软流塑地层盾构穿越夹岗过街涵群桩处理关键技术

Key Technologies for Shield Machine Passing through Piles under Box Culvert in Soft Fluid-plastic Strata

南京地铁三号线大明路站—明发广场站盾构区间穿越软流塑地层中的箱涵及其群桩基础,为确保盾构顺利穿越,文章介绍了4种群桩处理技术方案:方案1(拔桩、钢筋混凝土框架结构箱涵恢复、盾构正常掘进方案)、方案2(拔桩、桩基托换、恢复盖梁箱涵、盾构正常掘进方案)、方案3(矿山法隧道托换、盾构过站方案)和方案4(钢筋混凝土框架结构箱涵托换、矿山法隧道内截除桩基、隧道回填后盾构掘进方案),通过对方案进行对比分析,最终选择了方案4。然后介绍了软流塑地层矿山法隧道施工关键技术和盾构过矿山法隧道关键技术。通过对施工监测的数据进行分析,发现通过采取基底加固后箱涵托换、劈裂注浆加固地层后CRD工法施工矿山法隧道、矿山法隧道内桩基截除、盾构通过回填后的矿山法隧道等关键技术措施,确保了盾构顺利穿越过街涵群桩。

A shield bored tunnel of line 3 of Nanjing Metro crosses underneath a box culvert and its pile foundations are in fluid-plastic strata. In this paper, four pile foundation treatment plans are compared and analyzed： Plan A： removing the piles from the ground surface, reinforcing the box culvert, and proceeding with shield tunneling; Plan B： removing the piles from the ground surface, underpinning the pile foundations, restoring the box culvert and proceeding with shield tunneling ; Plan C ： cutting off the piles intervening into the mined tunnel scope, underpinning the pile foundations by using the mined tunnel structure, and the shield machine passing through the mined tunnel; and Plan D： underpin- ning the box culvert, removing the piles from inside the mined tunnel, backfilling the mined tunnel and proceeding with shield tunneling. Plan D is adopted in the end. The key technologies for mining tunneling and shield tunneling in fluid- plastic strata are presented. Based on the data collected from the site, it is established that the key measures taken, such as underpinning the box culvert after the foundation is reinforced, incorporating the CRD excavation method in the mining tunneling after the ground is reinforced by splitting grouting technology, removing the piles from inside the mined tunnel and shield tunneling through the mined tunnel, are important technologies in ensuring the safe passing of the shield machine through the pile foundations.