Study On Deformation Of Asphalt Concrete Core Gravel Dam On Deep Overburden Foundation

The deep overburden structure is uneven and the cause is complex.It is a poor and complicated geological foundation,which makes it difficult to construct water conservancy projects on deep overburden layers.Engineering construction needs to focus on engineering deformation and deep overburden prevention.Measures.Taking the asphalt concrete core wall gravel dam on the upper dam site of the Nglio Reservoir as an example,the engineering geological conditions analysis,numerical simulation of seepage flow in vertical anti-seepage system,sensitivity analysis of material parameters of dam and overburden,and dam filling are carried out.The research work of scheme optimization,stress and strain simulation of dam body and anti-seepage system is aimed at revealing the seepage,stress and strain characteristics of dam and overburden,and provides theoretical reference for similar projects.The main research contents and conclusions are as follows:(1)Based on Geo Studio software,a two-dimensional seepage numerical simulation of the vertical anti-seepage system of the dam body and the overburden layer was carried out.The results show that the internal immersion line of the dam body on the asphalt concrete core wall rises and falls with the change of the upstream water level.The internal immersion line of the downstream dam body is less affected by the water level and lower than the downstream drainage layer.After adopting the fully enclosed seepage prevention wall scheme,the dam The seepage flow of the body and the dam foundation is greatly reduced,and the seepage is effectively controlled;the water head difference between the dam body core wall and the dam foundation cut-off wall is large,the penetration ratio is large,and it is smaller than the allowable value of the specification,that is,the penetration stability requirement is met.(2)Based on the Duncan E-B constitutive model,the nonlinear characteristics of the dam body filling material and the covering material are fully considered,and the sensitivity analysis of the material parameters of the dam body and the covering layer is carried out.The results show that when the material parameters are reduced,the settlement of the dam body and the cover layer increases,and when the material parameters of the dam body and the cover layer fluctuate by 10% above and below the recommended value,the settlement of the dam body and the cover layer is less than 1% of the dam height.The parameter recommendation value can be used for subsequent chapter calculation;the maximum settlement of the dam body appears near the downstream of the core wall base,and the displacement of the dam body along the river is symmetrically distributed around the dam axis.The maximum displacement of the upper and lower reaches appears in the core wall and the upstream and downstream dams.The middle part of the slope slope;the maximum settlement of the cover layer appears at the junction of the cover layer and the dam body,and the displacement of the cover layer along the river is symmetrically distributed around the dam axis,and the maximum displacements of the upper and lower reaches occur at the bottom of the dam slope.(3)Establishing the two-dimensional model of ADINA,calculating and analyzing the deformation and stress changes of the dam body and the cover layer under the different layering filling methods.The results show that the more the number of filling layers,the longer the filling time,the corresponding dam body.The smaller the settlement and stress values are;the less the 16 layers are filled,the impact of the number of layers on the stress of the dam is not significant.With 24 filling steps,the corresponding settlement amount is relatively uniform for each step,and the total settlement increase does not appear too large or too small.In comparison,the settlement before the filling of the 19 th floor is relatively large,accounting for 91.02% of the total settlement.The corresponding filling height of the dam is 0～30.4m,which is 78.4% of the total dam height.(4)Establishing the three-dimensional model of ADINA and performing three-dimensional finite element static calculation analysis.The results show that the deformation of the dam body,the core wall and the anti-seepage wall along the axis of the dam is asymmetrical,and the deformation on the left bank side is significantly larger than the deformation on the right bank side.The main reason is that the dam foundation is thicker and the left bank is deeper,and the right bank side is relatively shallow.The difference is obvious.Under the dam’s own weight and water load,the dam body,the core wall and the seepage wall will appear as a whole.Slight left tilt deformation trend.The core wall and the cut-off wall have less deformation due to the support of the bedrock,especially at the contact edge.