桩承式半刚性加筋垫层路堤与路基稳定性分析

发布时间：2018-08-21 12:28

【摘要】：本文在现行桩承式半刚性加筋垫层路堤及路基稳定性计算理论与设计方法基础上,通过理论研究、数值分析、工程实例计算比较,对桩承式半刚性加筋垫层路堤的垫层厚度、地基承载力、地基沉降和路基边坡、路基挡土墙稳定性的计算与设计方法进行了较系统的分析与研究。主要工作和创新成果包括：1.建立了综合考虑不同桩径、不同桩间距、不同路基高度、不同筋材强度条件下的垫层厚度计算公式,可替代现行垫层厚度设计依靠经验取值的设计方法,从而提高垫层厚度设计的科学性与经济性。2.在分析桩承式半刚性加筋垫层路堤的力学作用机理与地基承载力影响因素的基础上,视桩承式半刚性加筋垫层路堤地基承载力等于桩体复合地基承载力、加筋垫层作用增加承载力、路基边坡土体压力作用增加承载力三者之和,采用叠加法原理得到了综合考虑基础刚度、桩体模量、桩间土体模量、桩径、桩长、桩距、置换率、垫层厚度、加筋拉力等参数的桩承式半刚性加筋垫层路堤地基承载力的实用计算理论与设计方法。研究结果表明：桩承式半刚性加筋垫层路堤地基承载力随基础刚度的减小、置换率的提高、加筋层数的增加、垫层扩散作用的加强而提高,筋材拉力对提高地基承载力起主要作用。3.推导了粘质土路基稳定性计算中求算相关角值的计算公式,并在此基础上重新编制了精度较高现行角值表,提高了计算精度。找到了软粘土路基某一边坡坡度的各种可能破坏面的最小稳定系数Kmin的解析公式,简化了该类路基边坡稳定性分析与计算过程。4.引入计算粘聚力和计算内摩擦角概念,建立了渗水性土路基稳定性计算与设计的新方法——公式法。公式法反映了路基高度、路基边坡坡度、路基稳定系数、路基土体计算参数之间数值对应关系,简化了渗水性土路基边坡稳定性分析与计算过程。5.通过力学分析,研究了填石路基边坡码砌层的力学作用,分析了填石路基稳定性影响因素,提出了填石路基稳定性计算与设计方法,克服了此类路基现行计算与设计方法的粗糙性与不科学性。6.采用静力平衡分析法,推导了挡土墙土压力非线性分布条件下合力作用点高度、抗倾覆稳定系数新定义计算公式,提出了抗倾覆稳定性计算与设计新方法。该方法计算得到的抗倾覆稳定系数小于现行规范法计算得到的抗倾覆稳定系数,采用不考虑土压力非线性分布的现行规范法进行挡土墙抗倾覆稳定性设计存在安全隐患。7.在挡土墙抗倾覆稳定系数新定义的基础上,建立了考虑地基反力力矩的挡土墙抗倾覆稳定性计算与设计新方法。挡土墙的抗倾覆稳定系数与地基极限承载力有关,地基极限承载力增大,挡土墙的抗倾覆稳定系数增大。该方法计算得到的抗倾覆稳定系数小于现行规范法计算得到的抗倾覆稳定系数,采用不考虑地基反力力矩的现行规范法进行挡土墙抗倾覆稳定性设计同样存在安全隐患。本文提出的桩承式半刚性加筋垫层路堤及路基稳定性的计算与设计方法是对已有相关技术的补充和完善。本文工作取得的计算与设计新方法可以用于指导实际工程的计算与设计。建议工程技术人员在工程实践中采用本文的计算与设计方法进行复核,并在必要时进行调整。
[Abstract]:Based on the current theory and design method of stability calculation of semi-rigid reinforced pile-supported cushion embankment and subgrade, through theoretical research, numerical analysis and comparison of Engineering examples, this paper calculates the thickness of cushion, bearing capacity of foundation, settlement of foundation and slope of subgrade, stability of subgrade retaining wall and so on. The main work and innovations are as follows: 1. The formula for calculating the cushion thickness under different pile diameters, pile spacing, subgrade heights and reinforcement strengths is established, which can replace the design method of cushion thickness depending on experience to improve the cushion thickness. 2. On the basis of analyzing the mechanics mechanism of pile-supported semi-rigid reinforced cushion embankment and the influencing factors of foundation bearing capacity, it is considered that the bearing capacity of pile-supported semi-rigid reinforced cushion embankment is equal to the bearing capacity of pile composite foundation, the reinforced cushion increases the bearing capacity and the soil pressure of embankment slope. The pile-supported semi-rigid reinforced cushion embankment foundation bearing capacity calculation theory and design method are obtained by using the superposition principle, considering the parameters of foundation stiffness, pile modulus, soil modulus between piles, pile diameter, pile length, pile spacing, replacement rate, cushion thickness, reinforcement tension and so on. The bearing capacity of the foundation of the semi-rigid reinforced cushion embankment increases with the decrease of the foundation stiffness, the increase of the replacement rate, the increase of the number of reinforcement layers and the strengthening of the cushion diffusion. The tensile force of the reinforcement plays a major role in improving the bearing capacity of the foundation. 3. The formula for calculating the correlation angle in the calculation of the stability of the clayey soil subgrade is deduced, and on this basis, the weight is increased. A new angle table with higher accuracy is compiled to improve the calculation accuracy. The analytical formula of the minimum stability factor Kmin of various possible failure surfaces of a soft clay roadbed slope is found, which simplifies the stability analysis and calculation process of the roadbed slope. 4. The concepts of calculating cohesion and calculating internal friction angle are introduced, and the seepage soil is established. Formula method is a new method for subgrade stability calculation and design. Formula method reflects the numerical correspondence among subgrade height, subgrade slope gradient, subgrade stability coefficient and subgrade soil calculation parameters. It simplifies the analysis and calculation process of seepage soil subgrade slope stability. 5. Through mechanical analysis, the paper studies the rock fill subgrade slope code masonry layer. The mechanical action of the rock-filled embankment is analyzed. The calculation and design methods of the stability of the rock-filled embankment are put forward. The roughness and unscientificity of the current calculation and design methods of the rock-filled embankment are overcome. A new formula for calculating stability coefficient is defined and a new method for calculating and designing anti-overturning stability is proposed. Hidden danger. 7. Based on the new definition of the stability factor of retaining wall against overturning, a new method for calculating and designing the anti-overturning stability of retaining wall considering the reaction moment of foundation is established. The anti-overturning stability factor of retaining wall is related to the ultimate bearing capacity of foundation, the ultimate bearing capacity of foundation increases, and the anti-overturning stability factor of retaining wall increases. The stability factor of anti-overturning obtained by this method is less than that calculated by the current code method. There are also potential safety hazards in the design of anti-overturning stability of retaining wall by using the current code method without considering the reaction moment of foundation. The calculation and design method for the stability of semi-rigid reinforced cushion embankment and subgrade with pile-supported structure are presented in this paper. The new method of calculation and design obtained in this paper can be used to guide the calculation and design of practical engineering. It is suggested that engineers and technicians should review the calculation and design method in engineering practice and adjust it if necessary.
【学位授予单位】：长沙理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U416.1

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