后压浆高承台群桩基础的承载特性研究

发布时间：2019-05-12 15:25

【摘要】：随着高层建筑以及各类大型跨江和跨海桥梁工程的不断建设,群桩基础的规模越来越大,桩径越来越大,桩长也越来越长,荷载作用下桩基础和土体共同作用的工作机理是一个很复杂问题,针对后压浆单桩基础的承载力计算方法较多,但这些方法有各自的优缺点及其适用范围、计算准确性不一,对于群桩基础与土体相互作用则更加复杂,一直未能得到有效的解答。本文首先系统分析了后压浆技术的国内外研究现状、岩土注浆理论、施工工艺及后压浆对于桩基础承载特性的作用机理等；然后以岩土注浆理论为指导,基于国内某超大群桩基础建设工程,运用大型非线性有限元分析软件ADINA建立了深厚软土层中九桩高承台群桩基础桩端注浆与未注浆两种情况下的桩-土相互作用的三维模型,通过计算对后注浆群桩基础的承载性能进行分析,具体开展了以下方面的工作： (1)计算并分析了群桩基础桩端采用注浆加固后桩端阻力的分布规律,群桩中角桩端部反力最大,边桩和中间桩均小于角桩,最大反力值达到9727934kN;工况六下最大反力达到3.064×107kN,后压浆能起到改善和平衡群桩基础中各单桩的不均匀受力的作用。 (2)计算了桩侧阻力的分布,桩侧阻力是从桩端以上一定高度开始逐渐向上发挥,这是由于高桩承台群桩基础受力后上段桩体首先产生弹性压缩,然后逐渐向下传递；由于桩端加固体的作用,桩端的位移受到限制,桩端以上一定范围内的桩侧阻力没有充分发挥,并且由于角桩和边桩的相对位移比中桩要大,其摩擦阻力的发挥先于中桩。 (3)计算得到群桩基础压浆前在竖向荷载作用下最大沉降达51.45cm,采用桩端注浆加固条件下的沉降22.58cm,可以减少沉降量43.8%,加固效果比较显著；承台施工阶段,最大沉降均发生在各角桩位置处,随着荷载的逐步施加,桩端压浆加固体对于群桩中各单桩的沉降起到了很好的协调作用,荷载加载完成阶段,群桩基础的沉降分布己趋于均匀； (4)压浆后群桩基础中处于同一深度位置处的桩身轴力分布规律与压浆前的相类似,群桩中角桩A的轴力最大、边桩B的轴力小于角桩A、中心桩C的轴力小于角桩和边桩。此外,群桩中各单桩的轴力分布在-45m以上比较均匀,-45m以下轴力依次减小。 (5)桩顶反力与桩顶沉降大致呈线性变化,相同沉降量A桩所承受的竖向荷载最大,因此在群桩桩位布置时应尽量增加角桩和边桩的比例,可以充分发挥群桩基础的整体承载性能。
[Abstract]:With the continuous construction of high-rise buildings and all kinds of large cross-river and sea-crossing bridge projects, the scale of pile group foundation is getting larger and larger, the pile diameter is getting larger and larger, and the pile length is getting longer and longer. The working mechanism of pile foundation and soil under load is a very complex problem. There are many methods for calculating the bearing capacity of post-grouting single pile foundation, but these methods have their own advantages and disadvantages and their applicable scope, and the calculation accuracy is different. The interaction between pile group foundation and soil mass is more complicated and can not be solved effectively. In this paper, the research status of post-grouting technology at home and abroad, geotechnical grouting theory, construction technology and the mechanism of post-grouting on the bearing characteristics of pile foundation are systematically analyzed. Then, guided by the theory of geotechnical grouting, based on the construction of a super-large pile group in China, A three-dimensional model of pile-soil interaction at the end of nine high cap pile groups in deep soft soil layer is established by using the large nonlinear finite element analysis software ADINA. Through the calculation and analysis of the bearing capacity of the post-grouting pile group foundation, the following aspects are carried out: (1) the distribution law of the resistance at the pile end strengthened by grouting is calculated and analyzed. The reaction force at the end of the corner pile group is the largest, the side pile and the middle pile are smaller than the angle pile, and the maximum reaction force is 9727934kN. Under the working condition, the maximum reaction force is 3.064 脳 107kN, and the post-grouting can improve and balance the uneven force of each single pile in the pile group foundation. (2) the distribution of pile side resistance is calculated, and the pile side resistance is gradually brought into play from a certain height above the pile end, which is due to the elastic compression of the upper section of the pile group foundation of the high pile cap and then the gradual downward transmission. Due to the effect of adding solid at the end of the pile, the displacement of the end of the pile is limited, the resistance of the side of the pile in a certain range above the end of the pile is not brought into full play, and because the relative displacement of the angular pile and the side pile is larger than that of the middle pile, the friction resistance is brought into full play before the middle pile. (3) the maximum settlement of pile group foundation under vertical load is 51.45 cm before grouting, and 22.58 cm of settlement under grouting at pile end can reduce settlement by 43.8%, and the reinforcement effect is remarkable. In the stage of cap construction, the maximum settlement occurs at the position of each angle pile. With the gradual application of load, grouting and solid at the end of the pile play a very good role in coordinating the settlement of each single pile in the pile group, and the completion stage of load loading. The settlement distribution of pile group foundation tends to be uniform. (4) the distribution of axial force of pile body at the same depth in pile group foundation after grouting is similar to that before grouting. The axial force of angle pile A is the largest, and the axial force of side pile B is smaller than that of angle pile A. The axial force of central pile C is smaller than that of corner pile and side pile. In addition, the axial force distribution of each single pile in the pile group is more uniform than-45m, and the axial force below-45m decreases in turn. (5) the reaction force of pile top and the settlement of pile top change linearly, and the vertical load of pile A with the same settlement is the largest, so the ratio of angle pile to side pile should be increased as much as possible when the pile group is arranged. It can give full play to the overall bearing performance of pile group foundation.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU473.1

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