双向地震作用下锯末混合土场地动力特性分析

Dynamic Characteristics of Sawdust-mixed Clay Site Model under Bidirectional Seismic Actions

在北京工业大学振动台台阵系统上开展了一系列锯末混合土地基自由场振动台模型试验,试验中模型箱采用装配式连续体刚性模型箱,试验中输入地震动时程采用ElCentro地震动记录、Taft地震动记录和天津地震动记录,地震动输入方向分为水平单向和水平双向。文中,重点考察了双向地震动输入下锯末混合土模型场地的动力特性及其变化规律,主要指标包括模型场地地震动反应的峰值加速度及其动力放大系数、加速度时程及其傅氏谱。试验结果表明:随着输入地震动强度的增大,同一测点反应的峰值加速度总体上在增大,而其加速度动力放大系数总体上呈现减小的趋势,反应的频谱组成从较高频率向较低频率移动;双向地震作用下锯末混合土模型场地的动力变化规律与单向地震作用下较为一致。

A series of shaking table tests on free-field sawdust-mixed clay site model under uniform earthquake excitation was conducted at the multiple shaking table testing systems in Beijing University of Technology.These tests were performed using a rigid prefabricated continuous model box.The test system was subjected to strong ground motions from El Centro record,Taft record,and Tianjin record.In this paper,we focused on the dynamic characteristics of the sawdust-mixed clay site model under bidirectional seismic actions,including the peak ground accelerations and their amplification factors,acceleration time histories,and their Fourier spectra for the site responses.The test results indicated that the increase in the intensity of ground motions increases the peak ground acceleration at the same test point;however,its acceleration amplification factor generally decreases and the main frequency components move from high to low frequency.The dynamic change rule of the sawdust-mixed clay site model under bidirectional seismic actions is consistent with that of one-directional seismic action.