Shield tunneling of the north wall and second section of Nanjing Metro Line 1

On April 20, 2021, the "Endeavour No. 2" shield tunneling machine slowly broke through the rock at the receiving shaft of Erqiao Park Station, marking the smooth completion of the shield tunneling on the right line of the second section of the fourth mark of the north extension of Nanjing Metro Line 1. Thus, the two - section double - line shield construction was successfully completed.

The D1N-TA04 standard for civil construction of the north extension of Nanjing Metro Line 1 consists of one station and two sections, in which the right line of the second section is 1069.903m in total length, and the radius of the minimum plane curve is 350m, which is in the shape of "S". The shield trawling through the upper soft and lower hard composite strata and the high strength weathered sand strata occupies 55% of the total length of the right line. During this period, it has repeatedly crossed residential houses and factories, underpassed special railway lines and closely crossed D1200 socket sewage pipeline and other construction structures, resulting in high safety and quality risks.

In order to ensure the smooth progress of shield construction, the project department plans in advance, organizes scientifically, and makes various preparations actively. One is to organize the review of the scheme, organize the relevant construction units and invite shield experts to demonstrate the special construction scheme, to ensure that the scheme is targeted, implementable and safe; The second is to strictly implement the safety technology disclosure, the team leader to the front-line operation personnel to explain the construction of dangerous points, safety measures and matters for attention, and effectively implement the safety responsibility to the individual; The third is to strengthen the monitoring inside and outside the tunnel, through the monitoring data analysis results, timely find problems, improve the construction plan, improve the risk control ability; Fourth, do a good job of segment selection, according to the attitude of shield tunneling, scientific selection of lining ring type, to ensure the quality of the tunnel forming; Fifth, timely grouting, synchronous grouting and shield tunneling at the same time, fill the shield tail building void in time, and if necessary, further fill with secondary reinforcement grouting to ensure the safety and stability of the surrounding environment; Six is to set up the test section, according to monitoring the test section driving data, and through the monitoring data and other support measures, summed up a set of detailed driving parameters, one by one to break the major risk sources.