Study On Influence Of Occurrence State Of Plastic Concrete Cutoff Wall On Dam Stability

As an important anti-seepage structure,plastic concrete anti-seepage wall has reliable anti-seepage effect and mature construction method,and is widely used in various dam anti-seepage projects.The occurrence state of the cutoff wall in the embankment(the occurrence state in this paper is the thickness and depth of the cutoff wall)has an important influence on the seepage form and stability of the project.This paper takes the typical dangerous section of the right section of the vortex of Huaibei levee as the research object,establishes a mathematical model,uses the finite element method for numerical simulation,and studies the influence of the occurrence state of plastic concrete cutoff wall on the safety of levee engineering.Based on the numerical simulation results and the normalized calculation of the construction period and cost,the optimal occurrence parameters of the cutoff wall of the levee section are proposed,and the slope stability and seepage-stress coupling analysis of the optimized levee project are carried out to comprehensively evaluate the optimal occurrence state of the plastic concrete cutoff wall.(1)Based on the selected typical embankment section,the influence of parameters such as the thickness and depth of the plastic concrete cutoff wall on the stability of the embankment is systematically studied,and the optimal occurrence parameters are proposed.In the research process,37 calculation schemes were designed and the anti-seepage effects of embankments with different occurrence states of cut-off walls and without cut-off walls were simulated respectively.Especially when the cut-off wall penetrates the underlying 2-2 fine sand layer into the 3 heavy silty loam relative impermeable layer,the seepage flow per unit width of the embankment foundation,the water head behind the cut-off wall under seepage,the seepage gradient at the bottom of the cut-off wall and the seepage gradient at the exit point of the embankment foot were compared and analyzed.Combined with the construction period and construction cost in the construction process of plastic concrete cutoff wall,the dimensionless analysis is carried out by normalized intersection method.Finally,the optimal occurrence state of cutoff wall is 0.4 m in thickness and 15 m in depth.(2)The design conditions at the inflection point of each hydraulic factor in the optimization of the occurrence parameters of the cutoff wall are selected.Combined with the ratio,the Bishop method and the Swedish method are used to model and calculate the anti-sliding stability of the embankment slope under different working conditions.The research shows that the anti-sliding stability safety factor of the embankment slope calculated under each working condition meets the standard value of the anti-sliding stability safety factor of the soil embankment;compared with the case without cutoff wall,the safety factor calculated by setting cutoff wall modeling is higher.When the thickness of occurrence is constant,the type of cutoff wall changes from semi-closed to fully closed with the increase of depth,and the calculated safety factor reaches the maximum.When the depth of the cut-off wall is certain,it is not that the larger the thickness is,the higher the safety and stability coefficient of the embankment slope is.Larger or smaller thickness may lead to slope instability of the embankment.(3)Based on the principle of seepage-stress coupling,through the replacement of the plastic concrete material,the superposition of the seepage field and stress field of the embankment is carried out,and the overall stress and strain of the embankment before and after the plastic concrete cut-off wall are analyzed.The calculation results show that the vertical displacement of the embankment and the plastic concrete cutoff wall reaches the maximum at the normal water level;under the design flood level,the maximum horizontal displacement of the embankment appears;there is stress concentration in the middle of the cut-off wall.Due to the different stiffness of the cut-off wall and the adjacent soil,the stress deformation is not coordinated,which causes the redistribution of the internal stress of the embankment,and the whole is in safe and stable operation.Figure [41] table [14] reference [61]...