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Singapore: building a tunnel under a nature reserve for a mass rapid transit line project

Bachy Soletanche Singapore has been working on the construction of the diaphragm wall for the tunnel connecting from Fairways Drive to Sin Ming Walk. The main challenges of the project: the presence of Singapore’s largest nature reserve above the CR202, but also the existence of very hard ground (granite) and difficult logistics conditions.

The Cross Island Line (CRL) is set to become Singapore longest fully underground line, with over 50km. This line is designed to cater to both current and upcoming developments in the eastern, western, and north-eastern parts of the city, creating connections between major hubs like Jurong Lake District, Punggol Digital District, and the Changi region.

This project revolves around excavating a 5km tunnel connecting Fairways Drive to Sin Ming Walk. Our scope of work will be on the construction of diaphragm wall for the launch shaft and facility building, with an estimated completion time of 3.5 months and 6 months respectively.

The launch shaft’s dimensions stand at 73m x 25m x 34m, while the facility building will measure 70m x 36m x 28m. A total volume of 11,000m3 of CR202 diaphragm wall will encompass both the launch shaft and facility building.

Bachy Soletanche Singapore have started machinery mobilization in August 2023 and guide wall construction by end of the month.

Environmental, technical and logistical challenges

What makes this project remarkable is not just the engineering expertise but its dedicated approach to environmental responsiveness. For instance, the ground above CR202 is the Central Catchment Nature Reserve (CCNR). CCNR is the largest nature reserve in Singapore which occupies over 2,000 hectares of forest.

One of the challenges we will face during the CR202 project is the intricate construction process due to the existence of elevated and extremely hard rock – widely known in Singapore as Bukit Timah granite. This situation extends the time needed to break and remove the rocks, consequently impacting the excavation speed. Therefore, when dealing with these rock formations, we must exercise caution to ensure safety and limit disruption to the surrounding natural environment.

The second challenge we have for CR202 is that there is only one access point for heavy vehicles during the construction operations which presents a logistical hurdle, requiring meticulous orchestration and synchronization of movement to ensure operational fluency.

As we progress, Bachy Soletanche Singapore remains steadfast in prioritizing health and safety, ensuring a safe work environment for all onsite personnel.

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