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Effects of hooked-collar on the local scour around a lenticular bridge pier

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International Journal of Sediment Research 2023年第1期38卷 1-11页

作者： Rashid Farooq Amir Hossein Azimi Muhammad Atiq Ur Rehman Tariq Afzal Ahmed Department of Civil Engineering International Islamic University Department of Civil Engineering Lakehead University College of Engineering and Science Victoria University Department of Civil Engineering University of Engineering and Technology James Watt School of Engineering University of Glasgow

This paper presents the results of comprehensive laboratory experiments to investigate the effects of hooked-collar on the scour development around a vertical pier with a lenticular cross section. The flow around the pier was uniform, steady, and under the clear-water condition. The axial scour profiles for cases without and with a lenticular hooked-collar were measured and the effects of hooked-collar dimensions and elevation from the bed were examined. To compute the efficiency of hooked-collar for scour prevention, the results of local scour for a bridge pier without a collar and a bridge pier with a plain collar, without a hooked wall, were used as benchmark data sets. A wide range of hooked-collar geometries such as the ratio of collar width to the pier width, Wc/Wp, ranging from 1.5 to 3.5, the ratio of hooked-collar wall height to the pier width, Hc/Wp, ranging from 0.15 to 0.6, and the ratio of collar elevation to the pier width, Ec/Wp, of-0.5, 0, and 0.5 were tested. The experimental results indicated that the equilibrium scour depth decreased with the ratio of hooked-collar to the pier width when Wcis twice the pier width, Wp. For Wc/Wp> 2, the scour depth was similar to the tests with an infinitely large pier width. In addition, the scour depth consistently reduced as the hooked-collar wall height, Hc, to the pier width, Wp, approached 0.3. The highest scour reduction efficiency was achieved when the hooked-collar being placed on the bed surface. Empirical models were developed for prediction of maximum scour depth near the lenticular bridge pier with a modified collar. The results showed that the volume of scour hole around a lenticular pier increased non-linearly with the maximum scour depth and it was independent of the hooked-collar geometry.

关键词： Local scour Erosion collar Hooked-collar Lenticular pier Scour countermeasure Steady flow

Partially decoupling and collar bonding of the encapsulated rebar rockbolts to improve their performance in seismic prone deep underground excavations

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International Journal of Mining Science and Technology 2019年第3期29卷 409-418页

作者： Reza Masoudi Mostafa Sharifzadeh Masoud Ghorbani Department of Mining & Metallurgical Engineering Curtin UniversityWestern Australian School of Mines (WASM)Australia Department of Mining Metallurgy and Petroleum EngineeringAmirkabir University of Technology (Tehran Polytechnic)TehranIran

Rockbolt is widely employed all over the world as an effective ground reinforcement element in order to secure the underground workplaces.Ordinary encapsulated rebar or rebar rockbolt is most popular and commonly used as reinforcement in a ground support system because of its accessibility,cost effectiveness and easy practicability.Reinforcement elements in a seismic condition such as rock burst have to dissipate the energy release of the dynamic impact via their deformation and ultimate load capacity,knowing that the former is more important.In other words,achieving early stiff behaviour along with large deformation capacity in rockbolts are the goals for new development in rock reinforcement.Yielding rockbolts are expensive while some of them have large deformation capability with low ultimate load capacity.In this paper,modifications were made on encapsulation of rebar rockbolts to utilise it effectively as a yielding reinforcement in seismic conditions.Applying a sufficient decoupled length in the shank of rebar rockbolts which industry has regularly been using to control the bulking of the stress fractured ground,improves the deformation capacity of the bolt.Additionally,leaving a collar bonding underneath of the bearing pad and plate removes the weaknesses of the head anchorage of rockbolt.Therefore the dynamic performance of the bolt is improved by these easily applicable modifications.The behaviour and performance of encapsulated rockbolts have been discussed first,then the effects of modifications are illustrated.The proposed modification of the rebars is not only cost effective but also easy to apply in the field and improves the performance of reinforcements in seismic prone zones.

