300m级特高土石坝施工期心墙沉降监控模型研究

心墙沉降是两河口高土石坝的控制性安全监测项目,结合室内试验、监测、施工进度等资料,研究了心墙砾石土的沉降特性,建立了施工期沉降监控模型。研究表明:沉降变形的发展呈明显的阶段性,即沉降环埋设初期的快速沉降期、填筑进度平缓进行的匀速沉降期以及填筑高峰期的加速沉降期;以填筑因子与时效因子为组合的监控模型具有良好的解析力与拟合度,计算实例4个测点判定系数R 2在0.938~0.972;施工期沉降产生的主导因素是填土层上覆的外压荷载,就已填筑高程1/2~2/3区段而言,施工期沉降变形所占的填筑分量与时效分量分别约占95%与5%;监控模型具有良好的外延性,在近1个月外延区间中预测误差不超过9.04 mm,通过不断延长建模时序以修正模型参数,可提高预测精度进而指导施工。

Study on Monitoring Model of Core Wall Settlement of 300 m-level Super High Earth-rock Dam during Construction Period

The core wall settlement is a controlled safety monitoring part for the high earth-rock dam in Lianghekou Hydropower Station.The settlement characteristics of the core wall gravel soil are studied in combination with the data such as indoor tests,on-site monitoring and construction progress,and a settlement monitoring model during the construction period is established.The research shows that,(a)the development of settlement deformation has obvious phases,that is,the rapid settlement period in the initial stage of the settlement ring embedment,the uniform settlement period during slow filling progress,and the accelerated settlement period in the peak filling period;(b)the monitoring model which takes the filling factor and time-effect factor as combination has good resolution and fit performance,and the calculation examples of 4 test points have the determination coefficient R 2 between 0.938 to 0.972;(c)the dominant factor of settlement during the construction period is the external pressure load on the filling layer,and for the section between 1/2 to 2/3 filling height,the settlement component and the time-effect component of the settlement deformation account for about 95%and 5%respectively;and(d)the monitoring model has good extension,and the prediction error when it extends in the past a month does not exceed 9.04 mm.By continuously extending the modeling time to modify the model parameters,the prediction accuracy can be improved and the construction can be guided.