循环水平荷载作用下桩基础的响应性状研究

发布时间：2018-01-11 19:00

本文关键词：循环水平荷载作用下桩基础的响应性状研究　出处：《福州大学》2014年硕士论文　论文类型：学位论文

【摘要】：实际工程中,桩基础不但要承受竖向荷载的作用,往往还承受风、波浪、地震、交通等循环水平荷载的作用。随着社会经济与科学技术的快速发展,许多桩基础的设计技术标准其实已经滞后于工程实践。现行规范对于受循环水平荷载作用下桩基础的水平承载力计算并无做出详细规定。本文通过研究不同影响因素下受循环水平荷载作用的桩基础的受力和变形等响应性状,得出相应的规律性结论,为循环水平荷载作用下的桩基础设计提供依据。通过对大量承受循环水平荷载作用下桩基础的调查以及现有设计资料的分析,确定了数值计算模型参数,采用PLAXIS大型岩土有限元分析软件作为计算平台,分析了不同土层条件、不同荷载条件、不同桩身物理条件以及是否含竖向荷载等情况下单桩基础和群桩基础的内力和位移响应情况,并结合桩侧土的动应力-应变关系对其进行相应的机理性探讨,根据数值计算结果,得到相应的结论如下：1、土层条件是影响桩基础水平承载力发挥的显著因素。随着变形模量的提高,桩身弯矩和剪力减小,动位移幅值减小,因此,提高变形模量有助于发挥桩基水平承载性能。此外,上层土的性质对单桩内力和位移的影响程度远大于下层土。2、桩土刚度比和桩长径比是影响单桩水平承载力的主要参数。通过算例可知,随着桩土刚度比的增大,单桩水平受力和变形均呈增大趋势；桩体长径比L／D由12增至18时,内力和位移响应呈减小的趋势,变形表现为刚体平移；L/D=20时,桩身弯矩、剪力和位移最小,变形模式为弯曲变形。L/D=22时,桩体产生弯曲失稳。本文算例中最佳长径比取为20。3、荷载条件是区别于静荷载的影响桩基础受力和变形性状的最重要因素。一定范围内,单桩在循环水平荷载作用下的受力和变形响应程度随循环次数的增大而增大,随荷载频率的增大而减小,随荷载幅值的增大而增大。4、竖向静载与循环水平荷载耦合作用下,较小的竖向力可以限制单桩的水平运动。但竖向力增大时,随着桩基础的水平运动,竖向力又会对其产生二阶弯矩,即所谓P-△效应,P-△效应会引起单桩的弯曲破坏。5、桩间距的大小对桩周土反力和各排桩的荷载分配都有着直接的影响。本文以三排桩为算例,桩距越大时,各排桩的受力逐步趋向均匀,算例条件下,当桩间距大于6D时,水平承载群桩的群桩效应已较微弱,可以忽略。
[Abstract]:In practical engineering, pile foundation should not only bear vertical loads, often under wind, wave, earthquake, traffic and other cyclic horizontal loads. With the rapid development of social economy and science and technology, the design standard of many pile foundation has lagged behind the engineering practice. The existing standard for under cyclic horizontal load under the horizontal bearing capacity of pile foundation calculation does not make detailed provisions. The pile foundation subjected to cyclic horizontal load through the effects of different factors on the stress and deformation response characteristics, obtained corresponding conclusions, provide the basis for the design of the circular pile foundation under horizontal load. Through the analysis of a large number under investigation the role of cyclic horizontal load pile foundation and the existing design data, the model parameters are determined by numerical calculation, as PLAXIS finite element large geotechnical analysis software Is the platform, analyzes the different soil conditions, different load conditions, internal force and displacement of the pile in different physical conditions and whether the bearing vertical load of single pile foundation and pile foundation in response to the situation, and combined with the pile side soil dynamic stress-strain relationship on the corresponding mechanism, based on the results of numerical calculation and get the corresponding conclusions are as follows: 1. Soil conditions are significant factors to play the horizontal bearing capacity of piles. With the deformation modulus increases, the pile bending moment and shear force decreases and the displacement amplitude decreases, therefore, improve the deformation modulus contributes to pile horizontal bearing capacity. In addition, the influence degree of upper soil properties the internal force and displacement of single pile is far greater than the lower soil.2, soil pile stiffness ratio and pile slenderness ratio are the main parameters affecting the horizontal bearing capacity of single pile. Examples show that, with the stiffness ratio of pile and soil increasing, the level of single pile The stress and deformation were increased; the pile length diameter ratio of L / D increased from 12 to 18, the internal force and displacement response was decreased, the deformation performance of rigid body translation; L/D=20, the pile bending moment, shear force and displacement minimum, deformation mode for.L/D=22 bending deformation, pile bending loss this is the best stability. In cases of long diameter ratio is 20.3, the load condition is the most important factor is different from the effect of static load pile foundation loading and deformation. In a certain range, single pile under horizontal load in the action of cyclic stress and deformation response degree increases with the number of cycles, decreases with the increase of load frequency, load amplitude increases with increasing.4, vertical static load and cyclic horizontal loading, vertical force smaller can limit the horizontal motion of single pile. But the vertical force increases, with the horizontal movement of the pile foundation, vertical force will affect the yield Two order moment, the so-called P- delta effect, P- delta effect can cause the bending failure of.5 single pile, pile spacing has direct influence on the pile soil reaction force and the pile load distribution. Based on the three row pile as an example, the pile spacing is large, each row the force of the pile gradually tends to be uniform, the example under the conditions when the pile spacing is greater than 6D, the horizontal bearing effect of pile group is weak and can be neglected.

【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU473.1

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