Research On The Effect Of The Construction Of Qingyi-Fujiang Bridge On The Fujiang Flow Field

Fujiang is originated from the northern foothills of Minshan Xuebaoding in Songpan County,Sichuan.It flows from high mountain area on the northwest of Sichuan to basin hills area on the southeast.It is the biggest tributary of all on the right bank of Jialing.It’s the source of drinking water to many cities,counties and districts. However Qingyi-Fujiang Bridge is an important part of the second ring road in Mianyang City. It attaches Qingyi Town to Shima Town in Mianyang.The bridge starts by Stake K34+412.00,ends by Stake K34+982.00and it’s570m long.It has5bridge openings and6bridge piers.Among them,NO.25NO.3,NO.4,NO.5are standing in the water while NO.l and NO.6are not. Cofferdam construction is mainly used in the process of building Qingyi-Fujiang Bridge over Fujiang.There are two different construction program.And the construction may take some effects on the river flow field.So there is a necessity to study on the effect on the original river flow field of the construction,to expand research,to know the area of effects cofferdam construction may take on the Fujiang flow field,so that we can guide the construction.This thesis simulates the flow field during the construction of Qingyi-Fujiang Bridge using Delft-3D.The simulation is mainly carried out for two different construction programs.It simulates the original2-D flow field before the construction,the2-D flow field during the construction in Program1,The2-D flow field during the construction in Program2and the2-D flow field after the construction. Changes of the flow field before and after cofferdam construction and area of effects construction may take in Program land Program2have been analyzed and compared.Then make sure which program takes less effects on the flow field by analyzing the results.According to the simulation results,neither of the two construction programs changes the original direction of the river. Cofferdam construction takes little effect on the entrances and exits or the whole study on the flow rate.Cofferdam construction slows down the flow rate of upstream and downstream of the river.It’s mainly because after the construction of the cofferdam,it may produce barrier effect on water so that to produce turbulence and vortex and slow down flow rate.Programl two cofferdams are built at the same time,it has bigger area of effect but shorter effect time so that the flow field can be stabilized in a shorter time.Program2has smaller area of effect but the effect lasts longer so that the flow field may take a longer time to be stabilized.All in all,both programs may take some effect on the river flow field and Program2takes less effect.