沟谷地形桩基竖向极限承载力评价方法研究
发布时间：2018-09-07 17:43
【摘要】：沟谷地形区域的地质、水文情况较为复杂，受限于道路建设成本及道路路线要求，致使部分桥梁桩基修建在斜坡上。沟谷地形的形成及发展主要是由沟谷流水侵蚀和坡面物质移动造成，因此该地区桩基又不可避免的遭到水流冲刷的影响。 本文阐述了斜坡及水流冲刷后桩基竖向承载机理，建立了斜坡和水流冲刷后桩基的整体受力模型，首次提出了考虑边坡系数与临坡距耦合条件下的斜坡桩基侧摩阻力影响系数的计算公式，以及考虑冲刷深度的冲刷后侧压力引起摩阻力影响系数的计算公式，形成了沟谷地形桩基竖向承载力评价方法，对该地区桥梁桩基的设计、养护、评估具有重大意义。 在分析斜坡对桩基竖向极限承载力的影响时，结合斜坡桩基竖向承载机理，通过有限差分软件FLAC3D进行建模计算，分析其对竖向极限承载力、桩端极限阻力、桩侧极限摩阻力的影响。通过数值计算结果可知，边坡系数、临坡距对桩基竖向极限承载力的影响主要集中在对桩侧极限摩阻力的影响；二者与桩侧极限摩阻力呈正相关，且二者存在耦合相关，当二者减小时对桩侧极限摩阻力敏感性增强。 在分析冲刷对桩基竖向极限承载力的影响时，通过有限差分软件FLAC3D中的NULL单元模拟桩周土的冲刷过程，分析其对极限承载能力、桩端极限阻力、桩侧极限摩阻力以及桩周土的侧压力的影响。通过数值计算结果可知，冲刷深度对桩基竖向极限承载力的影响主要集中在对桩侧土压力引起摩阻力的影响；按照高承台模式计算冲刷后桩基竖向极限承载力是不准确的。 在综合考虑斜坡、冲刷对竖向极限承载力影响以及桩基承载机理的基础上，提出斜坡桩基侧摩阻力影响系数和冲刷后侧压力引起摩阻力的影响系数，并通过对前面计算结果的回归分析给出两种系数的计算公式，最终总结得出了沟谷地形桩基竖向极限承载力计算公式。
[Abstract]:The geological and hydrological conditions in the valley terrain area are more complicated, which are limited by the cost of road construction and the requirements of road route, resulting in the construction of some bridge piles on the slope. The formation and development of the valley topography are mainly caused by the erosion of the gully and the material movement on the slope, so the pile foundation in this area is inevitably affected by the flow of water. In this paper, the vertical bearing mechanism of slope and pile foundation after water flow erosion is expounded, and the integral force model of pile foundation after slope and water flow erosion is established. For the first time, a formula for calculating the influence coefficient of the side friction of the slope pile foundation considering the coupling of slope coefficient and the distance between the slope and the slope is put forward, and the formula for calculating the influence coefficient of the friction caused by the lateral pressure after taking into account the erosion depth is also presented. The evaluation method of vertical bearing capacity of pile foundation in gully terrain is formed, which is of great significance to the design, maintenance and evaluation of bridge pile foundation in this area. When analyzing the influence of slope on the vertical ultimate bearing capacity of pile foundation, combined with the vertical bearing mechanism of slope pile foundation, the finite difference software FLAC3D is used to model and calculate the vertical ultimate bearing capacity and ultimate resistance of pile end. The influence of the ultimate friction resistance on the pile side. The results of numerical calculation show that the influence of slope coefficient and adjoining distance on the vertical ultimate bearing capacity of pile foundation is mainly concentrated in the influence of the ultimate frictional resistance on the pile side, and they are positively correlated with the ultimate frictional resistance of the pile side, and there is a coupling correlation between them. The sensitivity to the ultimate frictional resistance of the pile side is enhanced when both of them are reduced. When analyzing the influence of scour on the vertical ultimate bearing capacity of pile foundation, the scouring process of soil around pile is simulated by NULL element in finite difference software FLAC3D, and the ultimate bearing capacity and ultimate resistance of pile end are analyzed. The influence of the ultimate frictional resistance of the pile and the lateral pressure of the soil around the pile. The numerical results show that the effect of scour depth on the vertical ultimate bearing capacity of pile foundation is mainly concentrated on the influence of the soil pressure on the pile side, and it is not accurate to calculate the vertical ultimate bearing capacity of the pile foundation after scouring according to the high cap model. On the basis of considering the influence of slope, erosion on the ultimate vertical bearing capacity and the bearing mechanism of pile foundation, the influence coefficient of lateral friction of slope pile foundation and the coefficient of friction caused by lateral pressure after erosion are put forward. The formulas for calculating the vertical ultimate bearing capacity of pile foundation in gully terrain are given by regression analysis of the results of the previous calculation.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U443.15
本文编号：2228964
[Abstract]:The geological and hydrological conditions in the valley terrain area are more complicated, which are limited by the cost of road construction and the requirements of road route, resulting in the construction of some bridge piles on the slope. The formation and development of the valley topography are mainly caused by the erosion of the gully and the material movement on the slope, so the pile foundation in this area is inevitably affected by the flow of water. In this paper, the vertical bearing mechanism of slope and pile foundation after water flow erosion is expounded, and the integral force model of pile foundation after slope and water flow erosion is established. For the first time, a formula for calculating the influence coefficient of the side friction of the slope pile foundation considering the coupling of slope coefficient and the distance between the slope and the slope is put forward, and the formula for calculating the influence coefficient of the friction caused by the lateral pressure after taking into account the erosion depth is also presented. The evaluation method of vertical bearing capacity of pile foundation in gully terrain is formed, which is of great significance to the design, maintenance and evaluation of bridge pile foundation in this area. When analyzing the influence of slope on the vertical ultimate bearing capacity of pile foundation, combined with the vertical bearing mechanism of slope pile foundation, the finite difference software FLAC3D is used to model and calculate the vertical ultimate bearing capacity and ultimate resistance of pile end. The influence of the ultimate friction resistance on the pile side. The results of numerical calculation show that the influence of slope coefficient and adjoining distance on the vertical ultimate bearing capacity of pile foundation is mainly concentrated in the influence of the ultimate frictional resistance on the pile side, and they are positively correlated with the ultimate frictional resistance of the pile side, and there is a coupling correlation between them. The sensitivity to the ultimate frictional resistance of the pile side is enhanced when both of them are reduced. When analyzing the influence of scour on the vertical ultimate bearing capacity of pile foundation, the scouring process of soil around pile is simulated by NULL element in finite difference software FLAC3D, and the ultimate bearing capacity and ultimate resistance of pile end are analyzed. The influence of the ultimate frictional resistance of the pile and the lateral pressure of the soil around the pile. The numerical results show that the effect of scour depth on the vertical ultimate bearing capacity of pile foundation is mainly concentrated on the influence of the soil pressure on the pile side, and it is not accurate to calculate the vertical ultimate bearing capacity of the pile foundation after scouring according to the high cap model. On the basis of considering the influence of slope, erosion on the ultimate vertical bearing capacity and the bearing mechanism of pile foundation, the influence coefficient of lateral friction of slope pile foundation and the coefficient of friction caused by lateral pressure after erosion are put forward. The formulas for calculating the vertical ultimate bearing capacity of pile foundation in gully terrain are given by regression analysis of the results of the previous calculation.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U443.15
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