Han Ximin

ximhan@126.com

WORK on Chunfeng Tunnel with the largest domestically made tunnel-boring machine (TBM) was officially initiated after a ceremony yesterday.

The mega TBM with a diameter of 15.8 meters, equivalent to the height of a five-story building, is said to be the largest TBM made in China. It is being used to bore the four-lane double-decked tunnel, set to relieve congestion on Binhe Boulevard.

One of the major infrastructure projects in the city’s “Go East” strategy, Chunfeng Tunnel runs parallel to Chunfeng Flyover to the north.

After the tunnel’s completion, a trip between Shangbu Overpass in Futian District and Xinxiu Overpass in Luohu District will take only six minutes.

The 5-km tunnel links Binhe Boulevard and the East Cross-border Expressway through the two overpasses. The tunnel section runs 4.82 kilometers and the TBM will bore 3.6 kilometers.

It is expected to be completed in 2021.

It will be Shenzhen’s first single-bore tunnel with a double-decked interior, providing four lanes and two continuous emergency parking lanes, three in each tube. Traffic on the two decks of each tube will run in opposite directions.

Working with a TBM of this size presents a number of major technical risks that need to be effectively managed. The TBM will cross 11 fault zones up to 431 meters wide and will negotiate a minimum curve radius of 750 meters, according to the manufacturer China Railway Tunnel Group.

Another point of concern for this project is settlement control, because the tunnel goes underneath a residential area, the city’s Metro Line 9, and other urban buildings and public infrastructure.

To mitigate the risks, the contractor, China Railway Tunnel Group, has implemented four circuit lines of air pressure control for the machine to minimize settlement during operation.