黑龙江地区土层剪切波速与埋深关系及其变异性对土层地震反应的影响

Relationship between shear wave velocity and burial depth in the Heilongjiang area and the impact of its variability on the seismic response of soil layers

摘要:

土层剪切波速是岩土体的固有属性,有显著的地域特征,对土层地震反应分析有重要影响。文章基于黑龙江地区重大工程场地地震安全性评价工作中的土层剪切波速资料,分别采用线性模型、二项式模型、幂函数和幂函数常数组合模型对各类土、粉质黏土、黏土、砂土、卵砾石土和风化岩进行统计回归,得到不同模型的拟合参数及拟合优度指标,给出了黑龙江地区常见土类的剪切波速与埋深的关系。剪切波速测试产生的系统误差对土层地震反应计算结果会造成一定的影响,以黑龙江地区为例,探讨了在不同强度地震作用输入下,不同场地剪切波速变异对土层地震反应结果(场地放大系数F_PGA,反应谱平台值β和特征周期T_g)的影响。结果表明:(1)土层剪切波速随着土层埋深的增加而增大;(2)总体而言,场地剪切波速负向变异使得F_PGA、β减小,T_g增大,正向变异与之相反;(3)剪切波速负向变异对F_PGA、β和T_g的影响明显远大于正向变异;(4)T_g对剪切波速变异最为敏感,F_PGA次之,β最低;(5)输入地震动越强,剪切波速变异引起的误差越大;(6)场地较软时,剪切波速测试准确性不可忽视,当测试结果偏大时,将对长周期建筑造成严重后果。

Abstract:

Shear wave velocity (vS), an inherent property of geotechnical materials with substantial regional characteristics, critically influences the seismic response of soil layers. Utilizing vS data from seismic safety evaluations at major engineering sites in the Heilongjiang area, statistical regressions were performed using linear, binomial, power function, and power-function-with-constant models across various soil types, including silty clay, clay, sand, gravelly soil, and weathered rock. The resulting fitting parameters and goodness-of-fit indicators for different models were obtained, providing insights into the relationship between vS and burial depth for common soil types in the Heilongjiang area. Systematic errors in vS measurements can impact seismic response calculations. Focusing on the Heilongjiang area, this study investigated how vS variability affects seismic response parameters, specifically the site amplification factor (FPGA), spectral plateau value (β), and characteristic period (T_g) under varying seismic intensities. Key results indicate the following: (1) vS increases nonlinearly with burial depth; (2) negative variations in vS generally reduce FPGA and β while increasing T_g, whereas positive variations produce the opposite effects; (3) negative variations in vS have a substantially greater influence on all three parameters than positive variations; (4) sensitivity to vS variability follows the order: T_g＞F_PGA＞β; (5) stronger input motions amplify errors caused by vS variability; and (6) for soft sites, vS measurement accuracy cannot be ignored and overestimation of test results may severely affect long-period structures.