【作者基本信息】 长沙理工大学, 道路与铁道工程, 2015, 博士
【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】This paper is based on the calculation theory and design method of pile supported embankment with semi-rigid reinforced cushion and subgrade stability.Then, the cushion thickness, the bearing capacity of foundation, the foundation settlement of pile-supported semi-rigid embankment with reinforced cushion and the stability of subgrade slope and embankment retaining wall are systematically analyzed and researched. The main work and innovative achievements include:1. A computational formula of cushion thickness, which is comprehensively considering the distinction between different pile diameters, pile spacing, heights of subgrade and reinforcement strength conditions, is established. This formula can replace the existing design method of cushion thickness, which based on the experiential values, hence, improving the scientific and economy of the design of cushion thickness.2. Based on the mechanic action mechanism and influence element of ground bearing capacity on pile-supported reinforced cushion embankment, considering synthetically foundation stiffness, rate of replacement, spreading action of cushion stress, pulling force of geogrid, earth suppress action of side slope, the calculation formula and inspection method were presented considering ground bearing capacity as pile compound foundation capacity under embankment and bearing capacity which is increased by reinforced cushion and earth suppress action of side slope on ground bearing capacity. The results show that ground bearing capacity increases with the decrease of foundation stiffness, the increase ofrate of replacement, geogrid layer number and spreading action of cushion stress. Pulling force of geogrid is a chief element for increasing ground bearing capacity.3. The computational formula of angle during the stability design in clay roadbed is proposed, and then rebuild the table of the angle with higher precise value, improving calculation precision. The analytic formula of the minimum stability coefficient (K min) of potential destructive damage in soft clay subgrade side slope is founded, simplifying the analysis and calculation process of the stability of subgrade slope.4. The new stability design and calculation method,formula method, of the water permeable subgrade is established, by bring in the cohesion and internal friction angle which is a new concept. The formula reflects the corresponding relations among the height, the slope and the soil stability coefficient of subgrade, simplifying the analysis and calculation process of seepage subgrade slope stability.5. Through mechanical analysis, the mechanical effect has been studied on the slope builds layer of rock filled subgrade, stability influence factors are analyzed on rock filled subgrade. The calculation and design method of the filling stone roadbed are established, in order to overcome the roughness and unscientific nature of the original calculation and design method for such type of subgrade.6. The equation for calculating the height of resultant force’s action point, the anti-overturning stability coefficient, and the new design method of anti-overturning stability of the retaining wall are established, which under the condition of nonlinear distribution of earth pressure by using the general static equilibrium analysis. The value of the stability coefficient calculated by the new method is less than the value calculated by the current standard method, therefore there is potential safety risks to use the standard method, which is not consider the nonlinear distribution of earth pressure, to design the coefficient of anti-overturn stability of retaining wall.7. The anti-overturning stability calculation and design method, which has considered the moment of ground reaction force, based on the new definition of retaining wall stability factor against overturning of retaining walls, is established. The coefficient of anti-overturn stability are related to the ultimate bearing capacity of foundation of retaining wall, the anti-overturning stability coefficient rised with the increasing of the ultimate bearing capacity of foundation soil. The value of the stability coefficient calculated by the new method is less than the value calculated by current standard method, so there are safety risks by using the current standard design method which does not consider the ground reaction force moment.