农村房屋地基砂垫层隔震系统振动台试验研究

为研究农村房屋的防震减灾措施,验证地基砂垫层的减震效果,制作了1/4缩尺的1层砌体结构模型,采用大型振动台进行了有地基砂垫层隔震措施与无隔震措施的对比试验。采用自行研制的大型叠层剪切模型土箱,地基土采用粉质黏土,砂垫层采用中粗河砂。进行多工况单向水平激励的模拟地震试验。结果表明:在峰值加速度为0. 1g和0. 2g的El Centro波激励下,地基砂垫层隔震系统主要依靠砂垫层的塑性变形消耗部分地震能量,从而减少了上部结构的地震反应;在峰值加速度为0. 4g的El Centro波激励下,一方面依靠砂土的塑性变形消耗部分地震能量,另一方面由于结构基础与地基土之间的相对滑移运动,限制了地震反应向上部结构的传递;在基础埋深范围内回填砂土的措施既促进了结构基础与地基土之间的相对滑移,又对上部结构的位移反应起到了较好的限制作用;地基砂垫层隔震系统可有效减小结构的加速度、层间位移、层间剪力,在峰值加速度为0. 4g的El Centro波激励下,楼层加速度峰值减小35%,层间位移峰值减小59%,层间最大剪力减小34%。

Experimental study on sand cushion isolation system for foundations of rural house by shaking table test

In order to study the measures of earthquake prevention and disaster reduction for rural houses as well as to verify the effect of sand cushion on the ground, a 1/4 scale masonry structure model was made, and a large shaking table test was carried out to compare the isolation measures with and without sand cushion on the ground. A large laminated shear model box developed by the authors was used in the test. Silty clay was employed in the foundation soil and medium coarse river sand was used in the sand cushion. Simulated seismic test was carried out by imputing horizontally unidirectional excitation under multi-working conditions. The results show that under the excitation of El Centro wave with peak accelerations of 0.1g and 0.2g, the foundation sand cushion isolation system mainly relies on the plastic deformation of the sand cushion to consume part of seismic energy, thus reducing the earthquake response of the superstructure. Under the excitation of El Centro wave with peak acceleration of 0.4g, on the one hand, the plastic deformation of sand consumes part of seismic energy; on the other hand, the relative slip motion between the foundation and the foundation soil restricts the transmission of earthquake response to the superstructure. The proposed measures of backfilling sand not only promote the relative slip between the foundation and the foundation soil but also play a better role in limiting the displacement response of the superstructure. The sand cushion isolation system for foundations can effectively reduce the acceleration, interlayer drift and base shear of the structure. Under the excitation of El Centro wave with a peak acceleration of 0.4g, the reduction rate of floor acceleration is 35%, the reduction rate of interlayer displacement is 59%, and the reduction rate of base shear is 34%.