溪洛渡特高拱坝初期蓄水工作性态分析研究

Performance analysis of Xiluodu super-high arch dam in impounding period

大坝各方面性能能否经受住首次蓄水的考验,是关系大坝安全的关键问题。本文针对溪洛渡拱坝,采用非线性有限元方法,考虑横缝的接触非线性,实现了大坝初期蓄水全过程模拟,分析了蓄水过程中坝体和坝基变形、应力的分布特征和变化规律,以及横缝应力和张开度的变化情况,并确定了保证接缝灌浆的安全蓄水水位。研究结果表明,在水荷载作用下,坝体和坝基发生向下游的顺河向变形和向两岸的横河向变形,坝体上游面主拉应力和下游面主压应力不断增大,横缝有压紧的趋势。同时,对坝体与坝基关键变形和应力的初期实测数据与计算成果进行了对比,二者规律吻合较好;并结合国内同类大坝工程的情况分析了蓄水变形实测值与设计计算值存在差异的原因。计算和监测结果表明,溪洛渡初期蓄水阶段大坝应力应变及横缝状态符合特高拱坝低水位运行特征,大坝蓄水整体安全有保障。随着蓄水位增加,需跟踪开展大坝混凝土与基础岩石实际参数的反馈分析,动态评价大坝整体的安全性能。

Whether a dam can undergo the test of impoundment is a key question of its safety. Based on the Xiluodu arch dam, considering nonlinear contact of transverse joints, the whole process of the first im-pounding is simulated by using nonlinear finite element method. The stress and the strain distribution char-acteristics of dam and foundation are investigated, and the stress and the aperture variation of transverse joints are analyzed. Besides, reasonable water level for good grouting of transverse joints is determined. On the whole, in impounding period, water loading causes the deflection of dam and foundation downstream and towards the banks of the river. Consequently, the principal tensile stress of dam on the upstream sur-face and the principal compressive stress of dam on the downstream surface are increasing, and the aper-ture variation of transverse joints tends to decrease. Meanwhile, the calculated results of the stress and the strain in some key areas of dam and foundation are compared with their monitoring results. They are in good agreements in their change rule and distribution regulation, and the reason for the difference between their values is analyzed by combining the situation of some domestic similar dams. In conclusion, the de-flection and the stress of dam and foundation and the behavior of transverse joints accord with running sta-tus of super-high arch dams under low water level, and the integrity stability meets the design require-ments in the first impounding period. With the increase of water level,the feedback analysis of the mechan-ical parameters of concrete and rock need to be conducted to achieve the dynamic evaluation of dam safety.