水库冰表层形变的现场观测与分析

冰层应变是决定静冰压力的主导因素。以红旗泡水库冰为例,开展不同方向上冰表形变的原位观测,改进现有冰温度应力计算模型来预测表层应力和评价边界约束、冰裂缝、风等环境因素对冰应力的影响。分析发现:冰层在边界约束下仍随冰温改变而伸长或收缩,日收缩量与膨胀量不等导致冰面产生残余形变,且呈各向异性;冰表层实际应变应由温度应变与环境调整应变组成,且第一主应变方向受寒潮和强风共同作用会发生偏转;冰应力模型表明环境调整应变可释放少量温度应力,但在冰温快速升高时,环境调整应变致使主应力明显高于温度应力。因此,静冰力计算模型不考虑因边界位移、冰层裂缝发展等引起的冰层形变(即环境调整应变)会产生较大误差。

Field observations and analysis of surface displacement of ice cover on reservoir

Ice strain dominates the static ice loads. Field investigations on surface ice displacements in six directions were conducted in Hongqipao Reservoir. An improved model was developed to predict the surface ice stress and to determine the impacts of environmental conditions, such as boundary constrains, ice cracks, and winds, on static ice stresses. The observations indicate that the ice cover is able to expand and contract under boundary constrains. Accumulated residual displacements are produced due to the daily differences between contractions and expansions, and show a significant anisotropy. The surface ice strain consists of thermal strain and environmentally adjusted strain. The first principal strain can rotate due to the joint impacts of cold spells and strong winds. Stress modeling argues that,generally,the environmental-ly adjusted strain reduces slightly the thermal stress. However, as the ice temperature increases sharply, it leads to a much higher stress than thermal stress. Accordingly, the ignorance of displacements due to boundary displacement and crack development (i.e. environmentally adjusted strains) would result in consid-erable error in predicting static ice loads.