| The overall bearing capacity of the arch dam and the stability against sliding of the abutment are always the important issues of arch dam engineering.This paper takes a typical arch dam as an example,by using the finite element software FLAC3 D,through a variety of analysis of stability analysis and evaluation methods of the bearing capacity of the whole arch dam and dam abutment,and the applicability of different analysis methods were discussed.(1)evaluate the overall bearing capacity of arch dam by overloadmethod.In condition of overload,water specific gravity overload method of bearing capacity evaluation of arch dam,has been used to analyzefive aspects of changes:arch abutment force,the displacement andplastic zoneof bam and its foundation,the displacement andplastic zone of right bam abutment.the distribution of arch dam from overload during deformation of dam foundation and the development of plastic zone,the abutment and the plastic zone of the five aspects of changes.(1)The distribution of the arch thrust on the base surface shows the characteristics of the transfer to the elevation of the middle part of the dam with the increase of overloading factor.From the ratio of normal and tangential arch abutment force,it can be seen that overloading is disadvantageous to the stability of abutment rock mass.(2)The dislocation curve of the fault has a sudden change when the overload factor is 7.75.(3)In the process of this method,the plastic zone of the right abutment is gradually developed from the low elevation to the middle high,and the plastic zone contects through when the overload factor is 7.75.(4)Overload safety coefficient-K1,K2,K3 and K4 has been discussed before,but K3 should benot only consider the feature point displacement curve,but also consider abutment deformation and yield of the dam.Through the analysis K1=1.0,K2=1.75,K3=6.75,K4=8.75 are obtained.In condition of water-level overload,the curve of arch abutment force is similar to that of water specific gravity,and an inflection point occurs in the dislocation momentum curve when overload coefficient is 2.1.But the plastic distribution of abutment is much smaller than that of water special gravity overloading method,and only has a certain development in middle and high elevation.K1=1.0,K2=1.4,K3=2.1,K4=2.2 are obtainedThe arch abutment force overload method is not suitable for evaluating the whole stability of arch dam because it does not consider the coordinated deformation between dam abutment and dam body.(2)the strength reduction method is used to evaluate the overall stability of the abutment of the right bank,and the safety reserve factor is 2.4.From the unstable mode,this method just reflects stability of abutment slope under gravity,and can not answer the engineering concern the stability of dam abutment specific instability mode.(3)the four kinds of calculation methods for the evaluation of the abutment stability has been used,I means reduction of key block,II means reduction of structure surface of key blocks,III means reduction of the structure of key blocks and III rock,IV means the block limit equilibrium method based onstress and deformation.(1)In the method of I,the failure mode of the right abutment is shallow sliding.(2)In the method of II and method III,the rock mass within the influence range of the arch thrust of the dam continuously produces deformation toward the slope with the reduction factor increasing,which can objectively reflect the instability trend of the key blocks.(3)Method IV has definite physical meaning,and the safety factor obtained is consistent with the rigid body limit equilibrium method.It shows that this method is more reliable for evaluating the stability of the key block of dam abutment. |
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