THE recent incidents of sinkholes on the streets of Kuala Lumpur and Selangor are worrying not just the public but also the authorities.
The spate of sinkholes appearing one after another in rapid succession, many of which are in high traffic and densely populated areas, is making cityfolk baffled as to why it is happening.
The answer lies in several factors that need to be understood as a complete picture and not in isolation.
Rainwater, leaking underground water pipes and vibration caused by construction were some contributing factors that encourage sinkholes to surface, a geotechnical engineering expert said.
Prof Dr Fauziah Ahmad of Universiti Sains Malaysia said sinkholes generally appeared when there was cavity or depression in the ground, causing soil to give way and leading to the collapse of the surface layer.
“This cavity can be caused by rainwater that seeps into the soil, causing soil to erode slowly.
“When the soil loosens up and is washed away, a cavity is created underneath the ground which causes it to sink.
“Water is the main culprit here as water flow can be strong and dynamic which easily erodes soil.
“The same goes for leaked or burst pipes where the soil is washed away over time.
“Sometimes, sinkholes can be caused by human error where pipes are damaged during open excavation by contractors, ” she told StarMetro.
From July 18 to-date, six sinkholes were reported in Kuala Lumpur.
Among them were two large sinkholes that appeared at Jalan Taman U-Thant.
One caused a portion of the road and the outer wall of an apartment block in Taman U-Thant to cave in.
The second sinkhole appeared about two hours after the first and a pipe that burst during the incident resulted in water supply disruption in the area.
The water pipes were later fixed and supply was restored.
The other four sinkholes appeared in Taman Seri Taming, Jalan Cheras, Jalan Gombak and at the junction of Jalan Sri Hartamas 1 in Taman Sri Hartamas.
On July 20, a sinkhole also appeared at Jalan Langat (Banting-bound) and Jalan Johan Setia in Klang, Selangor during an earth-boring project.
Meanwhile, in 2019, three sinkholes appeared in different parts of Kuala Lumpur, including a large one on Jalan Maharajalela that frightened motorists and other roadusers as this one “swallowed” up a MyVi!
The more notable sinkhole incidents date back to December 2014 when two sinkholes appeared at the Jalan Pudu-Jalan Imbi-Jalan Hang Tuah junction which resulted in the closure of several roads.
Kuala Lumpur City Hall (DBKL) had to fill up the sinkhole with 1,500cu metres of sand to prevent soil movement and fitted in steel sheet pile to strengthen the soil before using an open-cut method to build the underpass, instead of microtunnelling.
Prof Fauziah said sinkholes were unavoidable and an existing problem for every city in the world.
“Proper soil compaction of the road is vital.
“This reduces the chance of sinkholes happening as the road will be more stable if compaction is done properly.
“Contractors who do not compact the soil, after repair works are done through open excavation, will affect the stability of the soil, ” she said.
To prevent more sinkholes from happening, Prof Fauziah said the authorities must identify critical areas and sinkhole hotspots.
“For example, former mining sites are more susceptible to sinkholes.
“Once the authorities know
the condition of the land and where the cavities beneath the surface are, proper precautionary measures can be taken.“They must also ensure construction companies are thorough and detailed while carrying out site inspection before building roads and other structures, because it is vital that they know about an area’s history.
“Once the engineers understand the surroundings, they can factor in engineering considerations before building in that area, ” she said.
Pipe-burst due to ageing infrastructure was said to have contributed to the sinkholes that appeared on Jalan Taman U-Thant and another at the junction of Jalan Sri Hartamas 1 in Taman Sri Hartamas.
Air Selangor chief executive officer Suhaimi Kamaralzaman said not all sinkholes were caused by burst pipes and each incident should be investigated on a case-by-case basis.
“We need to study the cause of a sinkhole, whether it is due to third party works or soil movement or is it because of continuous flooding that contributed to burst pipes.
“If the pipes patah (snap), then it is not our fault but if the pipes are leaking, then it may cause a sinkhole to happen, ” he said during the review of Air Selangor 2019 performance report involving Kuala Lumpur, Putrajaya and Selangor at its headquarters in Jalan Pantai Baru, Kuala Lumpur.
Air Selangor is expected to allocate RM160mil to RM170mil for its pipe replacement programme this year, similar to last year’s amount for the same programme. When asked about the utility mapping to help contractors gauge the location of underground pipes, Suhaimi said Air Selangor had cooperated with local authorities in Selangor.
The local authorities, he said, agreed to become the point of contact for third-party works.
“Contractors will need to check with the local authorities, who will then check with us whether there are pipes that need to be shifted before construction work begins.
“Hopefully, this will reduce incidences of pipes bursting.
“We are trying to convince DBKL to adopt the same measures in Kuala Lumpur, ” he said.
“Currently, the Survey and Mapping Malaysia Department wants to spearhead a one-stop centre for all utility mapping.
“But some of the maps may be as built plans submitted by contractors and we still need to validate the maps.
“So, it is still best for contractors to check with us, ” he added.
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