Research On Long-term Deformation Of Dam Body And Safety Evaluation Of Cut-off Wall On Composite Foundation

With the earth-rock dams being widely used in various hydraulic structure engineering,its anti-seepage reinforcement,complex foundation treatment and stability analysis of dams have become the focus of many scholars.Concrete seepage prevention wall is the most commonly used anti-seepage structure for earth-rock dams.It is essential to carry out research on reasonable structural design,stress deformation analysis and crack failure mechanism.Due to the influence o.f complex topographic and geological conditions,the dams built on the overburden are strengthened by excavation,consolidation grouting and vibrating gravel piles,and reasonable numerical simulation analysis is carried out to ensure the safety of the dam.Sex and reliability are necessary.At the same time,there are gaps of different sizes between the granules of the dam and the rock,which are prone to slippage under the action of water load.Therefore,this paper considers the influencing factors such as rheology and humidification,and analyzes the long-term deformation law of dam operation stage to provide reference for dam monitoring and prevention.The main research contents are as follows:(1)Based on the design study of anti-seepage structure in earth-rock dam,the design of concrete anti-seepage wall weathering dam is applied to the design of a reservoir dam in Yunnan Province,and the numerical simulation is carried out to calculate the stress and deformation of the dam and impervious wall.Preliminary studies were conducted on the distribution of regular and extreme positions.It is concluded that the dam body settlement cloud diagram basically presents a symmetric distribution law on both sides of the anti-seepage wall,and the stress cloud diagram appears to be displaced on both sides of the anti-seepage wall.(2)Based on the study of the foundation mechanism of vibrating gravel piles and the calculation principle of composite foundation,the cover area of the right bank of the dam is reinforced.Two kinds of calculation schemes are designed to study the influence of vibrating gravel piles on the dam.The results show that the stress-deformation of the dam foundation and the anti-seepage wall is significantly reduced compared with the unreinforced foundation,which indicates that the foundation of the vibrating gravel pile has a good effect on the dam.(3)Based on the study of three-parameter rheological model and humidification theory,taking the concrete anti-seepage wall weathering dam built on the composite foundation as an example,considering the influence of long-term deformation of rockfill materials,three-dimensional simulation calculation is carried out to study the extreme value change of the dam.Regularity and long-term deformation characteristics of the dam body and cut-off wall.It is concluded that the rheology increases with the dam's operating years,and the maximum stress and displacement of the dam and anti-seepage wall increase,but it tends to be stable after 1 year of rheology.Therefore,under the combined influence of rheological and composite foundations,the simulation results can predict the stress and deformation law of the dam under long-term operation,improve the operating environment of the dam by strengthening the foundation,and provide a reasonable reference for the actual construction and operation detection process.(4)Based on the safety theory research of concrete anti-seepage wall,through the optimization design of material partition,the three schemes are designed based on the downstream left bank block area and numerical simulation calculation is carried out to analyze the safety of concrete cut-off wall.It is concluded that with the gradual increase of the area of the downstream stone material,the stress and displacement of the anti-seepage wall tend to decrease gradually,and the displacement of the river along the river varies greatly.The deflection curve of the anti-seepage wall of each scheme is studied.The law that the wall deflection develops downstream from the bottom to the top in the height direction is obtained.The numerical change is gradually increased first,and the stable deflection limit value fs is reached near the height of the 1/2 anti-seepage wall,and then gradually appears.The law of variation is reduced,and the stability limit deflection value of each scheme is basically twice the displacement of the top end,and the variation gap is large,which is not conducive to the safety and stability of the concrete anti-seepage wall.