The first phase of the CRL<\/span><\/a> \u2013 slated to be completed in 2030 \u2013 comprises 12 stations over 29km, from Aviation Park in Changi to Bright Hill. Ang Mo Kio station is one of the four interchanges on this stretch.<\/p>\nLTA group director for CRL Ng Choon Yeang, in response to queries on whether the suspension of tunnelling operations will result in delays to the completion of the first phase of CRL, said the team is still assessing the impact of the obstructions.<\/p>\n
Once traffic diversions are in place, more work will be done to investigate the obstructions before any further steps are taken, he added.<\/p>\n
\u201cWe will share more information when it is available to us,\u201d said Ng.<\/p>\n
As for why the obstructions were not discovered earlier, he said it was an unforeseen development because the wires were not detected during advance soil investigation works, and not reflected in drawings made available to the team during engineering studies.<\/p>\n
LTA, in response to queries, said soil investigation boreholes sample ground conditions only at set locations and intervals, and this type of ground anchor is difficult to detect unless a borehole intersects at a location where an anchor is present.<\/p>\n
\u201cAt this stage, there is no indication of similar undocumented anchors elsewhere along the tunnel alignment of Cross Island Line. The issue is specific to this location,\u201d it added.<\/p>\n
When the materials were first encountered during tunnelling works in May, LTA tried to first remove the thick wires entangled around the cutterhead before carrying on with tunnelling works.<\/p>\n
The cutterhead is the rotating steel wheel at the front of a tunnel boring machine, which excavates soil or rock.<\/p>\n
Between May and July, workers came across even more obstructions, and needed to intervene 100 times to stop the tunnel boring machine before removing the wires by hand.<\/p>\n
Along the way, 22 cutters \u2013 a component of the cutterhead \u2013 were damaged and had to be replaced, and about 800kg of wires were pulled out from the machine.<\/p>\n
Investigations later found that the wires were part of ground anchors \u2013 steel structures drilled into the ground \u2013 to temporarily support retaining walls or structures, and prevent them from shifting during construction.<\/p>\n
The Building and Construction Authority (BCA) and LTA, in a joint reply, said temporary ground anchors are usually erected and removed by those involved in the project, in line with approved plans.<\/p>\n
Both agencies are working with project parties, including the building contractors for AMK Hub, to establish the circumstances surrounding the presence of the ground anchors.<\/p>\n\nRunning into ground anchors during tunnelling works could damage the tunnel boring machine\u2019s cutter tools, disrupt tunnelling and pose safety risks to underground works and the roads above, said LTA.<\/p>\n
That is why tunnelling works came to a stop before ground improvement works \u2013 to strengthen and stabilise the ground where the tunnel is \u2013 began.<\/p>\n
Workers will then start removing the obstructions from the machine, before resuming tunnelling works in a safe and controlled manner, said LTA.<\/p>\n\n\nA ground anchor found in front of the tunnel boring machine\u2019s cutterhead.<\/p>\n
PHOTO: LTA<\/p>\n<\/figcaption><\/figure>\n
To enable these efforts, the 180m stretch of road at AMK Hub in Ang Mo Kio Avenue 3 will be reconfigured for about 1\u00bd years, starting from Nov 14.<\/p>\n
Changes include converting the three-lane east-bound carriageway \u2013 for motorists heading towards Ang Mo Kio Avenue 8 \u2013 into one bus-only lane.<\/p>\n
The three-lane west-bound carriageway \u2013 for those travelling towards Ang Mo Kio Central 1 \u2013 will become a two-lane road.<\/p>\n\n\nThe three-lane west-bound carriageway \u2013 for those travelling towards Ang Mo Kio Central 1 \u2013 will become a two-lane road.<\/p>\n
ST PHOTO: MARK CHEONG<\/p>\n<\/figcaption><\/figure>\n
The pick-up and drop-off point at AMK Hub will also have its traffic direction reversed, with exiting vehicles needing to stop at a new traffic light before they turn right towards Ang Mo Kio Central 1.<\/p>\n
Vehicles leaving the AMK Hub carpark also have to turn right towards 51@AMK mall when the new traffic arrangement is in place.<\/p>\n\nA new pedestrian crossing, complete with traffic lights, will be set up near the exit of the AMK Hub carpark.<\/p>\n
Pedestrians can still cross the road using the existing overhead bridge, although they will be able to access AMK Hub only through the second level, and not the ground floor, during the shopping centre\u2019s operating hours.<\/p>\n\n\nPedestrians can still cross the road using the existing overhead bridge via the second level of AMK Hub.<\/p>\n
ST PHOTO: MARK CHEONG<\/p>\n<\/figcaption><\/figure>\n
A range of traffic management options were studied, said LTA.<\/p>\n
Creating a bus-only lane at the AMK Hub stretch was the most practical approach because the road serves a number of bus services heading towards the Ang Mo Kio Integrated Transport Hub, and traffic volumes remain high even during off-peak periods, it added.<\/p>\n
Motorists can expect longer lines to enter AMK Hub during peak hours, with an added travel time of about 10 to 15 minutes, LTA said.<\/p>\n
Ng said: \u201cSafety remains our top priority. We understand the temporary traffic changes will cause some inconvenience to residents, motorists and businesses in the area.<\/p>\n
\u201cThese changes are, however, necessary to give our teams safe access and space to carry out the investigations, assessments and recovery works.\u201d<\/p>\n\nLTA said the area will remain safe for the public. It added that ground conditions around the mall will be monitored closely throughout the works.<\/p>\n
Cost implications are still being assessed as investigations and engineering assessments are ongoing. \u201cIt would be premature to speculate on responsibility or potential actions at this stage,\u201d said LTA.<\/p>\n
In response to queries, a spokeswoman from Link Asset Management, which manages AMK Hub, said the mall remains open and continues to operate as usual during works at the site.<\/p>\n
She said: \u201cVisitors can continue to access the mall, shop and dine.<\/p>\n
\u201cTo facilitate traffic movement, the exit route has been adjusted with clear directional signage in place to guide motorists and ensure a smooth journey to and from the mall.\u201d<\/p>\n