Channel Due to Mutual Constriction Structures: Laboratory-scale Model". Jurnal Profesi Insinyur Universitas Lampung 1, nr 1 (13.04.2020): 29–33. http://dx.doi.org/10.23960/jpi.v1n1.16.
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Pada beberapa tahun terakhir, permasalahan lingkungan telah menjadi hal yang sangat penting dalam proses pengambilan pada berbagai bidang rekayasa. Naturalisasi tumbuhanpada bantanran Sungai Ciliwung misalnya adalah salah satu contoh betapa aspek lingkungan telah diadopsi dalam manajemen sungai. Wahono (2002) menyatakan bahwa tumbuhan di bantaran sungai dapat mempunyai dampak yang analog dengan sebuah serial bangunan penyempitan. Untuk itu pengetahuan mengenai perilaku gerusan local akibat penyempitan berseri akan sangat penting untuk memahami resiko dari kerusakan bantaran dan bangunan sungai lain akibat gerusan local. Tujuan utama dari penelitian ini adalah untuk mengidentifikasi perilaku gerusan lokal akibat balok penyempitan berseri pada saluran terbuka dan lurus. Jarak antar balok dan lebar balok merupakan variabel bebas penelitian ini, sedangkan profil gerusan local merupakan salah satu variable tak bebas yang diteliti. Berdasarkan hasil analisa dari data penelitian, diperoleh tendensi bahwa dengan meningkatnya lebar balok penyempitan (dari 3 cm sampai 12 cm) serta dengan meningkatnya jarak antar balok (dari 0,5b sampai 5b), menghasilakn kecenderungan penurunan luasan daerah gerusan lokal dan kecepatan alirannya. Gerusan lokal minimum (luasan) terjadi pada balok dengan lebar 12 cm dan atau pada jarak 5b. Sedangkan gerusan local maksimum (luasan) terjadi pada balok dengan lebar 3 cm dan atau jarak 0,5b. Penyempitan pada kedua sisi saluran serta saluran yang berkelok-kelok dengan aliran tidak tunak direkomendasikan sebagai seting penelitian lanjutan dari hasil ini untuk mendekati kondisi alami sungai dan memberikan penjelasan ilmiah naturalisasi bantaran sungai. Penelitian model fisik dengan skala yang yang mendekati ukuran alamiahnya sangat direkomendasikan untuk mendapatkan hasil yang lebih realistik.
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Pearce, M. C., C. Jenkins, L. Vali, A. W. Smith, H. I. Knight, T. Cheasty, H. R. Smith i in. "Temporal Shedding Patterns and Virulence Factors of Escherichia coli Serogroups O26, O103, O111, O145, and O157 in a Cohort of Beef Calves and Their Dams". Applied and Environmental Microbiology 70, nr 3 (marzec 2004): 1708–16. http://dx.doi.org/10.1128/aem.70.3.1708-1716.2004.
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ABSTRACT This study investigated the shedding of Escherichia coli O26, O103, O111, O145, and O157 in a cohort of beef calves from birth over a 5-month period and assessed the relationship between shedding in calves and shedding in their dams, the relationship between shedding and scouring in calves, and the effect of housing on shedding in calves. Fecal samples were tested by immunomagnetic separation and by PCR and DNA hybridization assays. E. coli O26 was shed by 94% of calves. Over 90% of E. coli O26 isolates carried the vtx 1, eae, and ehl genes, 6.5% carried vtx 1 and vtx 2, and one isolate carried vtx 2 only. Serogroup O26 isolates comprised seven pulsed-field gel electrophoresis (PFGE) patterns but were dominated by one pattern which represented 85.7% of isolates. E. coli O103 was shed by 51% of calves. Forty-eight percent of E. coli O103 isolates carried eae and ehl, 2% carried vtx 2, and none carried vtx 1. Serogroup O103 isolates comprised 10 PFGE patterns and were dominated by two patterns representing 62.5% of isolates. Shedding of E. coli O145 and O157 was rare. All serogroup O145 isolates carried eae, but none carried vtx 1 or vtx 2. All but one serogroup O157 isolate carried vtx 2, eae, and ehl. E. coli O111 was not detected. In most calves, the temporal pattern of E. coli O26 and O103 shedding was random. E. coli O26 was detected in three times as many samples as E. coli O103, and the rate at which calves began shedding E. coli O26 for the first time was five times greater than that for E. coli O103. For E. coli O26, O103, and O157, there was no association between shedding by calves and shedding by dams within 1 week of birth. For E. coli O26 and O103, there was no association between shedding and scouring, and there was no significant change in shedding following housing.
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Liu, Xiao Fang, Dang Wei Wang i He Qing Huang. "An Experimental Research on Optimization of Trajectory Bucket for Spillway Tunnel Outlet at Sanliping Hydropower Project". Applied Mechanics and Materials 90-93 (wrzesień 2011): 2740–45. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.2740.
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Several optimized designs of trajectory bucket pattern for spillway tunnel outlet are compared in the experiment of Sanliping hydropower project integer physical model and the results show that energy dissipation of outflow nappe is sufficient after optimization and no scouring occur near the riverbank either at high water level or at low water level, which ensure the security of spillway structure. And these experimental results can provide a scientific foundation for the design of Sanliping project.
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Wang, Hua, Yijun Zhao, Fengnian Zhou, Huaiyu Yan, Yanqing Deng i Bao Li. "Suspended sediment distribution under varied currents in the largest river-connected lake of China". Water Supply 18, nr 3 (18.08.2017): 994–1004. http://dx.doi.org/10.2166/ws.2017.167.
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Abstract Poyang Lake was selected as the research area. Based on laboratory experiment, field investigation and numerical simulation, the spatial distributions of suspended sediment (SS) under the gravity-flow, jacking-flow and back-flow patterns were quantitatively analysed. An annular flume experiment was conducted to determine the critical starting shear stresses of the sediments in the flood and dry seasons. By numerical experiment, the SS transport under different flow patterns was explored. Several results stand out. (1) The critical starting shear stresses of the sediments in the flood and dry seasons were 0.35 N·m−2 and 0.29 N·m−2, respectively. (2) Due to the strongest flow disturbance and scouring effect, SS under the gravity-flow pattern was characterized by the highest loads. The lowest SS was observed during the jacking-flow pattern, which could be attributed to the lowest water level gap between the lake and external rivers. The loads ranged from 0.053 kg·m−3 to 0.068 kg·m−3. (3) Under the back-flow pattern, SS in the north lake was evidently influenced by the Yangtze River, and the mean value was approximately 0.12 kg·m−3. With the gradually weakened back-flow impact, the SS load was decreased from the north to the middle of the lake.
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Dalla Barba, Federico, i Francesco Picano. "Direct numerical simulation of the scouring of a brittle streambed in a turbulent channel flow". Acta Mechanica 232, nr 12 (13.10.2021): 4705–28. http://dx.doi.org/10.1007/s00707-021-03075-5.
