共查询到19条相似文献，搜索用时 171 毫秒
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基于FLAC^3D的锚索抗滑桩滑坡推力分布规律研究 总被引：4，自引：0，他引：4
采用FLAC^3D建立了预应力锚索桩板墙结构的三维数值模型,结合有限元强度折减法分析了不同预应力作用下锚索桩滑坡推力的分布规律,并通过改变桩后岩土体的弹性模量及性质、锚索的设置位置以及边坡强度安全储备系数等参数,对锚索桩滑坡推力的分布规律进行了系统的研究。结果表明,在地质条件不变的情况下,随着锚索预应力的增大,桩后滑坡推力的分布图形逐渐由梯形向矩形变化;预应力对桩后滑坡推力分布的影响,取决于其与桩背总桩土相互作用力的相对大小,而不是其绝对大小。说明预应力的大小是影响桩后推力分布形式的一个非常重要的因素,照搬普通抗滑桩固定不变的推力分布形式对锚索桩进行设计,显然是不合理的。 相似文献
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随着我国经济建设的发展,越来越多的基础设施修建在工程地质条件复杂的山区内,所形成的高填方工程往往不具备放坡的条件,因此如何解决高填方工程的稳定性已成为一项刻不容缓的课题。土工格栅加筋挡土墙因格栅材料具有特有的网孔结构,对土颗粒能产生极强的嵌固与咬合作用,在高填方工程中得到了越来越广泛的应用。本文基于有限元强度折减法建立了土工格栅加筋土挡墙的计算理论,并通过模型试验进行了验证。通过在某机场工程中的应用说明了土工格栅加筋土挡墙的适用性,以及基于有限元强度折减法进行加筋土挡墙设计计算的可靠性。 相似文献
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两种强度折减法确定边坡稳定系数适用性探讨 总被引：1，自引：0，他引：1
强度折减法确定边坡稳定性系数比传统极限平衡方法优势明显,但是两种常用的强度折减法哪种更适合一直存在争议。本文针对某工程算例分别采用两种强度折减法进行了边坡稳定性系数计算,并把计算结果和传统极限平衡方法进行了对比,结果表明快速拉格朗日分析法更适合应用在边坡稳定性系数确定方面。该法的计算结果和传统计算方法极其接近,并可以克服传统方法人为指定滑动面的重大缺点。 相似文献
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以往对建筑抗震性影响因素的研究仅限于施工材料、技术手段等外部条件,忽略了基坑土体安全系数、基坑状态对建筑抗震性的影响,一定程度上削弱了建筑的抗震性能。本文从基坑排桩角度对建筑抗震性的影响展开分析,通过有限元强度折减法获取土体的安全系数与基坑状态的判断标准,在该标准下基于土体安全系数采用有限元强度折减法计算公式,获取各个土层计算参数。基于该参数使用ABAQUS有限元软件构建基坑排桩有限元分析模型(土体和桩体分别采用莫尔-库仑弹塑性模型和二维弹性模型)。实验采用所提分析方法,从基坑排桩排距、刚度两方面对建筑抗震性能进行分析。实验结果表明,当基坑排桩排距进行适当取值时,建筑抗震性越好;双排桩的刚度越大,建筑抗震性越好,且随着刚度的增加建筑抗震性能趋于平稳。 相似文献
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在平面应变条件下,采用极限平衡和有限元法对锚固边坡稳定性评价过程的关键问题进行研究。将条分法对锚固边坡安全系数的定义推广到有限元法中,通过弹塑性有限元分析计算结构整体应力场,再结合虎克-捷夫法完成最危险滑动面的优化搜索。以天然边坡、渗流作用下锚固边坡及开挖锚固边坡为例,对比分析了条分法、有限元极限平衡法及有限元强度折减法三者在安全系数大小、滑动面形状、位置及对锚固作用处理上的差异。结合工程实例分析发现:同条分法相比,有限元方法所得到的安全系数更大,滑动面也更深,其中,有限元极限平衡法具有良好的计算精度,而条分法在一定程度上削弱了锚固效应,有限元强度折减法在一定程度上会放大了锚固结构的稳定效果。 相似文献
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基于强度折减原理的土坡稳定性分析中,对土体的抗剪强度指标c、φ采用不同的折减系数进行强度折减,较传统的强度折减法更符合土坡的失稳破坏机制。为了进一步探讨双折减系数法在土坡稳定性分析中的具体应用,编制了基于FLAC-3D和双折减系数法的土坡稳定性分析程序,该程序可求解出能使土坡折减至极限平衡状态时的不同折减系数组合。利用该程序对2个典型土坡进行稳定性分析,并将土坡安全系数的计算结果与传统的强度折减法和简化Bishop法进行对比分析。算例分析表明:双折减系数折减法能体现出不同土体的抗剪强度衰减特性的差异;双折减系数法中SRFmin(c、φ折减系数平均值的最小值)与另外两种方法求解的土坡安全系数很接近,建议采用SRFmin作为土坡的安全系数。 相似文献
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为实现震后路基边坡的快速修复,提出基于树根桩加固的震后公路路基边坡综合修复技术。根据路基震害及地质环境对路基边坡的影响分析因素,采用树根桩技术及气泡轻质填土技术修复路基边坡;利用三维有限差分法模拟树桩加固气泡轻质填土修复后路基边坡得到参数值,再结合强度折减法计算得到的路基边坡稳定系数,最后得到优化树根桩的设计参数,以实现震后路基边坡综合修复。以上方法通过仿真模拟实验,得到最优的树根桩排距为2.5 dm。 相似文献
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为研究抗滑桩合理桩间距以及荷载传递机制,首先以桩侧摩阻力为拱脚时的破裂面推导出以桩身为拱脚时的破裂角计算公式;然后引入对数螺旋线法确定桩间土体的滑移深度,以土拱效应为基础建立计算模型,求解考虑桩间土体滑移深度的合理桩间距表达式;最后对桩间净距的主要影响因素进行分析,包括滑坡推力、黏聚力、桩截面宽度以及高度。研究结果表明：由桩身和桩侧摩阻力同时作为土拱拱脚更符合实际受力状态,同时求得的土拱拱圈厚度和矢高小于以桩身为拱脚条件下相应值而大于以桩侧摩阻力为拱脚条件下的相应值,并且随桩埋深的增加而增大。 相似文献
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地震是诱发边坡破坏的重要因素之一,而抗滑桩是一种重要的边坡防治工程措施,因此开展地震作用下抗滑桩机理对于边坡防护具有重要的工程意义。本文以广东省梅州市茶阳车站为工程实例,运用ABAQUS软件建立三维模型,对地震作用下的桩土作用机理进行数值模拟分析。研究表明:(1)在地震作用下,边坡中上部水平位移较大,最大值为87.05mm,凹陷处水平位移远小于凸起处;(2)地震作用下抗滑桩会由于地震荷载产生远大于地震前的应力:静力作用下桩身最大值是147.24kPa,地震波输入14s时桩身最大值达到了326.36kPa;(3)地震作用下抗滑桩的应变亦远大于静力作用下的应变:静力作用下抗滑桩应变最大值是4.63×10~(-5),在地震波输入的第14s时桩身应变最大值是34.10×10~(-5)。因此在工程实践中对于地震作用下的抗滑桩边坡加固需要考虑桩的强度与刚度。研究结论对于边坡防治以及工程实践具有一定的指导意义。 相似文献
