近远场地震中土工格栅加筋土挡墙抗震特性的振动台试验研究

Large scale shaking table test on seismic behaviors of geogrid reinforced retaining walls under near-fault and far-field ground motions

地震中土工格栅加筋土挡墙的动态行为与抗震机理的认识还尚不清楚。采用叠层剪切型模型土箱开展大型振动台试验,基于量纲理论π定理的Froude常数设计试验模型,考虑近远场地震动影响,采用汶川地震中松潘远场波、什邡近场波和Taft中远场地震波,测试墙体加速度、加筋回填土加速度、墙体侧向变形、加筋区与非加筋区回填土表面震陷、加筋区填土超静孔隙水压力以及土工格栅应变特性,得出远场和中远场地震波对加筋结构产生了强烈的宏观反应特征,而近场波对加筋区填土超静孔隙水压力的微观反应影响显著,加速度和沉降反应特征表明土工格栅为柔性挡土墙提供了较强的抗震能力,格栅应变分布特征揭示了柔性挡土墙上受力分布规律。研究结果将为土工格栅加筋土挡墙抗震安全设计和工程施工提供依据。

The dynamic behavior and the aseismic mechanism of the geogrid reinforced retaining wall at present have not been understood very well. The laminar shear container of soil was used for the test model of the geogrid reinforced retaining wall,and its seismic behaviors were investigated by a large scale shaking table test. The similarity criterion of the test model was based on the Froude constant of π theorem. Under the near-fault and far-field ground motions,the SP far-field wave,the SF near-fault wave during Wenchuan earthquake and Taft mid-far-field wave were applied to studying the seismic behaviors of the geogrid reinforced retaining wall,including the wall acceleration,the acceleration of reinforced backfill soil,the lateral deformation of wall,the seismic subsidence of the backfill ground surface in the reinforced zone and unreinforced zone,the excess pore water pressure in reinforced backfill soil and strain characteristics of geogrid. The measured results show that the geogrid reinforced retaining wall exhibits strong macroscopic seismic response characteristics under the far-field and mid-far-field ground motions,while the test model exhibits strong microscopic seismic response characteristics under the near-fault ground motion. The seismic response characteristics of the acceleration and the subsidence may indicate that the geogrid layers play an important role in improving the seismic resistance of the retaining wall. The distribution characteristics of the geogrid strain may reveal the force distribution law along the flexible retaining wall.