软土地层单桩与群桩承载能力分析及关联性研究

发布时间：2018-03-22 18:20

本文选题：软土　切入点：单桩　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：群桩基础作为深基坑土体加固的主要方式之一在工程中日渐增多。但是目前对于群桩基础的研究存在薄弱环节,单桩与群桩之间的关联性分析还存在着许多盲目性,例如对于桩基础的研究不能仅仅考虑沉降方面,对于基桩的轴力、桩端阻力等方面都值得我们进行透彻的探讨。仅仅由单桩基础承载力估算的群桩基础承载力运用在桩基础设计中是不可靠的。同时,在正常使用过程中承载能力的不准确性也会造成群桩基础出现大量问题。在运用Midas/GTS数值模拟软件进行模拟过程中,提出了运用修正莫尔—库伦本构模型能够更好的模拟软土地层,避免了对桩基础模拟出现的偏差,提高了数值模拟结果的准确性。以Midas/GTS数值模拟为主要试验手段,《建筑桩基技术规范》JGJ94-2008为试验依据,对单桩基础进行模拟试验,讨论了单桩基础处于软质地基土中,在受荷载状态下的承载力性状。揭示了桩身轴力随着桩体埋深的增加而减小,桩身侧摩阻力承担荷载百分比要大于桩端阻力。采用规范中单桩竖向极限承载力经验参数法对模拟的单桩试验结果进行验证,证实试验模型的准确可靠。采用数值模拟的方法对桩间距为2.5d、桩长为15m的9根方格桩处于软土地基时的模型进行分析,讨论了群桩基础基桩中中心桩、边桩和角桩之间的差别,揭示了在同一承台下中心桩的沉降量最大,边桩次之,角桩最小。对于桩体轴力的分析,则呈现出角桩大于边桩大于中心桩的特征现象。桩身侧摩阻力承担荷载百分比方面中心桩承担最多,边桩次之,角桩最小,桩端阻力的承担荷载百分比反之。对于9根方格群桩下基桩桩间距的不同进行数值模拟试验分析,分别对群桩的沉降量、桩身轴力以及桩端阻力进行讨论,表现出当桩间距为3倍的基桩直径时群桩基础的承载能力为最优。针对基桩长度不同采用数值模拟的手段进行群桩基础承载力的对比讨论,从基桩的沉降量、桩身轴力以及桩端阻力方面分析出随着桩长的增加群桩基础承载力具有增加的趋势,但是桩长过长不会对群桩基础产生较大的有利效果。选定影响群桩基础承载力的主要因素为基桩桩间距和基桩长度,将单桩基础与群桩基础的承载力进行对比并探究之间的关系。在此基础上提出了单桩基础与群桩基础之间承载能力的关联性公式,为实际工程中估算群桩基础承载力提供了科学依据。
[Abstract]:Pile group foundation, as one of the main methods of soil reinforcement in deep foundation pit, is increasing day by day in engineering. However, the research on pile group foundation is weak at present, and the correlation analysis between single pile and pile group still has a lot of blindness. For example, the study of pile foundation should not only consider settlement, but also the axial force of foundation pile. The pile end resistance and so on are all worth our thorough discussion. It is not reliable to use the bearing capacity of group pile foundation which is estimated by single pile foundation bearing capacity in pile foundation design, at the same time, The inaccuracy of bearing capacity in normal use will also cause a lot of problems in pile group foundation. In the process of simulation using Midas/GTS numerical simulation software, It is proposed that the modified Mohr-Coulomb constitutive model can better simulate the soft soil layer and avoid the deviation of the pile foundation simulation. The accuracy of the numerical simulation results is improved. With Midas/GTS numerical simulation as the main test means and JGJ94-2008 as the test basis, the single pile foundation is simulated, and the single pile foundation is in the soft foundation. It is revealed that the axial force of the pile decreases with the increase of the buried depth of the pile. The bearing load percentage of lateral friction of pile is larger than that of pile tip. The empirical parameter method of vertical ultimate bearing capacity of single pile in the code is used to verify the simulated results of single pile test. It is proved that the test model is accurate and reliable. The numerical simulation method is used to analyze the model of 9 lattice piles with a distance of 2.5 days and a pile length of 15 m in soft soil foundation. The difference among the central pile, side pile and corner pile in pile foundation of group pile foundation is discussed. It is revealed that the settlement of the central pile under the same cap is the largest, the side pile is the second, the angle pile is the least. It shows that the angular pile is larger than the edge pile than the central pile, and the center pile bears the most load percentage, the edge pile takes the second place, and the angle pile is the smallest. The bearing load percentage of pile tip resistance is vice versa. Numerical simulation tests are carried out on the different spacing of foundation pile under 9 square pile groups. The settlement of pile group, the axial force of pile body and the resistance of pile end are discussed, respectively. It is shown that the bearing capacity of pile group foundation is optimal when the pile spacing is 3 times the diameter of foundation pile. The bearing capacity of pile group foundation is discussed by numerical simulation according to the difference of pile length, and the settlement of pile group is discussed according to the settlement of foundation pile. According to the axial force of pile body and the resistance of pile tip, the bearing capacity of pile group foundation increases with the increase of pile length. But the pile length is too long will not have a great beneficial effect on the pile group foundation. The main factors that affect the bearing capacity of the pile group foundation are the pile spacing and the pile length. The bearing capacity of single pile foundation and group pile foundation is compared and the relationship between the bearing capacity of single pile foundation and group pile foundation is discussed, and the correlation formula of bearing capacity between single pile foundation and pile group foundation is put forward. It provides a scientific basis for estimating the bearing capacity of pile group foundation in practical engineering.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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