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  3. The effect of sacrificial pile with the presence of gap and collar in reducing the depth of local scouring of the bridge foundation

The effect of sacrificial pile with the presence of gap and collar in reducing the depth of local scouring of the bridge foundation

Number of pages: 130 File Format: word File Code: 32537
Year: 2014 University Degree: Master's degree Category: Civil Engineering
Tags/Keywords: bridge - bridge foundation - collar - Decrease depth - gap - Local irrigation - sacrificial candle - scouring
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  • Summary of The effect of sacrificial pile with the presence of gap and collar in reducing the depth of local scouring of the bridge foundation

    Master's Thesis in the field

    Water Engineering - Water Structures

    Abstract:

     

    Effect of culvert with the presence of gap and collar in reducing the depth of local scouring of the bridge foundation

     

     

    One ??of the important issues in hydraulic engineering is the investigation of localized erosion around the bridge foundation. Local scour has the potential to compromise the structural integrity of the bridge foundation, thus causing it to fail when the foundation is weakened. For a safe and cost-effective design, it is necessary to control scour around the base. Local scour around the bridge base occurs due to flow separation and the development of eddies created around the base. Various methods have been proposed to prevent and reduce erosion around the foundation, such as sacrificial pile, collar and gap. By diverting the flow from around the base, these methods reduce the flow and local scouring. In this study, five candles were placed upstream of a single circular base to investigate the effect of the candle. Also, to investigate the collar effect, two circular and square collars with a relative size of 2.5 were used in three positions including on the bed and under the bed (D 0.1 and D 0.4 under the bed) to reduce scouring around the base. In the next step, a gap was created in the base with a length of 8 times the diameter of the base and a width of 0.3 times the diameter of the base, and its performance in reducing scour was checked. Finally, the combined use of these methods was investigated and used to reduce scouring. The results showed that the combination of piles and square collar has a greater effect in reducing scouring depth around single footings and group footings. The combination of piles and gap had a lesser role in reducing scouring depth around single footing. Combining the three methods at the same time did not produce good results. Also, the results showed that in the base group, the square collar of the scouring around the foundations placed in front and the sacrificial pile reduce the scouring around the foundations placed at the back more. style="direction: rtl;">1-1 Overview

    Bridges are among the most vital communication structures. Bridges are mostly built on rivers, so they are considered to be one of the most important and widely used river structures that have been used for a long time. Every year, as a result of floods in rivers, a large number of bridges are destroyed, just when they are most needed (Sanikhani et al., 2017).

    The occurrence of erosion around bridge foundations is one of the main reasons for the destruction of bridges. Thousands of bridges have been destroyed in the last thirty years in the United States, of which 60% were due to erosion. In addition to the loss of life, these destructions have caused millions of dollars in financial damage for the construction and reconstruction of bridges in America, which cost was estimated at 75 million dollars in 1973 and 1.2 billion dollars in 1993. Also, investigations in England showed that 49% of failures were due to scouring (Garcia 2008) [1]. Therefore, for a safe and cost-effective design, it is necessary to control scouring around the base of the bridge (Bag and Bagg, 2013)[2].

    Erosion of the bed and transport of materials separated from it by the scouring flow is called [3]. (Ministry of Energy, publication 549, 2018). The amount of reduction in the level of the bed, compared to the river bed, before the scouring begins, has been called scouring depth (Bag and Bagg, 2013). Since the river bed is eroded due to scouring and this erosion causes the bed to become hollow, it may bring serious risks to the nearby structures. Therefore, it is necessary for hydraulic engineers to be fully familiar with how scouring works (Shafa'i Bejestan, 2013).

    Although scouring has a long history in hydraulic science, due to its specific conditions and complexities, as well as the lack of a suitable relationship that can answer all conditions, it is still of special interest to researchers of hydraulic science and river engineering (Ministry of Power, Publication 549, 2010).

