Experimental Study On The Calculation Method Of Earth Pressure For High Filling Culverts

Culvert is the structure under filling soil. It was widely used in the hydropower engineering, the transportation engineering and the water supplied and drainage engineering. At present, there are various theories on earth pressure at home and abroad, but they are non-uniform and have shortcomings. The research results are mainly about the low filling culverts, less about the high filling culverts. While"The General Specification on Highway Bridge"stipulates that the Soil Column Method is adopted to calculate the vertical earth pressure above culverts, but it doesn't illustrate the applicable height. Now, the Soil Column Method is used to calculate the vertical earth pressure above culverts whose height is less than 20m, however there isn't explanation about high filling culvert whose height is more than 20m. Because of the complex relationship between the terrain conditions, the geological conditions, the structure, the construction process, and the settlement and deformation of the road embankment, the soil column method only considered some factors that made the high filling culverts have emerged various problems including the project cost waste and the structure security risk. Since the earth pressure theory on high filling culverts has deficiencies, it is necessary to re-examine calculation methods in order to make high filling culverts be security and economic rationality.By analyzing the existing earth pressure theories, basing on the similarity principle, this paper has taken on the indoor model test in the earth pressure theory on high filling culverts, done a series of studies and achieved some conclusions.(1) Designing on the experimental model and the experimental program. Basing on the similarity principle, have simulated the culvert structure, the culvert material and the earth pressure around the culvert, and have determined the experimental model which met the test needs. By choosing the test equipment and making the test procedure, have designed the reasonable and effective test program. The construction, loading and testing of the model have provided a basis for finding out the reasonable earth pressure theory and calculation method on high filling culverts.(2) The test shows: the earth pressure of high filling culvert doesn't linear with the filling height (h), and is non-linear. When the filling height is low, the earth pressure increases with the filling height, is a similar straight line and could be calculated by the Soil Column Method (σ=γh). While the filling height is high, the earth pressure gently increases with the filling height, is a curve and is obvious smaller than the result by calculating with the Soil Column method. Aiming at ensuring the security and economic rationality, should adopt the Limit Equilibrium method which has considered arching effect to calculate the earth pressure.(3) The soil arching exists above the culvert. It has obvious soil arching effect and instability. With the growth of filling soil height, a part of the earth pressure also is transmited to the top of the culvert that makes the earth pressure increase with the filling soil height on the top of the culvert, but the rate decrease and the pressure curve become more and more gentle. This instability is the main feature of the soil arching on the top of the high filling culvert.Through the indoor model test, this paper researched the regulation that the earth pressure changes with the growth of the filling height on the top of the culvert, and the arching effect. Basing on the results of the model test and the theory calculation has provided the reasonable calculation method on the earth pressure of high filling culverts. It makes the designed earth pressure be close to the actual earth pressure, which ensures the security and economic rationality of high filling culvert. This paper has provided the reference value of the earth pressure calculation and the structure design.