基坑开挖引起隧道水平变形的被动与注浆主动控制研究

对于邻近基坑的地铁结构保护问题,现有研究多集中于加强基坑自身支护体系、优化开挖方案等被动控制措施,此类方法缺乏在基坑开挖过程中对控制隧道变形的适时性和主动性,且会造成基坑造价提高、工期延长。以某邻近地铁结构的大面积基坑工程为例,分析了基坑施工中地铁结构的变形规律,进行了注浆对土体及隧道水平变形主动控制的试验及应用实践。在此基础上,通过数值模拟对几种隧道变形控制方法进行了对比和评价,并进行了注浆方案的优化研究。工程案例以及数值模拟结果均表明基坑分区分期开挖、分仓开挖、加强支护体系等被动控制措施具有较大局限性,而适时注浆主动控制隧道变形技术较为经济有效。在注浆策略上,多排孔注浆时“近距离、多孔位、小方量、由远及近”的注浆方案优于“远距离、少孔位、大方量、由近及远”的方案。主动注浆控制技术具有成本低、工期短、适时控制隧道变形等优点,条件适当时明显优于分区分期开挖等被动措施。

Passive control and active grouting control of horizontal deformation of tunnels induced neighboring excavation

For safeguarding metro structures adjacent to excavation, much attention has been paid to passive control measures, such as strengthening support system of excavation and optimization of excavation scheme. The passive control measures are not timely and active to alleviate tunnel responses during the construction process of excavation, and increase the cost and construction period of excavation. Based on a large excavation adjacent to a metro line, the development of horizontal deformation of metro structures during the construction process is analyzed, and field tests and application of grouting to active control of the horizontal deformation of soils and of tunnels are conducted. Furthermore, several control measures are compared and evaluated through numerical simulation, and the optimization of grouting scheme is also studied. The engineering case and numerical results reveal the great limitation of passive control measures, such as staged construction, zoned construction and strengthening support system, and effectiveness and economical efficiency of timely grouting to actively control tunnel deformation. In terms of grouting scheme, the grouting scheme of “close, more grouting holes, small grout volume, from far to near” is superior to the scheme of “far, less grouting holes, large grout volume, from near to far” in the case of multiple rows of grouting holes. As the active grouting technology has the advantages of low cost, short construction period and timely controlling tunnel deformation, it is obviously superior to passive control measures such as zoned and staged construction when the condition is appropriate.