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AbstractThe natural processes involved in the scouring of submerged sediments are crucially relevant in geomorphology along with environmental, fluvial, and oceanographic engineering. Despite their relevance, the phenomena involved are far from being completely understood, in particular for what concerns cohesive or stony substrates with brittle bulk mechanical properties. In this frame, we address the investigation of the mechanisms that govern the scouring and pattern formation on an initially flattened bed of homogenous and brittle material in a turbulent channel flow, employing direct numerical simulation. The problem is numerically tackled in the frame of peridynamic theory, which has intrinsic capabilities of reliably reproducing crack formation, coupled with the Navier–Stokes equations by the immersed boundary method. The numerical approach is reported in detail here and in the references, where extensive and fully coupled benchmarks are provided. The present paper focuses on the role of turbulence in promoting the brittle fragmentation of a solid, brittle streambed. A detailed characterization of the bedforms that originate on the brittle substrate is provided, alongside an analysis of the correlation between bed shape and the turbulent structures of the flow. We find that turbulent fluctuations locally increase the intensity of the wall-stresses producing localized damages. The accumulation of damage drives the scouring of the solid bed via a turbulence-driven fatigue mechanism. The formation, propagation, and coalescence of scouring structures are observed. In turn, these affect both the small- and large-scale structures of the turbulent flow, producing an enhancement of turbulence intensity and wall-stresses. At the small length scales, this phenomenology is put in relation to the formation of vortical cells that persist over the peaks of the channel bed. Similarly, large-scale irregularities are found to promote the formation of stationary turbulent stripes and large-scale vortices that enhance the widening and deepening of scour holes. As a result, we observe a quadratic increment of the volumetric erosion rate of the streambed, as well as a widening of the probability density of high-intensity wall stress on the channel bed.
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Vucelic-Radovic, Biljana V., Vjaceslav M. Nesic, Mirjana A. Demin i Mirjana M. Milovanovic. "The B Group Vitamins and Mineral Elements in the Selective Removal of Wheat Kernel Layers". Natural Product Communications 1, nr 11 (listopad 2006): 1934578X0600101. http://dx.doi.org/10.1177/1934578x0600101115.
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The objective of this study was to investigate how selective removal of the surface layers of whole wheat grains by abrasive scouring affects the distribution of mineral elements (macronutrients, micronutrients and trace elements) and the B group vitamins (thiamin, riboflavin pyridoxine, pantothenic acid and niacin) in three soft winter wheat varieties (Partizanka, Novosadska rana and Lasta). Although representing technologically different quality classes of wheat, the varieties were not significantly different in the B group vitamin contents, except for pyridoxine. Whole grains of all varieties exhibited very similar scouring behavior in reduction of vitamins: the most intensive investigated regime only slightly, but not significantly reduced the concentration of the B group vitamins. The nutritive value of scoured wheat grains with regard to the B group vitamins was preserved. The investigated minerals were: Na, K, Ca, Mg, Mn, Fe, Cu, Zn, Ni, Cr, Se, Pb and Cd. The concentrations of minerals in scoured wheat grains were significantly reduced, dropping on average to 65% of the initial values for macro and 55% for microelements. The change of concentrations with the duration of applied treatment followed different patterns for different elements. Furthermore, a different pattern of the change for the same element in different wheat varieties was noticed. This might be due either to different mechanical properties of bran and bran layer interfaces or genotypic variability in distribution of elements in wheat grain. Severe reduction in Pb concentrations was achieved leading to improvement of whole-wheat food safety.
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Ding, Changfeng, Chunguang Li, Lulu Song i Shaozhuo Chen. "Numerical Investigation on Flow Characteristics in a Mildly Meandering Channel with a Series of Groynes". Sustainability 15, nr 5 (24.02.2023): 4124. http://dx.doi.org/10.3390/su15054124.
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In single-bend channels or meandering channels, groynes are widely used as a river-training structure. Geometric factor is an important principle of groyne design. In this paper, the numerical method based on the Renormalization Group (RNG) k-ε turbulence model is used to study the effects of groynes with different lengths and orientations on the mean flow pattern and turbulence characteristics in a mildly meandering channel. The analysis shows that compared with equal-length groynes, the groynes arranged in descending order perform well in improving the flow velocity of the main channel, and the maximum longitudinal velocity at the channel center can be increased by 1.57 times the average velocity. However, at the same time, they bring higher Normalized Turbulent Kinetic Energy (NTKE) and Normalized Bed Shear Stress (NBSS) values. The attracting groynes arranged in descending order help to reduce scouring. The groynes arranged in ascending order reduce the velocity of the riverbank in some downstream areas and are suitable for bank protection. It effectively decreases the NTKE and NBSS around the groyne fields and can reduce the inner bank scouring of the mildly meandering channel. The findings are helpful for the management of meandering rivers.
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Helmi, Ahmed M., i Ahmed H. Shehata. "Three-Dimensional Numerical Investigations of the Flow Pattern and Evolution of the Horseshoe Vortex at a Circular Pier during the Development of a Scour Hole". Applied Sciences 11, nr 15 (27.07.2021): 6898. http://dx.doi.org/10.3390/app11156898.
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In the current study, a three-dimensional CFD model is utilized to investigate the variation of the flow structure and bed shear stress at a single cylindrical pier during scour development. The scour development is presented by seven solidified geometries of the scour hole, collected during previous experimental work at different scour stages. Different turbulence models are evaluated and the (k-ω) model is chosen due to its relative accuracy in capturing the flow oscillation and vortex shedding at the pier downstream side with personal computer computational and storage resources. The numerical results are verified against dimensionless parameters from different previous experimental works. This research describes in detail the flow structure and bed shear stress variations through seven stages of the scour hole development. The dimensionless area-averaged circulation coefficient (Ψi) is developed to evaluate the changes in the vortex strength through the scouring process by eliminating the calculation area effect. It was concluded that the circulation in the (Y) direction is the main driving factor in the development of the scour hole more than the circulation in the (X) direction. The ratio between the horseshoe vortex (HV) mean size and the scouring depth (DV/dS) in addition to the location of the maximum bed shear stress are investigated during different stages of the scour development.
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Nie, Xiao-Bao, Yun-Zi Tang, Chang-bo Jiang, Yuan-Nan Long, Pan-Pan He i Chao Xu. "Vertical distribution pattern of naidids in granular activated carbon filters and potential technology to control their penetration risk". Water Supply 18, nr 6 (31.01.2018): 1976–83. http://dx.doi.org/10.2166/ws.2018.020.
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Abstract Aquatic worms propagated in granular activated carbon (GAC) filter has become a troublesome problem for drinking water supply. This study investigated the vertical distribution patterns of naidids in GAC filter beds and assessed the effect of an additional sand bed, located below the GAC bed, in preventing naidids from being present in effluent. The results indicated that the vertical distribution data of naidids in the GAC filter bed were well fitted by a Gaussian distribution, and the location of peak population density was mainly affected by downward flow. Backwashing experiments revealed that additional pressure air scouring shifted the distribution pattern of naidids in the GAC filter bed, resulting in a significant enhancement in naidid removal efficiency. Additionally, the addition of a sand bed exhibited pronounced interception and inactivation effects on naidids, suggesting that it may be a very promising technology for preventing naidids propagated in GAC filters from being present in the effluent.
