本文選題：大尺寸模袋砂圍堰 + 軟土地基��； 參考：《華南理工大學》2016年碩士論文

【摘要】：模袋砂圍堰的理論分析、試驗研究遠滯后于工程實踐,工程上迫切需要對模袋砂圍堰相關問題給出更多合理解答。目前關于模袋砂圍堰的文獻屢屢見刊,然而,多局限于單個或者多個模袋充填物力學特性的研究,或模袋砂圍堰施工工藝的介紹,關于模袋砂圍堰穩(wěn)定性的研究,基本都是將模袋砂圍堰等效成均質土,然后采用邊坡穩(wěn)定性分析手段計算其整體穩(wěn)定安全系數(shù)。此法應用于堅硬地基上模袋砂圍堰尚可滿足工程要求,然而,軟土地基上模袋砂圍堰極限狀態(tài)下表現(xiàn)為地基土側向擠出,其本質是地基土的失穩(wěn)破壞,繼續(xù)采用邊坡穩(wěn)定性分析方法已失偏頗。因此,本文從地基承載力問題入手,采用數(shù)值分析手段基于強度折減理論對軟土地基上大尺寸模袋砂圍堰地基穩(wěn)定性展開相關研究。首先,歸納總結了目前模袋砂圍堰在國內外的研究現(xiàn)狀以及該領域尚待研究的問題,并在此基礎提出本文的研究課題及所采用的研究手段。采用大型有限元分析軟件Abaqus建立了天然軟土地基上大尺寸模袋砂圍堰的數(shù)值模型,基于強度折減理論分析了軟土地基上大尺寸模袋砂圍堰的變形特性及穩(wěn)定性規(guī)律,并對比了極限狀態(tài)下天然軟土地基上大、小尺寸模袋砂圍堰地基破壞時的差異表現(xiàn),而后通過敏感性分析,研究了圍堰坡比及地基淤泥層厚度對圍堰地基穩(wěn)定性規(guī)律的影響,得到了一系列結論。依次建立反壓平臺護腳、水泥土攪拌樁加固軟土地基及真空聯(lián)合模袋砂堆載預壓加固軟土地基的數(shù)值分析模型,分析了三種不同加固方法下大尺寸模袋砂圍堰地基的穩(wěn)定性規(guī)律,并得到了相應結論�；跇O限平衡理論,結合大尺寸模袋砂圍堰自身的特點——圍堰截面大,當?shù)鼗l(fā)生整體滑動剪切破壞時,圍堰地基下剛性核寬度小于大尺寸模袋砂圍堰的等效寬度(模袋砂圍堰頂寬跟底寬的平均值)——推導了天然軟土地基上大尺寸模袋砂圍堰地基的極限承載力計算公式。最后,基于彈性地基有限長梁理論推導了軟土地基上大尺寸模袋砂圍堰的模袋最大彎曲拉應力近似解析解的表達式。
[Abstract]:The theoretical analysis and experimental study of the sand cofferdam for moulding bags lag far behind the engineering practice. It is urgent to give more reasonable solutions to the problems related to the sand cofferdam in the mould bag.At present, the literatures on sand cofferdam of moulded bag are frequently published, however, most of them are limited to the study of mechanical properties of single or multiple filling materials, or the introduction of construction technology of sand cofferdam of mould bag, and the study of stability of sand cofferdam with mould bag.The sand cofferdam is basically equivalent to homogeneous soil, and then the overall stability safety factor is calculated by means of slope stability analysis.The application of this method to the sand cofferdam on the hard foundation can meet the engineering requirements. However, the ultimate state of the sand cofferdam on the soft foundation is lateral extrusion of the foundation soil, which is essentially the instability failure of the foundation soil.It is unbiased to continue to use slope stability analysis method.Therefore, starting with the bearing capacity of foundation, this paper studies the stability of large size sand cofferdam foundation on soft soil foundation based on strength reduction theory by means of numerical analysis.Firstly, this paper summarizes the current research situation of the sand cofferdam at home and abroad and the problems that need to be studied in this field, and puts forward the research topics and the research methods adopted in this paper.The numerical model of large size sand cofferdam on natural soft soil foundation is established by using the large finite element analysis software Abaqus. Based on the strength reduction theory, the deformation characteristics and stability of large size sand cofferdam on soft soil foundation are analyzed.The difference between the large and small size sand cofferdam foundation under the limit state is compared, and the influence of the slope ratio of cofferdam and the thickness of silt layer on the stability of cofferdam foundation is studied by sensitivity analysis.A series of conclusions have been drawn.The numerical analysis model of the soft soil foundation strengthened by cement soil mixing pile and the soft soil foundation strengthened by sand load preloading of vacuum combined mold bag is established in turn.The stability law of large size sand cofferdam foundation under three different reinforcement methods is analyzed, and the corresponding conclusions are obtained.Based on the limit equilibrium theory, combined with the characteristics of the large size sand cofferdam in the mold bag, the cofferdam has a large section, when the whole sliding shear failure occurs on the foundation,The width of rigid core under cofferdam foundation is smaller than the equivalent width of large size sand cofferdam (the average width of top width and bottom width of sand cofferdam). The formula of ultimate bearing capacity of large size sand cofferdam foundation on natural soft soil foundation is derived.Finally, based on the theory of finite long beam on elastic foundation, the approximate analytical solution of the maximum bending tensile stress of large size sand cofferdam on soft soil foundation is derived.
【學位授予單位】：華南理工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TV551.3

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