Precision achieved to ensure longevity of HZMB

A 34-hour accurate adjustment was made to shorten deviation to millimeter-level after the final closure joint was placed between the E29 and E30 immersed tubes of the Hong Kong-Zhuhai-Macao Bridge (HZMB) on May 2.

The HZMB subsea structure is world's longest tunnel deeply buried at the seabed. The immersed tubes encompassing 33 prefabricated concrete pipe joints and a 12-m final closure joint stretch 5,664 m in total. Each standard tube weighs almost 80,000 tons, is 180-m long, 37.95-m wide, and 11.40-m high. The technology and equipment used in the docking of the final joint are independently developed and globally initiated.

Rendering of HZMB

Witnessed by more than 10 experts and 99 journalists, the final joint docking on the 28-m-deep bed of the Lingding Sea realized a north-south linear deviation within 15 cm reference ranges, creating what is being called a miracle of "impermeability within one day."

On May 3, however, island-tunnel general director Lin Ming, who is also the chief engineer of China Communications Construction Co, raised an adventurous idea of making an installation adjustment to guarantee the 120-year life span of the bridge.

Lin Ming discusses accurate adjustment

Joel Van Stee, engineer of the final joint water-stop belt supplier Trelleborg AB in the Netherlands, objected the suggestion. He said that the fine tuning could lead to hundreds of millions of yuan in losses and even a tremendous accident if a collision were to occur.

After rounds of discussions, the adjustment was decided upon. Van Stee appeared to be moved by Chinese engineers who sought perfection and then he finally agreed with the tough decision.

The linear deviation was shortened to 0.8 mm on the east side and 2.5 mm on the west on May 4 after 34 hours of continuous work. Van Stee contended that the immersed tunnel of the HZMB is the best among the construction of 15 immersed tunnels he had participated and it reflects the world's highest-level bridging technology.

Bridge welding [Photos by Zhong Fan / Zhuhai Daily]

Tunnel Engineering Consultants (TEC), a Netherlands consulting company and international leader in immersed tunnel construction, sent a congratulation letter on May 5. It states, "Closure joint scheme has added an innovative and efficient concept for closure joint solutions and is a great contribution to immersed tunnel technology, which will benefit the immersed tunnel industry in China and the world."