特高拱坝建基面浅层卸荷机制与稳定分析

Study of shallow unloading mechanism and stability of foundation interface of super high arch dam

随着我国水电资源的大力开发,高坝建设日益增多,面对这些大规模的建设,拱坝的稳定问题成为拱坝设计中的关键重大问题。对于处在高地应力河谷的拱坝建设,由于开挖,地应力释放引起基础岩体卸荷,造成的浅层稳定问题,对高坝设计来说是个少有成例的问题。对此问题,如果采用概念不对,误导了计算,则将引入失误。对高拱坝建基面浅层卸荷特征、产生机制进行详细讨论,结合小湾高拱坝遇到的浅层稳定问题,提出了拱坝多余力,及浅层建基面面安全系数的求法,利用最大最小原理对小湾拱坝建基面浅层稳定进行分析评价,分析结果在小湾工程的设计中得到应用,文中提出的分析方法可以指导同类工程的设计。

Along with the vigorous development of hydropower resources,many super high arch dams are constructing in Southwest region of China.The stability of these arch dams is a key and important problem in the process of design and construction.As for those arch dams constructed in high ground stress valley,foundation excavation may lead to geostress release and unloading of rock mass,and then causes shallow stability problem,which has few successful example for us to learn how to design and reinforce foundation for super high arch dam under these geo-condition.To this problem,unsuitable concept may bring about wrong calculation or numerical simulation,and then lead error to occur during design process.A detailed discussion is conducted focusing on the characters and mechanism of shallow unloading of excavated foundation surface of super high arch dam.Based on the Xiaowan Arch Dam,the calculation method of unbalance force of abutment and surface factor of safety of dam interface are proposed.By employing maximum-minimum principle,the stability of foundation interface of Xiaowan Arch Dam was analyzed and evaluated for supervising the design.The analysis results show that the proposed method is effective to supervise design for those super high arch dams similar to Xiaowan Arch Dam.