| The rapid development of national economy and the large demand of transportation facilities led to the construction of the bridge across the river near become more and more,these bridges often be called bridge group,Because the projects has the smaller distance among the bridges,the long bridge opening,complex flow conditions and other reasons which make velocity increase an navigation perspective narrows and so on.In some degree,It will make the navigation conditions deterioration and add the difficulty of ship sailing in bridge area,leading to hit bridge safety accidents easily.This paper which simulated and analyzed the flow conditions and ship sailing in bridge area with different condition of layout scheme by using numberical simulation,ship model testing and physical model,while it based on research about different layout of Bridges Group In Xiang Jiang River.Under the existing bridge constraint put forwad a new reasonable site and layout scheme for bridge,It has a technical significance for solving similar conditions in continuous river bridge layout and other related issues in the furture.According to the characteristics of double track railway:uplink and downlink line can not cross in the plane,taking into account the restrictions on both sides of the railway marshalling yard location and relocation and other conditions,therefore,the new bridge must be located in upstream of the existing bridge site and can only be selected within a narrow range.The main layout scheme as follows:(1)New bridge located in the existing bridge downlink line up 40m,75m span layout scheme.New bridge be arranged above the existing Shanghai-Kunming downlink line upstream 40m(bridge axis spacing).it across the Xiangjiang River with 10 holes and span 75m continuous beam,its span 75m(clear span 70m),it takes 3th and 4th as the down navigation hole or 4th and 5th as a up navigation hole;Taking into account "the existing Shanghai-Kunming downlink line bridge" piers be tore down or not the two case;(2)New bridge between the existing bridge uplink line and the existing downlink line bridge,its span75m layout scheme.Bridge be arranged between the Shanghai-Kunming douwnlink line Bridge and Shanghai-Kunming downlink line(bridge axis spacing of about 20m),it takes 10-hole and 75m span continuous beams across the Xiangjiang River,new bridge piers should correspond with 2 bridge piers of the downstream,its span 75m(net cross 70m).it take 3th holes and 4th holes down or 4th holes,5th holes up;(3)New bridge located in the existing bridge downlink line up 40m,150m span layout scheme.Bridge be arranged in the existing bridge downlink line up 40m,150m span,merging 3th and 4th as the downstream navigable hole,Using 5th and 6th as the upstream navigable holes,these 2 holes should be keep in pace with the existing bridge group 3-4 and 5-6 holes with correspondingly;and only consider the case about the corresponding navigable hole that 3 old piers be reserved.At the same time,while it should clean the the shallow underwater between the Shanghai-Kunming Railway uplink line bridge and Tan intercity railway bridge.Specific conclusions are as follows:(1)The bridge reconstruction has many restrictions under the bridge group aera(uplink and do’wnlink lines can not cross,the new bridge down line must be located upstream of the existing bridge site uplink bridges;restrictions on both sides of the railway marshalling yard location and relocation and other conditions,the new bridge site downlink only selected within a narrow range;bridge construction existing bridge structure affect the safety and security of train operation,etc.).Taking the bridge site is located upstream of the existing bridge down line 40m,150m span layout program,from the navigation conditions,construction conditions and the demand of the Xiangjiang River shipping development point,which better than the other layout programs.(2)Comparative analysis of the flow field programs,As the smaller spacing within the bridge group area,span and the corresponding arrangement at the same pier,within the influence of sphere,the smaller distance between the bridge and the bridge group velocity zone is relatively uniform vertical distribution,the flow pattern is also better.In terms of the flow regime,the building and rebuilding bridges of bridge group river(mutual influence between the bridge),In the case of the span can not increase(or even a cross through),The new bridge pier should choose the same type and same span piers corresponding arrangement,while selecting or less equidistant spacing of layout,can bridge the flow regime of relatively homogeneous group of area.(3)When the group reaches the bridge built or rebuilt bridges,there are many factors to affect navigation safety.if the spacing between the bridges are smaller,it can increase the span arrangement,even a cross navigable.as a described 40m,150m span bridge upstream scheme to add bridge across(150m).if the condition can not increase the span,it can based on the layout which has been built around the vicinity of the bridge bore holes and other navigation environment specific circumstances to determine,as a described in the bridge site upstream 40m,150m span program,it take measure to transverse dispersion navigable hole up and down position(5-6 hole upstream,hole 3 to 4 downstream). |
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