The First Intersection Tunnel of the Second Phase Construction of Kunming Metro Line 6

At 19:16 on January 25, along the left line of Juhua Station to East Bus Station in the fifth construction area of the second phase of Kunming Rail Transit Line 6, the cutter head of Hairuike Earth Pressure Balanced Shield Machine burst out slowly, marking the completion of the first 1155m long shield tunnel in the second phase of Kunming Rail Transit Line 6 in 2019.
     The tunnel started on October 28, 2017. There are four main difficulties to overcome in construction: first, the long-standing dormitory group of the provincial Agricultural Reclamation and Petroleum Company; second, the railway track of the West Freight Yard, with precise ground settlement control; third, the metallurgical dormitory building with pile foundation is difficult to grind piles; fourth, the shield machine crosses the upper soft and lower hard sections for a long distance, which makes the construction organization difficult. Driving control is difficult. In order to ensure the safety of shield construction, the project department should increase the monitoring frequency and do well in the analysis of monitoring data so as to control the parameters of shield tunneling speed, cutter head torque, Jack elongation, synchronous grouting volume and grouting pressure. Ten annular grouting holes are added to each annular segment, and double grouting of cement and sodium silicate is used for the second grouting of "less grouting" in order to better fill the same conditions. Stepping grouting solidifies the voids caused by water loss and drying shrinkage, reduces settlement, and effectively avoids large-scale landslides and accidents of inclination or even collapse of surface structures. "The second phase of Line 6 project has a tight schedule and heavy tasks. As a key node project, it is particularly important for us to fulfill the construction schedule on time to ensure the completion of the whole project on time," said Bai Zhifeng, project manager. "For this reason, the project department actively plans and organizes the construction in full use of pre-festival time. Nowadays, tunnels in all sections are connected on time, so that the second phase of Metro Line 6 can be completed on time. Cheng's completion on schedule and the timely opening of Metro Line 6 laid a good foundation.