砂卵(砾)石动剪切模量比与阻尼比的试验研究

Experimental Research on Dynamic Shear Modular Ratio and Damping Ratio of Sandy Gravel Soil

砂卵(砾)石的动剪切模量比和阻尼比是河谷地貌场地地震反应分析的重要参数,对设计地震动参数的确定有重要影响。本文利用商洛市地震小区划项目砂卵石的动三轴试验结果,结合其他砂卵(砾)石动三轴试验结果,分组统计得到了稍密、中密、密实砂卵(砾)动三轴试验的推荐结果。建立了典型场地模型,研究了其动剪切模量比和阻尼比的不确定性对场地地震反应的影响。研究表明:动剪切模量比、阻尼比平均值±1倍标准差的不确定性对砂卵石场地峰值加速度的影响较小,说明了分组及统计结果的合理性;不同概率水平下,动剪模量比、阻尼比的变化导致高频部分反应谱有明显差异,0.04—0.1s的反应谱变化范围在20%左右,但对大于1.0s的长周期反应谱影响很小。针对砂卵(砾)石动剪切模量比和阻尼比的研究对提高工程场地设计地震动参数的可靠性具有重要意义。

The dynamic shear modulus ratio and damping ratio of sand gravel are important parameters for seismic response analysis of valley geomorphic sites, which have an important impact on the determination of design ground motion parameters. In this paper, based on the project of Shangluo Seismic Microzonation, the dynamic triaxial test of sandy pebbles has been performed. Combined with the other results of sandy gravel, the recommended results of slightly dense, medium dense and dense sandy gravel were obtained. By building the typical site model, the influence of the dynamic shear modulus ratio and the damping ratio uncertainty on the seismic response of the site is studied. The results show that the uncertainty of the average of the dynamic shear modulus ratio and the damping ratio ±1 times the standard deviation has little effect on the peak acceleration of the sandy pebble site, and the rationality of the grouping and statistical results is explained. Under different probability levels, the change of shear modulus ratio and damping ratio leads to a significant difference in the response spectrum of high frequency. The response spectrum of 0.04-0.1s range from about 20%, but it has little effect on the long period spectrum of more than 1.0s. The study of dynamic shear modulus ratio and damping ratio of sandy gravel has great significance to improve the reliability of the designing ground motion parameters.