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在总结国内外振动台试验用土箱的基础上,研制了一个15层叠层方钢管框架并辅之以双侧面钢板约束的叠层剪切型模型土箱,钢管框架层间相对运动和垂直振动方向两边界的自由运动大大削弱了土箱边界效应。平行振动方向土箱两侧安装4根立柱,立柱上安装与土箱侧壁接触的若干轴承以限制箱内土体的转动。采用正弦波激振的扫频法测量了模型土箱的自振频率,与ABAQUS软件模拟的计算结果基本一致;采用脉冲信号激振的自由振动法,测量了土箱的阻尼比;进行了正弦波和地震波激励的自由场地振动台试验研究,测试了模型地基地表和1m深处的加速度时程,提出边界效应指数作为衡量土箱边界效应的指标并对几种土箱进行了比较。结果表明:设计的叠层剪切型土箱能较好地模拟自由场地的边界条件,比较理想地削弱了边界上地震波的反射或散射效应。
On the basis of summarizing domestic and foreign shaking table test soil box, a 15-story laminated square steel tube frame and a double-sided steel constrained laminated shear model soil box, steel pipe frame relative movement and vertical vibration The free movement of the two sides of the direction greatly weakened the boundary effect of the soil box. Parallel to the direction of vibration installed on both sides of the earth box four columns, the column installed on the sidewalls of the soil contact with a number of bearings to limit the soil inside the box rotation. The natural frequency of the model soil box was measured by the swept-frequency method of sine wave excitation, which was basically the same as that of the ABAQUS software simulation. The damping ratio of the soil box was measured by the free vibration method of pulsed signal excitation. Wave field and seismic wave excitation. The acceleration time history of the model ground surface and 1 m depth was tested. The boundary effect index was proposed as an index to measure the boundary effect of the soil box and several kinds of soil boxes were compared. The results show that the design of the laminated shear-type soil box can simulate the boundary conditions of the free space well and weaken the reflection or scattering effect of the seismic waves on the boundary ideally.