管棚保护下框架桥顶进工程高程控制分析

Analyses on Elevation Control of Bridge Shield Tunneling Project

大直径管棚保护下直接顶进预制箱涵技术是近年来国内发展起来的一种全新的施工技术,但其难度大,理论发展不完善,可借鉴的经验少.依托南昌市新龙岗大道下穿向莆铁路工程,根据实际工程情况建立力学分析模型,计算框架桥下钢管的受力,并根据钢管的受力情况假定钢管为Winkler弹性地基梁,运用弹性地基梁理论建立钢管挠曲微分方程并求解该微分方程,从而计算出框架桥顶进过程中的钢管挠曲变形,进而确定顶进过程中框架桥高程偏差情况.理论分析表明,底排管棚的支撑和引导作用有助于框架桥推进,并能有效遏制框架桥"栽头"和"抬头"现象,对于现场工程施工具有很好的参考价值.

The direct jacking technology under the protection of pipe shed is very strict to the control of subgrade deformation,and there is little related research on the theories at home and abroad. Based on the actual engineering situation,the mechanics analysis model is established to calculate the force of the steel pipe under the frame bridge.According to the stress condition of the steel pipe,the steel pipe is assumed to be the Winkler elastic foundation beam.Based on the beam theory,the differential equation of steel pipe is established,and which is solved to calculate the deflection deformation of the steel pipe during the jacking process of the frame bridge,and then the height deviation of the frame bridge during the jacking process is determined. The theoretical analysis shows that the support and guidance of the bottom pipe shed contribute to the advance of the frame bridge and can effectively curb the phenomenon of " sink" and " rise" of the frame bridge.During the process of frame bridge advancement,the control about the phenomenon of " rise" very important. With the increase of the length of the frame bridge,it can gradually curb the the phenomenon of the " rise" of the frame bridge.