基于XFEM的砼重力坝强震破坏模式及抗震安全评价

Seismic failure mode and safety evaluation for concrete gravity dams based on XFEM

扩展有限元法(XFEM)通过在相关节点的影响域上富集非连续位移模式,使对非连续位移场的表征独立于单元边界,可有效描述混凝土中裂纹扩展。采用XFEM对Koyna重力坝地震破坏过程进行分析,结果表明,大坝开裂破坏分布与Koyna大坝实际破坏情况及文献中的模型试验结果相符,验证计算模型的有效性。将其应用到国内某混凝土重力坝,得到强震作用下动力响应及破坏模式,并据此评价大坝抗震安全性及抗震超载潜能。研究表明,强震作用下,大坝首先在下游折坡出现裂缝并扩展至上游面形成贯穿性裂缝,同时在坝踵、上游坡度变化处出现开裂破坏;该重力坝在设计地震作用下,尚有1.59～1.76倍的超载裕度,其抗震安全性能满足设计要求。

The extended finite element method （XFEM） can make the characterization of discontinuous displacement field independent upon element boundaries through enriching discontinuous displacement mode in the influence domain of related nodes. With this capacity, XFEM can effectively describe the crack propagation in concrete. Here, the damaged process of Koyna gravity dam during earthquake was analyzed with XFEM, the distribution of cracking damage was consistent with the actual condition and the model test results in literatures, it verified the validity of the XFEM calculation model. Then, this technique was used to analyze a domestic concrete gravity dam, and its dynamic response and failure mode during strong earthquake were obtained. Based on these results, the seismic safety and overload potential of the dam were assessed. The results showed that cracks initially emerge at the change position in the downstream slope and then extend to the upstream surface of the dam to form penetrating cracks; at the same time, the dam heel and the change position in upstream slope are also prone to suffer cracking destruction; the overload margin of the concrete gravity dam under the designed seismic loads is 1.59 -1.76 times, it meets the design requirements of seismic safety.