动剪切模量Gd与阻尼比D是岩土体地震反应分析的两个主要参数，而初始状态是动力参数主要影响因素之一。通过大型动三轴试验，研究了应力比与含水状态对松散堆积体Gd与D的影响。试验结果表明，应力比Kc对松散堆积体最大动剪切模量Gdmax有重要影响，一定范围内（Kc=1～3），Kc越大，最大动剪切模量Gdmax越大，在Hardin公式基础上发展了一个考虑Kc影响的经验公式。对比松散堆积体饱和与风干两种状态的Gd/Gdmax-?dn（归一化动剪应变）关系曲线，发现风干状态下松散堆积体的Gd/Gdmax-?dn关系表现出更明显的非线性，另外风干状态阻尼比略大于饱和状态。应用改进的Gdmax经验公式与Gd/Gdmax-?dn关系进行了松散堆积体地表的地震反应谱分析，计算结果表明，应力比与含水状态对地表加速度反应谱有重要影响。

The dynamic shear modulus Gd and the damping ratio D are two main parameters in geomaterials seismic response analysis and the initial condition is one of the principal factors affecting the dynamic parameters. This paper studies the effects of initial stress ratio and moisture condition on dynamic shear modulus Gd and damping ratio D of loose deposit with large-scale dynamic triaxial tests. The experimental results show that the stress ratio Kc has important effect on the maximum dynamic shear modulus Gdmax of loose deposits. In a certain range of Kc=1-3, the stress ratio is larger, the maximum dynamic shear modulus is greater. Based on Hardin’s equation, an improved empirical equation considering the effect of stress ratio is proposed. By comparing the two Gd/Gdmax-?dn curves of saturated and air-dried loose deposits, the curve under air-dried condition is found to shows more obvious nonlinearity than the one under saturated condition. Moreover, the damping ratio under air-dried condition is slightly greater than the one under saturated condition. The proposed improved empirical equation of Gdmax and the nonlinear relationships of Gd/Gdmax-?dn are used to analyze the ground response spectrum of loose deposits. The calculation results show that the stress ratio and moisture condition influence the ground response spectrum obviously.