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  3. Investigation of scouring and downstream protection methods of river hydraulic structures (case study of the second bridge of Minab river)

Investigation of scouring and downstream protection methods of river hydraulic structures (case study of the second bridge of Minab river)

Number of pages: 121 File Format: word File Code: 31330
Year: 2013 University Degree: Master's degree Category: Civil Engineering
Tags/Keywords: Flood currents - Hand protection of hydraulic structures - Hydraulic structures - Local scouring - Manual hydraulic structures - River hydraulic structures - scouring - scouring phenomenon
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  • Summary of Investigation of scouring and downstream protection methods of river hydraulic structures (case study of the second bridge of Minab river)

    Master's Thesis: Civil Engineering (M.S.C)

    Trend: Hydraulic Structures

    Abstract

    Minab River is the most important fresh water river in Hormozgan Province. This river is the drainage of the surface waters of the Minab catchment area, and two bridges have been built on it, the first one is the connecting road to Minab city and the second one is 1500 meters after the first bridge on the Minab-Jask ring road. The subject of this research is to investigate scouring phenomenon on the foundations of the second bridge of Minab. The effect of scour on water structures including bridges is one of the important topics in civil engineering and river engineering, bridges are one of the oldest engineering structures. One of the most important factors in the destruction of bridges is the problem of local erosion around its foundations. This type of erosion can be identified by the cavity that forms around the structure. If this hole expands in depth, it can cause damage and eventually collapse of the bridge. In order to accurately investigate the flow and predict the local scour around the bridge piers, it is necessary to understand the flow pattern around the piers. By fully understanding the flow, the flow field can be modeled completely by solving the governing equations, and along with solving the sediment transport equations and relying on significant advances in Computational Fluid Dynamics (CFD) [1], an accurate method can be obtained to estimate local erosion around these structures. In the upcoming research, the simulation was carried out using Flow-3d software, which is capable of simulating flow turbulence in three dimensions. For this purpose, using the Shallow water model, the characteristics of the flow, including water level, speed, pressure, etc., due to the flow of discharge with a return period of 100 years (2723) were calculated in the range from the beginning of the first bridge to 100 meters downstream of the second bridge of the Minab river. Then, using the Sediment scour model, Figure 3 investigated the scouring process development around the foundations of the second bridge of Minab river. The results show that the most scouring occurs in the third, fourth and fifth foundations. Keywords: local scouring, computational fluid dynamics, Minab river bridge, Flow-3D model. Chapter one

    Introduction

    One of the structures whose destruction has irreparable consequences is bridge foundations. In recent years, the local scouring of bridge foundations during flood flows has caused the destruction of bridges more than other factors, and for this reason, it has been the subject of many researches conducted in the last hundred years, and this issue has occupied the minds of researchers for years. Today, the scientific principles of structural design of bridges are well known. But until now, there is no single theory to estimate the local erosion around the bridge foundations, which is due to the complexity of the erosion problem. According to a complex process, the flow hitting the base turns into a horseshoe vortex and causes the flow to separate from the base and create a rising vortex. Design, calculation and construction of bridge foundations are one of the most important and sensitive stages of a bridge construction project, especially when this bridge is located at the crossing of a river. At this time, the designer must analyze the hydrological and hydraulic information of the area to choose the length and number of openings and the minimum depth of the foundations. One of the most important things that can be mentioned in this regard is the information about the level of erosion of the bed, which if not taken into account, one should witness dangerous consequences, including threatening the stability of the bridge and ultimately its destruction. (Breusers et al., 1991)

    1-1-Necessity and Research Objectives

    Every year, many bridges are destroyed all over the world, the destruction of these bridges is caused by not considering the role of hydraulic factors in the design of bridges. Most of the problems we face after building foundations are due to lack of full and sufficient attention to issues such as predicting the rise of water upstream of the foundations or estimating erosion around the foundations and methods of reducing it. In order to determine the depth of erosion in the vicinity of foundations, it is necessary to know enough about this phenomenon and the flow pattern around it in order to determine a suitable method for estimating the depth of erosion. Normally, three practical methods are used to determine and predict scour depth.. These methods include:

    Physical models

    Using special and equipped equipment, in order to measure the behavior of scour created in the place of foundations

    Mathematical and computer models

    The first and second methods are completely experimental methods and are based on testing and observation. The second method is a precise method that is more suitable for built foundations, and with the help of it, the existing problems are identified and the desired design is protected and strengthened against scouring threats. The main problem in this regard is that the equipment with scouring behavior measurement capabilities used in this method are very expensive and expensive. Therefore, most of the studies and researches carried out are in the form of physical models and the equations related to determining scour depth are also presented based on these models. Using the first method, it is possible to check the behavior and extent of erosion for foundations under construction and built foundations, but unfortunately, the results obtained from physical models are not reasonable and acceptable in most cases, because in this research, many of the complexities of the flow range around the foundations are considered very simple and most of the parameters are spared. (Qiping Yang, 2005)