    Bridges cause scouring in rivers for several reasons. First, in order to shorten the length of the bridge, the cross section of the bridge is considered narrower than the river section, which increases the flow speed and shear stress in the bed and causes scouring (scouring due to narrowing [4]) (Ministry of Energy, Publication 260, 2011). Second, due to the presence of the support, a three-dimensional system of eddy currents is produced around them, which causes the grains to be separated from the bed and local washing [5]. This type of scouring is very important due to the complexity of the currents created. If there is general erosion [6] in the river, it will be added to the erosion resulting from the construction of the bridge (

    1-1 Necessity of conducting research

    So far, many studies have been conducted on erosion, and due to the complexity of this phenomenon, researchers are still trying to find new methods to reduce erosion. Therefore, for designing For bridges with a high reliability factor, it is necessary to accurately estimate the maximum scour depth around the bridge base and control it with the help of different methods. In general, there are two basic methods to control scour, non-hydraulic methods that control scour by protecting the bed and hydraulic methods that protect it by diverting the flow around the base (Melville and Sutherland [1], 1989).

    Method Hydraulics is used to change the flow pattern and reduce the intensity of the eddies created around the base. Since the downward flow, the horseshoe eddy and the rising eddy are the most important scouring factors, any factor that can reduce the strength of these three currents can control scouring. So far, more than ten different methods of this category have been proposed in scouring control methods, including creating a gap in the foundation [2], installing a collar [3] around the foundation, installing sacrificial piles [4], submerged blades [5], stringing the foundation [6], etc. (Tafraj Norouz et al., 2012) [7]. The single pier of the bridge is done. If the use of combined methods can reduce scour to a great extent.

    Also, the use of each of the mentioned methods and their combined use in the base group has received less attention, while due to the complexity of the flow pattern around the base group compared to the single base, it is necessary to conduct more studies in this field.

    ABSTRACT

     

    THE EFFECT OF SACRIFICIAL PILE WITH SLOT AND COLLAR ON REDUCTION OF LOCAL SCOUR AROUND BRIDGE PIER

     

    BY

    ZAHRA GHASEMI GAVARTI

     

    One ??of the important issues in hydraulic engineering is inspection of local scour depth around bridge pier. The local scour has the potential to threaten the structural integrity of the bridge pier, therefore it causes failure when the foundation of the pier is weakened. For safe and economic design, scour around the bridge piers is necessary to be controlled. Different methods have been proposed to prevent and reduce the scouring around the bridge piers such as sacrificial piles, collar and slot. These methods bring about reducing the flow intensity and the local scour with diverting the flow around the pier. In this study, for investigating the influence of sacrificial piles, five piles were placed in the upstream of single cylindrical pier. Also, for investigating the influence of collar, a circular and square shape collars, with relative dimension were used in three positions including on and in the bed (0.1D and 0.4D in the bed) to decrease scouring around the pier. In the next step by providing a slot through the pier, with length and width of 8 times and 0.3 times of the pier diameter respectively, the performance of slot in reducing scouring was investigated.

  • Contents & References of The effect of sacrificial pile with the presence of gap and collar in reducing the depth of local scouring of the bridge foundation

    List:

