管幕预筑法顶管施工顺序对地表沉降的影响

以太原火车站管幕预筑法（PPM）大直径顶管群施工为背景，采用有限差分软件FLAC^3D对优选的8种有代表性的顶管群施工顺序进行数值模拟，研究不同大直径顶管群施工顺序下的地表变形特征. 试验结果表明：先施工管幕上排顶管的方案所引起的地表沉降量小于其他方案，与先施工管幕下排顶管的施工方案相比，其所引起的地表沉降要小1 cm；管幕上排顶管与周围土体之间形成管间微型土拱，并在管幕上方密排顶管之间形成组合土拱效应. 该组合土拱效应不仅可以承担一部分管幕上覆荷载，而且可以减小管幕下排顶管施工对地表的扰动，有效减小了管幕预筑法密排顶管群施工所引起的地表沉降.

Influence of construction sequence of pipe jacking by pipe-roof pre-construction method on ground surface settlement

Taiyuan Railway Station’s application of the large-diameter pipe-roof pre-construction method (PPM) was used as the engineering background. A finite difference method software (FLAC^3D) was employed to numerically simulate the eight representative pipe jacking construction sequences, to study the surface deformation characteristics under the construction sequence of the large diameter pipe jacking group. The test results show that the surface settlement caused by the first construction of the pipe jacking scheme was less than other schemes, and the ground settlement caused by the construction scheme was 1 cm smaller than that of the construction scheme of the pipe jacking scheme first. An inter-pipe soil arch was formed between the upper row of jacking pipes on the pipe-roof and the surrounding soil, and a combined soil arching effect was formed between the dense row of jacking pipes above the upper pipe. The pipe soil arching effect can not only bear part of the overburden load of the pipe roof, but also reduce the disturbance of the ground surface caused by the construction of the pipe jacking under the pipe-roof. The combined soil arching effect can effectively reduce the ground surface settlement caused by the construction of the dense row pipe jacking group with the pipe-roof pre-construction method.