What Is Kuala Lumpur’s Ground Made Of & How Does It Relate To Sinkholes?
The latest sinkhole incident at Jalan Masjid India has drawn conversation about Kuala Lumpur’s bedrock foundation which is mostly soft limestone.
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The recent sinkhole incident in Jalan Masjid India last Friday which swallowed up a woman has drawn a conversation about Kuala Lumpur’s foundation and terrain.
Some were surprised to find that there was a large current running underground. However, in this case, the woman was washed away by the strong current in the sewage pipe.
Strong underground currents?
— Tired & Sakit 🇲🇾 (@tulunsokit) August 23, 2024
Is KL built on some soft rock or limestone? https://t.co/WcayITKTDR
As it turns out, Kuala Lumpur’s foundation or bedrock is made out of mostly limestone and quartz with varied distribution across different city areas.
The limestone is prevalent in the northern and central parts of Kuala Lumpur, forming the Kuala Lumpur Limestone Formation. Meanwhile, quartz is prominent in the Klang Gates Ridge.
The Kuala Lumpur Limestone Formation, a geological unit dating back to the Permian period, dominates major areas in the city. The formation contributed to the formation of caves and karst features in certain areas.
Karst is a weak limestone formation. It’s described as very soft and tends to get pasty like chalk mixed with water. As such, if the underlying karstic limestone bedrock is not dealt with appropriately, it will pose foundational issues in construction works and the possibility of sinkholes in some areas.
The issue of soft limestone bedrock under Kuala Lumpur surfaced during the construction of the Petronas Twin Towers. The unique construction challenge was covered in a National Geographic documentary titled “Megastructures: Petronas Twin Towers.”
In the original location, one-half of the site was decayed limestone while the other half was soft rock.
The whole site had to be moved 61 metres to allow the buildings to sit entirely on the soft rock with the world’s deepest foundations. The solid foundation comprised of 104 concrete piles ranging from 60 to 114 metres to be bored deeply into the ground.
In addition, a concrete raft foundation, comprised of 13,200 cubic metres of concrete, was continuously poured for 54 hours for each tower. The concrete raft measures 4.6m thick and weighs 32,500 tonnes.
Another area with large limestone bedrock is the Kenny Hill Formation. The Kenny Hill Formation sits at the top of the overlying graphitic schist known as the Hawthornden Schist.
So, is Kuala Lumpur actually safe to live in?
The newly-appointed Mayor Datuk Seri Maimunah Mohd Sharif said the city remains safe and refuted claims that said otherwise.
She said the Kuala Lumpur City Hall would only consider it unsafe if studies provided evidence to the contrary.
She shared that the situation around Jalan Masjid India and Kuala Lumpur is under control and safe for visitors. In addition, residents and businesses can proceed with their daily routines as usual.
The Kuala Lumpur City Hall had also activated a task force comprising the police, the Fire and Rescue Department, the Civil Defence Department, and the Minerals and Geoscience Department to assess and investigate the area’s safety.
The 48-year-old Indian national woman who fell into the sinkhole is yet to be found. So far, the search and rescue operation only found a pair of her slippers near the sinkhole.
The authorities completed inspections of all six manholes from Jalan Masjid India to the sewerage pond in Pantai Dalam (along the 7km sewage line) yesterday.
READ MORE: Cave Under KL Is Fake News, UM Has No Geologist Named Dr Sarah Jamal
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