考虑残余体应变的土石坝地震永久变形分析

Analysis of earthquake induced permanent deformation of rockfill dam considering residual volumetric strain

地震永久变形是评价土石坝抗震稳定性的一个重要依据,其合理计算需要同时考虑材料的残余体积应变和残余剪切应变的影响。因此,在过去提出的永久变形等效节点力计算方法的基础上,通过考虑剪切压缩耦合作用来反映残余体积应变对地震永久变形的影响,并推导了相应的模量矩阵,明确了参数选择和计算步骤。对典型单元体的残余变形模式进行了分析,计算得到的剪切应变和体积应变大小均与理论值相符,验证了模量矩阵的可靠性。在此基础上,对心墙堆石坝和面板堆石坝的算例进行了计算,重点分析了竖直向、顺河向和横河向3个方向永久变形分布,并与实测规律进行比较。计算结果表明,考虑残余体应变之后,所提方法能够反映土石坝地震永久变形以沉降为主、水平变形相对较小的特点,可更为合理地反映地震永久变形的规律。

The earthquake induced permanent deformation is a key index for aseismic safety evaluation of rockfill dam. In order to calculate the permanent deformation reasonably, both residual volumetric strain and residual shear strain induced by the earthquake loading should be taken into account. For this reason, the method presented by LIU Hart-long is modified. In the modified method, the residual volumetric strain is modeled by a shear-dilation-based approach. The derivation of the dilatancy modulus matrix is given in detail; and the calculation parameters and the analysis steps are also introduced. To test the reliability of dilatancy modulus matrix, the permanent deformation mode of a typical element is analyzed, the computed shear strain and volumetric strain are in good coincidence with the theoretical values. After that, the proposed method is used to calculate the earthquake induced permanent deformation of a core rockfill dam and a concrete faced rockfill dam. The computed distributions of the vertical, longitudinal and transversal permanent displacements are studied in detail. By comparing with the measured results, it is found that the dam deformations are mainly residual settlement; and the horizontal displacements are relatively small. It is proved that the proposed method can catch the features of the permanent deformation behavior of rockfill dam and it can give more reasonable results.