Consultant engineer involved in Highland Towers probe calls on authorities to be more vigilant.
Zeezy Global geotechnical and environmental consultant Aziz Noor said in view of the Tanjung Bungah landslide on Oct 21 that took the lives of 11 workers, all authorities, not only in Penang but throughout Malaysia, should keep an eye on all steep slopes as disaster might strike at any time.
He said although a hill slope might appear fine from the outside, it could be on the brink of collapse due to water pressure and vibrations from the surrounding environment.
“Most of these slopes are clay mixed with sand. Clay has an affinity (stick together). At particle level, they can hold up.
“When water comes down steep slopes they break the affinity of these particles. And yet they still hold up but it just speeds up the time of the collapse.
“That is why they do not fall right away. They are a time bomb, a disaster waiting to happen,” he said at a talk hosted by Penang Forum today.
Aziz, an American-trained environmental and geotechnical expert, was manager of an independent consultant engineering firm investigating the aftermath of the Highland Towers collapse in Ulu Kelang, Selangor, in 1993, in which 48 people were killed.
He said hills cut beyond their “natural angle” were the ones to watch out for.
“A hill slope that is cut beyond its natural stable angle is not a stable slope. Such slopes are at high risk of failure and can end up in landslides.
“When you have bare slopes like that, the portion of runoff is large; the steeper the slope, the faster the ‘teh tarik’ (mud slide) comes down.
“Basically, when the water runs off faster, the more erosion it causes, and the faster it will go down to lower-lying areas and cause flash floods with silt,” he said.
Aziz said to prevent such disasters from happening, engineers ought to cut hills at a more natural angle and ensure drain holes are built into them.
He said drain holes would release the “water stress” that might be building up beneath the slopes.
Aziz stressed that these measures were not one-off solutions and required constant monitoring from all parties.
“Ordinary folk might think, okay, looks like a nice concrete wall. But you do not know what is going on underneath, and hence, you need to maintain the hillslopes from time to time.
“That is why you see the slopes on our PLUS highway are constantly being maintained. It is something you do not mess around with,” he said.
Aziz said many construction sites cut corners by placing plastic sheets on cut hillslopes, which would not help much in preventing landslides.
“This is akin to putting a band-aid on a very sick person,” he said.
On the Tanjung Bungah landslide, Aziz said the state authorities must beef up their monitoring teams and place them on full patrol at all sites in the state.
“We need all the ‘jabatan’ (departments) to wake up and not sleep behind the wheel. Present-day laws are adequate to enforce and punish those who flout the law.”
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