新光大桥桥墩钢板桩围堰的优化设计与监测

Optimal Design and Monitoring of Steel Sheet Pile Cofferdams of Xinguang Bridge

新光大桥5#和6#桥墩支护方案采用钢板桩加钢支撑的支护体系,用石粉导渗的不封底方案.文中着重介绍了该围堰支护体系方案的优化设计,并将设计结果和监测结果进行比较,探讨了两者在钢板桩桩身位移上产生较大差异的主要原因:(1)在钢板桩墙受力的初期,桩之间存在相互滑动,致使墙整体刚度显著削弱,变形量比设计值大,后期随着桩之间相互作用的增大,相对滑动被约束,墙的整体刚度得到恢复,此时的变形增量与设计值相近;(2)由于钢板桩间的纵向接头刚度小于钢板桩本身的刚度,致使变形在接头附近集中.文中最后指出,在进行钢板桩围堰支护体系的设计时,钢板桩在不同的受力阶段应取不同的模量,支撑的安全系数应比钢板桩的大.

The 5# and 6# cofferdams of Xingguang Bridge are retained by steel sheet pile walls and steel struts structure. Rock powders are used to resist the seepage force. In this paper, the optimal design of the retaining structure is introduced. A comparison between the designed results and the monitored results is also carried out to investigate the main causes of the obvious differences in pile deformation. It is found that （ 1 ） during the initial loading of steel sheet pile walls, the slippage of piles occurs, which results in a great decrease in the total rigidity of the walls and brings about a deformation larger than that of the designed value; while in the later loading phase, the interaction between piles increases and the relative slippage is restricted, thus resulting in a recovery of the total rigidity and a deformation increment similar to the designed one; and （2） the deformation mainly centers around the joints because the rigidity of longitudinal joints between piles is weaker than that of piles. It is thus concluded that, when designing a retaining system, the wall module should be varied according to the loading phases of piles, and that the safety coefficient of steel struts should be larger than that of steel sheet piles.