不同厚度层状边坡动力响应的模型试验研究

Model Test on Dynamic Response of Layered Slopes with Different Thicknesses

摘要:

采用振动台物理模拟试验方法,以4种不同覆土厚度的层状边坡模型为研究对象,水平输入振幅逐渐增大的正弦波加速度,分析了结构面上覆不同厚度土层对动力作用下边坡的稳定影响.研究了在动力作用下边坡的破坏位置和性质、破坏形式及最危险覆土厚度,验证了坡面放大效应与高程的关系,采用MIDAS/GTS软件对模型试验进行振型分析,分析了模型边坡的自振频率与覆土厚度的变化关系.试验结果表明：①模型破坏时最先出现的裂缝在边坡的中上部,且6 cm覆土厚度的模型对振动的响应最大,对应到实际工程中时12m厚度土层覆盖的边坡是最应该注意防护的.②不同厚度的土层破坏的形式不同：当土层厚度较薄时模型破坏较迅速,基本沿结构面发生整体滑动破坏,且滑动呈现一定的流体特性;当覆土较厚时裂缝先在模型中上部出现,随着振动的持续裂缝继续发展,最后发生整体性崩塌.③随着高程的增加峰值加速度总体呈放大趋势,但最大值出现在边坡中上部而非坡顶,说明不仅均质边坡有加速度的高程放大效应,层状边坡也具有加速度的高程放大效应.

Abstract:

Using shaking table tests,we studied four layered slopes with different overburdened soils by increasing the horizontal sine acceleration time history as the input to analyze the impact of the thickness of the overburdened soils on the stability of the layered slopes.The failure position,property,pattern,and disadvantageous thickness of the overburdened soil were thoroughly investigated,and the relationship between the slope magnifying effect and the altitude was verified.A mode analysis was conducted for the test model using MIDAS/GTS to study the relationship between the self-vibration frequency and the thickness of the overburdened soil.The test results indicated the following:(1)The first failure plane was observed in the middle and the upper parts of the slope where the maximum response was found to be in the model slope in the case ofthe 6-cm-thick overburdened soil.(2)The failure patterns were different for the slopes with different thicknesses of the overburdened soil.In the case of the slope of a relatively thick overburdened soil,the fissures occurred first on the higher part of the slope and kept spreading until the entire slope collapsed in the avalanche mode.(3)With an increase in the altitude,the peak acceleration tended to increase as well,but the maximum value was observed in the middle and the upper parts instead of at the crest of the slope,which implied that the altitude magnifying effect occurred not only in the homogenous slope but also in the layered slope.