    Physical scales, flow characteristics and boundary conditions in models Small scale (laboratory conditions) should be extracted from the prototype [1] or real conditions and according to the laws of hydraulic analogy. Geometric similarity is usually necessary for all physical models. On the other hand, the Reynolds similarity for models in which the flow around solid bodies is examined and the Froudi similarity for models including flow with a free surface are important and should be considered. The mentioned simplification and the saving of many parameters in the physical models is due to the fact that in the physical model of scouring around the foundations, it is not possible and practical to consider all the mentioned similarities. This method is basically based on theories and mathematical relationships, so that at first, a mathematical model is prepared by using the relationships related to erosion and the theories presented in relation to hydraulics and erosion of foundations. After this stage and according to the prepared mathematical model, a computer model that can be adapted to different conditions and states of this phenomenon is made. (Richardson et al., 1998)

    In our beloved country of Iran, many bridges are destroyed every year due to the scouring phenomenon and cause great loss of life and money and sometimes irreparable. The statistics of table (1-1) show that despite the improvement and promotion of technical knowledge about the design of bridge structures and the advancement of construction technology, the amount of destruction of bridges has increased. Therefore, it seems necessary to investigate this phenomenon as much as possible in a correct and principled way in order to achieve accurate and acceptable results. Especially, carrying out quantitative research using specialized software and computer models can increase civil engineers' knowledge of this phenomenon and fill the gap in this field. Obviously, the realization of this important will reduce the cost of design, implementation and maintenance of river water structures in similar cases. While providing a suitable platform for similar and other researches.

    The purpose of conducting this research can be divided into two main and sub-parts:

    A- Main objectives: The main purpose of this research is to numerically model the scope of the second bridge of the Minab River and investigate the extent of scouring process development in the foundations of this bridge and provide appropriate solutions to control, reduce and prevent erosion caused by scouring in this scope.

    B- Objectives Sub: After modeling the scope of the second bridge of the Minab river, parameters such as flow level profile, velocity distribution, around the foundations and the river bed will be investigated and evaluated. It is designed to have different methods to solve problems in the field of fluids and hydraulics. In this research, it is assumed that this software has the ability to model erosion in bridge foundations with non-level bed and can predict information related to the hydraulic conditions of flow and sediment on the model.

  • Contents & References of Investigation of scouring and downstream protection methods of river hydraulic structures (case study of the second bridge of Minab river)

    List:

    Abstract

    Chapter One (Generalities of Research)

    1-1-Research Necessity and Objectives- 3

    1-2- Research Hypotheses: 5

    1-3- Research Method- 5

    1-4- Research Structure- 6

    Chapter Two (Overview of Research)

    2-1- Scabies- 8

    2-1-1- Types of scabies in terms of occurrence- 8

    2-1-1-1- General scabies- 8

    2-1-1-2- Contractive scabies- 8

    2-1-1-3- Local scabies- 9

    2-1-2- Types Scouring in terms of sediment transport-10

    2-1-2-1-Clear water scouring-10

    2-1-2-2- Scouring in the state of moving bed (living) 10

    2-1-3- General scouring-13

    2-2- Scouring mechanism around water structures-13

    2-3- Methods of studying and investigating scouring phenomenon- 17

    2-3-1- Theoretical method- 17

    2-3-2- Experimental method- 17

    2-3-3- Numerical method- 18

    2-4- Research background- 19

    2-4-1- Review of laboratory studies conducted in the world and Iran- 19

    2-4-2- An overview of the numerical studies of bridge base scour in the world and Iran during the last few years 27

    2-4-3- An overview of the studies conducted on the Minab river in the past years 31

    Chapter three (Governing equations and their solution method)

    - 3-1- Introduction of Flow-3D software: 33

    3-2- Governing equations Flow: 35 - 3-3 Turbulence modeling by Flow3D software: 38 - 3-4 - Sediment transfer - 42 - Chapter 4 (Materials and Methods) - 4-1 - Introduction of the study area - 49 - 4-1-1 - Introduction of the second bridge of the Minab River: 49 - 4-2 - Morphology of the case span Study of Minab River- 50

    4-3- Geology of Minab River (from Esteghlal Dam to the second bridge of Minab River) 51

