为解决大断面、浅覆土工况下箱涵推进微扰动施工问题,以上海市田林路下穿中环线地道工程为依托,预先施工62根口字型 钢管幕,箱涵推进使用断面为19.84 m×6.42 m的土压平衡封闭式掘进机。 介绍大断面箱涵推进的管幕顶进质量控制、开挖面稳定 技术、同步推进系统、特种泥浆施工技术以及微扰动施工效果。 工程实践表明: 1)封闭式土压平衡箱涵掘进机与上部钢管幕一起 成为保证中环线路面沉降的“双保险”; 2)掘进机开挖面前方约15 m范围(约为箱体高度2.5倍范围)内土体受到影响,上部钢管 幕承载量约为26.5%; 3)建立同步注浆(A浆)与补充注浆(B浆)2个独立的注浆系统,注浆充盈系数选为4倍建筑空隙,能够使路 面出现微隆状态; 4)箱涵推进期间中环线最大沉降±1 cm,使得大断面箱涵推进达到微扰动状态。

The micro-disturbance construction of box culvert under the condition of large cross-section and shallow cover is a problem to be solved. Hence, 62 square-shaped steel pipe curtains are pre-constructed, and a closed EPB boring machine with the largest cross-section area of 19.84 m × 6.42 m around the world is adopted in the underpass project of Tianlin Road crossing the Central Ring Line in Shanghai. And then the pipe curtain jacking quality control, excavation surface stabilization technology, synchronous propulsion system, special slurry construction technology and microdisturbance construction effect of large cross-section box culvert propulsion construction are introduced. The engineering practice shows that: (1) The closed EPB box-culvert boring machine together with the upper steel pipe curtain forms a double-insurance to the surface Central Ring Line. (2) Soil 15 m ahead of excavation face is affected, which is about 2.5 times the height of the box; and the load-bearing capacity of the upper steel pipe curtain is about 26.5%. (3) Two independent grouting systems of synchronous grouting (grout A) and supplementary grouting (grout B) are established; and the filling coefficient of grouting is chosen as 4 times of the building void, which would induce micro-uplift of pavement. (4) The maximum settlement of the Central Ring Line during the propulsion of the box culvert is ±1 cm, which realize micro-disturbance construction.