Analysis And Test On Mechanical Property Of High-backfill And Long-spancorrugated Steel Pipes Culvert

Increasing the the moment of inertia of cross section, the corrugated shape of long-span steel pipe culverts could increase the bearing capacity and stability of the structure. Corrugated steel pipe culvert is vastly used in foreign nations because of the advantage of it such as the adaptive capability of foundation deformation, construction convenience and low expense etc. To explore the effect of the different stiffness between soil and steel, and soil settlement on the mechanical performance of corrugated steel plate(pipe) and the vertical earth pressure on the pipe, a finite element(FE) analysis as well as a field test on this structure has been performed. The research contents and results are as follows:(1)Summarizing existing calculation theory and code of the vertical earth pressure of culverts, and judging their scope of application, this paper proposed a more optimized finite element modeling method for long-span corrugated steel pipe culverts under high backfills. Soil-structure interaction has been considered in the finite element analysis model and the nonlinear characteristics of soil and the contact element have been introduced.(2)The effects on vertical soil pressure on the corrugated steel pipe culverts and soil arching effect of pipe diameter, size of corrugated pipe, parameters of backfilling soil, flexibility and the effect of multi-pipes were fully studied, and the results showed that: the top of the pipe vertical soil pressure and soil arching effect decrease with the increase of the diameter of pipe diameter; the effect of the structure of corrugated pipe impacts heavily on vertical soil pressure on pipe; the nonlinear characteristics of soil is the decisive factor to the soil arching effect, the vertical deformation decrease with the increase of the elastic modulus of the soil, poisson’s ration, internal friction angle, cohesive force, etc., while the other parameters work inversely. The corrugated steel pipe is still rigid when the flexible coefficient(?)(?)is less than 1, and in this situation, the soil arching effect is obvious and easily produced; the effect of multi-pipes on the distribution of the vertical earth pressure on the effect of multi-pipes should not be ignored.(3)A good match is observed between the results of the FE analysis and the field test, which indicates that the optimized FE model can satisfy the precision requirement of the design. The results show that the deformation and radial earth pressure of these two parallel corrugated steel pipes(2-φ5.5m) increase with the increase of the depth of cover; the distribution of radial earth pressure around the pipes shows an elliptical shape. It is also found that the static response of the two parallel pipes under high backfills is basically the same as that of the single pipe, except that the maximum radial earth pressure occurs in different positions. For the two pipes, it is located either southwest or southeast of the pipe cross sections. Different results derived from Genral Code for Design of Highway Bridge and Culvert,FE analysis and the field test data are also compared. It shows that, the magnitude of the maximum radial earth pressure from Code is the largest, while that of the minimum radial earth pressure from Code remains the smallest(4)Arranging cable in the cross section of pipe can reduce the deformation and increase the vertical earth pressure on the corrugated steel pipe culverts effectively, but has little impact on the equivalent stress of structure, the effect of arranging cable at the maximum diameter along the horizontal direction is most obvious; Adopting EPS as reducing-load materials has a remarkable effect, the top of the pipe vertical soil pressure is only 46.85% of self-weight; The difference of the mechanical performance of structure is very small between concrete foundation and gravel foundation, compared with concrete and gravel foundation, the deformation of pipes increases and the stress of pipes decreases for soft foundation, which indicates that the corrugated steel pipe culverts can well adapt the foundation with low bearing capacity and strength.