动力离心试验反演分析砂土模量阻尼比特征与可靠性

Inverse analysis of characteristics and reliability of sand shear modulus and damping ratio through dynamic centrifuge tests

基于阵列加速度记录获取土体剪应力-剪应变响应的反演分析方法,已在岩土模型试验和强震观测中得到诸多应用,但在求取剪切模量、阻尼比方面鲜见研究。利用一组动力离心模型试验,探讨加速度记录反演分析的动模量、最大模量、阻尼比等参数变化特征和影响因素,并结合经典公式对其可靠性进行评价。结果表明:获得动模量和阻尼比集中于0.01%~1%剪应变范围,数据离散性较小,随剪应变、埋深、孔隙比等变化趋势与既有认识吻合,表明选取的积分位移方法和剪切梁分布函数的合理性;不同荷载下各埋深的动模量和阻尼比数据,均良好服从Hardin双曲线模型,相关系数分别≥0.98和≥0.97;最大模量与孔隙比负相关,随埋深呈近似线性增长,证明动力荷载带给土体的振密效果;与单元试验结果相比,模型试验获得剪切模量略低,而阻尼比偏高,与单元试验的应力边界、加载方式等相关,分别验证定性和定量上反演分析动力离心试验应力-应变本构关系和模量阻尼比的可靠性。研究内容与结论为发展动力离心试验数据分析方法和提升土体动力本构关系认识、建立重要方法与有益参考。

The inverse analysis method for obtaining shear stress-strain response in soil based on acceleration array records has been applied in model tests and strong earthquake observations,but there are few studies on calculation of the corresponding shear modulus and damping ratio.A set of dynamic centrifugal model tests are used to discuss the characteristics and influencing factors of dynamic modulus,maximum modulus and damping ratio with the inverse analysis method based on acceleration array records,and its reliability is evaluated in combination with the classic formula.The results show that the dynamic modulus and the damping ratio are concentrated in the shear strain range of 0.01%—1%,and the data scatter is small.The variation trends of the dynamic modulus and the damping ratio with the shear strain,buried depth and void ratio are consistent with the general consensus,which reflects the rationality of the integral method and shear beam distribution function.The dynamic modulus and damping ratio data under different buried depths and loadings all obey the Hardin hyperbolic model well,and the correlation coefficients are larger than 0.98 and 0.97,respectively.The maximum modulus is negatively correlated with the void ratio and grows linearly with the buried depth,which proves the compacting effect of the vibration loads on the soil.Compared with the soil element test results,the shear modulus obtained in the model test is slightly lower while the damping ratio is slightly higher,which are related to the stress boundaries and loading methods of the element tests.The inverse analysis reliability of the shear stress-strain constitutive relation,shear modulus and damping ratio in dynamic centrifuge model tests is estimated qualitatively and quantitatively.The research work and conclusions provide important suggestions and useful references for the development of data analysis methods in dynamic centrifuge test and the insight of soil dynamic constitutive relation.