The left side of shield tunnel section of fengxihe station of the first phase of line 17 of chengdu metro is unblocked

At 12:30 on May 17, the tunnel of the left line between the first phase of line 17, wuho hospital station and fengxihe station area, was successfully completed, becoming the third tunnel of line 17 and the first section of chengdu metro to adopt the shaft free spiral shield tunnel.

The shield tunneling method was adopted to construct the 1.6-kilometer left tunnel between wuho hospital station and fengxi river station.

Line 17 is an important express line connecting the central urban area of chengdu with the peripheral areas of wenjiang and shuangliu, with a designed speed of 140 kilometers per hour. The total length of the line is about 26.1 km, with 9 stations, including 2 elevated stations and 7 underground stations.

Chengdu wenjiang area is mainly composed of sand and pebble strata with large particle size and high strength, some of which have particle size exceeding 90cm, and some of which are accompanied by fine sand. In addition, the underground water system is well developed, and the strata are strongly permeable with permeability coefficient of 25-28 meters/day.

uring the construction of large-diameter shield tunneling machine, it is difficult to control the balance of soil pressure, poor self-stability, and difficult to control the assembly quality of tunnel segments, which is described as "drilling in the flowing sand and gravel pile".

Since Aug. 31, 2018, since the initial success of shield machine, elaborate organization, chengdu subway overcome difficult, in strict accordance with the "control undervoltage, fully grouting, deep measurement, active protection" and "strictly control the parameters, the evaluating formation hole hidden dangers, contrast analysis of monitoring data, security emergency rapid disposal" requirements such as construction, complex geological conditions, overcome the urban trunk road traffic pressure, peripheral aging residential houses, many underground pipeline, wide range of major risk source distribution, ultra-small curve and a series of problems of turning, make the construction rapid step on track, smoothly through the shield interval.