武汉市区土体剪切波速与深度的经验关系

Relationship between Shear-wave Velocity and Soil Depth in the Wuhan Area

通过对武汉市区3个主要地质单元共8 305个剪切波速数据的分析整理,分别运用线性函数、一元二次多项式函数、指数函数对武汉市区不同地貌单元不同土类的剪切波速与深度的关系进行统计回归,得到其经验关系。结果表明,武汉市区土体剪切波速与埋深相关性比较明显;一元二次多项式函数的拟合效果最好。将实测数据与利用经验关系得到的预测值进行对比检验,两者基本吻合,可供武汉市区场地剪切波速数据缺乏时参考使用。

A large number of site seismic safety evaluations of major projects have recently been carried out in the Wuhan area, and, from these works, data on the shear-wave velocity of soil from the engineering geological borehole were collected. These data were obtained at different depths in the borehole. The area around Wuhan city was divided into four geological engineering zones according to rock and soil type. The first zone was analogous to the first terrace in the Yan gtze and Hanjiang Rivers, and the second zone was analogous to the second terrace in these river. The third zone was analogous to the second terrace in the Yangtze and Hanjiang Rivers. The fourth zone was analogous to the exposed area before the quaternary bedrock. The statistical work in this paper included shear-wave velocity data of 8,305 measure points. In the first zone, 880 measure points of silty clay with depths ranging from 1 m to 52 m, 630 measure points of clay with depths ranging from 1 m to 54 to 42 m, 955 measure points of silt points of silty fine sand with depths m, 295 measure points of silt with depths ranging from 2 m sand with depths ranging from 1 m to 48 m, 1,164 measure ranging from 1 m to 76 m, 1,433 measure points of fine sandwith depths ranging from 1 m to 70 m, 804 measure points of medium-coarse sand with depths ranging from 1 m to 75 m, and 469 measure points of gravelly soil with depths ranging from 3 m to 72 m were made. In the second zone, 440 measure points of silty clay with depths ranging from 1 m to 36 m and 239 measure points of clay with depths ranging from 1 m to 42 m were made. In the third zone, 503 measure points of silty clay with depths ranging from 1 m to 36 m and 239 measure points of clay with the depths ranging from 1 m to 38 m were made. The maximum shear-wave velocity of all drilling boreholes exceeded 500 m/s. Thus, the depth of all drilling boreholes was consistent with the requirements of the engineering site seismic safety evaluation （GB17741-2015）. By using three statistical models of the first-order linear equation, exponential equation, and unary polynomial equation of two degree, the empirical relationship between shear- wave velocity and depths of different conventional soil types in three geomorphic units were respectively obtained. Results showed an obvious correlation between shear-wave velocity and soil depth. Overall, the polynomial equation in one two-order showed the highest fitting accuracy. Comparison between the measured and predicted values showed very minor differences. This re sult indicates that the relationship between shear-wave velocity and soil depth is reliable and reasonable. Taken together, the results of this work could be used as a reference when shear- wave velocities are not tested for sites.