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Sisinggih, D., S. Wahyuni i A. Rasyid. "Flow and sediment transport in a sharp river bend using a 3D-RANS model". IOP Conference Series: Earth and Environmental Science 930, nr 1 (1.12.2021): 012033. http://dx.doi.org/10.1088/1755-1315/930/1/012033.
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Abstract Flow dynamics and sediment transport in a river bend have recently been studied using experimental and numerical investigations. A three-dimensional numerical modeling model named NaysCUBE was used in this study to describe the flow pattern and process of sediment transport in a sharp river bend as a complement to the prior work of the physical hydraulic model. The model uses the RANS equation to simulate flow where a fully complex 3D flow is governed. Despite the limitations of the RANS model, NaysCUBE well reproduces the flow pattern and turbulence phenomena in a movable bed channel with sharp curvature. Compared with data from a prior experiment, the morphological adjustment is simulated sufficiently. The three-dimensional flow structures are useful for determining the appropriate countermeasures for local scouring and riverbank protection.
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SATO, Natsumi, Kosuke IIMURA, Hirokazu IKEDA i Ryuichi ISHIBASHI. "EFFECTS OF COASTAL FOREST ON TSUNAMI OVERFLOW PATTERN AND LOCAL SCOURING AT LANDWARD TOE OF EMBANKMENT". Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 75, nr 2 (2019): I_721—I_726. http://dx.doi.org/10.2208/jscejhe.75.2_i_721.
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Zhang, Bohu, Zhiyong Zhang, Fuyuan Chen i Kun He. "Study on the Morphological Evolution of the Oujiang Estuary, China, in the 21st Century". Journal of Marine Science and Engineering 11, nr 2 (8.02.2023): 378. http://dx.doi.org/10.3390/jmse11020378.
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Based on four years of spatially synchronous topographic data of the Oujiang Estuary from 2002 to 2019, the variations and physical mechanisms of estuarine evolution driven by natural conditions and human activities since the beginning of this century were analyzed. The results show that the evolution of the Oujiang Estuary has changed dramatically in the past 20 years. From 2002 to 2019, the net sediment erosion of the estuary was 163.44 million m3, and the average bed elevation of the river-dominated section (RDS), transition section (TS) and tide-dominated section (TDS) decreased by 4.61 m, 1.30 m and 2.14 m, respectively. In addition, the pattern of the shoal channel had changed, and the river facies coefficient (width–depth ratio) decreased by 16–64%. The evolution of the Oujiang Estuary is mainly caused by human activities (such as sand mining, reclamation). Sand mining is the direct cause of riverbed undercutting, and the large undercutting of riverbed terrain causes the increase in tidal power in the estuary and further causes river channel scouring. In the last 20 years, the average annual tidal range of the estuary increased by 0.19–1.14 m, and the flood discharge increased by about 17–80%, with an average value of 58%. The impact of tidal power on the evolution and development of the estuary has increased significantly. Apart from sand mining, reclamation projects such as the Wenzhou shoal outside the mouth also cause the local velocity of the tidal current section to increase, which aggravates the scouring trend of local river sections downstream. The scouring and silting changes in the Oujiang Estuary since the beginning of this century are the result of the adjustment of the estuarine system in response to the strong intervention of human activities.
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Majeed, Hayder Q., Basim Sh Abed i Ali Khairi Ibrahim. "Countermeasure of Riverbanks Local Scour and Deposition Using Different Shapes of Multiple Groynes with Different Spacing". Mathematical Modelling of Engineering Problems 9, nr 5 (13.12.2022): 1277–81. http://dx.doi.org/10.18280/mmep.090515.
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In current study a computation fluid dynamic (CFD) technique was used to investigate the effect of groynes shape and spacing on the scour pattern and the maximum scour depth in open channel flow. CFD model have been validated throughout comparing the numerical results with three previous experimental studies for a single groyne located in open channel with three different shapes (L, quadrant, and parabola shapes). The comparison revealed very good agreement between numerical results of the maximum scour depth with the results of all experimental models. Moreover, investigations of the effect of multi-groynes (three groynes and four groynes) arranged in parallel with constant spacing and also with variable spacing have been done, the results showed that the best spacing between groynes equal to the length of the groyne itself, Finally, the CFD model have been used to investigate the best pattern for the groynes having different shapes arranged respectively, the results show that the pattern starting with parabola shape gives minimum scouring depth.
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Djunur, Lutfi Hair. "Study On Scouring and Protection of USBR-III Type Downstream of Spillway". Jurnal Teknik Sipil dan Perencanaan 24, nr 1 (30.04.2022): 62–71. http://dx.doi.org/10.15294/jtsp.v24i1.34196.
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Abstract. In the downstream part of the spillway building, especially in the flood way, occurs phenomenon of changing flow conditions from super critical to sub critical which causes a hydraulic jump and used by energy absorbers to reduce flow energy. The hydraulic jump in the floodway causes scouring of the bottom, particularly in the unprotected downstream spillway. Using 3 different dimensional baffle block models provides three different discharge variations in four flow simulations. Based on the results of the analysis and planning of the baffle block, it is found that the effectiveness in protecting the downstream scour of the spillway, namely baffle block dimensions of 1:1, 1:3 and 1:5. The three models of baffle blocks are used to determine the change in channel cross-section, scour pattern, scour volume and flow parameters that occur in downstream of spillway. The results showed that without baffle block was 32.80%, 1:1 baffle block was 43, 24%, 1:3 baffle block was 10.01% and 1:5 baffle block was 47.77%. The results of the drainage simulation showed that the higher the water level and the velocity of the flow at the bottom of the channel, the less the flow will be and will not be able to lift the bottom material of the channel
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Johnson, W. Carroll, Mark A. Boudreau i Jerry W. Davis. "Cultural Practices to Improve In-Row Weed Control with Cultivation in Organic Peanut Production". Weed Technology 26, nr 4 (grudzień 2012): 718–23. http://dx.doi.org/10.1614/wt-d-12-00019.1.
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Cultivation is a proven means of weed control in organic peanut. However, weeds present in-row often escape control. Research trials were conducted in Ty Ty, GA to modify cultural practices to help suppress weed emergence in-row. Modified cultural practices were three row pattern/seeding rate combinations; twin rows (four rows on a seedbed) seeded at the recommended (1X) seeding rate that produced 13 seed m−1in each row, twin rows seeded at the 2X seeding rate that produced 23 seed m−1in each row, and wide rows (two rows on seedbed) seeded at the recommended seeding rate that produced 23 seed m−1. Four cultivation regimes were evaluated; cultivation with a tine weeder at weekly intervals for 6 wk, cultivation with a tine weeder at weekly intervals for 8 wk, scouring with a brush hoe at vegetative emergence followed by the tine weeder for 6 wk, and a noncultivated control. There were no interactions between row pattern/seeding rates and cultivation regimes for any parameter measured. There was inconsistent response of weed control and peanut yield to row pattern/seeding rates. Weed control and peanut yields were similar with tine weeding for 6 wk, 8 wk, or with the brush hoe followed by the tine weeder. Weed management in organic peanut was not improved by altering peanut cultural practices that facilitate quicker canopy closure, and the use of narrow row patterns should not be based on attempts to improve weed control in organic peanut. Narrow row patterns provide other benefits to organic peanut production and those attributes should influence decisions on the choice of row pattern, not weed control.
