Construction of Two of the Three Civil Work Contract Packages Underway

Indonesia, an island nation made up of over 17,000 islands, is facing worsening traffic congestion and air pollution in its capital, Jakarta, due to rapid economic growth. The Jakarta Mass Rapid Transit (MRT) North-South Line, spanning 24 km, was planned to address these issues. Phase 1 (L=16 km) contract package completed in March 2019, involved our company for three civil work contract packages out of five in total.
Construction is underway on Phase 2A, extending the line 5.8 km northward from the operational segment. Our JV is responsible for two of the three contract packages : CP201 and CP202.

Core of the MRT Network

Construction of CP201, the most central section of Phase 2A, began in June 2020. This contract package includes two 2-level underground stations—Thamrin Station and Monas Station—spanning a 2.7 km stretch, along with six shield tunnels connecting these stations to each other and other stations.
Thamrin Station is located on Thamrin Road, a hub for government offices and the central bank. It will also serve as a transfer station for the planned East-West Line, positioning it as a core hub for Jakarta’s future MRT network, which will connect in all directions. Monas Station is situated in Merdeka Square, near the National Monument (Monas), a symbol of Indonesia’s independence. Nearby are landmarks such as the Indonesian National Museum, visited by the Emperor of Japan in June 2023, and the Presidential Palace.

Twice the Length of a Typical Station

Thamrin Station, including its stabling track area, is 441 meters long—roughly twice the length of a typical station. It is being constructed using the open-cut method.
Sato, the CP201 Project Director, explains:
“Thamrin Station is located on a major road frequently used by government officials, so minimizing traffic disruptions is critical. We’ve minimized the work areas and strategically rerouted roads while progressing through the long open-cut section, including intersections. The soft, clayey soil also required us to take comprehensive measures to prevent ground deformation and protect nearby structures. During the design phase, we analyzed potential ground movement and developed countermeasures. We closely monitored conditions during construction to ensure safety at every step.”

Ground Anchors Found Underground

After construction began, several underground obstructions were discovered, including ground anchors left behind from the construction of a building west of Thamrin Station. These anchors created challenges for the diaphragm wall construction.
Sato explains:
“We didn’t know the anchors' exact number or precise locations. We conducted exploratory boring from the surface to identify them and monitored conditions during the diaphragm wall excavation. Where anchors were encountered, we considered design changes and construction measures, such as adjusting the wall’s depth and implementing additional measures like ground improvements and temporary supports during station excavation.”

Challenges of Box Jacking

The underground pedestrian passage connects Monas Station to an entrance near the National Museum and crosses a major road frequently used by government officials. Given its proximity to the National Monument, a popular tourist attraction, and the high-profile nature of the road, non-open cut methods were required. A large box structure measuring 12.2 meters wide and 6.1 meters high was pushed about 60 meters beneath the road, with just three meters of soil cover, using the box jacking method to address these challenges. Undertaking a project of this scale with such minimal soil cover is highly uncommon and presented significant technical challenges.

Four-Level Underground Stations

Construction of the CP202 commenced in July 2022, about two years after CP201. This contract package includes Harmoni Station, a two-level underground station, as well as Sawah Besar and Mangga Besar stations, both four-level underground stations, connected by four shield tunnels. Harmoni Station at the southern end is the arrival point for the shield machines launched from CP201.
The CP202 faces unique challenges due to its proximity to existing buildings and canals, which limit the available construction area. Measures to prevent settlement of existing buildings caused by construction were carefully considered from the bidding stage. These measures included partial ground improvements and extensive monitoring to ensure precise and cautious management throughout the project.
At Sawah Besar and Mangga Besar stations, the platform levels are split vertically due to space constraints, creating a four-level underground design. These stations require excavation depths approximately 1.5 times deeper than Harmoni Station, significantly increasing the excavation volume. To construct the station box, existing roads were diverted to the opposite side of the canal to create work areas. Harmoni and Sawah Besar stations are located on the west side of the canal, while Mangga Besar Station is on the east side. Canal decking was constructed to address the canal crossing between Sawah Besar and Mangga Besar stations, allowing construction to proceed with minimal disruption.

Simultaneous Construction of Three Stations

The CP202 required the simultaneous construction of three stations, significantly increasing the project’s complexity. Tagawa, the Project Director for CP202, explained:
“After about a year of discussions with road management authorities, we diverted roads and simultaneously began the main construction of the station box at all three sites. Given that the start date for CP202 was significantly later than the other contract packages in Phase 2a of the North-South Line extension, we had to progress with the construction of all three stations at the same time to meet the opening target.”
Regarding the challenges of simultaneous construction, Tagawa noted:
“The construction peak has been to occur across all three stations at the same time, which required securing supply chain’s capable of handling the high volume of work. While it would be simpler from a management perspective to assign one partner company per activity for all three stations, we chose to split the work among multiple companies to hedge risks, such as labor shortages or material supply issue.”

Tunneling Underneath the Canal

One notable aspect of the tunnel construction is the transition of the shield machines, launched in parallel from Harmoni Station, into an upper-lower configuration (stuck tunnels) midway before reaching Sawah Besar Station, a four-level underground station. They maintain this alignment as they cross underneath the canal at an angle before arriving at Mangga Besar Station. While the tunneling itself is relatively straightforward in terms of soil conditions, some obstruction removal is required in the canal crossing section. Progress is expected at a rate of 10 to 15 meters per day, based on conditions observed in other contract packages. However, once the shield machines reach Sawah Besar Station, lower shield machine must be skidding within the station box (B4 platform level) before being relaunched toward Mangga Besar Station, adding complexity to the coordination with the station’s construction schedule.

Paving the Way for the East-West Line

Looking ahead, Sato shared his vision:
“Despite the many challenges, we are fully committed to seeing this project through to success. Every team member faces their own pressures and difficulties, but they tackle these obstacles with a strong sense of responsibility. My goal is to create an environment where these talented staff can transform challenges into motivation and find real fulfillment in their work."
Tagawa added, “Our success with Phase 1 and CP201 was key to securing the CP202 contract. But this is not where our efforts end. With the Jakarta MRT East-West Line expected to move forward soon, I am committed to ensuring this project sets the stage for future opportunities.”
CP201 is scheduled for completion in November 2025, with CP202 set to finish in December 2029. Shimizu remains dedicated to contributing to infrastructure development on a global scale.