弯曲冰块在顺直河段中的输移条件

针对弯曲冰块在顺直河段中的输移条件,以春季封冻河道的冰盖破裂机理为基础,根据水动力学、热力学、固体力学及气象水文等学科理论,综合考虑水力、热力、河势及地貌特征等影响因素,引入顺直河道固体边壁的约束条件,建立力学分析模型,进而提出了弯曲冰块在顺直河道中输移所需最小流量即临界流量的判别准则,并对其适用性及相关参数进行了研究分析。应用黄河河曲段的原型观测资料对该准则及相关参数进行了率定及验证,结果表明提出的针对弯曲冰块在顺直河段输移的临界流量计算值与实测值较为接近,可以认为该输移判别准则能够较好地用于判别弯曲冰块在顺直河段中的输移情况。此外,根据实测资料提出了反映热力消融对冰盖体厚度减小、强度降低等的综合系数表达式,可用于没有开河历史观测资料河道的冰情研究。

Transport criterion for bending ice-blocks in straight river reaches

As for the transport criterion for bending ice-blocks in straight river reaches,based on the ice-cover fracture mechanism of frozen rivers in spring,a mechanical model is established by introducing the constraints of solid walls of straight rivers according to the theories of hydrodynamics,thermodynamics,solid mechanics and hydrometeorology by comprehensively considering hydraulic conditions,thermal conditions,river regimes and topographic features.The criterion of the minimum flow discharge required for transport of bending ice-blocks in straight river reaches is put forward,that is,the critical flow discharge.Its applicability and the relevant parameters are analyzed.The criterion and the relevant parameters are calibrated and validated by means of the data of field observations in Hequ reach of Yellow River.The results show that the calculated values of the critical flow discharge for the transport of bending ice-blocks in straight river reaches are close to the observed ones.Accordingly,the proposed criterion can be appropriately used to determine the transport of bending ice-blocks in straight river reaches.In addition,according to the observed data,a mathematical expression is put forward for the comprehensive coefficient,which reflects the decrease of thickness and strength of ice-covers induced by thermal thawing,and it can be employed to study ice situations of river reaches without historical observation data of break.