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Hassan, Zahraa F., Ibtisam R. Karim i Abdul-Hassan K. Al-Shukur. "Effect of Interaction between Bridge Piers on Local Scouring in Cohesive Soils". Civil Engineering Journal 6, nr 4 (1.04.2020): 659–69. http://dx.doi.org/10.28991/cej-2020-03091498.
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Local scour at the piers is one of the main reasons of bridge foundation undermining. Earlier research studies focused mainly on the scour at a single bridge pier; nevertheless, modern designs of the bridges comprise wide-span and thus group of piers rather than a single pier are usually used to support the superstructure. The flow and scour pattern around group of piers is different from the case of a single pier due to the interaction effect. Reviewing the literature of local scour around bridge piers group revealed that the local scour around bridge piers group founded in cohesive soil bed was not investigated, and most of the scour studies were related to scour in cohesionless soils. The objective of the present study is to investigate the effect of the interaction between two in-line (tandem) circular bridge piers of variable spacings founded in cohesive soil on the local scour. A set of laboratory flume experiments were conducted under the clear-water scour condition to investigate this effect. This study is the first that investigates experimentally the scour around group of bridge piers in cohesive bed. It was found that the maximum scour depth at the upstream pier of the two in-line piers occurred at a spacing of two times the diameter of the pier, scour at the downstream pier was reduced due to a sheltering effect, the interference effect will be reduced for pier spacings larger than three times of the pier diameter. A recent pier scour equation was used to estimate the scour depths at the two in-line piers in cohesive soil and compare the estimated value with the measured scour depths in the laboratory. The comparison indicated that the proposed scour equation overestimates the scour depths at both the upstream and the downstream pier.
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Zhao, Qinghe, Yifan Zhang, Shanshan Xu, Xiaoyu Ji, Shuoqian Wang i Shengyan Ding. "Relationships between Riparian Vegetation Pattern and the Hydraulic Characteristics of Upslope Runoff". Sustainability 11, nr 10 (24.05.2019): 2966. http://dx.doi.org/10.3390/su11102966.
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Riparian vegetation plays a vital role in inhibiting soil and water loss, but few studies have quantified the relationships between vegetation spatial pattern and the hydraulic characteristics of upslope runoff. This study investigated how hydraulic characteristics (e.g., runoff coefficient, flow regime, flow resistance, and flow shear stress of overland flow) responded to differences in vegetation cover (15% and 30%), slope gradient (5°, 10°, 15°, and 20°), and vegetation pattern in the riparian zone along the lower Yellow River, China, based on landscape pattern analysis and a runoff scouring experiment with flow rates of 9 and 15 L/min and an experimental plot size of 1 m × 3 m. We found that runoff generation on shallow slopes was moderated by increasing vegetation cover, but that this moderating effect decreased on steeper slopes. The regime of overland flow switched from laminar and subcritical on the 5° slope (Fr = 0.56–0.87) to laminar and critical on the 10°, 15°, and 20° slopes (Fr = 1.02–2.18). Flow resistance increased with vegetation cover and flow rate and decreased with slope gradients, and it was larger on shallow slopes with high vegetation cover. Flow shear stress had a range of 1.42–3.55 N m−2, and it increased with increasing slope gradient, vegetation cover, and flow rate. The hydraulic characteristics of upslope runoff, especially flow resistance, were significantly related to vegetation pattern at both the landscape and class levels. Flow resistance was negatively related to patch density, and positively related to perimeter–area fractal dimension and connectance index. The influencing mechanism of landscape patterns on soil erosion processes is dependent on the landscape scale, since the relationships between flow resistance and some landscape pattern indices (aggregation index, effective mesh size, and splitting index) were opposite at the landscape level compared to the class level. We conclude that fragmented vegetation distributions reduce flow resistance, and that riparian vegetation could be managed to inhibit slope erosion by increasing flow resistance.
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Akib, Shatirah, Afshin Jahangirzadeh i Hossein Basser. "Local scour around complex pier groups and combined piles at semi-integral bridge". Journal of Hydrology and Hydromechanics 62, nr 2 (1.06.2014): 108–16. http://dx.doi.org/10.2478/johh-2014-0015.
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Abstract This research presents an experimental study on the scouring mechanism at semi-integral bridge piers. Based on laboratory experiments, this study focuses on the relationship between scour depth in complex pier groups and combined piles bridge and various parameters including the variation of inflow velocity, distance, and time. 1 200 data were collected for flow velocity and scour. The flow pattern and scour were analyzed for different flow discharges and flow depths. The results showed that the scour development with respect to time was greater for higher flow depth and bigger flow discharge at semi-integral bridges. In addition, the equilibrium scour depth increased with the approach flow depth around piers at semi-integral bridges. Velocity distribution also affected the scour development. It decreased when approaching the bridge but increased from upstream to downstream of the flume.
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Wilms, Mayumi, Arne Stahlmann i Torsten Schlurmann. "INVESTIGATIONS ON SCOUR DEVELOPMENT AROUND A GRAVITY FOUNDATION FOR OFFSHORE WIND TURBINES". Coastal Engineering Proceedings 1, nr 33 (25.10.2012): 35. http://dx.doi.org/10.9753/icce.v33.structures.35.
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Due to insufficient insights about the scour development around the STRABAG gravity foundation, the Franzius-Institute conducted small- and large-scale physical model tests in wave flumes on a scale of 1:50 and 1:17 in order to investigate the wave-induced scouring phenomena around the foundation and to design a scour protection system. The tests on scour development without a scour protection system show that the main areas which are vulnerable to scour are the contact areas of the foundation. Furthermore, the experiments show that a scour protection system is necessary for the given and investigated wave boundary conditions; the performance of the selected protection system using geotextile sand containers is verified. Additional numerical simulations indicate an amplification of the resulting flow around the foundation under combined loads (waves and current), but without significant change of the flow pattern
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Matsuura, Troy, i Ronald Townsend. "Stream-barb installations for narrow channel bends — a laboratory study". Canadian Journal of Civil Engineering 31, nr 3 (1.06.2004): 478–86. http://dx.doi.org/10.1139/l04-017.
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Phase 1 of an ongoing laboratory study of a novel form of stream-bank protection structure is described. "Barbs" are dike-like stone structures designed to protect the (usually unstable) outside-bank regions of channel bends. These low-profile structures point upstream into the flow and typically extend to about 1/4-way across the channel. By disrupting near-bank velocity gradients they promote sediment deposition along the eroding outside-bank region. Their presence also modifies the "helicoidal"-type flow pattern of the bend such that secondary currents, which would otherwise attack the outside-bank, are redirected towards the center of the channel. This novel form of bank protection structure is currently undergoing field tests on selected bends on a number of shallow "wide" streams in Illinois, USA. While initial results are encouraging, additional studies are necessary to develop design criteria for their wider application. In phase 1 of this study, the effectiveness of different arrangements of barb groups, in both 90° and 135° moveable-bed bend sections of a hydraulically "narrow" rectangular channel, are investigated. For each hydraulic condition considered, the channel-bed scour profiles generated by the different barb groups are compared to corresponding "reference" profiles generated in the absence of barbs. Judging the effectiveness of the different barb groups in promoting long-term stability of the outside-bank region is based on two criteria: (i) percent reduction achieved in scouring in the vicinity of the outside-bank and (ii) degree to which the channel thalweg (deepest portion) is moved from the outside-bank region towards the center of the channel.Key words: barb, channel bends, local scouring, bank erosion, bank protection, secondary currents.
