| With the development of national economy by leaps and bounds, underground culvert is widely used in water conservancy, highway, railway, etc, and its importance of security becomes obvious day by day. It is reported that there are some trouble in the management constantly. Although there are many formulations about vertical soil pressure on top of trench-buried culvert, there are limitations in all of them. Existing theories relating to culverts that based on soft foundation are few, even some engineering use pile foundation when culverts are built on soft foundation. The result is that culverts crack even destruction. In this paper, based on the model testing, research is done deeply and systematically on the vertical soil pressure on top of projecting culvert and trench-buried conduit using finite element analysis. The main contents and fruits of this paper are as follows:(1) A series of model testing are done about trench-buried culvert based on stiff foundation and sand soil. On one hand, we observe the settlement of every sign buried in soil, and get the displacement contour of backfilled soil in different height and section. On the other hand, we measure the distortion of pressure cells by using electric apparatus which buried around culvert and calculate the vertical soil pressure coefficient K_s, then the connection between K_s and height of backfilled soil H, width of groove bottom B, gradient m is studied. The results show that: When B/D=1, K_s on top of culverts buried in rectangular section groove decreases monotonously, When B/D≥2, K_s increases at first and decreases later, K_s increases while the groove is wider at the same height of backfill. K_s on top of culvert buried in trapezoidal section groove increases at first and decreases later and increased while the slope of groove is gentler.(2) The model testing was simulated with the data in the testing by the software ANSYS, then the vertical soil pressure coefficient on the top of culverts and the displacement field of soil are gotten. It is clear to see that the software is reliable for calculating the vertical earth pressure on the top of culvert. Besides, the paper also simulated vertical earth pressure field of culverts. The results show that distribution of vertical earth pressure on culverts is smaller in the middle and larger on both sides, while in the bilateral of culvert plane, the distribution is lager in the middle and smaller on both sides. The influence height of culverts to vertical earth pressure increases when B/D is lager.(3) Based on the above simulation of stiff foundation and stiff conduit the paper develops simulation range. Culvert which based on soft foundation is simulated roundly by adding new elements to open out the properties of culvert under soil load. The results include quantitative relation between soil pressure coefficient K_s and foundation-backfilled soil flexibility module ratio E_d / E_l. Itis concluded that vertical earth pressure is influenced by flexibility module of foundation. When B/D=1, the smaller the flexibility module of foundation is, the lager the coefficient of vertical earth pressure is in the whole stage of fill. When B/D≥1.5, the smaller the flexibility module of foundation is, the smaller the coefficient of vertical earth pressure is in the stage of low fill and the trend is opposite in the stage of high fill. For projecting conduit, the smaller the flexibility module of foundation is, the smaller the coefficient of vertical earth pressure is in the whole stage of fill.In conclusion, the study method used in this paper, especially the research of culvert based on soft foundation, is a sample to settle underground project problems. Although the results have significant action in culvert foundation reinforcement, section optimization and load reduction measures etc., it needs to be checked up in practice. |
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