利用SDT-20型动三轴仪探究了黄土在双向动荷载下的动剪切模量特性。试验结果表明：初始循环偏应力和径向动荷载幅值对黄土的动剪切模量-动剪应变曲线没有明显影响，其对黄土的动剪切模量-循环次数曲线却有明显影响，初始循环偏应力和径向动荷载幅值越大，相同循环次数下黄土的动剪切模量越小。动剪切应变相等时，黄土的动剪切模量随固结比的增大而增大。双向动荷载作用下黄土存在临界循环偏应力，其值为0 kPa。当循环偏应力小于临界值时，动剪切模量随动剪应变的增大而增大；当循环偏应力大于临界值时，动剪切模量随动剪应变的增大而减小。利用拐点动剪切模量折减的方式，并同时结合修正Hardin-Drnevich模型，实现了对黄土在双向动荷载下动剪切模量-动剪应变关系的描述。经验证，模型的适用性较好。

The dynamic shear modulus of loess under bidirectional dynamic loading is determined by using a SDT-20 dynamic triaxixal apparatus. The experimental results show that although the initial cyclic deviatoric stress and radial vibration amplitude trivially influence the Gd-γd (dynamic shear modulus-dynamic shear strain) curves of loess, they can significantly affect Gd-N (dynamic shear modulus-cycle number) curves of loess. The dynamic shear modulus at the identical cycles decreases with the increase of initial cyclic deviator stress and radial vibration amplitudes. At the same dynamic shear strain, the dynamic shear modulus of loess increases significantly with the growth of consolidation ratio. There exists a threshold of cyclic deviator stress under bidirectional dynamic loading condition, which is about 0 kPa. When cyclic deviator stress is lower than the threshold, the dynamic shear modulus of loess increases with the growth of dynamic shear strain, but when cyclic deviator stress is higher than the threshold, the dynamic shear modulus decreases with the growth of dynamic shear strain. By reducing the shear modulus at the inflection point and with the modified Hardin-Drnevich model, the Gd-γd relationship of loess under the bidirectional dynamic loading condition is quantitatively described, and the applicability of the proposed model is demonstrated.