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Li, Kun Peng, Shu Kui Chen, Huai Bao Ma i Ting Wang. "Study of Processes in Shaping High Floodland and Deep-Cut Channel in Xiaolangdi Reservoir". Applied Mechanics and Materials 212-213 (październik 2012): 407–12. http://dx.doi.org/10.4028/www.scientific.net/amm.212-213.407.
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The simulation test on the late sediment storage period in shaping program of high floodland and deep-cut channel on the Xiaolangdi reservoir, and the evolution of high floodland and deep-cut channel, for the Xiaolangdi reservoir sediment retaining period reasonable reservoir operation mode, provide reference for reservoir extending service life.The study shows that:①Formation of High floodland and deep-cut channel evolution, which based on the beach sediment uplift and slot synchronization channel and then washed down the process, whether the erosion and scour quantity to whether can form high floodland and deep-cut channel topography is essential;②The tributary of the riverbed is equivalent to extending transversely, tributary river sedimentation process and topographic condition and tributary junction of the main river deposition pattern and process and other factors are closely related, tributary cross-sectional deposition morphology is mostly parallel to the raising tendency, department branch flow entrance there was a sandbar;③the reservoir during the flood period rainfall scouring camera, in favor of hyperconcentrated flow is generated, to a certain extent, recovery tank capacity, play long term use of reservoir.
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Gutt, Julian, i Vladimir M. Koltun. "Sponges of the Lazarev and Weddell Sea, Antarctica: explanations for their patchy occurrence". Antarctic Science 7, nr 3 (wrzesień 1995): 227–34. http://dx.doi.org/10.1017/s0954102095000320.
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Seventy-three sponge species were caught at 23 stations on the continental shelf of the Lazarev and Weddell Sea (Atlantic sector of the Southern Ocean). Tedania tantula was the most often found species amongst the 63 demosponge species caught and among the five hexactinellid species Rossella racovitzae was most common. The stations were classified according to their species inventory, and so the individual stations of the resulting four groups were rather uniformly dispersed over the entire investigation area. The species composition of adjacent stations varied considerably. There was no discernible relationship between the biological set of data and any combination of the available environmental characteristics of the stations. The sponge fauna of the, so far very poorly investigated, Lazarev Sea did not differ considerably from that of the adjacent Weddell Sea. The only species to be recorded for the first time on the Antarctic continental shelf were Homaxinella flagelliformis and Hyrtios arenosa. Small scale environmental events such as iceberg scouring, or biological characteristics such as extremely slow growth and budding reproduction are thought to generate the patchy distribution pattern.
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Lu, Wanyun, Jiaqi Sun, Yongxue Liu, Yongchao Liu i Bingxue Zhao. "Seasonal and Intra-Annual Patterns of Sedimentary Evolution in Tidal Flats Impacted by Laver Cultivation along the Central Jiangsu Coast, China". Applied Sciences 9, nr 3 (3.02.2019): 522. http://dx.doi.org/10.3390/app9030522.
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Human activities such as the rapid development of marine aquaculture in the central Jiangsu coast have had a marked impact on the tidal flat morphology. This research focuses on characterizing the spatial expansion of laver cultivation and its influence on the sedimentary evolution of tidal flats in the central Jiangsu coast. First, seasonal digital elevation models (DEMs) were established using 160 satellite images with medium resolution. Then, laver aquaculture regions were extracted from 50 time-series satellite images to calculate the area and analyze the spatial distribution and expansion of these areas. Finally, seasonal and intra-annual sedimentary evolution patterns of both aquaculture and non-aquaculture regions were determined using the constructed DEMs. Our results show that aquaculture regions have gradually expanded to the north and peripheral domains of the entire sand ridge since 1999 and by 2013, the seaward margins of each sandbank developed into dense cultivation regions. Additionally, the aquaculture regions increased from 11.99 km2 to 295.28 km2. The seasonal sedimentary evolution patterns indicate that deposition occurs during the winter and erosion during the summer. Thus, the aquaculture regions experience deposition in certain elevation intervals during the laver growing period and in the non-growing period, alluvial elevation intervals in the aquaculture regions are eroded and erosive ones are deposited in order to maintain the balance between scouring and silting. The sedimentary evolution of each sandbank is heterogeneous due to their different locations and the difference in sediment transport. The intra-annual evolution pattern is characterized by deposition in the high tidal flats and erosion in low ones. Hydrodynamic conditions and laver cultivation dominate partial sedimentary evolution, which gradually shapes the beach surface.
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Sun, Dong Po, Li Da Zhang, Xiao Lei Zhang i Peng Tao Wang. "Numerical Simulation of Flooding Effects on Estuarial Reach after Pier’s Construction". Applied Mechanics and Materials 212-213 (październik 2012): 752–58. http://dx.doi.org/10.4028/www.scientific.net/amm.212-213.752.
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Recent years, there were many piers constructed in tail reach of Yongjiang River. This made river channel in estuarial reach shrank gradually, which in turn influenced the shipping ability of estuarial area. Taking Qingshuipu pier that would be constructed in the left bank of Yongjiang river estuarial reach as an example, a numerical simulation have been done, and resistance parameter had been proved reasonably by author. The flow pattern, backwater height and channel scour-fill intensity near the pier trestle have been studied in different kinds of flood and tidal stencils. In engineering project, the trestle prevents flood from diffusing by dipping into the river. Meanwhile, backwater and deposition occur in the bank, which have impact on flow capacity. If the siltation in the area accumulates, then, point bar could not be scoured adequately in great flood period, which will force mainstream to move towards right bank. Based on the backwater and local scouring and silting situation near the pier trestle, the author puts forward a revised proposal and gains a preferable result. So, reasonable pier arrangement is the important condition for keeping steady and healthy to the tail reach of tidal river.
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LIN, MENG-YU, i LIANG-HSIUNG HUANG. "Vortex shedding from a submerged rectangular obstacle attacked by a solitary wave". Journal of Fluid Mechanics 651 (29.03.2010): 503–18. http://dx.doi.org/10.1017/s0022112010000145.
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This study investigates the two-dimensional flow of a solitary wave that passes over a submerged rectangular obstacle using a Lagrangian-type numerical method. The main purpose is to investigate vortex generation and evolution caused by the obstacle. The numerical method is based on the combination of vortex methods and boundary integral methods using the Helmholtz decomposition. The simulated flow pattern is compared with the experimental measurements in detail, and the overall agreement is reasonably good. A series of simulations were performed with various wave heights to study the effect of wave height on vortex generation and evolution. The relation between the vorticity field and the drag experienced by the obstacle is also discussed. In the presented cases, the effects of the generated vortices are preserved over a long period, and may cause local scouring of the foundation at the lee side of the obstacle. The deformation of the solitary wave is not much affected by the presence of the vortices, but the drag is significantly affected by the vorticity field. An almost linear relationship between the Reynolds number and the maximum magnitude of the drag (positive and negative) is observed.
