场地土层渗透性差异对砂土液化的影响研究

A Study of the Effect of Permeability Difference of Depositional Architecture on Sand Liquefaction

目前国内外的砂土液化判别方法主要是基于易液化土层的原位测试资料建立,未考虑其周围相邻土层的渗透性差异。理论上讲,在地震荷载作用下,相邻土层渗透性差异对液化土层超孔隙水压累积具有影响。基于原位静力触探和钻孔资料,建立了新西兰地震中砂土液化场地剖面,分析表明地表液化分布区域与场地土层结构特征显著相关。物理模型试验和数值模拟计算结果表明,高渗透性的砾石土层对相邻液化土层超孔隙水压累积影响显著,其影响程度可以采用土层竖向等效渗透系数表征,等效渗透系数增大时,易液化土层超孔隙水压力累积明显变小,降低了液化势。因此,需要在砂土液化判据中考虑相邻土层渗透性差异因素,进而提高液化判别结果的准确性。

Current methods for identifying sand liquefaction,both in domestic and international contexts,are primarily based on in-situ testing data from easily liquefiable soils,without adequately considering the permeability differences between adjacent soil layers.However,under seismic loads,these permeability differences can significantly influence the accumulation of excess pore water pressure in liquefied soils.A study based on static cone penetration and drilling data from liquefaction sites in New Zealand established a detailed profile of sand liquefaction during earthquakes.The analysis revealed that the distribution of surface liquefaction was closely linked to the structural characteristics of the site's soil layers.Further investigation through physical model experiments and numerical simulations demonstrated that high-permeability gravel layers have a pronounced effect on reducing the accumulation of excess pore water pressure in neighboring liquefiable soils.This influence can be quantitatively characterized by the vertical equivalent permeability coefficient of the soil layer.As the equivalent permeability coefficient increases,the accumulation of excess pore water pressure in liquefiable soils significantly decreases,thereby reducing the potential for liquefaction.Therefore,to enhance the accuracy of liquefaction assessments,it is crucial to account for permeability differences between adjacent soil layers in the sand liquefaction criteria.This would lead to more reliable predictions,especially in areas where soil permeability varies.