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causative factors and explores what lessons have been learned from those cases. The main example is the collapse with fatalities of a 30m deep excavation alongside the Nicoll Highway in Singapore in 2004.
ERRORS CAUSED COLLAPSE AT NICOLL HIGHWAY. The Government today released the final report by the Committee of Inquiry (COI) into the Nicoll Highway collapse. The COI concluded that critical design errors led to the collapse of part of the earth-retaining wall system, which killed four workers.
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- Project Details
- Modeling Undrained Behavior
- Curved Diaphragm Walls
- Utility Crossings
- Poor Strutting System
- Sway Stability of Open Stiffeners
- Telltale Signs
- Comparison of Results
- Conclusions
The collapse was located in the south-central part of Singapore island. The land transport agency of Singapore had wanted to build a circular metro line (Circle Line 1 Stage 1 – Contract C824) connecting the suburban areas of Singapore to the central business district in the downtown area. Excavation work for a cut-and-cover tunnel was underway and...
In designing a multi-stage excavation, the use of software is often required. Although, in many cases, the drained behavior of soil is critical for excavation works (due to unloading), undrained behavior is still relevant and appropriate for soil such as marine clay, which has very low permeability. The software used to design the cut-and-cover tun...
The curved alignment on the metro line plan meant that the retaining walls had to follow this curvature. It should be noted that curved diaphragm walls posed many challenges for design and construction. First, the usual 2-dimensional (2-D) plane strain analysis adopted for a section design would not capture the effects of curvature, which runs in t...
Existing underground utilities have to be protected from damage during excavation. Sometimes, utilities may be diverted away from the excavation area before construction commences, but this is not always possible. There will be occasions where project parties are required to contend with existing utilities in the way of the excavation activities. I...
There were many inadequacies in the design of the strutting system in C824. Due to the design-and-build nature of the contract, the contractor wanted a very lean design. The curved diaphragm walls and close vertical spacing of the struts (obstructing ease of construction) did not help. In C824, it was found that some walers were discontinuous. Some...
During construction, it was found that some of the plate stiffeners for the strut and waler connection had buckled. The contractor thought that this happened due to more load being transferred through the strut’s flanges, resulting in the plate stiffeners being inadequate. Unknown to the contractor, the inadequacy of the steel stiffener plates was ...
A large-scale infrastructure project such as C824 inevitably required a large team of project personnel for design and on-site during construction. Despite the large team of engineers, supervisors, client representatives, and contractors present on-site, none of the project parties realized that the numerous abnormal sightings were telltales signs ...
It is sometimes useful to check computer output using simple rules of thumb. Designers can use apparent wall pressure diagrams where lateral pressure pa acting on the wall = γH(1-m4cu/(γH)) to estimate the strut load. Using m = 0.4, cu = 30 kPa, γ = 18 kN/m3, H = 33m, pa works out to be 0.9 γH = 535 kN/m2. Adding a surcharge of 20 kPa (assume Ka = ...
The safety of temporary construction might sometimes take a backseat because they are constructed only for a relatively short period to facilitate permanent construction. Parties are sometimes tempted to adopt lower safety standards for temporary works. However, this can be a costly mistake, especially for a large-scale project involving complex si...
Apr 20, 2024 · Col Mohamed Nazim and Col Chew Keng Tok speak to CNA about their experiences during the Nicoll Highway collapse in 2004, and how the SCDF has evolved since then.
- Aslam Shah
Apr 20, 2024 · Saturday (Apr 20) marked the 20th anniversary of the Nicoll Highway collapse that left four dead and three injured. One man was never found.
- Aslam Shah
The Nicoll Highway collapse occurred in Singapore on 20 April 2004 at 3:30 pm local time when a Mass Rapid Transit (MRT) tunnel construction site caved in, leading to the collapse of the Nicoll Highway near the Merdeka Bridge. Four workers were killed and three were injured, delaying the construction of the Circle Line (CCL).
excavation adjoining the Nicoll Highway Station box had collapsed. This caused soil subsidence of the immediate surrounding area, which propagated rapidly, covering approximately 100 130u m area and sucking in