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抗滑桩广泛应用于边坡支护工程,但路桥不稳定边坡抗滑桩对其进行加固时,其在地震作用下的动力响应问题仍未定论。以道真至瓮安高速公路河槽大桥不稳定边坡治理工程为依托,以SIMQKE_GR软件拟合地震设计反应谱,利用FLAC3D有限差分软件建立数值模型,对比地震作用下抗滑桩等支挡结构设立与否对路桥不稳定边坡的动力响应变化规律的影响。结果表明:（1）加速度放大系数无论是沿坡内还是抗滑桩,其值沿竖向均存在一定的震荡变化,但在抗滑桩支护情况下,其震荡幅度明显变小,加速度放大系数变化更平稳。（2）速度放大系数随着高度的增加逐渐减小,未加抗滑桩时速度放大系数在顶层附近出现大幅度波动,添加了抗滑桩的情况下其震荡幅度明显趋缓,变化更稳定。（3）坡体在施加抗滑桩后,治理效果明显,残余位移最大值由无抗滑桩的16.9 cm变为有抗滑桩的1 cm,但最大值均位于边坡表层碎石土和粉质黏土附近。 相似文献
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The anti-slide support structure is widely used in the anti-seismic reinforcement of bridge foundations, but related experimental research was processing slowly. Based on the prototype of the Jiuzhaigou bridge at the Chengdu-Lanzhou Railway, a 3-D simulation model was established on the basis of the shaking table model test, and the rationality of the dynamic analysis model was verified by indicators such as the bending moment of the bridge piles, peak soil pressure, and PGA amplification factors. The results show that the inertia force of the bridge pier has an important influence on the deformation of the pile foundation. The bending moment and shearing force are larger in lateral bridge piles, and the maximum value is near the pile top. The PGA amplification factor is stronger in the back of the rear anti-slide piles and so is it in front of the bridge pier, and the soil is prone to slip and damage. The bedrock is rigid and the dynamic response is maintained at a low level. The anti-slide piles in the rear row play a major role in the anti-seismic reinforcement design, and the anti-slide piles in the front row can be used as an auxiliary support structure. 相似文献
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对由碎石桩和CFG桩构成的多桩型复合地基的作用机理进行分析,通过数值模拟,对多桩型复合地基的动力特性进行研究,探讨桩型配比、桩径、桩长、CFG桩桩体刚度和碎石桩桩体渗透性等设计参数对多桩型复合地基动力特性的影响。研究结果表明:相同条件下地震期多桩型复合地基的动变形小于碎石桩复合地基而大于CFG桩复合地基,震后沉降量相对较小,在工程设计时碎石桩与CFG桩的桩型配比宜为4∶5;随桩体长度、桩体直径和CFG桩刚度的增加,多桩型复合地基地震期的竖向动变形逐渐减小;随碎石桩桩体渗透性的增加,多桩型复合地基中的超动孔隙水压力减小,震后沉降量降低。 相似文献
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Based on the requirement of seismic reinforcement of bridge foundation on slope in the Chengdu-Lanzhou railway project, a shaking table model test of anti-slide pile protecting bridge foundation in landslide section is designed and completed. By applying Wenchuan seismic waves with different acceleration peaks, the stress and deformation characteristics of bridge pile foundation and anti-slide pile are analyzed, and the failure mode is discussed. Results show that the dynamic response of bridge pile and anti-slide pile are affected by the peak value of seismic acceleration of earthquake, with which the stress and deformation of the structure increase. The maximum dynamic earth pressure and the moment of anti-slide piles are located near the sliding surface, while that of bridge piles are located at the top of the pile. Based on the dynamic response of structure, local reinforcement needs to be carried out to meet the requirement of the seismic design. The PGA amplification factor of the surface is greater than the inside, and it decreases with the increase of the input seismic acceleration peak. When the slope failure occurs, the tension cracks are mainly produced in the shallow sliding zone and the coarse particles at the foot of the slope are accumulated. 相似文献
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工程上广泛采用基于Winkler模型的层状地基反力系数法对桩土水平动力响应进行分析,该方法忽略了地基土剪切作用的影响,与工程实际有一定偏差。另外,对桩土的非线性相互作用和如扩底桩、楔形桩等变截面桩问题常用的传递矩阵法或中心差分法,计算过程较为繁琐。基于Pasternak地基模型和Adomian分解方法,提出一种考虑地基土剪切作用的桩土水平动力相互作用近似计算方法,该方法计算简便且结果精度较高,对变截面桩问题有很好的适用性;并基于该方法,对扩底桩水平动力响应问题和影响因素进行分析。结果指出,扩底半径和上部桩周土弹性模量对扩底桩水平动力响应影响较大,随着扩底半径的增加和桩周土弹性模量的增大,扩底桩水平振动位移幅值逐渐减小。另外,在较低频率的荷载激励下,应考虑土层对桩的剪切作用。 相似文献
