拱北隧道管幕工程顶管间距计算分析

Calculation and Analysis of Pipe Jacking Spacing for Pipe-roof Project of Gongbei Tunnel

为使管幕相邻顶管之间能够形成稳定土拱,防止管幕周围土体发生局部坍塌,需要合理控制管幕顶管间距。针对全断面支护管幕工程,结合管幕支护机制,运用土拱效应理论,对管幕顶部、中部、底部3个特殊位置形成的管间土拱进行分析,建立相应的管间土拱模型,分析土拱的受力情况;运用土体的极限平衡条件对拱顶和拱脚进行稳定性验算,得出顶管间距的控制式。针对港珠澳大桥拱北隧道管幕工程,结合管幕所在地层的土体参数,对隧道顶管间距进行计算分析,得出拱北隧道顶管间距为0.47 m。与工程顶管间距实际取值(0.35 m)相比,计算值略微偏大,符合工程实际情况,说明建立的管间土拱模型是合理的。

A stable soil arch between adjacent pipe jacks should be formed to prevent local collapse of the soil around the pipe-roof.Hence,the spacing of the pipe jacking should be rationally controlled.The soil arch between pipes formed at the top,middle and bottom of the full-face supported pipe curtain project is analyzed by soil arch theory based on supporting mechanism of pipe-roof;and the corresponding models of soil arch between pipes are established to analyze the force distribution of soil arch.The pipe jacking spacing control equation is obtained by using limit equilibrium condition of soil mass to check the stability of arch top and arch feet.The soil parameters of pipe-roof of Gongbei Tunnel of Hong Kong-Zhuhai-Macao Bridge are analyzed to calculate the pipe jacking spacing,and the calculation result is 0.47 m,which is larger than actual value and indicates the rationality of the model mentioned above.