砂类土最大动剪切模量的新预测模型

A new prediction model of small-strain shear modulus of sandy soils

根据不同级配的南沙和西沙群岛珊瑚砂最大动剪切模量G0的共振柱试验结果,发现相同有效围压σ’0下不同级配、不同海洋珊瑚砂的G0分布范围存在上、下界限。最大孔隙比emax和最小孔隙比emin是可以综合反映砂类土级配和颗粒形状特性的状态参量,G0界限值与极限孔隙比(emax和emin)状态下的G0外推结果相吻合。相同的σ’0下,珊瑚砂的G0下限值G0min随emax的增大而减小,G0上限值G0max随emin的增大而减小。根据不同σ’0下G0min与emax及G0max与emin关系建立了预测珊瑚砂G0界限值的经验公式,不同孔隙比e状态下的G0可以根据界限值G0min、G0max按相对密实度Dr非线性插值获得。新的G0预测模型对同一类别、不同级配的砂土具有较好的普适性。对于不同类别的砂土,引入与矿物组分有关的系数a对模型进行修正,采用文献中大量的G0试验结果对模型进行了验证,新的G0预测模型的普适性明显优于传统Hardin模型。

A series of resonant column tests was conducted on coral sands from the Nansha and Xisha Islands of the South China Sea with different grain gradations.It is found that there are upper and lower limits in the small-strain shear modulus,G0 distribution ranges of coral sand from different seas and with different gradations under the same effective confining pressureσ’0.The maximum and the minimum void ratios,emax and emin,are comprehensive state parameters for effectively characterizing the particle gradation and shape characteristics of sandy soils.The limit values of G0 are consistent with the extrapolated G0 results at emax and emin.Under the sameσ’0,the lower limit values of G0(G0 min)and the upper limit values of G0(G0 max)of coral sand decrease with the increasing emax and emin,respectively.Empirical formulas for predicting the G0 limit values of coral sand are established based on the relationship between G0 min and emax,and the relationship between G0 max and emin under differentσ’0.The G0 of coral sand with various void ratios e can be determined by nonlinear interpolation using the values of G0 min,G0 max and the relative density Dr.The new G0 prediction model has good universality for sands with similar morphology and mineralogy of the particle forms and different gradations.For other types of sandy soils,a correction coefficient a is introduced to consider the effect of the mineral composition on G0.The general applicability of the new G0 prediction model,superior to the common Hardin prediction model,is validated by the G0 experimental data published in the literatures.