特高拱坝建基面岩体选择的工程类比法研究

为确定坝高超过200 m的特高拱坝建基面可利用岩体的选择标准,对国内7座特高拱坝建基岩体的利用情况进行了综合评价,通过工程类比法分析了特高拱坝建基面可利用岩体的选择因素,提出了特高拱坝建基面可利用岩体的选择标准。研究表明,特高拱坝及坝基在荷载作用下的破坏模式为压破坏和剪破坏,要求拱坝建基岩体应具有足够的承载能力、抗变形能力、抗剪切能力以及抗滑稳定性。国内特高拱坝建基面可利用岩体的选择主要是以岩体质量分级为综合评价指标,不同坝基部位可选择不同质量级别的岩体;Ⅱ级岩体是特高拱坝的优良的建基岩体,中部建基面可以有效地利用部分Ⅲ₁级岩体,上部可适当利用Ⅲ₂级岩体;对于特高拱坝坝基,变形模量和黏聚力略大于规范建议值;特高拱坝建基面可利用岩体选择以荷载及应力水平为基础,以拱坝稳定为前提,以变形、强度等力学参数为依据,以岩体质量级别为具体表征,按不同高度分区域进行多因素综合论证和选择。

Criterion of Rockmass Selection for Super-high Arch Dam Foundation Based on Engineering Analogy Method

The criterion for available foundation rock mass of super-high arch dams over 200 meters is proposed through analyzing the factors of selecting available rock mass by engineering analogy method. The utilization of excavated foundation rock mass of seven super-high arch dams in China is investigated. Compression failure and shearfailure of super-high arch dams and dam foundations under loading pose requirements on the quality of dam foundation: sufficient bearing capacity, deformation resistance, shear resistance, and anti-sliding stability. In China, classification of rock mass quality is the general evaluation indicator for the selection of foundation rock mass of super-high arch dams. Different qualities of rock mass are required at corresponding positions: class-Ⅱ rock mass is regarded superb for the foundation rock mass of super-high arch dam; class-Ⅲ₁ could be used for the middle part of foundation; and class-Ⅲ₂ for the upper part. The deformation modulus and cohesive strength of rock mass in practical engineering are larger than the values suggested in specification. In conclusion, the selection of available rock mass for foundation surface of super-high arch dam is a process involving the demonstration of multiple factors on the premise of dam stability with mechanical properties and rock mass quality classification as general evaluation indicators.