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The seismic response of pile foundations is a very complex process involving inertial interaction between structure and pile foundation, kinematic interaction between piles and soils, seismically induced pore-water pressures (PWP) and the non-linear response of soils to strong earthquake motions. In contrast, very simple pseudo-static methods are used in engineering practice to determine response parameters for design. These methods neglect several of the factors cited above that can strongly affect pile response. Also soil–pile interaction is modelled using either linear or non-linear springs in a Winkler computational model for pile response. The reliability of this constitutive model has been questioned. In the case of pile groups, the Winkler model for analysis of a single pile is adjusted in various ways by empirical factors to yield a computational model for group response. Can the results of such a simplified analysis be adequate for design in all situations?The lecture will present a critical evaluation of general engineering practice for estimating the response of pile foundations in liquefiable and non-liquefiable soils during earthquakes. The evaluation is part of a major research study on the seismic design of pile foundations sponsored by a Japanese construction company with interests in performance based design and the seismic response of piles in reclaimed land. The evaluation of practice is based on results from field tests, centrifuge tests on model piles and comprehensive non-linear dynamic analyses of pile foundations consisting of both single piles and pile groups. Studies of particular aspects of pile–soil interaction were made. Piles in layered liquefiable soils were analysed in detail as case histories show that these conditions increase the seismic demand on pile foundations. These studies demonstrate the importance of kinematic interaction, usually neglected in simple pseudo-static methods. Recent developments in designing piles to resist lateral spreading of the ground after liquefaction are presented. A comprehensive study of the evaluation of pile cap stiffness coefficients was undertaken and a reliable method of selecting the single value stiffnesses demanded by mainstream commercial structural software was developed. Some other important findings from the study are: the relative effects of inertial and kinematic interactions between foundation and soil on acceleration and displacement spectra of the super-structure; a method for estimating whether inertial interaction is likely to be important or not in a given situation and so when a structure may be treated as a fixed based structure for estimating inertial loads; the occurrence of large kinematic moments when a liquefied layer or naturally occurring soft layer is sandwiched between two hard layers; and the role of rotational stiffness in controlling pile head displacements, especially in liquefiable soils. The lecture concludes with some recommendations for practice that recognize that design, especially preliminary design, will always be based on simplified procedures. 相似文献