Study On Rockfill Rheological Properties And Pre-settlement Control Measures Of High CFRD

Concrete faced rockfill dam is widely used because of its adaptability,safety and economy.However,in recent years due to larger dam deformation than expected,extrusion damaged panel and large leakage of some projects occured while the construction of several 200m high CFRD was success and learned valuable experience at the same time,some industry experts expressed concern and questioned about the completion of grade 250 m or higher CFRD.As a result of the development of cascade hydropower and the need of water resources allocation,a large number of high dam projects in China will be built in the future.Therefore,it is of great practical significance to carry out the research on the 300m CFRD.The core problem is that the dam deformation control problem is not solved completely.The deformation of CFRD contain instantaneous and post deformation.The former is caused by the weight of the dam and the water load.It occurs simultaneously with the load.The latter is the long-term rheological deformation after the dam is completed and stored.As an important part of the deformation of the dam,it is an important research object of the CFRD deformation control.In this paper,the following research work is carried out around the rheology of high rock fill dam:(1)Through literature,the paper discussed the relationship between rheological deformation with time of Shen Zhujiang three parameters,Li Guoying seven parameters and Chen Zhanlin nine parameters rheological models;the paper analyses the relationship between time related parameters with stress state in the model;the paper proposed the measurest that need to be adopted in practical engineering application.The volumetric rheology is not consistent with the shear rheological parameters.The test value needs to be reduced by 100 times when it is used in actual dam.(2)Developping and improving rockfill rheological deformation stress deformation analysis program in construction period;Combined with the world's highest rockfill dam of Shuibuya dam(height 223m)project,the paper simulates the dam deformation during the dam filling,water storage and operation period using three-dimensional finite element method;rheological deformation of rockfill has been calculated during the construction period.Tt increases the displacement of the dam structure,and the relative displacement of cushion and the panel,the panel stress is also increased along the slope and axial extrusion,the opening amount of the vertical joints on both sides of the panel is increased by rheology deformation.It can be seen that the deformation of rockfill rheology makes the deformation of impervious structure increased and deteriorates panel properties.Because of the longer construction period,it is necessary to carry out the calculation of rockfill rheology in the damming period of actual CFRD project.(3)Due to the scale effect,it is difficult to using the Laboratory test result reflect the creep deformation of actual rockfill dam.Therefore,it has become a trend that the deformation parameters of rockfill are obtained by inversion.Based on the observation data of dam deformation,the joint inversion of instantaneous and rheological deformation parameters of dam material has been carried out.Joint inversion can avoid the technical problems of separating the rheological deformation from the instantaneous deformation of rockfill dam.Before the inversion carried out,this paper chose the awaiting inversion parameters through sensitivity analysis.For those parameters that are not sensitive to the monitoring point settlement,this paper adopts their experimental value directly.In the process of parameter optimization,two kinds of intelligent optimization algorithms,such as multi population genetic algorithm(MPGA)and multi population particle swarm optimization(MsPSO)are adopted to ensure the reliability of the inversion parameters.Finally,the paper uses the inversed parameter to calculate the dam displacement,and found that the error between the calculated settlement and the measured settlement of the monitoring point is significantly reduced,which indicating that the inversed rheological parameters can reflect actual situation of the rockfill dam deformation better,it reveals the necessity of the rheological parameters inversion.(4)Based on coupling instantaneous and rheological deformation,the paper uses self-developed finite element numerical analysis program to study the deformation control measures of super high CFRDs.According to the Shuibuya project practical experience,the paper simulates the process of construction and impounding.The results show that the existing deformation control measures is empirical;the paper develops the construction process of 300 m high model dam considering the optimization of the flood and the construction period.The void phenomenon of panel appeared on the top of each panel stage in the process of pouring are simulated by the finite element method.Based on the above contents,this paper proposes the new deformation control measures for the 300 m super high CFRD.