Study On Soil-culvert Interaction And Structural Characteristics Of Culvert In Transverse And Longitudinal Direction

As the rapid development of China's highways, the number of the new culverts across the highway is growing and the number of new culvert design type is also increasing. Prefabricated horseshoe buried culvert is one of the new culvert types. Prefabricated culvert will be widely used and promoted because of its advantages such as reasonable design type, standardized design, factory prefabri cation and assemble assembly, construction convenient, obvious economic benefit, and so on. However, the research and application of fabricated culverts start relatively late in China. Currently, there is no relatively maturity analysis and design theory for design and construction of pipeline.Based on the above-mentioned background, the purpose of this paper is the study on the soil-culvert interaction and structural characteristics of the culvert in transverse and longitudinal direction. First of all, a large scale physical model test is carried out. The soil-culvert response subjected to backfill load and traffic load were monitored and tracked. The test results show that the compressibility of soil between the culvert top and two sides is different. When the backfill around the culvert is compressed under external loads, the earth pressure on the culvert generated at the same time. It is because the top of the culvert can not only bear the weight of soil column, but also bear the shear force passed by nearby soil column. The concentration phenomenon of earth pressure occurs. The affect of partial load on the culvert is more unfavorable. With the cyclic dynamic load increasing, the cumulative vertical deformation of soil increases. Under the same vertical cycle dynamic load, the cumulative vertical deformation of soil increases with the increasing of vibration time. When vibration times are to a certain number of times, the cumulative vertical deformation is to stabilize after.Then, based on the measurement results from the full-scale physical model testing and Marston's theory, a more reasonable analytical model of earth pressure around the culvert has been proposed and the principal calculation parameters are determined based on the test data. The test results with various buried depths on culvert top show that the proposed model can describe the earth pressure distribution around the culvert effectively. The different factors of the earth pressure on the culvert are analyzed by the numerical analysis method, including the backfill characteristics, foundation soil properties, geometry of the culverts, culvert stiffness, rolling load, trench terrain and so on.Then, the internal force of culvert in the model test is calculated by different methods. The analysis on the culvert characteristics subjected to the traffic load shows that the concrete mark affects unobviously the maximum bending moments of the culvert plates. The maximum bending moments of the culvert plates increase with plate thickness increasing and with the increasing of buried soil depth. The earth pressure on the top of culvert under vertical load and the maximum earth pressure on the top plate of culvert under partial load increase with the increasing of the traffic design speed. The analysis on the structural characteristics of the arch culvert under seismic load indicate that the seismic load on the culvert affects the most greatly the bending moment increment of the connected post between the two culvert holes.As the base of longitudinal analysis on buried culvert, multilaminate model for soft clay is presented in detail. Numerical implementation of inherent anisotropy and destructuration of structured clay are also presented. The user-defined soil models are added to PLAXIS via a dynamic link library file successfully. The accuracy of the model is verified by laboratory test data. The analysis results of the a typical project on structured soft clay show that multilaminate model of soft clay can simulate structural characteristics of soft soil and predict the deformation of soft soil subjected to loads.The more reasonable longitudinal mechanical model of underground culvert is established based on Pasternak foundation model. The deflection curve of culvert is derived and longitudinal mechanical properties are analyzed. The security identified method of buried culvert are proposed.Finally, some research results are applied in buried culvert design for Liu-Wu highway.