| There are a lot of high fills to utilize the excavations and protect the enviroment in the course of highway building of mountainous place, and at the same time the culverts beneath these high fills must be constructed for drainage. However, because lack of the reasonable earth pressure theory for design of these culverts, some of them fail in the period of construction or after completion of work for using smaller size of structure, in some case over big size of culvert structure are designed to bear the uncertain pressures on the culverts and led to more cost. Based on the occasion above, the earth pressure theory and the method of load reduction are studied through model test and numeric simulation to find a reasonable earth pressure theory for the culverts beneath the high fill. The fruits of research in the thesis as follow:(1) The principle of variation of earth pressures on the culverts beneath the high fills are investigated in the thesis. The principle of variation of earth pressures on the culverts located in different topographies of galley, including located in narrow valley, wide valley , the foot of slope and the middle of slope are studied through model test and numeric simulation. The test results show the principle of variation of pressures on culverts beneath high fill is similar ,it is that, even if the embankment is filled up to a higher height, the earth pressures can still partly transfer to the top of culvert, as a result the pressures on the culvert increase nonlinearly with the variation of height of fill and further the pressures are obviously lower than theoretical value by σ=γH. (2) The arching action above the culvert is investigated in the thesis. The resultsof model testing and numeric simulation indicate that the arching action above the culvert will appear as the fills up to a certain height, but as the fills around the culvert are breaking rock the arching action is different from the arching action above the cave in stable rock, instability is the characteristic of arching action above the culvert.(3) A nonlinear theory of earth pressure calculation is presented in the thesis. Based on the principle of variation of earth pressures on the culverts under different conditions, including topography, span of culvert, density of fill and the type of structure, and the property of arching action above the culvert, a nonlinear earth pressure theory for culverts beneath high fill is presented, the theory suggests the earth pressure on the culverts beneath high fill can be calculated with the formula σ=ξγHm as the fill up to higher height. Compared the nonlinear theory with other theory of earth pressure for the cave in stable rock and soil, it is shown the pressures calculated by nonlinear theory are bigger than by theory for cave in stable rock and soil, but less than the value of pressures by linear formula σ=γH. This is because of the arching action above the culvert is unstable while this feature is considered in nonlinear theory of earth pressure calculation. From above, a conclusion is drawn that the nonlinear earth pressure theory is a reasonable method of pressure calculation for culverts beneath the high fill.(4)Based on the results of model test and numeric simulation, the nonlinear formulas of earth pressure under various boundary conditions are given, and come to the conclusion that the earth pressures should be calculated with nonlinear formula as the height of fill over 16 meters, on the other cases with formula σ=γH.(5)A method of reinforcement bridge load reduction for culverts beneath the high fill is presented in the thesis. The mechanism of reinforcement bridge load reduction as follow: the structure of reinforcement bridge is composed of three parts, including reinforcements, load reduction ditch filled with lower density of soil and compacted soil around the culvert, in the structure of bridge the reinforcements are arranged on the load reduction ditch in layer, because of the density of fill in ditch is different from the density of fill...
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