    Chapter One: Introduction

    1-1 General. 2

    1-2 Necessity of conducting research. 4

    1-3 research objectives. 5

    1-4 review of the contents of other chapters 6

    Chapter Two: review of previous researches

    2-1 Introduction. 8

    2-1-1 scrubbing. 9

    2-1-2 types of scouring. 9

    2-1-2-1 general scrubbing (natural). 9

    2-1-2-2 scrubbing due to cross section reduction. 10

    2-1-2-3 local scrubbing. 10

    2-1-3 scrubbing in terms of sediment transport. 11

    2-1-3-1 rinsing in clear water. 12

    2-1-3-2 scrubbing in living bed (containing sediment). 13

    2-1-4 local scouring mechanism in single base. 14

    2-1-5 scouring mechanism in the base group. 16

    2-1-6 separation area of ??flow lines around the bridge base. 18

    2-2 basic scouring. 19

    2-3 methods to reduce abrasion and recommendations 23

    2-3-1 creating a protective cover around the base. 24

    2-3-2 Reducing the power of vortices 24

    2-3-2-1 Sacrificial candle. 25

    2-3-2-2 gap. 27

    2-3-2-3 collar. 29

    2-3-2-4 sunken pages. 32

    2-3-2-5 combined methods. 32

    4-2 basic group. 33

    5-2 Lack of past studies. 35

    Chapter Three: Materials and Methods

    3-1 Introduction. 37

    3-1-1 sacrificial candle 38

    3-1-2 gap. 39

    3-1-3 collar. 41

    3-1-4 basic group. 43

    3-2 Parameters related to scouring of the bridge base. 44

    3-2-1 Flow depth. 44

    3-2-2 current intensity. 45

    3-2-3- Time. 48

    3-2-4 base diameter. 49

    3-2-5 Size of particles and granulation of sediments. 50

    3-3 laboratory equipment 51

    3-3-1 channel or flume. 51

    3-3-2 Metal platforms. 52

    3-3-3 Altimeter. 53

    3-3-4 water supply system. 54

    3-3-5 Electric flow meter. 55

    3-3-6 flow control device. 56

    3-4 test methods. 56

    Chapter Four: Discussion and Results

    4-1 Introduction. 59

    4-2 scouring in single base. 62

    4-3 Comparison of collar performance 63

    4-3-1 The best location of the collar on the base. 63

    4-3-2 collar length size in reducing abrasion. 64

    4-3-3 Comparison of collar shapes in reducing abrasion. 64

    4-4 Comparison of scour reduction methods in a single foundation. 66

    4-5 Comparison of combined methods in single base. 68

    4-6 scours in the base group. 70

    4-6-1 scouring in the binary base group in the flow direction. 70

    4-6-2 scrubbing in the ternary base group in the flow direction. 71

    4-6-3 scrubbing in the double base group perpendicular to the flow direction. 73

    4-6-4 scrubbing in the triple base group perpendicular to the flow direction. 73

    4-7 Comparison of scour reduction methods in state G2. 74

    4-8 Comparison of scour reduction methods in G3 mode. 78

    4-9 Comparison of scour reduction methods in G2V and G3V modes. 82

    4-10 Examining the shape of the scour hole. 84

    4-10-1 shape of scour hole in the presence of a sacrificial pile 85

    4-10-2 Checking the shape of a scour hole in the presence of a square collar. 88

    4-10-3 The shape of the scour hole in the presence of a gap. 90

    4-10-4 The shape of the scour hole in the presence of a circular collar. 91

    4-10-5 shape of the hole in the presence of the sacrificial candle and square collar. 91

    4-10-6 The shape of the hole in the presence of the candlestick and the circular collar. 92

    4-10-7 The shape of the hole in the presence of the sacrificial pile and the gap. 93

    4-10-8 The shape of the hole in the presence of the candle holder, square collar and gap. 93

    4-10-9 The shape of the hole in the presence of the candle holder, the gap and the circular collar. 94

    4-10-10 hole shape in the presence of a rhombic collar. 95

    Chapter Five: Conclusion

    5-1 Summary of results. 97

    5-2 suggestions. 99

    Resources

    Persian sources. 100 English sources. 101

    Appendix

    Dimensional analysis. 106

     

    Abstract and title page in English

     

    Source:

     

    Asadi Perto, A., Iqbalzadeh, A., Javan, M. (2013). "Numerical investigation of the effect of gap on the flow pattern around the bridge foundation", volume 24, number 1, pages 103 to 114, Ab and Khak Journal, University of Tehran. (1381). "Guideline for determining the depth of erosion and methods to deal with it in the area of ??bridge foundations", Ministry of Energy, Publications of the country's management and planning organization, publication 260.

     

    Bahrami, M., Chamani, M. R., Haiderpur, M.(1383) "Scrubbing of the rectangular piers of the bridge's rounded face", First National Congress of Civil Engineering, Sharif Technology, Isfahan University of Technology. (1386). "Guidelines for Erosion and Sedimentation Studies in River Management", Ministry of Energy, Publications of the Country Management and Planning Organization, Publication 383.

