News: ‘Shotcrete’ caused collapse

The Star, 30 Dec 2012

KUALA LUMPUR: The Bukit Setiawangsa landslip was likely caused by the unsuitable slope protection method used for the hill, according to experts.

Universiti Kebangsaan Malaysia Assoc Prof Dr Tajul Anuar Jamaluddin said the wall used to protect the slope was known as a “shotcrete” wall which prevents water from entering the soil.

“However, water can still seep into the slope from areas not covered by the wall but the wall also prevents water from flowing out.

“In other words, water can flow in but not out.

“When this happens, the groundwater pressure builds up and breaks through the wall, causing the landslip,” he said when contacted.

Dr Tajul, who teaches geology, said shotcrete walls were also not meant to be built on highly metamorphic rocks at Bukit Setiawangsa, which are not strong enough.

“The proper slope protection for such rocks should be something permeable like a high tensile strength wire mesh wall.

“This method allows water to seep in and out and vegetation to grow to prevent erosion,” he said.

Dr Tajul said that improper use of the shotcrete wall was common in Malaysia.

“Shotcrete walls should only be applied for granite slopes which are solid.

“However, they are commonly used because they are three to four times cheaper than the permeable walls,” Dr Tajul said.

He added that the Bukit Setiawangsa slope was cut too high and steep at 60° while houses were built too close to the edge.

Sensitive land development specialist Dr Tew Kia Hui said shotcrete walls were designed to prevent erosion but should not be constructed in areas with unstable earth.

“Such walls cannot withstand a heavy load above the soil. This includes houses, apartments and boulders,” he said.

Source: http://thestar.com.my/news/story.asp?file=/2012/12/30/nation/12518320&sec=nation