All post on this blog is the summary/abstract of paper presented in various conferences by the person mentioned at the end of the post. Any data or digital copy, if needed please request officially to the address; Senior Assistant Director, Landslide Forensic Unit, Slope Engineering Branch, Block F, 12th Floor, JKR H/quaters 50582 Kuala Lumpur, MALAYSIA. or refer to the first name on any of the abstract at the same addrtess.

Friday, January 15, 2010

Soil Nail slope/wall collapsed in Malaysia – never ending story.


Soil Nail is commonly used in Malaysia especially in cut slope. The basic concept of soil nailing is to reinforce and strengthen the cut slope by installing closely-spaced steel bars, called ‘nails’, into a slope as construction proceeds from ‘top-down’. The spacing of soil nail normally used was range between 1 to 2 m at centre to centre and install using grid type or diamond type and the diameter of nail is 100mm. Several type of length was use such as 6m, 9m and 12 m length. This process creates a reinforced section that is in itself stable and able to retain the ground behind it. The reinforcements are passive and develop their reinforcing action through nail-ground interactions as the ground deforms during and following construction.


The popularity of soil nail slope is due to its technical suitability, ease of construction and is relatively maintenance free. The range of soil nail slope height up to more than 40m and then the gradient was normally range between 2:1 up to 4:1. In Malaysia, Soil nail was installed with guniting for erosion protection at the soil nail area. Even though soil nail was design in line with international practice, slope failure still occurred.

Why it happened especially in Malaysia? This matter is still questionable. Is it due to design aspect such as using wrong data /wrong assumption /mistake on theory/ mistake on correlations/ lack in assumption/ less experience/ unsustainable condition on slope and so on, but at the end of the day, an engineer always blame nature to protect his mistake, otherwise act of god?

So far, those are the soil nail failure investigation that I involved;

1. Slope Failure at CH 6100 Route 59, Ringlet to Tanah Rata, Cameron Highlands, Pahang.

On 24 February 2004, a soil nail slope at Chainage 6100 of Federal Route 59 failed. The failure debris blocked the entire two lanes of the road, covering 50 m of its length. While there was no injury, the road had to be closed for a period of 7 days, during which the failure debris was cleared, the slope inspected, the road repaired and other works undertaken to ensure safety prior to re-opening of the road.

.The slope was stabilized using 100mm diameter nailed with bar size 25mm dia. The penetration length is 12m length with spacing 1m c/c. The slope was failed during construction stage of project. An investigation of the slope failure was carried out. The investigation included a review of review of existing record, failure investigation, causes of the failure and conclusion. It was found that, factors such as geological, physical and human factor have caused to the failure but which factor contributes more to the failure is still the question. What can I say, it is very hard to find the human factor causes of failure because majority geotechnical experts have their own theory rather than expose the truth?????


Photo on soil nail failure.




2. Soil nailed wall collapsed at MRSM Bentong, Pahang.

On 6 December 2009, a soil nailed wall at MRSM Bentong, Pahang failed. The failure debris damaged all the entire sewage treatment plant. It was lucky that the failure was happened during school holidays, whilst there was no injury. Site visit was conducted a day later to overview the condition. Some technical issues were found during the site visit.

The slope was stabilized using 12m length of nail with spacing 1.5m c/c and the slope high is more than 36m high. From observation at the critical cross-section of the failure, the bond and tensile failure of reinforcement was not found. The slip failure was beyond the penetration length of soil nail. No detail investigation was carried out from our team. Nevertheless the mechanism and causes of failure still can be predicted based on evident that was found from the observation. The failure was under the external stability condition.

Based on visual inspection, the failure occurred due to the removal of the support by earthwork activity, steeping the slope and constructing the soil nail wall was unable to strengthen the global stability.

     A cross-section & mechanism of the soil nailed slope failure

    Photo on soil nailed wall failure at MRSM Bentong.



In conclusion, the effectiveness of soil nail to stabilize the slope still need deeper research. So far, no research was carried out to study the effectiveness of soil nail in Malaysia prospective because no research paper was found regarding Malaysian context. Most paper carried out were only focus on case study and design aspect none discuss on developing reliable theory on the effectiveness on slope soil to stabilise the slope in Malaysia.

Friday, January 1, 2010

Landslide Warning System for Mount Pass, Malaysia Based on Surface Monitoring Technique

Interesting paper from Mr. Suhaimi Jamaluddin presented on Landslide Conference 2008 in Sendai Japan. Happy new year to you and hope to meet you in EGU 2010 Meeting in Vienna on mid year 2010.

Landslide Warning System for Mount Pass, Malaysia Based on Surface Monitoring Technique

Suhaimi Jamaludin1), Kamal Bahrin Jaafar, Che Hassandi Abdullah and Ashaari Mohamad

Abstract

A large landslide began in September 2003 in a newly-cut highway slope in a mountainous area of the State of Perak Malaysia. This site is located at the 44th kilometer of the Simpang Pulai – Kuala Berang Highway, and known as Mount Pass. The size of the mass is so huge, about 190m high and between 200m to 430m wide. Estimated volume of the unstable mass is about 2 to 3 million cubic meters. To reduce the consequences of catastrophic collapse of the active landslide, early warning system based on surface monitoring technique using robotic total station (SOKKIA SRX) was established. Background of the landslide, selected monitoring technique, proposed prediction model and analysis of the landslide movement pattern based on captured dataset will be presented in this paper.

Keywords: early warning system, surface monitoring technique, prediction model, landslide movement pattern

HAPPY NEW YEAR 2010

HAPPY NEW YEAR 2010 TO ALL STAFF, SLOPE ENGINEERING BRANCH ESPECIALLY TO STAFF OF LANDSLIDE FORENSIC UNIT, SLOPE ENG. BRANCH, JKR HEADQUARTERS.

Meeting on strengthening forensic investigation at Langkawi

On 27 December Landslide Forensic Unit. CKC JKR headquarters conducted a meeting to strengthen the forensic investigation. Several paperwork was tabled to discuss and find solution on how to improve investigation method, setup KPI for unit/person and review and improve SOP of Landslide Forensic Unit and etc. KPI for LFU has been setup. Five major tasks for LFU were identified. All staff needs to achieve at least 90% KPI for year 2010. All the best to all of you.