下蜀土边坡地震稳定性的大型振动台试验研究(Ⅰ)——模型试验设计

为研究下蜀土边坡的地震稳定性,选用天然下蜀土,按照Meymand的相似法则,对一坡高为0.5m、宽度为1.05m、坡角为45°的模型边坡进行了几何相似常数为20的1g大型振动台模型试验详细设计。首先,运用数值模拟的方法确定了模型边坡尺寸适当的边界范围,模型边坡地基厚度、坡脚前缘和坡肩后缘长度均取为0.5m;其次,按照确定的模型几何尺寸设计了符合试验要求的模型箱,其内壁净尺寸(长×宽×高)为1500mm×1050mm×1100mm,属刚性模型箱,且不会与模型边坡发生共振;最后,制定了包括加速度和位移在内的数据量测策略,运用拟静力法求得下蜀土边坡平均屈服加速度为0.561g,综合确定了地震动峰值(PGA)按0.1g、0.3g、0.6g和0.9g的顺序逐级加载的原则,并制定了详细的试验步骤,从而可保障试验得到可靠的结果。

Large-scale Shaking Table Test of Seismic Stability of Xiashu Loess Slopes(Ⅰ): Design of Model Test

Using natural Xiashu loesses and applying the law of similitude after Meymand,a detailed design of a 1g large-scale shaking table model test with a similarity factor of 20 for a model slope with a height of 0.5m,width of 1.05m,and slope angle of 45°was carried out aiming at investigating the seismic stability of Xiashu loess slopes.Firstly,appropriate boundary range of the model slope with a depth of the model slope base,a distance from the model slope toe to the left slope boundary and the one from the model slope crest to the right slope boundary all of 0.5m was identified by means of numerical analysis;Secondly, a rigid model box,which had internal dimensions of 1050 mm by 1500 mm in size and 1100 mm in height according to the determined dimension of the model slope was designed well meeting the requirements of the test and would not cause resonance with the model slope;Finally,tactics of measurements including accelerations and displacements were established,the average critical acceleration of the model slope of 0.561g was determined using the pseudostatic method,a series of loading rules were comprehensively identified in terms of the sequences of the peak ground acceleration(PGA) of 0.1g,0.3g,0.6g and 0.9g,and detailed test procedures were established,which gave a powerful guarantee for the test.