【摘要】：吹砂圍堰是以"模袋砂"為防護(hù)邊坡,堤心采用水力吹填海砂的方式而建成一種人造圍堰形式。作為一種新型的施工技術(shù),吹砂圍堰由于施工周期短、工程造價(jià)底、取材方便、環(huán)境污染小等優(yōu)點(diǎn),正在被廣泛的應(yīng)用在江、河、湖、海的圍堰工程建設(shè)中。近年來,許多工程嘗試性的將吹砂圍堰作為現(xiàn)澆結(jié)構(gòu)橋梁支架的人造地基。但是,其承載能力及變形性能能否滿足要求還鮮有人研究。論文以唐山市納潮河2#大橋?yàn)楣こ桃劳?研究了模袋砂的增強(qiáng)機(jī)理,運(yùn)用ANSYS軟件建立圍堰有限元模型,分析了在支架和上部結(jié)構(gòu)作用下圍堰的變形性能,并分析了不同施工階段圍堰沉降對主梁受力性能的影響。首先,通過理論分析研究了模袋砂的增強(qiáng)機(jī)理,提出了在不同埋深條件下模袋內(nèi)填充砂的等效粘聚力計(jì)算公式;推導(dǎo)出模袋砂在自重和填充內(nèi)壓作用下的形狀公式;分析圍堰護(hù)坡頂寬度、單個(gè)管袋高度、邊坡坡度和邊坡高度等對圍堰砂袋擠出穩(wěn)定性的影響。其次,運(yùn)用有限元軟件建立單個(gè)充砂袋的有限元模型,分析了在自重及外荷載作用下砂袋內(nèi)填充砂的應(yīng)力和應(yīng)變分布規(guī)律;并通過建立圍堰有限元模型,研究了在不同厚度的混凝土板和鋼墊梁剛度條件下圍堰的豎向、橫向變形規(guī)律;根據(jù)橋梁實(shí)際施工方式,分別計(jì)算圍堰沉降在主梁澆筑時(shí)、早齡期階段對截面開裂影響,并分析早期沉降引起線形誤差對結(jié)構(gòu)后期受力影響,根據(jù)計(jì)算結(jié)果對施工階段提出合理建議。最后,通過對圍堰沉降實(shí)測值的分析發(fā)現(xiàn),圍堰早期沉降快,沉降穩(wěn)定周期長,主要表現(xiàn)為前200天圍堰沉降基本達(dá)到最終沉降值的90%;在200～900天之間圍堰沉降還在緩慢發(fā)展,900天以后圍堰沉降基本穩(wěn)定;通過對圍堰兩側(cè)和圍堰中間沉降觀測數(shù)據(jù)對比發(fā)現(xiàn),圍堰中間早期沉降速率小于兩側(cè)沉降速率,但是后期沉降速率略大于圍堰兩側(cè)沉降速率,這主要是因?yàn)閲咧醒肱潘畻l件較差,固結(jié)沉降發(fā)展較緩。吹砂圍堰在納潮河2#橋南北兩岸淺水區(qū)引橋施工中,通過清除淤泥和布置如安排等措施,有效的降低了圍堰沉降并提高了圍堰安全性,取得良好的應(yīng)用效果,可以為以后類似工程提供借鑒。
[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.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：U445.57

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