【摘要】 拉西瓦水电站坝基地应力达30~70 MPa,坝基的开挖将会引起坝基回弹进而发生卸荷破坏,岩体质量下降,基础处理困难。因此,选择减轻坝基卸荷破坏程度的开挖型式是拉西瓦工程坝基开挖设计中研究的重要技术问题。文章介绍了拉西瓦拱坝坝基的地质和地应力环境;用平面非线性有限元、三维非线性有限元等不同的方法对平底开挖和反弧开挖等不同的坝基开挖型式进行了分析;对坝基开挖卸荷规律、应力屈服范围、坝基回弹数值等进行了研究。成果表明,采用光滑反弧型开挖,河谷应力集中区随坝基开挖向建基面下部转移,坝基开挖过程中未出现明显岩爆、剥离等高地应力现象;反弧型开挖较传统的平底开挖,坝基两侧应力集中现象、应力屈服范围等情况得到改善,坝基卸荷破坏有所减弱。为高地应力区的拱坝坝基开挖设计提供了可以借鉴的经验。更多还原

【Abstract】 The terrestrial stress in Laxiwa dam foundation is 30~70 MPa.The excavation of dam foundation would result in dam foundation rebound and loadoff failure,and drop of foundation rock mass quality,which makes it difficult to prepare foundation treatment.Through analytic justification,proper excavation design of dam foundation is an important means to guarantee the quality of rock mass.This paper presents geological and terrestrial stress state of Laxiwa arch dam foundation.The analyses were made for various types of excavation on the basis of plane nonlinear finite element method,3-D nonlinear finite element method.The study was also carried out for loadoff regularity due to dam foundation excavation,stress yielding scope,rebound number of dam foundation.The results indicate that stress concentration zone in valley will be shifted with the dam foundation excavation underneath the dam foundation by use of the smooth ogee excavation method,and the stress of exposed rock decreases greatly.This is the main reason that no obvious rock burst or/and stripping due to high terrestrial stress occurs during dam foundation excavation.The smooth ogee excavation has much improvement compared to the traditional flat-bottom excavation,and the stress concentration at both sides of dam foundation,stress yield extent and the dam foundation loadoff failure have somewhat been mitigated.Through actual excavation monitoring,it has presented some experience and reference for excavation design of arch dam foundation in high terrestrial stress zone.更多还原