【作者】 李荣建；

【导师】 李广信； 于玉贞；

【作者基本信息】 清华大学 ， 土木工程， 2008， 博士

【摘要】 抗滑桩是边坡加固的常用措施之一,地震作用及其诱发饱和地基液化往往导致加固结构破坏及滑坡;因此,研究边坡内抗滑桩抗震加固机理具有重要的学术意义与实用价值。本文研制了微混凝土抗滑模型桩,进行了一系列抗滑桩加固边坡的动力离心模型试验,开发了大变形三维动力固结有限元程序并对模型试验相应的原型进行了数值模拟分析,取得了以下主要研究成果:1.研制了更加严格满足相似关系的微混凝土抗滑模型桩,使之可以较好地反映原型钢筋混凝土桩动力响应和破坏特点,克服了采用高强度替代材料制作的模型桩在相似关系方面存在的问题,拓宽了微混凝土模型桩的应用范围。2.根据动力离心模型试验结果研究了无水条件下的边坡抗滑桩抗震加固效果及动力响应特点:桩径从小到大变化时,抗滑桩由静力断桩破坏到静力稳定动力断桩,再到桩体呈弹性动力响应,边坡变形和自振周期相应地由大逐渐减小,加固效果逐渐增强,抗滑桩内弯矩时空分布发生了本质性的变化。高桩位可更有效地发挥抗滑桩承载能力,抑制了坡顶地震变形,但坡脚位移相对较大;中桩位时坡顶位移较大,但坡脚位移较小。3.根据动力离心模型试验结果分析了饱和地基条件下无加固边坡与抗滑桩加固边坡的地震动力响应特点:前者由于饱和地基液化导致坡脚滑动,诱发边坡整体产生较大变形;后者虽然坡脚产生局部滑动,但由于抗滑桩加固效果良好,边坡变形相对较小,加固边坡整体较为稳定。与无水时相比,有水时抗滑桩动力附加弯矩增幅较大;与低水位时相比,高水位条件下发生了滑坡和断桩;表明水位条件对边坡抗滑桩受力及加固效果的影响较为显著。4.利用Pastor-Zienkiewicz III广义塑性本构模型和饱和砂土固液两相体耦合动力固结理论,开发了大变形动力固结三维有限元程序。首先利用该程序对典型模型试验相应的原型进行了模拟,通过数值计算结果与试验结果的对比验证了所开发程序的可靠性。然后通过数值计算拓展了位移和超静孔压分布等动力响应信息,结合试验结果深入研究了地震过程中桩-土运动相互作用规律以及抗滑桩抗震加固机理。计算还可预测边坡抗滑桩动力断桩及断桩时刻等。更多还原

【Abstract】 Earthquake-induced slope failures are popular in China and all over the world, and the stabilizing pile is one of the most common tools to prevent landslides. Therefore, the aseismic reinforcing mechanism of stabilizing piles in slope is an important topic in geotechnical earthquake engineering.In this paper, model concrete piles were produced, and a series of dynamic centrifuge model tests on pile-reinforced slopes were carried out, as well as a computer code was developed to analyze the three-dimensional dynamic consolidation problems. On the basis of the results of centrifuge modeling and numerical simulation, the aseismic reinforcing mechanism of stabilizing piles in slope was investigated. The main work and results are summarized as follows.1. A model concrete with similar mechanical properties as common concrete was designed to produce model piles. This kind of model piles is suitable for small scale model tests and can satisfy more strictly with the similarity criteria. Therefore, these model piles can reflect properly the dynamic response and failure characteristics of prototype reinforced concrete piles and overcome the model scale contradiction between the model and prototype resulting from the higher strength alternative materials, which are commonly used to make model piles.2. According to the results of dynamic centrifuge modeling, the aseismic effect and dynamic response of stabilizing piles in slope were investigated. Along with increasing the dimension of cross section of pile, the stable state of piles changes from statically failing to statically stable and dynamically failing then to dynamically stable, the deformation and nature period of the reinforced slope decreases, and the distribution of bending moment along pile changes essentially. This implies that the aseismic effect of stabilizing pile relies strongly on the dimension of cross section of pile. When the piles are installed near the crest of slope, the bearing capacity of piles can be mobilized sufficiently, while the deformation of the crest of slope is reduced effectively with the relatively large deformation of toe of slope. In contrast, when the piles are installed in the middle part of slope, the deformation of the crest of slope is bigger with the smaller deformation near the toe of slope.3. The dynamic behaviors of plain and pile-stabilized slopes with saturated subgrade were analyzed on the basis of dynamic centrifuge tests. In the former slope, the large deformation is induced by the slide of the toe of slope because of liquefaction of saturated subgrade during earthquake. The latter one maintains stable globally with smaller deformation because of the effective reinforcement of piles, although the toe of slope slides locally due to liquefaction of saturated subgrade. In contrast with the reinforced slope without water, the excess dynamic bending moment in piles increase sharply on condition that the subgrade is saturated. When the water level is high, landslide occurs and the piles break. This indicates that the water level has an important influence on the dynamic behavior and stabilizing effect of piles.4. A computer code for simulating three-dimensional dynamic consolidation with large deformation was developed based on the Pastor-Zienkiewicz III constitutive model for sand and Biot’s dynamic consolidation theory. The results of numerical simulation for the prototypes of some typical model tests, such as excess pore pressure, the response acceleration and the bending moments in piles during earthquake agreed well generally with those of experiments, so that the reliability of the numerical program went through the benchmark in the complicated condition. Then, by combination of the fields of deformation, excess pore pressure and moments of pile obtained form the calculation and the results of centrifuge modeling, the characteristics of the kinematic interaction between pile and soil and the aseismic reinforcing mechanism of stabilizing piles in slope were investigated. Moreover, the numerical analysis can predict the stable state of the stabilizing piles and the moment when the piles break during earthquake.更多还原