谷幅收缩对高拱坝变形及应力状态的影响

Influence of Valley Contraction on Deformation and Stress State of High Arch Dam

溪洛渡拱坝蓄水初期出现了较为明显的谷幅收缩现象,且量值远超同类工程,有必要开展谷幅收缩变形对拱坝变形及应力状态的影响研究。针对坝体已经历的三次完整蓄水-消落过程,对各条测线谷幅变形进行函数拟合,在此基础上,计算了各个蓄水-消落周期下,正常蓄水、死水位工况下坝体变位和坝体应力,对比分析了考虑谷幅收缩变形对大坝位移、应力及分布规律的影响。结果表明,正常蓄水工况下,在变形方面,一定幅度的谷幅变形引起坝体向上游变形趋势,可以部分抵消水沙压力造成的坝体向下游变形作用,使大坝变形减小;在应力方面,一定幅度的谷幅收缩会大大降低上游坝面坝踵拉应力和下游面坝体压应力,改善大坝受力状态。死水位时,随着谷幅收缩的加大,上游面主压应力持续增加,下游坝面主压应力先减小后增大,并在下游面将产生一定拉应力。研究表明,当前谷幅变形作用下,大坝具有较大的安全裕度。在预测极限谷幅状态下(VDL04测线谷幅收缩70.04 mm),溪洛渡高拱坝应力应变处于安全状态。

Xiluodu arch dam valley contraction deformation phenomenon is more obvious during initial impoundment,and the measured value is far more than similar engineering projects. It is necessary to study the influence of valley contraction on the deformation and stress state of high arch dam. For the three full cycles of water storage and water discharge,the measured contraction of valley width was fitted to each survey line. On this basis,dam displacement and stress are calculated for normal and dead water level of each impoundment cycle. Dam displacement,stress distribution in consideration of progressive valley contraction are compared and analyzed. The results show that the deformation caused by water and sand pressure can be partially offset by a certain range of valley deformation under normal water level condition. A certain range of valley contraction deformation will reduce the tensile stress of upstream dam heel and downstream compressive stress,thus improve the stress state of the dam under the normal water condition. Under dead water level,with the increase of the valley contraction,the principal compressive stress of upstream dam face continues to increase,the principal compressive stress of the downstream dam surface decreases firstly,then increases,and tensile stress occurs at the downstream face. The results show that the dam has a large safety margin under the deformation of the current valley contraction. The stress and strain of Xiluodu high arch dam are in a safe state under the limit valley contraction deformation state（ VDL04 survey line showed the valley contraction would be 70. 04 mm on convergence）