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Need for geophysics studies to identify underground cavities

Source from: New Straits Times, Original Article

LETTERS: Sinkhole is one of the natural disasters that may be caused by natural or human activities in limestone areas. Kuala Lumpur, which is underlain by limestone formation, is undergoing rapid and extensive urbanisation and development.

The problem with limestone is its solubility and decomposition when it reacts with rainwater. Vibration and disturbance due to nearby construction work may also trigger sinkholes. There have been many incidents of sinkholes in Kuala Lumpur, especially after heavy rain.

In November 2019, a sinkhole opened up in Jalan Maharajalela when an underground pipe burst. A car fell 3m into the gap. A day after, another sinkhole appeared in Jalan Pinang, causing a massive traffic crawl.

Another sinkhole cropped up in Jalan Dewan Bahasa dan Pustaka, about 700m from the sinkhole in Jalan Maharajalela, just within 48 hours. A sinkhole at the Jalan Imbi-Jalan Pudu intersection happened along the same stretch in 2014.

On top of that, a giant sinkhole swallowed a part of a street and also the walls of a luxury condominium complex near the United States Embassy in Ampang Hilir in July last year.

More sinkholes appeared near the Kampung Pandan roundabout in September last year as a result of tunnel boring work. In January this year, a 10m deep crack occurred on a 50,000 sq feet land near Jalan PKPS in Kampung Bestari Jaya, Selangor.

In 1995, a sinkhole 3m in diameter and 1.5m in depth opened up in Jalan Lidcole due to construction work involving piling and excavation nearby. Subsequently, a ground depression in Jalan P. Ramlee in 1993 that was 10 times greater than the Jalan Lidcole incident occurred due to bored piling activities in the area.

Incidents of apparent land subsidence against groundwater extraction were reported at the Subang Hi-tech Park in 1998. A total of 20 units of chain shop factories were affected.

Sinkholes also happen in other parts of the world. A massive 65 feet deep sinkhole created chaos among commuters in downtown Fukuoka in southwestern Japan when the entire width of a major five-lane road caved in.

In Manchester, the United Kingdom, two sinkholes appeared due to heavy rainfall in the northwest, the first in August 2015 and the second a month later.

In China, five people were killed when a 10m wide sinkhole opened up in front of the gates of an industrial estate in Shenzhen in 2013.

In 2016, at least three people died when they fell into a huge sinkhole that swallowed a section of the road and passers by in central Henan province.

Investigations showed that the collapse might have been caused by water pipes buried under the road breaking up due to the rain.

In January this year, an enormous sinkhole swallowed a bus along with pedestrians in China, sparking an explosion that killed six people with 10 more missing.

Almost all sinkholes are triggered by construction activities mainly due to the lowering of groundwater table, groundwater seepage, and the imposing of additional loads and vibrations. In some occasions, it is due to the direct punching of the cavity cover by borehole or piling activities.

The sinkholes caused by burst pipes could be attributed to multiple factors, including intense earthworks resulting in the removal of soil, its movement, an increase in the water table and flow, as well as increase in rainfall. Climate change may also be one of the contributing factors as heavy rainfall could cause the natural moisture of the soil to change.

Therefore, it is crucial for the relevant agencies to conduct detailed geophysics studies prior to constructing physical infrastructure to identify the underground cavities.

Senior lecturer, Faculty of Civil Engineering, UiTM, Pasir Gudang, Johor

The views expressed in this article are the author’s own and do not necessarily reflect his official position

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