土质场地重力式挡土墙地震土压力振动台实验研究

EXPERIMENTAL STUDY OF SEISMIC EARTH PRESSURE OF GRW ON SOIL SITE

汶川震区路基挡土墙震害表明,地震动荷载作用下重力式挡墙的位移、破坏与基础场地形式有关,除岩质场地和土质场地挡墙所共有的外倾形式,土质地基挡土墙还表现有整体推移及下部向外推移的倾转变形等复杂模式,因此地震土压力大小及分布也将受到这种复杂土-结相互作用的影响。基于碎石土及风化花岗岩填料的土质场地重力式挡土墙大型振动台模型实验,对挡土墙地震土压力及变形模式开展了对比研究,发现在强震作用下,土质地基挡墙因基础约束较弱而产生位移,并伴随明显的墙—土分离现象,致使实测地震土压力较之抗震设计规范计算值偏小(0.4g峰值加速度下约小6%～15%),但作用点高度变化不大。由实验结果与现行抗震规范计算值的安全系数对比,认为对土质场地挡墙的地震土压力计算,按现行国内抗震设计规范基本能满足实际工程抗震设计需要;对于地震区挡墙设计,在允许挡墙发生少量容许位移的前提下可采用内摩擦角较大、自稳能力更好的墙背填料以减少地震土压力。

Based on Wenchuan earthquake damage survey,displacement and destruction of retaining wall under earthquake are related to the wall-based site form,In addition to the common form of extraversion on the rock site and soil site,The retaining wall on the soil site also perform whole movement and the lower passage rotating deformation complicated form,So the size of the seismic earth pressure and distribution will also effected by the complexity soil-struction interacting.Based on large-scale shaking table model test of GRW filled crushed gravel and decomposed granite,Compared seismic earth pressure and deformation,Experiments show that under strong earthquakes,due to the weak constraints of soil foundation,retaining wall occurred displacement and wall-soil separation,These lead to the measured seismic soil pressure smaller than design codes calculated（about 10% smaller at 0.4g peak acceleration）,but the point of pressure application changed little.By compared the test measured with the design codes calculated seismic soil pressure safety factors of GRW.Show that to the soil foundation retaining wall,the seismic soil pressure calculated by current seismic design codes can meet the engineering needs of seismic design,If small displacement of retaining wall can be allowed in retaining wall design for earthquake zone;adopting filling material of the back wall which presents greater internal friction angle and better self-stable ability may reduce the seismic soil pressure.