【摘要】：橋墩沖刷是橋梁水毀的主要原因之一。橋墩沖刷不但受許多因素影響,而且橋墩周圍水流結(jié)構(gòu)也很復(fù)雜。下降水流、橋墩兩側(cè)的馬蹄形漩渦、橋墩尾部的尾流漩渦、橋墩兩側(cè)和橋墩墩后由床面附近釋放的小漩渦,這幾種漩渦體系組成了橋墩周圍復(fù)雜的水流結(jié)構(gòu)。雖然國內(nèi)外很多專家對(duì)橋墩沖刷進(jìn)行了大量試驗(yàn)和分析,但是對(duì)于橋墩沖刷的防護(hù)仍處于探索階段,傳統(tǒng)的橋墩防護(hù)方法都是被動(dòng)的抵抗橋墩的沖刷,本文研究的是一種可以安裝在橋墩上的新型防沖結(jié)構(gòu),其名字為“環(huán)翼式防沖板”,環(huán)翼式防沖板是主動(dòng)降低下降水流對(duì)橋墩的沖刷,從而達(dá)到防護(hù)目的。 本試驗(yàn)是在三種流量、不同防沖板類型組合的工況下,量測(cè)最大沖坑深度及各測(cè)點(diǎn)三維瞬時(shí)流速。通過分析最大沖坑深度、橋墩周圍三維時(shí)均流速及三維相對(duì)紊動(dòng)強(qiáng)度,得出最佳防沖板類型及環(huán)翼式防沖板最大沖坑深度計(jì)算公式。主要研究成果包括： (1)對(duì)于2-2斷面,隨著水深不斷變化,半幅比整幅防沖板的時(shí)均縱向流速變化范圍大；’設(shè)置防沖板之后,時(shí)均橫向流速在2測(cè)線0.3倍水深處有極值。設(shè)置防沖板明顯減小了靠近河床底部的垂向流速。設(shè)置防沖板之后整體橫向相對(duì)紊動(dòng)強(qiáng)度大于無防沖板工況。 (2)對(duì)于5-5斷面,設(shè)置防沖板前后縱向流速分布形狀相似。整幅防沖板和半幅防沖板的縱向相對(duì)紊動(dòng)強(qiáng)度減小程度相差不大。整幅防沖板所在位置以下測(cè)點(diǎn)的垂向相對(duì)紊動(dòng)強(qiáng)度大于半幅防沖板。 (3)整幅防沖板與半幅防沖板對(duì)各斷面2測(cè)線的三維時(shí)均流速影響效果幾乎相同。 (4)環(huán)翼式防沖板為半幅時(shí)的防沖刷效果比整幅好,環(huán)翼式防沖板長(zhǎng)軸和短軸越大,防沖刷效果越好,其中長(zhǎng)軸a是主要影響因素。 (5)根據(jù)實(shí)測(cè)數(shù)據(jù),得出半幅環(huán)翼式防沖板最大沖坑深度擬合公式
[Abstract]:The bridge pier scour is one of the main reasons of bridge water destruction. The scour of pier is not only affected by many factors, but also the structure of flow around pier is very complex. The downward flow, the horseshoe vortex on both sides of the pier, the wake vortex at the tail of the pier, and the small vortex released from the side of the pier and behind the pier from near the bed surface constitute the complex flow structure around the pier. Although many experts at home and abroad have carried out a lot of tests and analyses on the scour of the pier, the protection of the scour of the pier is still in the exploratory stage, and the traditional protection method of the pier is to resist the scour of the pier passively. In this paper, a new type of anti-scour structure which can be installed on the pier is studied, which is called "ring wing type anti-scour plate". The annular wing type anti-scour plate is active to reduce the erosion of bridge pier by descending current, thus achieving the purpose of protection. Under the conditions of three kinds of flow rate and different types of anti-scour plate, the maximum depth of scour pit and the 3D instantaneous velocity of each measuring point are measured. Based on the analysis of maximum scour depth, 3D mean velocity around pier and relative turbulent intensity, the formula for calculating the optimum type of anti-scour plate and the maximum crater depth of annular wing anti-scour plate is obtained. The main research results are as follows: (1) for 2-2 section, with the constant change of water depth, the time average longitudinal velocity of half amplitude is larger than that of the whole plate; After setting the anti-punching plate, the average transverse velocity has extreme value in the depth of 0.3 times water of the 2 measuring line. The vertical velocity near the bottom of the river bed is obviously reduced by setting the anti-scour plate. The relative turbulent intensity of the whole transverse is higher than that of the non-punching plate after the anti-punching plate is set. (2) for section 5-5, the shape of longitudinal velocity distribution is similar before and after the anti-punching plate is installed. The longitudinal relative turbulence intensity of the whole plate and the half plate is not different. The vertical relative turbulence intensity of the whole plate is higher than that of the half plate. (3) the effect of the whole plate and the half plate on the 3-D mean velocity of each section 2 line is almost the same. (4) the anti-scour effect of the annular wing plate is better than that of the whole plate, and the larger the long axis and the short axis, the better the scour prevention effect, in which the long axis a is the main influencing factor. (5) based on the measured data, a fitting formula for the maximum depth of the scour hole of the half-amplitude annular flange plate is obtained.
【學(xué)位授予單位】：內(nèi)蒙古農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：U442.32;U443.22

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本文編號(hào)：2376823