关键词： Rockbolt Tunnel support collar bonding Seismic rock support Tunnelling

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Analytical solution of electromagnetic field generated by induction logging tool in a fan-ring slot of drill collar while drilling

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Science China(Technological Sciences) 2009年第7期52卷 2128-2137页

作者： LIU FuPing WANG AnLing YANG ChangChun Beijing Institute of Graphic Communication Beijing 102600China Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China

Based on the structural characteristic of metal drill collar for induction logging while drilling, we have given the analytical formulae of lengthways fields Ez and Hz when the tool is located in a fan-ring shaped slot of drill collar by the boundary conditions of electromagnetic field, and derived the other components of electromagnetic field in and out the fan-ring slot from Ez and Hz. In the other intervals of formation, where the drill collar is a solid cylinder, the analytical formulae of field are educed through the method of variable coefficient. The total analytical solutions of field in whole space have been obtained. With the help of the analytical formulae, we have also given numerical examples and analyzed the distributive characteristic of electromagnetic field. From the computational results we find that the secondary scattering field Hz is in a linear relation with the conductivity of stratum. The characteristic of field is very useful for induction logging while drilling, which can be used to measure and analyze the logging responses of the stratum conductivity. This paper sets up a theoretical foundation for us to study the distrbutions of field and to direct the design of logging instruments.

关键词： drill collar logging while drilling induction logging while drilling fan-ring shaped slot

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Reduction of local scour at river confluences using a collar

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International Journal of Sediment Research 2017年第3期32卷 364-372页

作者： Nargess Amini Behnam Balouchi Mahmood Shafai Bejestan Department of Civil Geological and Mining Engineering Ecole polytechnique de Montréal Department of Hydraulic Structure School of Water Engineering Shahid Chaman University of Ahvaz Department of Water and Environmental Engineering School of Civil Engineering Shiraz University

River confluences(RCs) are important features within river systems where the three dimensional(3 D)flow structures and the downstream mixing of flows can cause deep scour holes. Despite this, few methods have been proposed to control scouring at RCs. In this study, application of a collar was experimentally examined for local scour control at the point where two rivers flow together. In particular, experimental tests were done with and without collar application at three different locations. The results reveal that the scour depth is directly proportional to the discharge ratio, i.e. the ratio of lateral discharge to that in the channel downstream of the confluence, and the densimetric Froude number(Frg).In addition, installation of a collar at RCs can decrease the scour depth up to 100%, thus completely avoiding the scour process. The results also show that by increasing the Frg the optimal installation location for a collar changes and moves towards the river bed level. Using a collar can also reduce the height of the point bar formed downstream of the confluence. The outcomes of the study allow derivation of an equation for predicting scour depth when a collar is applied as a countermeasure. The analysis of this equation shows that the estimates are mostly affected by the Frg.

关键词： Scour River confluence Discharge ratio Densimetric Froude number collar

Simultaneous use of cable and collar to prevent local scouring around bridge pier

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International Journal of Sediment Research 2012年第3期27卷 394-401页

作者： Elham IZADINIA Manouchehr HEIDARPOUR Department of Water Engineering Agricultural CollegeIsfahan University of Technology

Various methods to control scour around bridge piers have been proposed.In the present study the application of cable or collar and a combination of cable and collar were examined experimentally,as countermeasures against local scouring at a smooth circular bridge pier,close to threshold flow conditions of initiation of uniform sediment motion.The results show that the simultaneous use of cable and collar has high efficiency in reducing the scour depth.The best configuration was found for a cable-pier diameter ratio of 0.15 and thread angle of 15°,in which the scour depth in upstream of the pier reduced to about 53%.In the case of a pier protected with cable and collar the scouring postponed more than pier protected with collar and the rate of scouring is less than in pier protected with collar.These advantages can reduce the risk of pier failure when the duration of flood is short. The results indicate that the scour reduction increases as the cable diameter increased and the thread angle decreased.

关键词： Scour Bridge Pier collar Cable

Scour countermeasures for cylindrical piers using riprap and combination of collar and riprap

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International Journal of Sediment Research 2010年第3期25卷 313-321页

作者： Amir R. ZARRATI Mohammad R. CHAMANI Abolfazl SHAFAIE Milad LATIFI Dept. of Civil and Environmental Engineering Amirkabir University of Technology Dept. of Civil Engineering Isfahan University of Technology Dept. Civil Engineering Isfahan University of Technology

Various methods are proposed to control scouring around bridge piers. In the present study application of riprap alone and combinations of riprap and collar were examined experimentally for scour control around cylindrical bridge piers. Tests were conducted with seven riprap sizes and with two different sizes of collars. Empirical equations were developed for stable riprap diameter for two cases of piers with and without collar protection. Extent of riprap layer is also presented for these two cases. The results showed that in the range of b/dR≤7.5 (where b is pier diameter and dR is riprap size) using a collar reduced the stable riprap size. It was also concluded that using collar reduced the riprap layer extension in front and sides of the pier.