    4-4- Hydrology of Minab watershed- 51

    4-5- Estimating water flow at Minab Dam site-52

    4-6- Vegetation of the studied area of ??Minab River- 53

    4-7- Measurement of field and laboratory data required by software models-54

    4-7-1- Preparation of large-scale topographic maps of the studied area 54

    4-7-2- Sampling of river bed and wall sediments 55

    4-7-2-1- Sediment grading test-55

    4-7-2-2- Required equipment 55

    4-7-2-3 Test method- 55

    4-7-3- Determination of roughness coefficient based on the visits and granulation results of bed materials and vegetation- 57

    4-7-4- Characteristics of bed sediments- 57

    4-7-4-1- Average diameter of particles) : 57

    4-7-4-2- Sediment density: 57

    4-7-4-3-Drag coefficient: 57

    4-7-4-4-Porosity: 57

    4-8- Model preparation: 57

    4-8-1-Control section: 57

    4-8-2- Method description: 58

    4-8-3 Shallow water model definition: 58

    4-8-4- CCHE2D model- 59

    4-8-4-1- Required data of CCHE GUI model: 60

    4-8-5- Model calibration- 60

    4-8-6- Entering information into Flow-3D software to prepare Shallow water model: 65

    4-8-6-1- Time: 65

    4-8-6-2- Gravitational force and Shallow water): 66

    4-8-6-3- Fluid physical characteristics, unit system: 66

    4-8-6-4- Model geometry: 66

    4-8-6-5- Meshing: 67

    4-8-6-7- Boundary conditions: 68

    4-8-7- Entering information into Flow3D software to prepare sediment scour model: 69

    4-8-7-1- Time: 69

    4-8-7-2- Gravity force, viscosity, disturbance model and sediment scour: 69

    4-8-7-3- Physical characteristics of fluid, unit system: 70

    4-8-7-4- Meshing: 70

    4-8-7-5- Boundary conditions: 71

    Chapter five (discussion and conclusion)

    5-1- Investigation of flow in the studied area: 73

    5-2- Investigation of velocity distribution, flow pattern and scour around bases 2,1 and 3-76

    5-2-1- Checking the speed distribution and flow pattern- 76

    5-2-2- Checking scouring- 77

    5-2-3- Comparison of the current situation with the model, bases 1 to 3: 79

    5-3- Checking the speed distribution, flow pattern and scouring around bases 4,5 and 6-80

    5-3-1- Checking Velocity distribution and flow pattern- 80

    5-3-2- Erosion survey- 81

    5-3-3- Comparison of the current situation with the model, bases 4 to 6- 83

    5-4- Velocity distribution survey, flow pattern and erosion around bases 7,8,9 and 10- 85

    5-4-1- Velocity distribution and flow pattern analysis- 85

    5-4-2- Examination of scouring- 86

    5-4-3- Comparison of the current situation with57

    4-7-4-3-Drag coefficient: 57

    4-7-4-4-Porosity: 57

    4-8- Model preparation: 57

    4-8-1-Control section: 57

    4-8-2- Method description: 58

    4-8-3 Shallow water model definition: 58

    4-8-4- CCHE2D model- 59

    4-8-4-1- Required data of CCHE GUI model: 60

    4-8-5- Model calibration- 60

    4-8-6- Entering information into Flow-3D software to prepare Shallow water model: 65

    4-8-6-1- Time: 65

    4-8-6-2- Gravitational force and Shallow water): 66

    4-8-6-3- Fluid physical characteristics, unit system: 66

    4-8-6-4- Model geometry: 66

    4-8-6-5- Meshing: 67

    4-8-6-7- Boundary conditions: 68

    4-8-7- Entering information into Flow3D software to prepare the Sediment scour model: 69

    4-8-7-1- Time: 69

    4-8-7-2- Gravity force, viscosity, disturbance model and Sediment scour: 69

    4-8-7-3- Physical characteristics of fluid, unit system: 70

    4-8-7-4- Meshing: 70

    4-8-7-5- Boundary conditions: 71

    Chapter five (discussion and conclusion)

    5-1- Investigating the flow in the studied area: 73

    5-2- Investigating the velocity distribution, flow pattern and scouring around bases 2,1 and 3-76

    5-2-1- Checking the speed distribution and flow pattern- 76

    5-2-2- Checking scouring- 77

    5-2-3- Comparison of the current situation with the model, bases 1 to 3: 79

    5-3- Checking the speed distribution, flow pattern and scouring around bases 4,5 and 6-80

    5-3-1- Checking Velocity distribution and flow pattern- 80

    5-3-2- Erosion investigation- 81

    5-3-3- Comparison of the current situation with the model, foundations 4 to 6- 83

    5-4- Investigation of velocity distribution, flow pattern and erosion around foundations 7,8,9, and 10- 85

    5-4-1- Velocity distribution investigation and flow pattern- 85

    5-4-2- Erosion investigation- 86

    5-4-3- Comparison of the current situation with the model, foundations 7 to 10-88

