考虑材料随机性的胶结砂砾石重力坝结构可靠度分析

Material randomness-considered analysis on structural reliability of cemented sand-gravel gravity dam

胶结砂砾石重力坝是一种新材料坝,具有造价低廉、施工快速、安全环保等优势,符合现在坝型选择趋势。总结实际工程情况,目前该坝型存在材料非均匀性突出的问题,对结构安全的影响不明。为此,根据胶结砂砾石材料力学性能参数统计规律,为表现材料非均匀性,将该材料的弹性模量和黏聚力模拟为随机场,结合《胶结颗粒料筑坝技术导则》(SL 678—2014)5.3小节中的应力分布要求,以坝体内部胶结砂砾石材料出现主拉应力的可能性作为结构可靠度的评价指标,用随机有限元法进行结构可靠度计算,并将其结果与材料均质确定性有限元计算结果比较。结果表明:结构可靠度计算结果具有可靠性,材料不均匀对坝体结构安全带来较大负面影响。为提高坝体结构安全,推广该新材料坝,为该坝型的设计、施工提供建议如下:在施工过程中需要对胶结砂砾石材料的弹性模量这一参数进行重点控制;需要在坝踵、坝趾附近适当提高胶结砂砾石材料和混凝土的强度等级,并加强施工质量控制。

The cemented sand-gravel gravity dam is a type of new material dam with the advantages of lower construction cost,fast construction,safety and environmental protection,etc.and then conforms with the trend of the dam type selection at present.In accordance with summarizing the relevant actual engineering status,the problem of material non-uniformity is prominent at present for this type of dam,from which the impact on the structural safety is not so clear.According to the statistical laws of the mechanical property parameters of the cemented sand-gravel material,the elastic modulus and cohesion of the material are simulated as random fields for expressing the non-uniformity of the material,and then the structure reliability is calculated with the stochastic finite element method by taking the possibility of the occurrence of principal stress in the cemented sand-gravel material inside the dam body as the index for evaluating the structure reliability in combination with the stress distribution requirement specified in the section of 5.3 in the“Technical Guideline for Cemented Material Dams”(SL 678—2014),from which,the result is compared with that from the finite element calculation made on the material homogeneity certainty.The result shows that the structure reliability calculation result is reliable,thus the non-uniformity of the material is to bring a larger negative impact on the structural safety of the dam body.In order to enhance the structural safety of the dam body and popularize this type of new material dam,some suggestions for the design and construction of this type of dam are given as the follows:the elastic modulus of the cemented sand-gravel material is necessary to be emphatically controlled during the construction,while the strength degrees of both the cemented sand-gravel material and the concrete at the dam toe and the dam heel are necessary to be appropriately enhanced,moreover,the construction quality control must be strengthened as well.