吹砂围堰对现浇桥梁施工和受力性能影响研究

发布时间：2019-01-29 19:16

【摘要】：吹砂围堰是以"模袋砂"为防护边坡,堤心采用水力吹填海砂的方式而建成一种人造围堰形式。作为一种新型的施工技术,吹砂围堰由于施工周期短、工程造价底、取材方便、环境污染小等优点,正在被广泛的应用在江、河、湖、海的围堰工程建设中。近年来,许多工程尝试性的将吹砂围堰作为现浇结构桥梁支架的人造地基。但是,其承载能力及变形性能能否满足要求还鲜有人研究。论文以唐山市纳潮河2#大桥为工程依托,研究了模袋砂的增强机理,运用ANSYS软件建立围堰有限元模型,分析了在支架和上部结构作用下围堰的变形性能,并分析了不同施工阶段围堰沉降对主梁受力性能的影响。首先,通过理论分析研究了模袋砂的增强机理,提出了在不同埋深条件下模袋内填充砂的等效粘聚力计算公式;推导出模袋砂在自重和填充内压作用下的形状公式;分析围堰护坡顶宽度、单个管袋高度、边坡坡度和边坡高度等对围堰砂袋挤出稳定性的影响。其次,运用有限元软件建立单个充砂袋的有限元模型,分析了在自重及外荷载作用下砂袋内填充砂的应力和应变分布规律;并通过建立围堰有限元模型,研究了在不同厚度的混凝土板和钢垫梁刚度条件下围堰的竖向、横向变形规律;根据桥梁实际施工方式,分别计算围堰沉降在主梁浇筑时、早龄期阶段对截面开裂影响,并分析早期沉降引起线形误差对结构后期受力影响,根据计算结果对施工阶段提出合理建议。最后,通过对围堰沉降实测值的分析发现,围堰早期沉降快,沉降稳定周期长,主要表现为前200天围堰沉降基本达到最终沉降值的90%;在200～900天之间围堰沉降还在缓慢发展,900天以后围堰沉降基本稳定;通过对围堰两侧和围堰中间沉降观测数据对比发现,围堰中间早期沉降速率小于两侧沉降速率,但是后期沉降速率略大于围堰两侧沉降速率,这主要是因为围堰中央排水条件较差,固结沉降发展较缓。吹砂围堰在纳潮河2#桥南北两岸浅水区引桥施工中,通过清除淤泥和布置如安排等措施,有效的降低了围堰沉降并提高了围堰安全性,取得良好的应用效果,可以为以后类似工程提供借鉴。
[Abstract]:Sand blowing cofferdam is a kind of artificial cofferdam which is constructed by hydraulic sand filling in the core of the embankment. As a new construction technology, sand blowing cofferdam is widely used in the construction of river, lake and sea because of its advantages such as short construction period, low construction cost, convenient material selection and low environmental pollution. In recent years, many projects try to use sand blowing cofferdam as artificial foundation of cast-in-situ bridge support. However, whether its bearing capacity and deformation performance can meet the requirements is rarely studied. Based on the Nanchao2# Bridge in Tangshan City, this paper studies the strengthening mechanism of sand bag, establishes the finite element model of cofferdam with ANSYS software, and analyzes the deformation performance of cofferdam under the action of support and superstructure. The influence of cofferdam settlement at different construction stages on the mechanical behavior of the main beam is analyzed. Firstly, through theoretical analysis, the reinforcement mechanism of mold bag sand is studied, and the equivalent cohesive force calculation formula of mold bag sand under different burial depth is put forward, and the shape formula of mold bag sand under the action of self-weight and filling internal pressure is deduced. The influences of the top width of cofferdam slope protection, the height of single pipe bag, slope gradient and slope height on the extrusion stability of cofferdam sand bag are analyzed. Secondly, the finite element model of a single sand-filled bag is established by using the finite element software, and the distribution of stress and strain in the sand-filled sand-bag under the action of deadweight and external load is analyzed. By establishing the finite element model of cofferdam, the vertical and transverse deformation of cofferdam under the condition of different thickness concrete slab and steel cushion beam stiffness is studied. According to the actual construction mode of the bridge, the influence of cofferdam settlement on the section cracking in the early age stage of the main girder is calculated respectively, and the influence of the linear error caused by the early settlement on the stress of the structure in the later stage is analyzed. According to the calculation results, reasonable suggestions are put forward for the construction stage. Finally, through the analysis of the measured value of cofferdam settlement, it is found that the early settlement of cofferdam is fast and the stable period of settlement is long, which mainly shows that the settlement of cofferdam reached 90% of the final settlement value in the first 200 days. The settlement of cofferdam is still developing slowly in the period of 200 ~ 900 days, and the settlement of cofferdam is basically stable after 900 days. By comparing the settlement data between the two sides of cofferdam and the middle of cofferdam, it is found that the early settlement rate of cofferdam is smaller than that of both sides of cofferdam, but the late settlement rate is slightly larger than that of both sides of cofferdam. This is mainly due to the poor drainage conditions in the central cofferdam and the slow development of consolidation settlement. During the construction of sand blowing cofferdam in the shallow water area along the north and south sides of Naichao River Bridge, the silt removal and arrangement such as arrangement can effectively reduce the cofferdam settlement, improve the safety of cofferdam, and obtain good application effect. It can be used for reference for similar projects in the future.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U445.57

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