软土地层管幕群顶进的相互作用及闭合姿态的实测分析

管幕群在地下穿越工程中对保护穿越对象发挥着关键作用。为了施工形成严格封闭的管幕群,需要每根顶管进行高精度的顶进施工,而众多相邻顶管顶进的相互作用极为复杂,导致每根顶管的姿态变化及管幕群最终闭合误差呈现不确定性。依托于某大型“管幕-箱涵”工法顶进穿越中环线工程项目,采用实时监测手段对管幕群顶进过程中各钢管的姿态与变形进行了记录,在此基础上分析研究了各类钢管在顶进过程中的相互作用以及管幕群贯通闭合后的姿态与变形规律。结果表明:①顶管之间的相互作用体现为先施工顶管(先管)对后顶进钢管(后管)姿态的约束、导向作用,相对偏差大致控制在4 cm以内;②受到钢管纵向刚度的影响,70%钢管姿态纠偏明显滞后于机头姿态变化,前期偏差累积较大,在末端顶管刚度随长度增加而减少,在强行纠偏下,顶管偏差变化幅度较大;③管幕群的闭合姿态在始发端及加固区段均保持良好;在中段各钢管出现明显变化,甚至部分钢管间拉开较大;在接收端,大部分钢管偏移相对减小。

Field investigations on interaction between jacking pipes and closure of pipe roofs in soft ground

The pipe roofs play a key role in protecting the passing objects in underground crossing projects. In order to construct a strictly closed pipe roof, high jacking precision of each pipe is required. However, the jacking interaction of various adjacent pipes is extremely complicated, which brings uncertainty to the attitude change of each pipe jacking and the final closure error of the pipe roof. This study relies on a certain project crossing a middle ring line by the large-scale ‘pipe roof-box culvert’ method and uses the real-time monitoring approach to record the attitude and deformation of each steel pipe during the jacking process of the pipe roof. Based on the measured data, the interaction of various pipes in the process of jacking as well as the attitude and deformation of the closed pipe roof is analyzed. The results show that: (1) The interaction between the pipes is reflected by the constraint and guiding effects of the previous pipe jacking (anterior pipe) on the attitude of the rear jacking pipe (posterior pipe), and the relative deviation is generally controlled within 4 cm. (2) Affected by the longitudinal stiffness of the steel pipe, the attitude correction of 70% pipes lags behind the machine head which results in relatively large accumulative deviation at the previous stage, but with the decrease of the longitudinal stiffness, the attitude of the pipe changes sharply at the receiving terminal under hard correcting. (3) The attitude of closed pipe roof is well maintained at the originating terminal and the reinforced zone. An obvious change occurs in the middle section, and some pipes even have a large distance among them. Finally, at the receiving terminal, the deviation of most pipes is relatively reduced.