格型钢板桩结构承载机理及数值计算方法研究

发布时间：2018-06-26 10:31

本文选题：深厚软土地基 + 格型钢板桩　；参考：《天津大学》2016年博士论文

【摘要】：在我国社会、经济发展最活跃的渤海湾沿岸、连云港以南的苏北沿海、长江口、杭州湾、闽江口、珠江口和海南岛西北部等沿岸海域,广泛分布着深厚软弱土地基,给港口与海岸工程建筑物设计带来巨大困难。在软土地基上进行港口与海岸建设是无法回避的问题。采用适合软弱土地基条件的新型海岸工程结构,是目前在软基上建造防波堤和码头的有效手段。格型钢板桩结构由若干单块钢板桩在现场通过锁口连接拼装成圆形、椭圆形或多边形的格体并打入地基后形成,是适用于软弱土地基条件的水工建筑物。然而,相比类似的筒型基础结构,格型钢板桩结构与土之间相互作用更为复杂,承载机理和破坏模式尚不清楚,缺乏可靠的设计与计算方法,限制了格型钢板桩结构的应用。另外,波浪等循环荷载通过堤身、抛石基床和砂质土置换层传递给软土地基的循环应力对软土强度和变形特性的影响及循环荷载作用下软土地基上格型钢板桩防波堤的承载机理、破坏模式和稳定特性等,也是有待解决的问题。本文结合实际工程,以格型钢板桩防波堤和码头为主要研究对象开展一系列的研究工作。主要内容和结论如下:1.针对格型钢板桩结构的几何特性和结构特点,在大型有限元软件ABAQUS上,建立格型钢板桩防波堤结构稳定性及格体环向应力分析的三维静力有限元模型。采用壳体单元模拟薄壁板桩,在相邻板桩之间设置铰接连接器模拟板桩之间的相对转动,并考虑铰接连接器之间的摩擦作用;土体应力应变关系采用Mohr-Coulomb本构模型来模拟,格型钢板桩与其内、外土体之间的滑移、张裂和闭合采用接触面单元模拟。为方便大量数值计算,同时建立不考虑板桩间铰接特性的壳体单元模型和整体的实体单元模型的简化建模方法。并建立格型钢板桩防波堤稳定性分析的有限元加载系数法和码头稳定性分析的有限元强度折减法,以及格体强度有限元分析方法和格内土体剪切变形有限元分析方法。针对工程算例,验证了有限元数值模型对格体环向应力分析以及稳定性分析的准确性。2.针对具体工程算例,系统分析了格型钢板桩防波堤在波浪静力荷载作用下的结构整体位移特性、格仓内土体剪切变形特性、格体内、外土压力分布以及格体环向应力等特性,并研究了格型钢板桩结构在波浪静力作用下的承载机理和破坏模式,为格型钢板桩结构的工程应用和实用设计、计算方法的建立奠定基础。将不考虑板桩之间铰接特性的壳体单元有限元模型和实体单元有限元模型计算结果与考虑板桩之间铰接特性的壳体单元有限元数值模型计算结果进行比较分析,分别探讨格型钢板桩薄壁特性和铰接特性对格型钢板桩防波堤的破坏模式、格仓内土体剪切变形特性、格体内外土压力分布以及格体环向应力等的影响,给出适合实际工程设计的格型钢板桩结构简化建模方法。对格型钢板桩码头开展大量有限元数值模拟,得到格型钢板桩码头的破坏模式,并对格型钢板桩码头的稳定性进行研究。3.对格型钢板桩防波堤数值模型进行模态分析基础上,采用三维弹塑性隐式动力分析步对格型钢板桩结构在波浪循环荷载作用下的整体位移和环向应力等动力响应特性进行分析,建立格型钢板桩防波堤动力稳定性分析方法,并与静力模型结果进行比较,为考虑软土地基循环弱化效应的格型钢板桩结构动力运算奠定基础。4.基于软黏土孔压发展模型和动三轴试验成果,建立了软黏土不排水强度随循环荷载作用次数和动、静应力以及围压水平变化的动力计算模型。基于不排水强度动力计算模型和M-C屈服准则,在大型有限元软件ABAQUS平台上进行二次开发,建立了考虑软土地基不排水强度循环弱化效应的动力有限元法,并对动力有限元法的正确性进行验证。5.基于动力有限元法,建立考虑软土地基循环弱化效应的格型钢板桩结构三维有限元数值分析模型,并建立考虑软基不排水强度循环弱化效应的结构稳定性分析方法。对软土地基在循环荷载下的孔压增长特性、软土不排水强度和变形特性及软土地基上格型钢板桩防波堤结构的承载机理、破坏模式和稳定特性等进行研究,并与静力、拟静力方法计算结果进行对比。6.为方便工程设计人员直接应用,基于有限元分析成果,提出了格型钢板桩防波堤稳定性分析的简化算法。采用有限元方法对无锚板桩码头稳定性计算模型结果进行对比验证,为格型钢板桩码头抗倾稳定性分析的简化设计计算提供依据。针对简化算法适用范围的局限性,建立考虑格型钢板桩码头几何特性、受力机理、转动点位置等因素的极限平衡方法,对抗倾覆稳定性安全系数进行准确计算。结合有限元数值成果并参照现有规范的计算方法,建议了格体内部填料抗剪切变形验算方法,并建立格型钢板桩结构锁口应力验算方法。以上实用设计计算方法具有较高的精度,且相比有限元方法更为简单实用。
[Abstract]:In our country, the most active Bohai bay along the coast of the economy, the coastal waters of North Jiangsu, the Yangtze Estuary, the Hangzhou Bay, the Hangzhou Bay, the Minjiang mouth, the Pearl River mouth and the northwest of Hainan Island are widely distributed in the coastal waters of the south of Lianyungang, and it is very difficult for the design of port and coastal engineering buildings. Construction is an unavoidable problem. It is an effective means to build a new coastal engineering structure suitable for soft ground base conditions. It is an effective means to build a breakwater and a wharf on the soft ground. However, the interaction between the structure and the soil is more complex than the similar cylindrical foundation structure, and the bearing mechanism and failure mode are not clear. The lack of reliable design and calculation methods restrict the application of the structure of the lattice steel sheet pile. In addition, the cyclic loads such as waves pass through. The influence of cyclic stress on soft soil foundation, such as embankment body, riprap bed and sandy soil replacement layer, on soft soil strength and deformation characteristics, and the bearing mechanism, failure mode and stability characteristics of lattice steel sheet pile on soft soil foundation under cyclic loading are also a question to be solved. The main contents and conclusions are as follows: 1. in view of the geometric and structural characteristics of the lattice steel sheet pile structure, on the large finite element software ABAQUS, the three-dimensional static finite element model of the structural stability of the lattice steel sheet pile and the analysis of the circumferential stress of the lattice pile is established. The shell element simulates the thin wall plate pile, and the relative rotation between the plate piles is simulated between the adjacent plate piles, and the friction between the articulated connectors is considered. The stress and strain relationship of the soil is simulated by the Mohr-Coulomb constitutive model. The slip, the crack and the close contact surface between the lattice steel sheet pile and the inner soil and the outer soil are used. In order to facilitate a large number of numerical calculations, the simplified modeling method of the shell element model and the solid element model which does not consider the hinge joint characteristics of the plate pile is established, and the finite element loading coefficient method and the strength reduction method for the stability analysis of the lattice steel sheet pile and the strength reduction method of the stability analysis of the wharf are established, as well as the strength of the lattice. The finite element method of finite element analysis and the finite element analysis method for the shear deformation of the soil soil. According to the engineering example, the finite element numerical model is used to verify the accuracy of the stress analysis of the lattice and the accuracy of the stability analysis.2. for specific engineering examples. The