关键词： Scour Countermeasures Cylindrical Piers collar Riprap

Study on the Application of Turndown collar Pattern

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Journal of Donghua University(English Edition) 2001年第2期18卷 116-118页

作者：张祖芳尚笑梅 Fashion Inst. Dong Hua Univ. Shanghai 200051 China

The relation between lining collar and face collar in the collar pattern designed by experiments and theoretical calculation is elucidated. In spite of the same constructions, the collar's shape and the fabric's thickness influence on the pattern of lining collar and the face collar, especially on the back center of the Iining and the two collar angles. The thicker the fabric, the more, with a proportional relation, the total variation. It is supposed that this work has made some contribution to the collar pattern design.

关键词： lining collar face collar fold line basic ease of turndown collar variation in the back center variation in the collar angle.

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Experimental study on local scour around single oblong pier fitted with a collar in a 180 degree flume bend

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International Journal of Sediment Research 2010年第3期25卷 304-312页

作者： Alireza MASJEDI Mahmood SHAFaEI BEJESTAN Abdolkarim ESFANDI Islamic Azad University Ahwaz Branch Shahid Chamran University Khuzestan Science and Research Branch Islamic Azad University

In this work, investigation on the development of local scour around an oblong pier in a 180 degree flume bend is presented. Scour hole can cause failure of the bridge especially during the river floods. In this study, the use of oblong collars for reducing the effects of local scour at a bridge pier is presented together with the time aspect of the scour development. Tests were conducted using one oblong pier in positions of 60degree under one flow conditions. The study was conducted using a physical hydraulic model operated under clear-water conditions in cohesionless bed material. In this study, the time development of the local scour around the oblong pier fitted with and without collar plates was studied. Investigated was the effect of size and elevation collar on the time development of scour and its efficacy at preventing scour at a bridge pier. The time development of the scour hole around the model pier with and without a collar installed was compared with similar studies on bridge piers. The results of the model study indicated that the maximum depth of scour is highly dependent on the experimental duration. It was observed that, as the minimum depth of scour occurs for the square collar at width of 3B placed at elevation of 0.1B below the bed and the size of a collar plate increases, the scour decreases. Measuring depth of scouring based on experimental observation, an empirical relation is developed with regression coefficient 95%.

关键词： Oblong pier Scour depth Time development collar 180 degree bend

Precipitation behavior of P550 steel for non-magnetic drill collars during isothermal aging at 650–900℃

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Journal of Iron and Steel Research(International) 2022年第4期29卷 636-646页

作者： Li-wei Xu Huai-bei Zheng Hua-bing Li Zhou-hua Jiang Shu-cai Zhang Jiang-tao Yu Hao Feng Yue Lin School of Metallurgy Northeastern UniversityShenyang 110819LiaoningChina State Key Laboratory of Metal Material for Marine Equipment and Application Anshan 114002LiaoningChina

Precipitation behavior of P550 steel for non-magnetic drill collars was investigated by microstructure characterization as well as thermodynamic calculation.The results demonstrate that the main precipitate formed at 650–900℃was cellular Cr_(2)N,and its precipitation depended heavily on the aging temperature.The most sensitive precipitation temperature of cellular Cr_(2)N was 750℃.At 750℃,the cellular Cr_(2)N exhibited fast-slow precipitation kinetics with the aging time prolonging.The initial precipitation of cellular Cr_(2)N was governed by the short-range intergranular diffusion of Cr.During long-term aging,its growth was controlled by the long-range bulk diffusion of Cr.In addition,cellular Cr_(2)N induced the precipitation of r phase ahead of the cell after long period of aging.Increasing the nitrogen content resulted in the increment of both the nucleation site and the driving force for the cellular Cr_(2)N,which jointly promoted its precipitation.

关键词： P550 steel Non-magnetic drill collar Precipitation behavior Cellular Cr_(2)N r Phase Nitrogen