    5-5- Investigation of velocity distribution, flow pattern and erosion around foundations 10 to 15- 89

    5-5-1- Investigation of velocity distribution and flow pattern- 89

    5-5-2- Erosion investigation, 90

    5-5-3- Comparison of the current situation with the model, foundations 11 to 15-92

    5-6- Investigation of velocity distribution, flow pattern and erosion around foundations 16 to 19-94

    5-6-1- Investigation of velocity distribution and flow pattern- 94

    5-6-2- Scaling investigation- 95

    5-7-Conclusion- 96

    5-8-Suggestions: 97

    Sources:

    Persian sources: 100

    Non-Persian sources: 102

    Source:

    Persian sources :

    Books

    Saifi, A; Najafi, S.; Riahi, H.; (2012). "Fluid dynamics design and modeling and analysis of results in Flow-3D", first edition, Andisheh Sera Publishing House: Tehran. (1384). "Hydraulics of Sediment Transport, Third Edition", Shahid Chamran University of Ahvaz Publications.

    Salehi Neishaburi, A; Nasiri Saleh, F (1387). "Turbulence models and their application in hydraulics". First edition, Water Engineering Research Institute of Tarbiat Modares University: Tehran. Qasemzadeh, F. (2012). "Simulation of hydraulic problems in flowtri-D", first edition, Novavar Publications: Tehran.

    Mahmoudian Shushtri, M. (2007). "Principles of Flow in Open Channels Volume I", Second Edition, Shahid Chamran University Publications: Ahvaz.

    Mahmoudian Shushtri, M. (2007). "Principles of flow in open channels, volume two", second edition, Shahid Chamran University Press: Ahvaz. Thesis: Abadzadeh, A; (2012). "Numerical modeling of scour around the bridge foundation in moving bed conditions with FLOW-3D software", master's thesis, Islamic Azad University, Science and Research Unit, Hormozgan.

    Baghdadi, 2019. Numerical investigation of localized scouring caused by horizontal and submerged jets with Flow 3D model. Master's thesis in Civil Engineering, Tehran University of Science and Research. Jaafarpour, A; (2012). "Organizing and determining the location of river bed and wall protection structures using the CCHE2D model (Case study: Minab Dam downstream)", Master's Thesis, Hormozgan University. The studied area up to the first bridge. Khosravi, Gha; (2011). "Numerical simulation of flow and sedimentation by CCHE2D model (case study: Pichan Road downstream of Minab)", master's thesis, Hormozgan University. The studied area up to the first bridge.

    Rostami, F. (1386). "Numerical study of the sub- and supercritical flow from the dam lake to the Tandab spillway leading to the hydraulic jump pond. Master's thesis, Khajeh Nasiruddin Tosi University of Technology, Faculty of Civil Engineering"

    Kanani, A. (2012). "Prediction of scour around the base of the inclined group using neural network and fuzzy system optimized with genetic algorithm". Master's Thesis in Civil Engineering, Hormozgan University of Science and Research.

    Nazari, Abbas. Master's Thesis, "Controlling and reducing the local scouring of the bridge foundation by using gaps in the group of rectangular foundations with round tips". "Manual of local erosion calculation methods". Sadri, A. (2015). "Final report of basic extraction of sand from Minab river", moderator: Amir Kabir University of Technology, School of Mining, Metallurgy and Petroleum Engineering

    Qurbani, B; Haiderpour, M. (1384). "Control and reduction of local erosion by simultaneous use of slitting and grinding". Report of the inter-university research project, Faculty of Agriculture, Shahrekord University and Isfahan University of Technology

    Deputy Planning and Strategic Supervision of the President, 1390. "Guidelines for calculating local erosion"

    Articles

    Arunghi, H.; Farsadizadeh, D.; Hosseinzadeh Delir, A.; Fakheri Fard, A; (1388). "Determining the dimensions of the rectangular collar to reduce scouring of the bridge foundation," Journal of Water and Soil Science, Volume (19): pages 51 to 64. Arianfar, A. and Shafa'i Bejestan, M. (2008), "Investigation of shear stress distribution in the area of ??split bridge foundations using the FLUENT model," 7th Iranian Hydraulic Conference, Shahid Abbaspur University of Water and Electrical Engineering, Tehran. Hakimzadeh, H. (1387). "3D Numerical Investigation of the Flow Pattern and Shear Stress of the Bed around Conical Foundations," Marine Engineering Journal, Year 6, Number 11, Pages 16 to 24.

    Beheshti, A; Atai Ashtiani, B. (2013). "Floating in smooth water conditions around the base group".

Investigation of scouring and downstream protection methods of river hydraulic structures (case study of the second bridge of Minab river)
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