structural overall position of the lattice steel sheet pile breakwater under the action of the wave static load is systematically analyzed. The characteristics of shear deformation, the characteristics of the shear deformation in the silo, the distribution of the internal pressure in the body, the distribution of the outer earth pressure and the cyclic stress of the lattice, and the bearing mechanism and failure mode of the lattice steel sheet pile under the static wave action are studied, which will lay the foundation for the engineering application, the practical design and the establishment of the calculation method for the lattice steel sheet pile structure. The finite element model of the shell element and the finite element model of solid element are compared with the calculation results of the finite element numerical model of the shell element considering the hinge characteristics between the piles and the plate pile, and the failure mode of the lattice steel sheet pile and the hinge characteristics to the breakwater of the lattice pile is discussed respectively. The shear deformation characteristics of soil, the distribution of the internal and external pressure of the body and the ring stress of the lattice, give the simplified modeling method of the lattice steel sheet pile structure suitable for the actual engineering design. A large number of finite element numerical simulation is carried out on the lattice steel sheet pile wharf, and the failure mode of the lattice steel sheet pile wharf is obtained, and the stability of the lattice steel sheet pile wharf is stable. On the basis of the modal analysis of the numerical model of the lattice steel sheet pile breakwater,.3. is used to analyze the dynamic response characteristics of the structural steel sheet pile under the action of wave cyclic loading and the dynamic response characteristics of the lattice steel sheet pile structure under the wave cyclic loading are analyzed, and the dynamic stability analysis of the lattice steel sheet pile is established. In comparison with the static model, the foundation.4. based on the pore pressure development model of soft clay and the dynamic three axis test results are established to calculate the dynamic operation of the lattice steel sheet pile structure with the soft soil cyclic weakening effect. The dynamics of the undrained strength of soft clay with cyclic loading times, dynamic, static stress and confining pressure level are established. Based on the dynamic calculation model of undrained strength and the M-C yield criterion, two times are developed on the ABAQUS platform of large finite element software, and the dynamic finite element method is established to consider the cyclic weakening effect of the undrained strength of the soft soil foundation. The correctness of the dynamic finite element method is verified by the dynamic finite element method based on the dynamic finite element method, and the consideration of the dynamic finite element method is established to consider the dynamic finite element method (.5.). The three-dimensional finite element numerical analysis model of the lattice steel sheet pile structure of soft soil foundation, and the structural stability analysis method considering the cyclic weakening effect of the soft foundation undrained strength, the pore pressure growth characteristic of soft soil foundation under cyclic loading, the undrained strength and deformation characteristics of soft soil and the lattice steel sheet pile on the soft soil foundation The bearing mechanism, failure mode and stability characteristics of the breakwater structure are studied, and compared with the static and pseudo static calculation results,.6. is used for the convenience of engineering designers. Based on the results of the finite element analysis, a simplified algorithm for the stability analysis of the breakwater of the lattice steel sheet pile is proposed. The results of the stability calculation model of the wharf are compared and verified, which provides the basis for the simplified design and calculation of the anti tilt stability analysis of the grid type steel sheet pile wharf. In view of the limitation of the application range of the simplified algorithm, the limit equilibrium method of considering the geometric characteristics, the force mechanism and the position position of the lattice steel plate pile wharf is set up to resist the stability of the overturning stability. The coefficient of sexual safety is calculated accurately. Combining the numerical results of the finite element and the calculation method of the existing specifications, the method of checking the shear deformation of the internal packing of the lattice is proposed, and the method of checking the stress of the lattice plate pile is established. The above practical design method has high accuracy and is simpler and more simple than the finite element method. Use.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：U656

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