曲靖盆地粉质黏土、黏土土动力参数的统计分析

Statistical analysis dynamic parameters of silty and clay in Qujing basin

土动力参数是土层地震反应分析中不可或缺的重要参数,且区域性特点较强.曲靖断陷盆地主要发育于晚新生代以来,上新世沉积层厚约600 m.地层主要以湖积、冲积相为主,多以薄层或透镜体形态分布.文中收集了曲靖盆地内89个场地的92组粉质黏土和107组黏土的动三轴试验数据,进行了统计分析,并通过土层地震反应分析计算,与袁晓铭的推荐值和《工程场地地震安全性评价工作规范》(DB001—94)中给出的规范值进行对比.结果表明:3种不同的土动力参数存在较大差异,对土层地震反应分析结果亦有较大的影响,随着超越概率的降低,对峰值加速度、反应谱和特征周期的影响更加明显;本文统计的土动力参数与实际值对应的土层地震反应分析结果较接近,因此本文统计的粉质黏土和黏土土动力参数在曲靖盆地具有一定的代表性和适用性,在Ⅱ、Ⅲ级工程场地地震安全性评价工作中具有一定的借鉴和参考作用.

Soil dynamic parameter is one of the important parameters for seismic response analysis of soil layer,which has strong regional characteristics.Qujing basin is a faulted basin developed since Late Cenozoic Era.The Pliocene to Quaternary sedimentary thickness reach to six hundred meters.The stratum formation is mainly composed of lack deposition,grade alluvial and alluvial faces with the shape distribution of a thin layer or lens.In this paper,triaxial test dynamic parameters of silty and clay from 92 and 107 samples groups in 89 sites in Qujing basin region are collected and analyzed.Through the soil seismic response calculation and compared by recommended values from Yuan Xiaoming and values recommend in the code for seismic safety evaluation of engineering sites(DB001—94).The results show that our statistical values of dynamical parameters are great different from the other two kinds of recommended values.The effects of different dynamical parameters on site seismic response are obvious and with lower exceeding probability,the influences on peak acceleration,response spectra and characteristic period are more obvious.The results of site response analysis from the statistical values and test values are close.The statistical values can be used for reference in the Ⅱ、Ⅲ levels of work for seismic risk assessment of engineering projects in Qujing basin.