基于内聚力模型的高心墙堆石坝坝顶裂缝模拟及其成因分析

Modeling of dam crest cracks of high core rockfill dam based on cohesive zone model and crack formation analysis

将基于弹塑性断裂力学的内聚力模型引入有限元法,采用非线性界面单元,通过定义界面单元的法向和切向应力与张开和滑移变形之间的关系描述裂缝发生后的界面力学特性,模拟某高心墙堆石坝的坝顶裂缝。计算过程中考虑筑坝材料的流变和湿化变形。研究结果表明:基于内聚力模型的有限元法计算出的裂缝与实际情况比较吻合。采用该方法计算了蓄水期之后3年的坝顶裂缝,裂缝变化幅度微小,较为稳定,且并未深入心墙。在首次蓄水的过程中,上游堆石流变和湿化变形较大,上下游坝壳料沉降不均匀程度也较大,因此,坝体变形不协调导致坝顶出现纵向裂缝。

The cohesive zone model based on elastoplastic fracture mechanics was introduced to the finite element model. Using nonlinear cohesive interface elements and defining the relationship between normal-tangential stresses and opening-slipping deformation of interface elements, interfacial mechanical characteristics of cracks were described. This method was employed to simulate crest cracks of a high core rockfill dam. Rheological and wetting deformation of the dam materials was taken into account in the calculation process. The results show that cracks calculated by this method are in satisfactory agreement with the actual situation. The dam crest cracks that develop three years after impounding are predicted. The cracks develop slightly and are relatively stable, without developing into the core wall. The rheological and wetting deformation of upstream rockfill are relatively large during the first impounding process and the degree of settlement non-uniformity between upstream and downstream dam materials is also large, and therefore uncoordinated deformation of the dam causes the longitudinal cracks in the crest region.