山东Ⅱ、Ⅲ类场地地震动峰值加速度放大效应分析

Exploration for amplification effects of peek ground motion in the sites of typesⅡ＆ Ⅲ in Shandong Province

摘要:

利用山东地区实测的Ⅱ类场地358 个钻孔和Ⅲ类场地140 个钻孔的地震动峰值加速度，计算了各个钻孔不同超越概率的土层地震动峰值加速度的放大系数ks，结果表明:(1) 同类场地土层放大系数ks值总体符合正态分布，既有相对集中性，也有离散性;(2) 随着基岩面输入地震动强度的增大，ks值降低，且Ⅲ类场地ks值降低较Ⅱ类的更为明显;(3)Ⅱ类场地随着基岩输入面埋深的增加，ks值呈增加趋势，约达20m 深后基本趋于稳定，而Ⅲ类场地基岩输入面埋深的增加对ks值的影响不甚显著;(4)Ⅱ类场地50 年超越概率10% 的平均ks值(1. 47) 略高于《中国地震动参数区划图》使用的全国平均ks值。本文尝试讨论了山东地区Ⅱ、Ⅲ类场地不同强度基岩峰值加速度输入的ks调整值。

Abstract:

In this paper，amplification coefficient ( ks ) of peek ground motion with different exceedance probability in types Ⅱ and Ⅲ sites，Shandong Province was estimated by analyzing the data of seismic response of soil layer from 358 and 140 drills from types Ⅱ and Ⅲ sites separately. From the results，one can conclude that: (1) the scatter plot of ks data shows that it generally obeys normal distribution; (2) ks decreases with the increase of the strength of incident ground motion，a phenomenon more apparent in type Ⅲ sites than in type Ⅱ sites; (3) for type Ⅱ site，with the increase of depth of the top surface of bedrock where ground motion incident，ks would increase gradually to a stable value until it reaches a depth up to approximately 20 meters or larger，while type Ⅲ site ks is normally insensitive to the depth; (4) the average of ks for type Ⅱ site is 1. 47，slightly larger than that used in the Seismic Ground Motion Parameter Zonation Map of China ( GB18306 － 2001 ) ． The paper also discusses the rectified value of ks for different strength of incident ground motion in type Ⅱ and Ⅲ sites in Shandong Province．