盾构隧道近接下穿地下大型结构施工影响研究

Study on construction influence of shield tunnels traversing adjacently under underground large-scale structure

建立了盾构掘进三维有限元模型,针对不同的盾构推进力和同步注浆未及时起到支撑作用的施工工况,采用数值模拟和室内相似模型试验方法进行了盾构隧道近接下穿地下大型结构施工的影响研究。研究结果表明,盾构掘进对地下结构周围土体扰动有限,不会产生隧道整体漂移。抗拔桩对地下结构的支撑作用明显,使得地下结构底板的拉应力和压应力交替出现,从而减小了应力量值。新建隧道和既有隧道衬砌结构受力是安全的,不需进行特殊设计。建议在近接地下结构之前10m处,调整盾构机姿态,放慢掘进速度,并将推进力控制在10000kN以内,以确保施工的安全进行。

A 3D FEM model of the shield driving was established. Under the construction conditions of different shield driving forces and without in-phase grouting, mutual influences of construction of shield tunnels traversing adjacently under existing underground large-scale structures were studied with the numerical simulation and 3D model tests. It was shown that the shield driving exerted a limited effect on the underground structures, the ＂excursion＂ of existing tunnel did not occur. The effects of uplift resistant piles on the underground structure were obvious. Tension stress and compression stress of the bottom board in the underground structure occurred alternately, thus the maximum absolute value of stress decreased. Linings of newly-built tunnel and exiting tunnel were safe during the construction and operation, and the special design for linings was not needed. To ensure the safety of construction, it was necessary to use the measurements to adjust the pose of the shield to slow down the driving speed and to control the driving force within 10000 kN, when the shield machine was walking at a distance less than 10 m from the edge of upper underground structures.