    Binam. (1390). "Guidelines for local scour calculation methods", Ministry of Energy, Publications of the Deputy President's Planning and Strategic Supervision, publication 549. Thanikhani, H., Hosseinzadeh Delir, A., Farsadizadeh, D. (2007) "Performance of square collars in reducing scour around bridge foundations", 4th National Congress of Civil Engineering, Tehran, University of Tehran. A. (2016) "Usage of submerged plates to control scour around the foundations of a rectangular bridge with a round nose", volume 45, number 3, pages 301 to 310, Civil Engineering and Mapping Journal, Faculty of Engineering, Tabriz University. (1387) "Improvement of the geometric design of the foundation shape of bridges", volume 1 number 6, pages 15 to 20, Omran, Retrofit and Improvement, Shahid Bahonar University of Kerman. (1390). Sediment transfer hydraulics. Second edition, number of pages: 549, Shahid Chamran University of Ahvaz Publications. Aqli, M., Zamardian, M. (1391). "Effect of collar and cable on scour depth around bridge foundation in river arch", volume 36, number 3, pages 31 to 40, water and soil magazine, University of Tehran.

    Houshmand, D. (1389). "Investigation of the local erosion reduction structure around the bridge foundation" master's thesis, Shiraz University. (2006). "Experimental Investigation of Clear-Water local scour at pill group." Journal of hydraulic engineering., Vol.132, No.10, P.1100-1104.

     

    Alabi, P.D. (2006). Time development of local scour at bridge pier fitted with a collar. MA thesis, University of Saskatchewan, Canada.

     

    Ahmed Mohammed, T., Megat Mohd Noor, M.J., Ghazali, A. H., Yusuf, B., Saed, K. (2006). "Physical modeling of local scouring around bridge piers in erodible bed." Journal of. King Saud Univ, Vol.19, No.11, P.195-207.

     

    Abdelazim, M. N., Gamal, M. M., Yasser, M. A., Amira, A. F. (2009). "Optimal shape of collar to minimize local scour around bridge pier." Thirteenth International Water Technology Conference, Zagazig University, P.1283-1294.

     

    Babaeyan-Koopaei, K., Valentine, E.M. (1999). "Bridge pier scour in self-formed laboratory channels." The XXVIII IAHR Congress. PP.22-27.

     

    Beg, M., Beg, S. (2013). "Scour reduction around bridge pier A Review." International Journal of Engineering Inventions, Vol.2, No.7, PP. 15-7.

     

    Chow, V. T. (1967). Open Channel Hydraulic. Mc Graw.Hill Book Company, ING.

     

    Chang, F.F.M., Karim, M. (1972). "An experimental study of reducing scour around bridge piers using piles. Report.” South Dakota Department of Highways, Pierre, SD, USA.

     

    Chiew, Y.M. (1992). "Scour protection at bridge piers." Journal of Hydraulic engineering., Vol.118, No.11, PP.1260-1269.

     

    Chiew Y.M., Lim, F. H. (2000). "Failure behavior of riprap layer at bridge piers under live-bed conditions." Journal of Hydraulic Engineering., Vol.126, No.1, PP.43–55.

     

    Entesar, A.S. (2013). "Reduction of scour around bridge pier using a modified method for vortex reduction." Alexandria Engineering Journal, Egypt.Vol.52, No.3, P.467-478.

     

    Anonymous (2005). Bridge Scour Manual. Florida Department Of Transportation, 129 P.

     

    Gao, D., Posand, L.G., Nodrin, C.F., (1993). "Peir scour equation used in China." Journal of Hydraulic Engineering, Vol.99, No.40, P.1031-1036.

     

    Garde, R.J., Kothyari, U.C. (1998). "Scour around bridge pier" Journal of Proceedings of the Indian National Academy, Vol.64, No.

The effect of sacrificial pile with the presence of gap and collar in reducing the depth of local scouring of the bridge foundation
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