堆石料湿化变形特性大型三轴试验研究

Large-scale triaxial test study on wetting deformation characteristics of rockfill materials

堆石料浸水湿化易导致其和心墙之间变形的不协调,从而在坝顶部位产生纵向裂缝,危害大坝安全。通过对某水电站筑坝堆石料开展大型三轴压缩试验和三轴湿化试验,分别研究了加载和湿化过程中剪胀比与应力比之间的关系,以及湿化应变与围压和应力水平的关系。结果表明:湿化试样的峰值强度与初始饱和试样的峰值强度基本相同,即试样湿化时的应力水平对其峰值强度几乎没有影响,但试样的最终体变明显受到湿化时应力水平的影响。因此,计算土石坝湿化变形宜基于单线法试验;三轴湿化试验时的固结围压和应力水平均对湿化应变具有显著影响,围压越高,湿化体积应变越大,湿化应力水平越高,轴向湿化应变越大,据此提出了一个考虑围压和应力水平影响的湿化应变计算模型;堆石料在加载和湿化过程中服从不同的应力剪胀方程,在构建湿化变形的弹塑性模型时,应采用不同的塑性势函数分别描述堆石料加载应变方向和湿化应变方向。研究成果对土石坝湿化变形模拟和坝体裂缝预测具有一定的指导意义和工程应用价值。

The wetting of rockfill material can easily lead to the uncoordinated deformation between it and the core wall,thus causing longitudinal cracks at the top of the dam and endangering the safety of the dam.Through the largescale triaxial compression test and triaxial wetting test of rockfill materials of a hydropower station,the relationship between dilatancy ratio and stress ratio during loading and wetting process,and the relationship between wetting strain and confining pressure and stress level were studied respectively.The results show that the peak strength of the wetting specimen is basically the same as that of the initial saturated specimen,that is,the stress level of the specimen during wetting has little effect on its peak strength,but the final volume change of the specimen is obviously affected by the stress level during wetting.Therefore,the calculation of the wetting deformation of the earth-rock dam should be based on the single-line test.The consolidation of confining pressure and stress level during the triaxial wetting test has a significant effect on the wetting strain value.The higher the confining pressure,the larger the wetting volume strain,the higher the wetting stress level,and the larger the axial wetting strain.Based on this,a wetting strain calculation model considering the influence of confining pressure and stress level is proposed.In the process of loading and wetting,rockfill materials obey different stress dilatancy equations.When constructing the elastoplastic model of wetting deformation,different plastic potential functions should be used to describe the loading strain direction and wetting strain direction of rockfill materials respectively.The research results have certain guiding significance and engineering application value for the simulation of wetting deformation and crack prediction of earth-rock dams.