Recently, the "Zhixing" shield machine used in the TP1.4 bid section of the Taopu Wastewater Treatment Plant rainwater storage project, constructed by Tunnel Engineering Co., Ltd. Shanghai Tunnel Engineering Co., Ltd., successfully passed beneath Metro Line 14 and elegantly completed a "curved encounter."

This crossing section is located in the Zhenru Station–Tongchuan Road Station interval of Shanghai Metro Line 14, where the 4.91-meter-diameter sharp-curve shield "Zhixing" directly confronted various "extreme" challenges.

01 Environmental "Extremes"

At ground level is the intersection of Lanxi Road and Guchuan Road, where road traffic is busy and surrounding utilities are complex. Underground, the tunnel cover reaches 33 meters, and the full cross-section lies in the ⑦2 silty sand layer and confined aquifer. The soil has strong permeability, and under deep cover and high water pressure, the risk of tail seal leakage is high.

02 Curve "Urgency"

The horizontal alignment of the crossing section is a right-turn R500 curve. Passing beneath the rail transit will increase the difficulty of controlling segment ring elevation differences and the tunnel axis.

03 Speed "Rapidity"

The crossing distance totals 37 rings (37 meters). Under the premise of ensuring the safety of rail transit operations, an uninterrupted crossing must be carried out quickly and efficiently within the operating window.

In response to multiple difficulties, the tunnel team carefully planned and made every effort to safeguard the crossing milestone:

Before crossing

The project team of Tunnel Engineering Co., Ltd. Shanghai Tunnel Engineering Co., Ltd. formulated a plan half a year in advance and specifically strengthened the shield machine's functional configuration; carefully surveyed the surrounding utilities; set up a trial section to determine parameters; repeatedly conducted structural surveys of the Line 14 tunnel; and worked with all relevant units to jointly ensure construction support.

During crossing

The project team of Tunnel Engineering Co., Ltd. Shanghai Tunnel Engineering Co., Ltd. maintained 24-hour duty, monitored and adjusted shield advancement parameters in real time, strictly controlled simultaneous grouting volume, and ensured complete material supply. The shield maintenance team stood by on the front line to ensure the shield machine's condition.

Ultimately, the maximum settlement during crossing was 4.8 mm, twice as good as the standard.

The ultra-"extreme" challenge is ongoing 

The Taopu TP1.4 bid shield tunnel has a total length of 3,254.2 meters and involves four sharp-curve sections with radii of R65 meters, R70 meters, R75 meters, and R80 meters. At present, the tunnel team has successfully completed the R80-meter sharp-curve construction and will launch an assault on even more "extreme" challenges.