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.