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地基土地震液化诱发的侧向扩展可导致桩基侧移过大甚至失效破坏,但如果场地存在冻土层,情况则变得复杂。通过试验研究了在地震作用下冻土、液化土和单桩三者之间的相互作用,分析了由于存在冻土层这一因素对地基液化和桩基承载性能的影响。试验中土体盛放在一个柔性模型箱当中,分为上下两层:下层为饱和砂土,上层为模拟冻土层。模拟的钢管桩嵌入土体之中,上部设有附加集中质量。测试过程中选取不同等级的调幅地震波对装置进行激励加载,分别观测桩身应变、桩与冻土层位移以及砂土内的孔隙水压力等参数。试验结果显示:地基土液化时,冻土层限制孔隙水排出而致使地基液化程度急剧发展,从而导致桩基的侧向变形快速增长;随着地震激励的增强,冻土层与桩体接触部位可能因挤压出现局部破损,导致二者分离;冻土层端面处桩体变形存在突变,此处桩体易于失效。
Lateral expansion induced by seismic liquefaction of foundation soil can lead to excessive or even failure of lateral displacement of piles, but the situation becomes complicated if there is permafrost in the site. The interaction between frozen soil, liquefied soil and single pile under the action of earthquake is studied through experiments. The influence of the factors of frozen soil layer on the liquefaction of foundation and the bearing capacity of pile foundation is analyzed. In the experiment, the soil is contained in a flexible model box divided into two layers: the lower layer is saturated sand and the upper layer is the simulated frozen layer. The simulated steel pipe pile is embedded in the soil with an additional concentrated mass on the upper part. In the testing process, different levels of amplitude-modulated seismic waves were selected for excitation and loading of the device, and the parameters of pile strain, pile-soil permafrost displacement and pore water pressure in sand were observed. The results show that when the foundation soil is liquefied, the liquefaction of the permafrost layer restricts the release of pore water, which leads to the rapid development of the liquefaction of the foundation. As a result, the lateral deformation of pile foundation grows rapidly. With the enhancement of seismic excitation, May be due to squeezing the local damage, resulting in the separation of the two; frozen soil layer at the end of the deformation of a sudden change, where the pile easy to failure.