非挤土桩对于砂土地层地震液化的影响机制研究

Study on the mechanism of the influence of non-squeezing pile on seismic liquefaction in sandy soil

如何通过工程措施实现地基抗液化能力的有效提升,是岩土工程领域近年来研究的热点问题之一。非挤土桩作为地基处理的常用措施,其加固后地层的抗液化能力能否得到提升,在学术界还存在着一定争议,主要原因是其对于砂层地震液化的影响机制尚未明确。针对该问题,本文开展了干砂及饱和砂土原状场地与非挤土桩加固场地的超重力模型试验,通过对比不同试验中地层的动力响应与超静孔隙水压力的发生发展规律,首次发现非挤土桩对于地层的作用机制并非仅有“刚度效应”,还有因振动过程中桩-土变形不协调而产生的附加作用力,该作用力将显著提升浅层土体的应力及应变水平,加大其液化的可能性,且随着埋深增加,该附加作用力逐渐变小,“刚度效应”将逐渐占据主导地位,相关研究成果可为进一步揭示非挤土桩抗震加固机理、评估其加固效果提供一定的基础和支撑。

Enhancing the effective anti-liquefaction capacity of foundations through engineering measures has been an important research focus in the field of geotechnical engineering in recent years.As a commonly used measure for foundation treatment,whether the anti-liquefaction capacity of the stratum can be improved after the reinforcement of non-squeezing piles is still controversial in the academic community,mainly because the mechanism of its influence on sandy soil liquefaction is not clear.In response to this problem,this paper carried out geotechnical centrifuge model test on the undisturbed sites with dry sand and saturated sandy soil and the sites reinforced by non-squeezing pile.By comparing the dynamic response and the development law of excess pore water pressure of the stratum in different experiments,it has been found for the first time that the mechanism of non-squeezing piles on the stratum is not only the“stiffness effect”,but also the additional force generated by the deformation mismatch between the pile and the soil during the vibration process.This additional force will significantly increase the stress and strain level of shallow soil,increasing its possibility of liquefaction.With the increase of buried depth,this additional force gradually decreases,and the“stiffness effect”will gradually become the dominant factor.The relevant research results can provide some basis and support for further revealing the anti-seismic reinforcement mechanism of non-squeezing piles and evaluating its reinforcement effect.