| Box culvert is widely used in the development of modern expressway because of its good structural mechanical performance and strong foundation adaptability.For many years,our country mainly adopts the method of pouring on site to make box culverts,but the process is complicated,the construction is slow,and the quality is difficult to control centrally.In order to overcome these disadvantages,prefabricated box culvert came into being.The prefabricated box culvert studied in this paper is composed of four selfstabilizing components: roof,bottom plate and two side walls.For this new structure,although there were some research results of design theory and construction technology,the stress and deformation of this new structure during the implementation of layered filling was not clear.Based on the new expressway construction from Songyuan to Tongyu(Jimeng boundary)of Tieke expressway,the field test of the new prefabricated box culvert was carried out in this paper.Based on the construction practice of compaction of 15 cm per layer,the stress and deformation characteristics of the culvert under various working conditions were analyzed.The finite element model of culvertsoil structure was established,and the theoretical and measured results were compared to verify the correctness of the model,and then analyzed the influence of asymmetric backfill,elastic modulus of soil and filling height.Based on the wavelet neural network,the deformation of culvert was predicted intelligently.The main research contents of this paper are as follows:(1)On the basis of practical engineering,the field test of prefabricated box culvert under shallow overburden was carried out to study its mechanical deformation characteristics in the process of layered filling compaction.Results indicate that the roof keeps concave,left and right side walls keep outside convex,and the convex reaches the maximum when the fill is compacted to the hinge position(2.55m),then the convex amplitude decreases significantly under the constraint of the fill on both sides,and reaches the minimum when the top of the culvert(3.90m).When the fill exceeds the top of the culvert,the concave amplitude of the upper roof and the convex amplitude of the left and right side walls increase significantly under the load on the top of the culvert;(2)Based on the actual situation of the prefabricated box culvert,the constitutive model of the culvert structure and the surrounding filling materials was proposed,the contact definition of the culvert hinge was made,and the initial earth stress balance was carried out,the stress and deformation characteristics of the structure under various working conditions were analyzed,and the reliability of the culvert soil model was verified by comparing the theoretical data with the measured data;(3)Based on the culvert-soil model,the influence of culvert under the action of asymmetric backfill and different elastic modulus,filling height was analyzed.The results show that the asymmetric backfill has the greatest influence on the culvert in the initial filling stage.Selecting the backfill soil with large elastic modulus will greatly improve the mechanical deformation performance of the structure.At the intial stage of overburden on the top of culvert,the effect of live load on force and deformation of culvert is relatively obvious,but with the increase of filling height,the effect of live load becomes smaller and smaller.When the height reaches 10 m,the effect of dead load is mainly considered,and the effect of live load can be ignored;(4)Based on the measured deformation value of prefabricated box culvert in the early stage,the wavelet neural network was used to predict the deformation of the measured point in the later stage,and the predicted value was compared with the measured value.The accuracy of wavelet neural network prediction model was evaluated by introducing the average absolute percentage error.The calculation results show that the prediction model has good accuracy. |
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