高土质心墙坝坝顶裂缝模拟方法及应用

Simulation method for crest cracks in high earth core rockfill dams and its application

土质心墙坝坝顶裂缝是目前高土石坝建设及运行中常遇到的病险,其发生和发展大大增加了工程的安全风险。基于扩展有限元的位移模式提出了坝顶裂缝的模拟方法并将其运用到瀑布沟土心墙坝坝顶裂缝模拟中。首先介绍了坝顶裂缝模拟方法的基本原理,其后采用神经网络遗传算法对瀑布沟心墙坝典型监测点监测数据进行了反演,采用反演得到的模型参数同时考虑筑坝料湿化、流变及固结,进行了瀑布沟心墙坝坝顶裂缝模拟。结果表明:采用反演参数计算得到的坝体变形与监测资料较为吻合;蓄水后坝体最大沉降3.27m,向上游最大水平位移1.17m,上游堆石料湿化沉降最大达0.48m,上游坝壳的湿化变形作用导致了坝顶上下游的不均匀变形;模拟得到的坝顶裂缝首次发生在满蓄后,距离坝轴线4.75 m位置处,1个月内裂缝扩展至1.75 m深度(坝顶填土内,未扩展至心墙),运行10 a间坝顶裂缝未发生实质性发展;此外,不考虑上游坝壳湿化时坝顶未有裂缝产生,考虑湿化而不考虑流变时坝顶裂缝扩展深度最大为1.25 m,最大张开宽度为2.7 cm。相关成果可为类似特高土心墙坝工程预防坝顶裂缝的发生提供相关参照。

The crest cracks are the common dangers during construction and operation of high earth core rockfill(ECRD)dams.The occurrence and propagation of the crack increases the safety risk of the project greatly.The simulation method for crest crack based on the displacement mode of the extended finite element method(XFEM)is put forward and introduced into the crack simulation of Pubugou ECRD.Firstly,the basic principle of the simulation method is introduced.Then,the measured data of typical monitoring points of Pubugou ECRD are inverted by using the neural network genetic algorithm.XFEM modelling of the 2-D model is conducted using the parameters obtained by inversion to reflect the wetting,rheological and consolidation of dam materials.The results show that the dam deformation is in good agreement with the monitoring data.The maximum settlement of the dam is 3.27 m after impoundment,the maximum upstream horizontal displacement is 1.17 m,and the maximum wetting settlement of upstream rockfill is 0.48 m.The wetting deformation and reservoir water pressure exert a certain dragging effect on the top of the dam,which directly leads to the crest cracks.The cracks at the top of the dam occur for the first time after full storage,4.75 m away from the axis of the dam,and 1.75 m-deep cracks extend within one month(in the filling at dam top without extending to the core wall).The cracks on the top of the dam have not propagated substantially during 10 years of dam operation.The simulated results are close to the measured values.