有孔锥—柱管桩开孔应力集中系数及桩身极限承载力研究

发布时间：2018-01-08 08:10

本文关键词：有孔锥—柱管桩开孔应力集中系数及桩身极限承载力研究　出处：《南昌航空大学》2017年硕士论文　论文类型：学位论文

【摘要】：有孔锥形管桩具有倾斜侧面,加大了桩土接触面积,使其受力更合理,更能发挥桩侧土体的侧摩阻力;同时,作为复合地基竖向增强体,有孔锥形管桩上端尺寸变大,增大了复合地基面积置换率,从而可提高复合地基承载力。但在沉桩施工过程中,锥形管桩存在接桩不便、处理深度不足、挤土效应明显等缺点。现提出一种有孔锥-柱管桩技术,在加大地基处理深度的同时,桩周土体中超孔隙水可通过桩孔主动进入管桩内腔,从而加速超孔隙水压力消散,减小超孔隙水压力最大值,减小锥-柱管桩的挤土效应并提高土的抗剪强度。但开孔必将导致结构的几何连续性遭到破坏,产生明显的应力集中,从而降低结构的承载能力和使用寿命。因此,本文围绕有孔锥-柱管桩开孔方式、管桩侧壁开孔所产生的应力集中系数大小和分布范围、桩身极限承载力折减规律等关键问题,采用模型试验和数值模拟相结合的方法,研究单向、双向和星状开孔在桩身受力时,桩身应力集中系数分布规律和极限承载力折减情况,为有孔锥-柱管桩技术的应用推广提供试验基础。主要研究成果如下:(1)有孔锥-柱管桩应力集中系数试验表明:在三种开孔方式中,星状桩型应力集中系数分布范围最小,桩身受力均匀。孔径为5mm的各桩型应力集中系数普遍低于孔径为6mm各桩型,应力集中系数的大小主要影响因数是孔径直径,锥度对应力集中系数分布范围和系数值影响不明显。所有桩型中孔径为5mm的星状桩型受力性能最佳。(2)桩身极限承载力试验表明:三种开孔方式极限承载力性能星状桩型最优。孔径为5mm的各桩型极限承载力折减情况明显低于孔径为6mm的各桩型,开孔孔径越大桩身极限承载力折减越严重;有孔锥-柱管桩极限承载力性能最好的是开5mm孔径锥度为1/80的星状桩型。(3)桩身应力集中系数数值模拟研究表明:有孔锥-柱管桩柱形段应力集中系数值要高于锥形段;其桩身锥度的变化对其应力集中系数影响不大;孔径的大小是影响应力集中系数大小的主要因素,应力集中系数的分布范围受开孔方式的影响。在三中开孔方式中,星状有孔锥-柱管桩的应力集中系数分布范围最集中。开孔孔径越小其应力集中系数越小,其中孔径为5mm的各桩型应力集中系数值最小。所有桩型中孔径为5mm的星状桩型受力性能最优。(4)由于试验误差的存在,试验所得应力集中数值小于数值模拟所得的数值;但应力集中系数分布规律基本一致,柱形段应力集中系数高于锥形段,开孔孔径越大应力集中系数越大;说明数值模拟管桩受压时的应力集中变化情况与试验过程一致。
[Abstract]:A hole conical pipe with inclined side, increasing the pile soil contact area, the stress is more reasonable, more can play the side friction of pile side soil; at the same time, as the vertical reinforcement composite foundation, pore size at the upper end of the tapered pipe pile composite foundation, increasing the area replacement ratio, which can improve the composite foundation the bearing capacity of pile sinking. But in the process of construction, conical pipe pile connection exists inconvenience, depth insufficient, compacting effect and other shortcomings. In this paper a hole cone cylinder pile technology, to increase the depth of foundation treatment at the same time, the soil around the pile in pore water through the pipe into the active cavity of pile hole thus, accelerate the dissipation of excess pore water pressure, the excess pore water pressure decreases the maximum squeezing effect of taper column pile and improve the shear strength of soil. But the hole will cause the structure of geometric continuity is destroyed, produce significant stress concentration, In order to reduce the bearing capacity of the structure and service life. Therefore, this paper around the hole cone column pile holes, pile side holes caused by stress concentration coefficient and distribution range, capacity reduction key rule of ultimate bearing pile, one-way research method, model test and numerical simulation with the two-way and star shaped hole in the force of pile, pile stress concentration coefficient distribution and ultimate bearing capacity reduction, provide experimental basis for application of hole cone cylinder pile technology. The main research results are as follows: (1) a test showed that the stress concentration coefficient of cone hole column pile: in three holes, star shaped pile stress concentration coefficient distribution of minimum force of pile diameter is 5mm. The uniform pile stress concentration coefficient is generally lower than the diameter 6mm of each pile type, should be the main influence factor is the size of the coefficient of stress concentration Aperture diameter, taper on the stress concentration coefficient distribution and numerical aperture is not obvious. All type of pile for pile type 5mm star was optimized. (2) show that the bearing capacity of pile: three holes of ultimate bearing capacity of pile type. The optimal performance of star shaped aperture type pile the limit for 5mm capacity reduction of each pile is obviously lower than the pore size of 6mm, the diameter of the holes is more serious reduction of bearing capacity of pile hole limit; cone cylinder pile ultimate bearing capacity is the best 5mm hole taper star pile type 1/80. (3) pile should be set in the numerical simulation of the force coefficient showed that the hole cone cylinder pile column section of the stress concentration coefficient is higher than that of the conical section; the change of the pile taper on the stress concentration coefficient has little effect; the pore size is the main factor affecting the stress concentration coefficient, the coefficient of stress concentration distribution fan Around the affected holes. In third holes, star has the most concentrated hole cone column pile stress concentration coefficient distribution range. The hole diameter is smaller and the stress concentration coefficient is small, the aperture of each pile type 5mm stress concentration coefficient of the minimum aperture pile all. In the star like pile type 5mm best mechanical properties. (4) because of the testing errors, the experimental stress concentration value is less than the simulated values; but the stress concentration coefficient distribution are basically the same, the column section of the stress concentration coefficient is higher than that of conical section, hole diameter greater stress the greater the concentration coefficient; that the change and test process of stress concentration in numerical simulation of pile compression.

【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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