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Et. al., Kuldeep R. Patel,. "Structural Response Of A Slotted Bridge Pier Under Blast Loading Using Finite Element Analysis". Turkish Journal of Computer and Mathematics Education (TURCOMAT) 12, nr 4 (11.04.2021): 413–22. http://dx.doi.org/10.17762/turcomat.v12i4.522.
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Bridge pier is a crucial part for the transportation in marine structures. Scouring is a major cause for the failure of the pier. slot among the other countermeasures increases the efficiency of scour reduction and minimizes the failure due to scour.as we provide the slot; the strength of the pier reduces compared to the conventional pier. change in reinforcement pattern in slotted bridge pier changes the behavior of the pier under similar loading conditions. blast occurrence has increased in recent times and rehabilitation of a structure and improvement of strength against explosion is necessary in structure. this paper studies the behavior of slotted bridge pier under blast loading and compares theoretical and analytical aspects for the same. Design criteria for blast load according to NCHRP 12-72 are followed to carry out theoretical load response of the pier under blast loading. Analytically the behavior of pier is checked using coupled eulerian lagrangian approach using ABAQUS software. a detailed eulerian domain and slotted pier with reinforcement is assembled in ABAQUS to analyze the behavior of pier under explosion using TNT of 100kg at a scaled distance of 4ft for the period of 0.02seconds. this design gave better result in terms of mitigating effects of blast on slotted bridge pier.
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Guemou, Bouabdellah, Abdelali Seddini i Abderrahmane Nekkache Ghenim. "Scour around Bridge Piers: Numerical Investigations of the Longitudinal Biconcave Pier Shape". Periodica Polytechnica Mechanical Engineering 62, nr 4 (1.08.2018): 298–304. http://dx.doi.org/10.3311/ppme.12263.
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The flow pattern around a bridge pier and the scouring phenomenon are very complicated. The basic mechanism causing local scour is the down-flow at the upstream face of the pier. It is understood that the horseshoe vortex is the key mechanism that leads to the local scour around pier; existing literature revealed that the strength of the down-flow, horseshoe vortex and the wake vortex are greater in the case of square piers compared to circular piers. In this paper we have investigated a new longitudinal biconcave bridge pier shape that reduces better the bed shear stress. For that purpose, a number of numerical simulations have been carried out using a Finite Volume Method (FVM) and for the turbulence model we have chosen the Detached Eddy Simulation (DES) for its capability to capture the rich dynamics of the horseshoe vortex at the upstream junction between the pier and the bed.The present study shows that the new longitudinal biconcave bridge pier shape reduces 10 % to 12 % the bed shear stress at the junction between the pier and the bed in other hand this shape increases the bed shear stress about 20 % but at a distance of D downstream the bridge pier in the flow direction.
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Saikia, Lalit, i Chandan Mahanta. "A Mass Balance Approach in Sediment Budgeting of Large Alluvial Rivers with special emphasis on the Brahmaputra in Assam". Journal of The Indian Association of Sedimentologists 38, nr 2 (31.12.2021): 15–24. http://dx.doi.org/10.51710/jias.v38i2.115.
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Morphology of an alluvial river channel is the consequence of erosion, sediment transport and sedimentation in a river. Sediment budget accounts for the sources, sinks and redistribution pathways of sediments, solutes and nutrients in a unit region over unit time. Human activities are the most important factors that affect the variation in the pattern of river sediment load. This paper discusses sediment budget of a few large rivers by review of literature and estimation of sediment budget of Brahmaputra River in Assam using mass balance approach. An attempt has also been made to discuss human and climatic impact on sediment load of major rivers of the world. Total sediment load in the Brahmaputra River at downstream location (India-Bangladesh border) was estimated to be 814×106 t/year. Considering 10% of sediment load of the Brahmaputra as bed load, suspended sediment load at downstream was estimated to be 733×106 t/year. Tributaries, bank erosion and scouring of river bed were found to contribute 52%, 27% and 21% respectively to sediment load of Brahmaputra at downstream locations. In spite of limitations of the dependable data, future complexity due to climate change impact and hydropower dam initiative in upstream of the River, the study is a simplified approach in sediment budgeting of the Brahmaputra.
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Terry, James P., Priya Kisun, Aminiasi Qareqare i Jyotishma Rajan. "Lagoon degradation and management in Yanuca Channel on the Coral Coast of Fiji". South Pacific Journal of Natural and Applied Sciences 24, nr 1 (2006): 1. http://dx.doi.org/10.1071/sp06001.
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Yanuca Channel is a narrow marine lagoon separating a low limestone island in Cuvu Bay from the south west Viti Levu mainland in Fiji, known as the ?Coral Coast?. Historical air photographs show significant changes in the drainage configuration of the lagoon and local Fijian landowners give accounts of degrading environmental conditions in the lagoon due to sediment infilling. This investigation found several processes were responsible for the aggradation. Large quantities of terrigenous sediments are discharged by streamwaters into the lagoon, as a consequence of the removal of estuarine mangroves and agricultural practices such as burning and grazing in adjacent catchments. A previous outlet into the bay became blocked in the 1980s after inappropriate sand mining and vegetation clearance caused accelerated coastal erosion. The altered lagoon drainage pattern has led to lagoon eutrophication and aggradation. Developed on the island is a large international resort complex; the resort causeway constructed across the lagoon to the island has a significant dam effect, impeding the flow of currents and preventing the periodic scouring of sand from the lagoon floor. Several modern and traditional management options have recently been implemented to improve lagoon conditions, through partnerships between NGOs, traditional landowners and the resort management. These include riparian reforestation and the establishment of marine protected areas to conserve coral reefs.
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Hassan, Waqed H., i Nidaa Ali Shabat. "Numerical Investigation of the Optimum Angle for Open Channel Junction". Civil Engineering Journal 9, nr 5 (1.05.2023): 1121–31. http://dx.doi.org/10.28991/cej-2023-09-05-07.
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Numerous natural and artificial streams, including those for irrigation ditches, wastewater treatment facilities, and conveyance structures for fish movement, have open channel confluences. The flow dynamics at and around the junction are intricate; in particular, immediately downstream of the junction, the flow creates a zone of separation on the inner wall along with secondary recirculation patterns. The structure of this complicated flow depends on several factors, including the flow rates in both channels, the angle of confluence, the geometry of the channels, including the longitudinal slope and bed discordance, the roughness of the boundary, and the intensity of the turbulence. It also has a significant impact on bed erosion, bank scouring, etc. The objective of the current work is to calculate the velocity profile and the separation zone dimensions for four angles (30o, 45o, 60o, and 75o) through the simulation process, and the best angle using a three-dimensional model. This work gives a detailed application of the numerical solution (Finite Volume) via Flow 3D software. Results for two flow discharge ratios, q*=0.250 and q*=0.750 were shown; the numerical model and the experimental results agreed well. The findings are consistent with past research and demonstrate how the main channel flow pattern is affected by changes in the channel crossing angle, as well as how greater separation zones are produced in the main channel when the flow discharge ratio q* (main channel flow divided by total flow) is smaller. Analysis revealed that the separation zone's smallest diameter will be at the 75ocrossing angle. Doi: 10.28991/CEJ-2023-09-05-07 Full Text: PDF
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Valizadeh, Rezvan, Ali Arman i Rasool Ghobadian. "The effect of the pipe angle and protective inclined apron on the scouring and sedimentation pattern around a semi-buried pipe in a 90° mild bend". Ocean Engineering 286 (październik 2023): 115711. http://dx.doi.org/10.1016/j.oceaneng.2023.115711.
