含水率对土体的弹性模量、黏聚力、内摩擦角以及土体密度都会产生影响。密实度一定的情况下，黏性土的多种力学参数会随着最佳含水率的出现而出现“峰值”效应。利用 FLAC3D 差分软件对不饱和土在地震作用下的动力响应进行了模拟和分析，探讨了土中含水率对于地下结构地震动力响应的影响规律。结果表明，在最佳含水率附近，土层的性质对于地下结构的作用来说是最良好的，此时结构的内力可取得最小值；顶板和底板的相对水平位移变化不大，并且位移的数值随着含水率的增加而逐渐减小；土体和结构的加速度峰值都随着含水率的增加而呈减小的趋势。%Moisture content of soil has definite effects on elasticity modulus, cohesion, internal friction angle and density of soil. Given compactness of soil, several mechanical parameters of soil will have“peak value” effect at the optimum moisture content. In this paper simulation and analysis on dynamic responses of unsaturated soil under seismic excitations are carried out by using Flac3D finite difference software, and the effect of moisture content on dynamic responses of underground structure under seismic excitations is investigated. Analysis results show that properties of soil at the optimum water content are optimal for the seismic responses of underground structures, because in this case the internal forces achieve the minimum values; the relative horizontal displacement of top and bottom slabs has not significant change, and the values of displacement are gradually decreasing with the increase of water content; and so does the maximum accelerations of soil and structure with the increase of water content.
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