不同影响因素下路用黄河泥沙动剪切模量和阻尼比试验及理论模型研究

Experimental investigation and theoretical models on dynamic shear moduli and damping ratios for Yellow River sediment under different influence factors

沿黄河高速公路建设过程中,黄河泥沙作为路基填料的可行性已经得到验证和重视,然而目前有关黄河泥沙作为路基填料的动力特性的研究较少.本文利用英国GDS动态三轴试验系统,对取自黄河中下游郑州段的泥沙进行应力控制的动三轴试验,探究了围压、相对密实度和试验频率对黄河泥沙动剪应力–动剪应变关系、动剪切模量G和阻尼比D的影响,绘制了动剪应力–动剪应变关系骨干曲线和滞回曲线.结果表明,黄河泥沙的动剪切模量、阻尼比与剪应变关系可以用Hardin双曲线模型描述,围压对G和D的影响较大、试验频率对G和D的影响较小.综合与其他土体的动力特性对比表明,黄河泥沙动剪切模量折减曲线规律以及阻尼比D曲线规律和其他土体相符,其动力特性更接近于粉土和砂土,但与其他土体并不完全一致,具有一定的特殊性.最后,本文考虑了围压、相对密实度的影响,并结合现有经验公式,建立可以较好描述黄河泥沙最大动剪切模量G_(max)与围压、孔隙比关系的经验公式,同时建立了动剪切模量比G/G_(max)和D的数学模型,拟合结果显示,建立的模型能较好地描述黄河泥沙的G/G_(max)和D随剪应变的变化规律.

The dynamic shear modulus and damping ratio are essential parameters for the site seismic response analysis of major projects.During highway construction along the Yellow River,the feasibility of using Yellow River sediment as a subgrade filler has been verified and valued.However,the dynamic characteristics of Yellow River sediment as subgrade filler are rarely studied.In this paper,the British GDS dynamic triaxial test system was used to perform dynamic triaxial stress control tests on the sediment taken from the Zhengzhou section of the middle and lower reaches of the Yellow River.A total of 11 groups of tests were performed to explore the effects of confining pressure,relative density,and test frequency on the dynamic shear stress–dynamic shear strain relationship,dynamic shear modulus G,and damping ratio D of Yellow River sediment.The backbone curve and hysteresis curve of the dynamic shear stress-dynamic shear strain relationship were plotted.The results show that the relationship between the dynamic shear modulus,damping ratio,and shear strain of Yellow River sediment can be described by the Hardin hyperbolic model,and confining pressure has the greatest influence on the dynamic shear modulus and damping ratio of Yellow River sediment.For a given shear strain condition,the larger the confining pressure is,the larger the dynamic shear modulus.When the strain level is large,the dynamic shear modulus increases with the relative density;the damping ratio decreases with increasing confining pressure and increasing relative density.Frequency has no obvious effect on the dynamic shear modulus and damping ratio.A comprehensive comparison with the dynamic characteristics of other soils shows that the dynamic shear modulus reduction curve law and damping ratio D curve law of Yellow River sediment are consistent with those of other soils,and their dynamic characteristics are closer to silt and sand,but not completely consistent with those of other soils,with certain particularity.Finally,considering the influence of confining pressure and relative density,combined with the existing empirical formula,an empirical formula that can better describe the relationship between the maximum dynamic shear modulus G_(max)and the confining pressure and void ratio of Yellow River sediment is established.Additionally,a mathematical model of the dynamic shear modulus ratio G/G_(max)and D is established.The fitting results show that the established model can better describe the variation in G/G_(max) and D with the shear strain of Yellow River sediment.This capability provides an important basis for the seismic design of Yellow River sediment as subgrade filler.