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Easterbrook, Don J. "Advance and Retreat of Cordilleran Ice Sheets in Washington, U.S.A." Géographie physique et Quaternaire 46, nr 1 (23.11.2007): 51–68. http://dx.doi.org/10.7202/032888ar.
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ABSTRACT Cordilleran Ice Sheet glaciations show characteristic patterns of advance and retreat, consisting of (1) advance out outwash, (2) glacial scouring, (3) deposition of till, (4) deposition of recessional outwash south of Seattle in the southern Puget Lowland, glaciomarine drift in the northern lowland, and eskers, kames, and small moraines on the Columbia Plateau. Radiocarbon dates show that the Puget and Juan de Fuca lobes advanced and retreated synchronously. The Puget lobe backwasted to Seattle by 13.4-14 ka yrs BP, where the thinning ice floated in seawater northward to Canada by 13 ka yrs BP depositing glaciomarine drift contemporaneously over 18,000 km2. Compelling evidence against the backwasting, calving, terminus model for the origin of the glaciomarine drift includes: 1) abundant 14C dates demonstrate simultaneous deposition of glaciomarine drift over the entire area; 2) stagnant-ice deposits closely related to glaciomarine drift are not consistent with an actively-calving, backwasting terminus; 3) irrefutable evidence for the nonmarine origin of Deming sand shows that Cordilleran ice was absent immediately prior to deposition of the overlying glaciomarine drift. The pattern of events in the northern Puget Lowland includes: 1) glacial loading under 1800 m of ice during the Vashon maximum; 2) rapid glacial thinning and floating of the ice deposited Kulshan glaciomarine drift 12-13 ka yrs BP; 3) emergence and deposition of fluvial Deming sand 11.5 ka yrs BP; 4) resubmer-gence and deposition of Bellingham glaciomarine drift up to -200 m, well beyond global eustatic sea level rise; 5) emergence 10.5-11.5 ka yrs BP and deposition of Sumas outwash on Bellingham glaciomarine drift; 6) Holocene eustatic sea level rise kept pace with isostatic rebound, thus, post-Sumas marine terraces are absent.
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Borgström, Ingmar. "Basal ice temperatures during late Weichselian deglaciation: comparison of landform assemblages in west-central Sweden". Annals of Glaciology 28 (1999): 9–15. http://dx.doi.org/10.3189/172756499781821904.
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AbstractThe mountainous area of west-central Sweden has a varied glacial morphology and three unique landform assemblages appear to mark areas of different basal thermal conditions during the decay of late Weichselian ice. A glacial geomorphological map was constructed through interpretation of aerial photographs at a scale 1:60 000. The relative abundance of landforms interpreted to indicate a frozen bed, a thawed bed, and late-frozen to thawed-bed conditions were used for a first-order reconstruction of the basal temperature pattern of the decaying ice sheet. The features used to outline areas with different temperature regimes during deglaciation are glacial scouring, flutings, eskers, meltwater channels, boulder blankets, Rogen moraines, relict surfaces and thermoerosion features.In the northern part of the area, as well as along most of the water divide to the Atlantic Ocean, the ice was warm-based during deglaciation. Glacially scoured bedrock, fluting/ drumlinization, subglacial eskers and extensive glacial lake sediments characterize the area. In the high mountain area, lateral meltwater channels are short and curve downslope to form chutes or eskers. The basal ice conditions changed from frozen- to thawedbed in a late stage of the late Weichselian cycle in most of the southern part of the area, shown by the Rogen moraines on both sides of the ice divide. However, substantial areas in the eastern and southern low mountains had frozen-bed conditions during the complete late Weichselian. In the high mountains in the north, only the summits were frozen.
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Gutt, Julian. "Some “driving forces” structuring communities of the sublittoral Antarctic macrobenthos". Antarctic Science 12, nr 3 (wrzesień 2000): 297–313. http://dx.doi.org/10.1017/s0954102000000365.
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Community analyses of the macrobenthos living on the Weddell Sea shelf revealed a distinct horizontal patchiness. Within some systematic groups a specific faunistic classification could clearly be defined, e.g. for asterozoans and holothurians. Whilst for fish, only a general zoogeographical pattern was discernible, there were some recognisable relationships to different microhabitats. The extreme differences in the distribution of sponges observed seems to reflect their highly variable biological characteristics. Studies using underwater imaging methods for benthic research have provided strong evidence for the ecological significance of two factors. The first, iceberg scouring, leads to a variety of simultaneous stages of recolonization, which result in an increase in beta-diversity. As a consequence, it is unlikely that regionally a stage approaching a theoretical climax will ever be attained. Secondly, the structural diversity of living substrata provides the basis for an additional variety of epibiotic species. Only weak or non-detectable correlations have been found between benthic assemblages and physical parameters, such as water depth, sediment type, bathymetric features and the abundance of deposited phytodetritus. This indicates a benthic system which is relatively uncoupled from processes in the water column. The combination of stable environmental conditions and disturbances taking place over long periods of time, which are partly a special feature of Antarctica's glacial history, shaped the diversity and faunal composition of the macrobenthos. Consequently, neither Houston's “intermediate-disturbance-hypothesis” nor Sander's “stability-time-hypothesis” can be rejected for this part of the Antarctic ecosystem.
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Perwita, Cholisina Anik, Faridha Aprilia, Sukir Maryanto, Harun Arrasyid i Aqyla Farah Tsabitah. "Hazards Mitigation of Lahar Flows on Semeru Volcano after the 4 December 2021 Eruption Based on PS-InSAR". International Journal of Disaster Management 5, nr 3 (20.03.2023): 193–202. http://dx.doi.org/10.24815/ijdm.v5i3.29098.
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Volcanic eruption is one of the phenomena that can change the volcanic landscape drastically. Monitoring of volcanic edifices after eruptions should be considered to further understand the potential hazards in the future. Satellite monitoring is a reliable technique for assessing deformation in a volcano. InSAR was applied to detect material build-up after the eruption phase of Semeru Volcano in December 2022. As a consequence of the opening crater along with the InSAR result, a lahar product after the eruption was deposited in the southwest direction. Significant deformations were indicated by PS-InSAR near the crater, which was characterized by a LOS displacement of -10 to -40 mm/year, indicating scouring of the pyroclastic material moving down the slope. The accumulation of pyroclastic flows from the abrading process below was detected in the proximal zone of Semeru, as shown by the positive LOS displacement ranging from 10 to 40 mm/year. The field survey conforms to the PS InSAR results, where unconsolidated material, ranging in size from gravel to boulders, piles up approximately 4-5 m in Curah Kobokan. Highly unconsolidated material tends to move easily by water and threaten the surrounding settlements. Overlying PS InSAR and drainage pattern in the flank of Semeru, concluding several locations that have a high-risk potential of being affected by lahar flows are Curah Kobokan, Supiturang Village, Pronojiwo District, then Tulungrejo, Pasropan Village, Pasrujambe District, Lumajang Regency.
