1. DAMAGED AND COLLAPSED INTERLOCKING CONCRETE PAVEMENT IN OUTFALL 10
I. AN OVERVIEW
On 7th November 2012 at 10:56 AM a portion of an interlocking concrete pavement in
Outfall 10 was found to be damaged where concrete blocks had been eroded directly to
the seabed due to unknown cause. The said collapsed area had also resulted creating
an open hole which risked not only the public but the entire outfall structure as well.
A comprehensive Defect Notification Report No. 460 dated on 7th November 2012 with
Reference No. MU-DL-01-2717 (see Appendix –A) was immediately submitted to
Parsons International Limited by Dripco Contracting Company, detailing the present
conditions of Outfall 10 and how safety was ensured temporarily in the area.
II. MAJOR CAUSES OF CONCRETE PAVEMENT DISINTEGRATION
As instructed by our Consultants, Parsons International Limited, an actual site visit
was carried out on 11th November 2012 to re-verify the main causes of the sudden
collapse of Outfall structure, and these are as follows:
A. Soil sedimentation and water erosion
Soil sedimentation is the result of water erosion. Erosion removes soil from the land
and carries it away by water action. It is the process in which soil particles are
carried from its point of origin by either natural or human reasons-enhanced
processes is deposited elsewhere on land surfaces or in water bodies. When the
water drops the soil, it settles into the bottom of the waterway. The soil particles
that are accumulated in the bottom of the waterway are known as sediments. The
process of depositing the sediment is known as sedimentation.
The affected side and damaged area of Outfall 10 as shown in Appendix -A was built
near an open dock or harbor where sea water underneath cannot be controlled and
has direct contact with the soil supporting the outfall structure. The direct contact of
water to the soil has caused the foundation to be weak due to slow sedimentation
and erosion that have been going on through time of contact. The soil sediments are
deliberately washed out and subsequently eroded by the water leading to
disintegrate the outfall underlying groundwork or foundation, thus concluding to
weaken the support of the its structure in general.
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2. B. Past construction of the new boundary wall
Soil Erosion is the process by which soil and rock are removed from the Earth's
surface by natural processes or factors such as wind or water flow, and
then transported and deposited in other locations.
While soil erosion is considered as natural process; however human activities have
seemingly increased and contributed to excessive problems brought by soil erosion
and further leading to disturbance and disintegration of the soil natural layer
through many ongoing industrial construction works such as excavations in
particular.
Relating to the above given facts, the past excavation work due to construction of
the new boundary wall within the perimeter of Outfall 10 area sometime on
September 2010 by Ghantoot Company cannot be denied as one contributory
factor to the cause as to why the outfall structure and its foundation had subsided
through time.
This site issue was reported to Parsons’ Site Office through Defect Notification
Report No. 285 dated on 18th September 2010, MU-DL-01-1860 (see Appendix –B).
III. SOLUTIONS AND RECOMMENDATIONS (refer to Appendix-C)
A. Installation of a temporary sheet pile to prevent the soil from further eroding or
collapse during excavation work as preparation to retaining wall construction.
B. Construction of retaining wall
A retaining wall has to be constructed beside the existing boundary wall to
protect the premises of Outfall 10. This wall will barrier and prevent the direct
contact between sea water and the underlying groundwork or foundation which
support the outfall structure.
C. Refilling of the displaced soil underneath
The large volume of the displaced soil must be refilled and compacted to create a
strong foundation or base for the reconstruction of the interlocking concrete
pavement.
D. Reconstruction of the interlocking concrete pavement
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3. IV. CONCLUSION
The damaged and eroded interlocking concrete pavement in Outfall 10 was due to
natural reasons brought by the processes of soil sedimentation and erosion which
led to weaken the groundwork or the natural layer of soil supporting the entire
outfall structure.
The aftermath or effects of human activities in nearby areas of Outfall 10 due to past
construction and excavation work made on September 2010 had also enhanced the
natural processes of soil erosion and sedimentation to occur; the excessive
mechanical excavations had resulted to disintegrate and disturbed the natural
layers of the soil in the area.
Public safety is presently at risk and the degree of damage caused by the Earth’s
physical and natural processes brought by human activities will then lead to severe
level if not repaired immediately or no solutions shall be considered to counteract
the main cause of the problem. This site issue therefore calls for an urgent and
competent action from the concern authorities.
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