The Optimized Design Study On The Structure Type For The High Fill Culverts

Since the reform and open policy, our country's highway traffic enterprise hasentered a new fast development time, when the road surmounts the run-off ditch,the brook ditch, the rivers, the artificial channel as well as removes the roadbedinside side ditch current of water, frequently needs to construct each kind of crossdrainage structure, but the culvert is most common small draining water structure.Along with the highway classification enhancement and the massive mountainousareas first-class highway construction, for which satisfies the road the high linearstandard request, crosses the ravine region high to fill the roadbed to increase, highfills the culvert structural design question to appear quite prominently, has becomeone of in present our country mountainous area first-class highway constructionimportant research topics.At present domestic and foreign scholars mainly concentrate about the highembankment culvert massive research in the function above the culvert the highearth fill pressure manifestation and the earth pressure value theoretically, butneglect the achievement to receive the strength main body the culvert itselfresearch. In the present criterion, continuously took the lap and the body as a knot ,not consider other styles.At present it is being in the fast develop time of the first-class highwayconstructs, there are many high fill roadbeds and the corresponding high fillculverts, the high fill culverts structural design and the application questions arequite prominent, therefore, relatively there are a lot of research about high fillculvert, but all is in the level of solution construction application the question, it islittle to see about earth pressure computation theory research results involving thecore question of the high fill culvert design, let alone in the high filled situation theachievement structure itself form optimization and the change research.In view of high fills culverts, this kind of draining constructions,increaseunceasingly in our country highway engineering, also cost high, at present the highfill structural styles which the culvert used obviously are unitary, while carrying onthe high filled culvert designs there ordinarily exists the phenomenon that peoplemove the standard, but not carry on the question actually which correspondingstructure in pattern analysis and so on application existed. This paper has carried onthe exploration in these aspects.There are a lot of high fills to utilize the excavations and protect the environmentin the course of highway building of mountainous place, and at the same time theculverts 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 forusing smaller size of structure, in some case over big size of culvert structure aredesigned to bear the uncertain pressures on the culverts and led to more cost. Basedon the occasion above, the earth pressure theory and the method of load reductionare studied through model test and numeric simulation to find a optimize theory forthe culverts beneath the high fill. The fruits of research in the thesis as follow:According to the concept and the method of optimizes at present while designingthe structure more popular to use, in this article I take the bending moment as themain comparative analysis content, and select the minimum bending moment asobjective function to analyze the optimization problem of each kind of patternculverts in the high earth fill situation.At present there are more than 20 kind methods to calculate the vertical earthpressure and the lateral earth pressure, but basically all of these are experience orcorrelation formula, which have the fit and unfit quality respectively, in this articlewhile carrying on the high fills culvert structure pattern optimization, in order toenhance the safety coefficient, enable the question to have the universality, Icompared vertical earth pressure as well as the lateral earth pressure computationalmethods which the present commonly used, and drew the conclusion that it isreasonable to use the earth pyramid method.In the article, I compared the moment values between the pattern of tiedconcretion and another pattern of pin joint, which is taken as the comparisonbenchmark pattern by "Bridge gauge", then drew the conclusion that the bendingmoment of lap middle decrement achieved 58.9%. Proposed that the tiedconcretion pattern is more reasonable in the high fills situation.According to the thought about two pin joints and no pin joints, in this article Ipropose the idea the lap culvert may use the small crown board. Confirmed thesmall crown board is better pattern than pin joint lap with the ANSYS software, thebending moment reduced remarkably. Moreover because the small crown boardcamber very little, therefore in the attachment point which lies in between lap andbody, horizontal stress does not increase too high, so the body does not need to addspecially thickness. So it is the high fills the culvert construction pattern which costlow, not difficult.Because semicircular arch camber high, the bending moment on the cross centerarch ring which is reduced by the horizontal thrust of skewback is also big, whichmay cause the bending moment which the arch ring receives to be small, basicallyto be at the bearing condition. At the same time I have analyzed the stress variationwhen the arch ring changes, to prove in the high earth fill (26m) situation, the 55cmthickness causes arch ring the tensile stress of the semicircle arch culvert veryslight sufficiently, to prove this size to be appropriate, but because rise of arch istoo high, which make the stress in the skewback place to be also big, nearby thisrequest skewback body to have the enough rigidity to provide the thrust force.This article explores to simulate the resisting force by the foundation localdistortion theory which is based on Winkler theory, using the spring unit. Knewthat, there is no the resisting force when the lap contains just tied. Meanwhile whileanalyzing synergy load of semicircle arch culvert between culvert and earth,discovering that it is no meaning to consider the resisting force significance theearth , but 1/3 arc arche culvert nearby the skewback position has the big earthresisting force existence, must be considering the local guerillas synergy system.