地震作用下地裂缝场地地表加速度响应的振动台试验研究

Shaking Table Test Study on Seismic Acceleration Response of Ground Fissure Sites under Horizontal Seismic Action

本文以西安地铁二号线穿越F6和F6'段地裂缝场地为原型,对水平地震作用下地裂缝场地地表加速度响应规律开展1∶15的振动台模型试验研究。试验时分别施加7种不同峰值加速度的El Centro波和Taft波激励,实测地裂缝场地表面6个测点的响应加速度值。试验结果表明:在El Centro波激励下,地裂缝场地地表响应加速度放大系数均大于1.0,但随着激励峰值加速度增大,放大系数以激励峰值加速度300gal为界呈"z"字形骤降;Taft波激励下,地裂缝场地表面响应加速度放大系数均大于1.0,但随着激励峰值加速度增大,放大系数以激励峰值加速度200gal为界呈两段折线形减小且渐趋平缓。在El Centro波和Taft波激励下,地裂缝场地表面的响应加速度放大系数均随着激励峰值加速度的增加而减小,但减小速率和变化形态因激励地震波不同而有差异。工程实践中,建议避免将工程结构布设于"y"形地裂缝间的楔形体中,或者采取切实有效的抗震或减震措施。

Based on the background of ground fissure sites where the subway line 2 crosses the ground fissure F6 and F16 in Xi＇an, the seismic response experiment of ground fissure sites under horizontal seismic action was ac- complished on the shaking table test system with a scale of 1 ： 15. Seven different conditions of exciting accelera- tion peak of El Centro wave and Taft wave were respectively loaded on the shaking table experiment to measure the response acceleration of 6 measuring points on the top of ground fissure model with acceleration sensor. The experiment results proved that, triggered by El Centro wave, the amplification coefficients of response ac- celeration on the top of ground fissure sites model were all over 1.0. However, with the increment of exciting peak acceleration, the amplification coefficients of response acceleration were decreasing rapidly in the shape of ＂z＂ when there was an inflection point and the excitation peak acceleration was equal to 300 gal. Furthermore, triggered by Taft wave, the amplification coefficients of response acceleration on the top of ground fissure sites model were all over 1.0. With the increment of exciting peak acceleration, the amplification coefficients were decreasing gradually when there was an inflection point and the excitation peak acceleration was equal to 200 gal. Triggered by both El Centro wave and Taft wave, the amplification coefficients of response accelera- tion on the top of ground fissure sites model reduced with the increase of the exciting peak acceleration. How- ever, the reducing rates and curve shapes varied with different exciting seismic waves. In the practice of engi- neering, structures should be avoided on the location of ＂y＂ shaped wedge ＂y＂ shaped between the ground fis- sures, or effective seismic control measures for construction structures should be adopted.