全夯式挤扩多头灌注桩单桩沉降机理与沉降特性研究
发布时间：2019-05-13 15:20
【摘要】：全夯式挤扩多头灌注桩是通过改进灌注桩制作工艺和施工设备,凭借在桩身不同部位设置“球型”扩大头,不仅可以提高承载力,同时还能克服沉管灌注桩普遍存在的缩颈、断桩、蜂窝及钢筋笼变形扭曲等问题的一种夯扩型桩。虽然全夯式挤扩多头灌注桩已经在许多工程中得到应用,但针对其承载机理、承载力计算、沉降特性等理论的研究仍是空白。本论文借助现场试验、室内模型试验、数值模拟和理论分析等多种方法对全夯式挤扩多头灌注桩的单桩承载机理、单桩沉降规律进行探索,研究扩大头在单桩沉降过程中发挥作用的规律,为全夯式挤扩多头灌注桩的单桩沉降设计提供依据,并以理论推导方式试着给出了该桩型的单桩沉降理论计算方法。论文研究主要获得了以下结论:1)在桩长和桩径相同的情况下,全夯式挤扩多头灌注桩的极限承载力与直桩相比有明显提高,且为2倍以上,与此相应,在同一桩顶荷载下沉降不足直孔桩的1/2。2)全夯式挤扩多头灌注桩因在桩身不同部分处存在扩大头,所以在其P~S曲线中存在明显的“台阶式”跳跃。通过改变不同扩大头间距可以调整相邻“台阶式”跳跃的出现间隔。桩身扩大头产生的“台阶式”跳跃幅度要大于桩端扩大头产生的跳跃幅度。3)增加全夯式挤扩多头灌注桩的扩大头数量能够有效增大其承载能力、减小桩顶沉降值。在本文试验条件中,同一桩顶荷载下,扩大头的数量越多,沉降值越小。当桩顶施加荷载作用达到4000N时,普通直桩的沉降量是多扩大头桩的4倍,单扩大头桩的沉降量是多扩大头桩的2倍。4)由于桩身扩大头的存在,桩侧摩阻力的分布特性和作用范围发生了改变。位于扩大头中下部的土体受到的扩大头的应力作用要明显大于桩侧摩阻力产生的应力值。扩大头对周边土体的作用规模大约是桩身直径的4倍。5)全夯式挤扩多头灌注桩的扩大头直径、桩身直径、相邻两个扩大头之间的距离、桩土刚度比、细长比等都能影响桩的沉降值。因而,进行桩基设计时,在满足承载力要求的条件下,可以根据工程场地地层条件选择合适的参数以减小单桩沉降值。6)基于Mindlin解和Geddes解,结合分层总和法,对全夯式挤扩多头灌注桩的单桩沉降进行探讨。通过室内模型试验和理论计算值对比表明,用本文给出的计算方法得出的计算值与试验实测值的误差在合理范围内,可以为将来设计工作提供参考。
[Abstract]:The full compaction extrusion multi-head cast-in-place pile is by improving the making technology and construction equipment of the cast-in-place pile. By setting up the "spherical" enlarged head in different parts of the pile body, it can not only improve the bearing capacity, but also overcome the common neck shrinkage of the sinking pipe cast-in-place pile. A rammed pile with deformation and distortion of broken pile, honeycomb and steel cage. Although the full compaction multi-head cast-in-place pile has been applied in many projects, the theoretical research on its bearing mechanism, bearing capacity calculation and settlement characteristics is still blank. In this paper, the bearing mechanism and settlement law of single pile of fully rammed extruded multi-head cast-in-place pile are explored by means of field test, indoor model test, numerical simulation and theoretical analysis. The law that the expansion head plays an important role in the settlement process of a single pile is studied, which provides the basis for the settlement design of the full compaction multi-head cast-in-place pile, and the theoretical calculation method of the settlement of the pile type is tried by means of theoretical derivation. The main conclusions of this paper are as follows: 1) under the condition that the length and diameter of the pile are the same, the ultimate bearing capacity of the fully rammed extruded multi-head cast-in-place pile is obviously higher than that of the straight pile, and it is more than twice as much as that of the straight pile. Under the same pile top load, there is an obvious "step" jump in the P 鈮，
本文编号：2475997
[Abstract]:The full compaction extrusion multi-head cast-in-place pile is by improving the making technology and construction equipment of the cast-in-place pile. By setting up the "spherical" enlarged head in different parts of the pile body, it can not only improve the bearing capacity, but also overcome the common neck shrinkage of the sinking pipe cast-in-place pile. A rammed pile with deformation and distortion of broken pile, honeycomb and steel cage. Although the full compaction multi-head cast-in-place pile has been applied in many projects, the theoretical research on its bearing mechanism, bearing capacity calculation and settlement characteristics is still blank. In this paper, the bearing mechanism and settlement law of single pile of fully rammed extruded multi-head cast-in-place pile are explored by means of field test, indoor model test, numerical simulation and theoretical analysis. The law that the expansion head plays an important role in the settlement process of a single pile is studied, which provides the basis for the settlement design of the full compaction multi-head cast-in-place pile, and the theoretical calculation method of the settlement of the pile type is tried by means of theoretical derivation. The main conclusions of this paper are as follows: 1) under the condition that the length and diameter of the pile are the same, the ultimate bearing capacity of the fully rammed extruded multi-head cast-in-place pile is obviously higher than that of the straight pile, and it is more than twice as much as that of the straight pile. Under the same pile top load, there is an obvious "step" jump in the P 鈮，
本文编号：2475997
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