常规土类动剪切模量比和阻尼比试验研究

Laboratory experimental study on dynamic shear modulus ratio and damping ratio of soils

采用共振柱自振试验方法给出国内常规上类动剪切模量比Ｇ／Ｇｍａｘ和阻尼比λ随动剪应变γ变化的平均曲线、推荐值和包线。使用的共振柱仪是由工程力学研究所原有共振柱改装而成，并经试验验证了改装后仪器的精度和可靠性。试验土类包括粘土、粉质粘土、粉土、砂土、淤泥和淤泥质土，土样来自国内十余个不同地区。采用折线双曲线拟合Ｇ／Ｇｍａｘ，λ随γ衰减关系，其中参数ａ和ｂ由最小二乘法对每次试验结果回归分析得到。对同类土，将所有ａ、ｂ值平均，用均值ａ和ｂ给出动剪切模量比和阻尼比与剪应变关系，从而得到了此类上 Ｇ／Ｇｍａｘ、 λ随γ变化曲线及推荐值。试验是在两种团结压力下进行，因而得到的结果分别适用于上体埋深小于１０ｍ和埋深１０ｍ～２０ｍ之间的两种情况。

The averaging curves, recommended values and envelopes of dynamic shear modulus ratio G/Gmax and damping ratio λ versus dynamic shear strain γ for 6 types of soils in China are presented in the paper using the free vibration method by resonant column apparatus. The refitted resonant column apparatus in the Institute of Engineering Mechanics is employed for the experimental investigation and its accuracy and reliability have been verified by the tests. The undisturbed soil samples, including clay, silty clay, silt, sand, muck and mucky soil, come from about ten different legions in China. The relation of G/Gmax-γis fitted by two hyperbolic equations and the relation of λ-γ is also fitted by two hyperbolic equations. The parameters a and b in the equations are obtained from regression analysis of each testing data by the least squares method. For the same type of soil, the mean values, a and b, are gotten by averaging all a and b for the same type of soil. The relations of G/Gmax-γ and λ-γ for each type of soil are then derived using the mean parameters a and b, and finally, the averaging curves and recommended values of G/Gmax-γ and λ-γ for the 6 types of soils are obtained. Because the laboratory test is performed under consolidation pressures, the presented results in the paper are suitable respectively for two depths of soil, less than 10 meters as well as between 10 meters and 20 meters.