路基对地基土液化特性的影响

]Influence of Embankment on Liquefaction Properties of Foundation Soil

摘要:

本文依托河海大学岩土所独立研发的程序WWCC，以广东省广珠东线中（山）-江（门）高速公路为工程背景，选取一处地基土层为基本模型，在三条不同地震波（人工波，汶川波E，汶川波N）作用下，通过动力有限元计算分析，对加载路基堆荷前后的地基土抗液化能力进行对比分析。结果表明公路地基在相同地震荷载作用下，增加路基堆荷后的抗液化能力明显提高，抗液化安全系数随着土层深度的增加逐渐增大，并通过改变路基的高度进一步分析路基荷载对地基土液化特性的影响。结果表明路基越高，地基土的抗液化能力越大。本文通过研究路堤对地基土液化特性的影响，证明路基荷载对公路工程抗液化是偏安全的。

Abstract:

The liquefaction resistances of foundation soil subjected to embankment loading and those without loading are compared and discussed by using the WWCC program developed independently by the Geotechnical Research Institute of Hohai University.Three different seismic waves and various heights of embankments are used to conduct dynamic finite element analysis of an embankment constructed in Guangdong, China.China has incurred multiple earthquakes；approximately one third of the total earthquakes in the country had magnitudes greater than 7.Earthquakes cause severe losses because many highways are located in earthquake prone areas.Such damage has attracted an increasing amount of attention from highway engineering academics because seismic loading causes liquefaction of ground soil.Foundation soil liquefaction occurs when pore water continuously accumulates and is influenced by the effect of embankment loading on foundation soil.The embankment loading causes a rapid increase in the pressure of pore water，and the shear strength approaches to zero，which leads to losses in sand bearing capacity and formation of the flow state.The main earthquake damage to roads located in liquefaction areas is large structure displacement.Damages to expressways caused by foundation liquefaction vary and include sinking, cracking，movement，breakage，and embankment collapse. At the present，many studies on foundation soil liquefaction focus mostly on natural foundation.A book titled “Specification of Earthquake Resistant Design for Highway Engineering” presents various liquefied standards.However，the criteria mentioned in this book are applicable only to the exploration stage；few studies have reported the effect of overlying buildings on the liquefaction properties of subgrade soils.Therefore，this paper studies the liquefaction resistance of subgrade soils in the highway engineering on the basis of previous research.When the natural foundation is subjected to additional embankment loading，the distribution of stress and pore water pressure in the foundation soils is changed.The effect of embankment loading on the foundation soil is so obvious that it is necessary to pay close attention on the research.In this study，three different seismic waves are used to conduct dynamic finite element analysis of an embankment.The results show that embankment loading significantly enhances the liquefaction resistance of subgrade soils，which means that the embankment loading has a positive effect on the liquefaction resistance of an expressway.The liquefaction resistance increases when the depth of the foundation soil increases；the highest increase was 38%.Moreover，a parameter study is conducted to further analyze the effect of embankment height on the liquefaction properties of subgrade soils.The results show that a higher embankment relates to higher liquefaction resistance.The influence of various heights is more obvious in deeper layers of foundation soil；that on shallow layers can be ignored. Based on the research of liquefaction properties of foundation soil subjected to embankment loading，it can be concluded that the liquefaction resistance of highways is markedly safer with an embankment load.