On 7th May 2013, a slope failure occured at Bukit Nanas Forest Reserve, burying 9 cars but thankfully resulting in no casualties or extra damage, although a section of Jalan Ampang had to be closed for several days. This EC discusses the engineering works done to mitigate, prevent and control future landslides around Bukit Nanas.

Geology of the Area

Bukit Nanas is underlain by Kenny Hill Formation rock, a typical sedimentary rock formation widely found in the vicinity of Kuala Lumpur and Klang valley. This Formation consist of  typical interbedded sandstone, siltstone and shale of Upper Silurian‐Devonian age. This rock Formation had been metamorphosed into a low grade metamorphism; sandstone been metamorphosed to quartzite, while shale became phyllite. Zainab Complex physical deterioration of the rock of Kenny Hill Formation in many  cut slopes due to unique weathering profile in the tropical cimate. The common  weathering profile of interbedded sandstone and shale. It consists of a relatively thin soil cover varying from 1 to 5m thick, and a weatherd rock zone which may be up to 30 meters thick. 

How's the weather up there?

JPS Wilayah Station, the closest rainfall station to the site, data of the intensity and frequency of the rain was studied, between 1st Feb - 7th May. Based  on  the  monthly  rainfall  intensity,  it shows that the pattern of monthly rainfall intensity increased from the month of February to April 2013. The monthly rainfall for April 2013 is recorded to be 503mm and the cumulative rainfall intensity from 1st May 2013 to the failure event was recorded to be 335mm which indicates that the failure area received heavy and frequent rainfall. The rainfall intensity during the event gave the reading of 147mm which is categorized as very heavy rainfall. 

Landslide Causes

Natural Causes:

1. Increase in water content
2. Erosion and weathering
3. Disturbance or loss of vegatative structures
4. Earthquakes and Volcanic activity

Human Causes:

1. Deforestation
2. Mining and Quarrying
3. Vibrations from machinery and traffic
4. Urbanization, agricultural and logging activities.

Landslide Engineering

There are a few ways slopes can be strengthened. The below image shows some construction techniques used in slope strengthening.

You will be asked to identify the techniques used here.

Logging Tasks

The area at GZ is always evolving - however I will keep up to date with the answers. Send the answers to the following via the message center and log the find.

1. Based on the information given above (and if unlucky, your personal observations), what caused the landslide to occur here. Choose as many factors as outlined above.
2. What 2 construction techniques were used to strenghten the slope? You might need to look at a nearby information board to get one of the answers. 
   • Of the one that you can see clearly at GZ, what other purpose do you think the structure serves?
3. At the moment of writing, there is a tarp covering the slope of the failure.
   • What is the main purpose of this tarp?
   • And why is it not a good preventive measure?
4. There is a hidden tunnel discovered during repair works of the slope. Take a photo of it with a personal item attached to prove your visit to the site. The answers need not be long (why use many word when few do trick?). I am not critical of the answers as long as you can prove your visit.