The biggest challenge in our underground construction works are the geological formations beneath Kuala Lumpur. For the MRT Putrajaya Line project, tunnelling works primarily face three types of key geological formations, namely Kenny Hill, Karstic Limestone and Granite, with most of the tunnel alignment situated in Grade V karstic limestone.
Extreme karst limestone is a geological formation formed through the gradual erosion of limestone by mildly acidic water over millions of years, leaving behind an elaborate labyrinth of unstable caverns, cliffs and pinnacles that run beneath the depths of Kuala Lumpur city. Due to the void-riddled nature of these underground passages, some cavities may become filled with water. Sinkholes and ground subsidence can then occur when disturbances to these underground water tables cause earth and other debris to shift, disrupting the equilibrium of the system.
With such unpredictable and complex geological conditions at play, controlling ground loss and pressure fluctuations in the midst of tunnelling works is vital to avoid sinkholes, reduce settlement and limit the impact on existing structures. To tackle these complex conditions, MMC Gamuda relies on our Variable Density (VD) Tunnel Boring Machine (TBM) (the first in the world when innovated during the MRT Kajang Line project) which is able to operate in multiple modes.