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Tu, Wenbo, Xiaoqiang Gu, Xianfeng Ma i Dawei Huang. "Analysis of Lateral Dynamic Response of Caisson Foundation in Layered Clayey Soils considering Scour-Hole Dimensions". Shock and Vibration 2020 (16.10.2020): 1–11. http://dx.doi.org/10.1155/2020/8827498.
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As a cross-sea or river deep-water foundation, it is clear that the caisson foundation will be subjected to significant lateral dynamic loads due to winds or waves and suffer from scouring under its long-term effect. In order to obtain the scour effect on the dynamic response of the foundation, an analytical model describing the scour-hole effect in terms of scour depth, scour width, and slope angle was constructed. Combined with the nonlinear Winkler theory, a method for the dynamic response of the caisson foundation considering the scour-hole dimensions was proposed. Comparisons against the results from the dynamic FEM demonstrate the reliability of this method. The effects of the scour width, slope angle, and scour depth on the dynamic response of the caisson were discussed. The results show that the scour depth affects the dynamic displacement and resonant frequency of the foundation most, whereas the scour width does less and the slope angle does the least; the dynamic response of caisson can be approximated as the case of the slope angle 5° and the scour width 5B when the slope angle is less than 5° and the scour width is greater than 5B, respectively; the effects of scour width and slope angle on the dynamic response of caisson have the similar change pattern in the displacement and resonant frequency when the scour depth is different. However, the effect of amplitude on dynamic response shows a nonlinear increase trend when the scour depth is relatively large.
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Gambi, Maria Cristina, Maurizio Lorenti, Giovanni F. Russo i Maria Beatrice Scipione. "Benthic associations of the shallow hard bottoms off Terra Nova Bay, Ross Sea: zonation, biomass and population structure". Antarctic Science 6, nr 4 (grudzień 1994): 449–62. http://dx.doi.org/10.1017/s0954102094000696.
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Quantitative and semi-quantitative samples of phyto- and zoobenthic organisms were collected by SCUBA diving at five stations along a depth transect from 0.5–16 m on the shallow hard bottoms off Terra Nova Bay, Ross Sea, Antarctica. The benthic associations were dominated by two macroalgal species (Iridaea cordata and Phyllophora antarctica) and by few animal taxa (mainly polychaetes, molluscs and peracarid crustaceans). Distribution at the community and species levels revealed a well-defined zonation pattern as a function of depth, governed mainly by sea ice scouring and melting. Zonation of vagile fauna was also affected by the effects of covering and architecture of the two dominant macroalgae. Species richness and diversity were higher in the Phyllophora-associated community, where habitat complexity and sheltering were higher. The highest faunal abundance (over 82 000 ind.m−2) and biomass (macroalgae and fauna wet weight 2392 g m−2) were recorded at 2 m depth in association with the Iridaea covering, where the harsher environmental conditions select a few taxa. The biomass values, even if underestimates of the whole community standing crop, are among the highest recorded in shallow austral biotopes. An autoecological and demographic analysis of the most abundant animal species revealed for some species (e.g. Laevilitorina antarctica and Paramoera walkeri) a quite complex population structure with up to three size classes, including juveniles. In some species, the cohort of juveniles showed a well-defined depth preference probably related to sheltering by the macroalgae. As a whole, the species analyzed showed various and contrasting reproductive strategies, despite the fact that the environmental conditions along the transect were relatively similar and quite selective.
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Subedi, Abhijit, Suresh Sharma, Anwarul Islam i Niraj Lamichhane. "Quantification of the Effect of Bridge Pier Encasement on Headwater Elevation Using HEC-RAS". Hydrology 6, nr 1 (19.03.2019): 25. http://dx.doi.org/10.3390/hydrology6010025.
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The deterioration of bridge substructure is a serious concern across the United States. The pier encasement is one of the most common practices for repairing and strengthening the bridge substructure. It is a rehabilitation process of existing pile piers during the repair or replacement of the bridge superstructure, which involves enclosing part of an existing pile pier with a polyethylene or PVC pipe large enough to provide at least three inches of concrete cover over the existing pier when filled. However, this process of enclosing pile piers might elevate water level due to increase in pier width, which could be hazardous in high-risk flood zones. Furthermore, it may create an adverse impact on the stability of the bridge due to scouring around the pier foundation. In order to gain knowledge on the backwater effect due to pile encasement, Hydraulic Engineering Center-River Analysis System (HEC-RAS) was used in this research to perform hydraulic simulations near the bridge sites. These simulations were carried out for various channel configurations and pier sizes with a wide range of flows, which resulted into 224 HEC-RAS models in order to investigate the effects of pile pier encasement on the headwater elevation. This study demonstrated that the water elevation measured in the upstream of the bridge showed no-rise condition, especially for wider channel sections with flatter slopes. However, the water elevation at the immediate upstream of the bridge was slightly higher, and the increasing pattern was only noticeable for a smaller channel width (20 ft), and specifically, for increased flow rate. As the area of flow was decreased resulting in increased water surface elevation due to encasement, a generic power equation in the form of Y = aXb was suggested for various channel slopes for the increased water surface elevation (Y) for each percentage decrease in channel area (X).
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Wu, Yang, Qiangling Yao, Baoyang Wu, Hongxin Xie, Liqiang Yu, Yinghu Li i Lujun Wang. "Strength Damage and Acoustic Emission Characteristics of Water-Bearing Coal Pillar Dam Samples from Shangwan Mine, China". Energies 16, nr 4 (8.02.2023): 1692. http://dx.doi.org/10.3390/en16041692.
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Long-term erosion and repeated scouring of water significantly affect the technical properties of coals, which are the essential elements that must be considered in evaluating an underground reservoir coal column dam’s standing sustainability. In the paper, the coal pillar dam body of the 22 layers of coal in the Shangwan Coal Mine is studied (22 represents No. 2 coal seam), and the water content of this coal pillar dam body is simplified into two types of different water content and dry–wet cycle. Through acoustic emission detection technology and energy dissipation analysis method, the internal failure mechanism of coal water action is analyzed. This study revealed three findings. (1) The crest pressure, strain, and resilient modulus in the coal sample were inversely related to the water content along with the dry–wet cycle number, while the drying–wetting cycle process had a certain time effect on the failure to the sample. (2) As the moisture content and the dry–wet cycle times incremented, three features were shown: first, the breakage pattern is the mainly stretching fracture for the coal specimen; second, the number and absolute value of acoustic emission count peaks decrease; third, the RA-AF probability density plot (RA is the ratio of AE Risetime and Amplitude, and AF is the ratio of AE Count and Duration) corresponds more closely to the large-scale destruction characteristics for the coal samples. (3) A higher quantity of wet and dry cycles results in a smoother energy dissipation curve in the compacted and flexible phases of the crack, indicating that this energy is released earlier. The research results can be applied to the long-term sustainability assessment of the dams of coal columns for underground reservoirs and can also serve as valuable content to the excogitation of water-bearing coal column dams under similar engineering conditions.