The sinkhole phenomenon – what causes them and how are they remediated?
08 May 2019
When it comes to ground issues, sinkholes can appear suddenly, often with dramatic and serious consequences.
While the ground may seem to
unexpectedly collapse, the reality is that sinkholes generally develop
over a period of time until the ground above simply loses support and
gives way, leaving a gaping hole.
Understanding what causes sinkholes
Sinkholes have been known to open up in all manner of locations – beaches and oceans, residential gardens, motorways, even shopping centre carparks. While sinkholes are a rare occurrence, there are a few common natural and man-made causes that can lead to the formation of a sinkhole, and these are usually exacerbated by flowing water. Nearby construction or excavation, leaking pipes, reclaimed landfill sites, as well as historical mining or tunnelling activity can also impact the stability or compaction of the surrounding layers of earth, leading to voids and potential sinkholes.
Groundwater – when water creates natural currents underground, the
ground below the surface layer may slowly erode or wash away, causing
voids to form. Over time, the underground void grows, causing the
surface layer of the ground to gradually become thinner and span
further, eventually caving in. In areas where the rock below the ground
is made up of limestone, which dissolves easily, sinkholes are more
common.
Heavy rainfall, floods, or leaking or burst drainage pipes can cause
excess
water to travel through the ground, washing out fines and causing
cavities, and potentially triggering a sinkhole.
Earlier this year, a burst water main was thought to be the cause of a
sinkhole that formed in the middle of a suburban
road in
Melbourne, partially swallowing a car.
Likewise, excess water was responsible for a sinkhole that formed in a
landscaped courtyard located within a residential complex in
Sydney’s Lane Cove.
Ground engineering specialists identified
the formation of a ‘void zone’ between the perimeter wall and the
adjacent natural rock supporting wall. Over time heavy rainfall soaked
into the courtyard lawn and slowly migrated through the ground towards
the void, washing away the soil beneath the courtyard, causing it to
erode and form a sinkhole.
The warning signs
Despite the surface layer of the
ground remaining intact, as an underground cavity forms and increases in
size, there are likely to be signs that indicate the presence of a void
or emerging sinkhole.
Recognising these signs and acting quickly, may help to put preventative
measures in place, thereby avoiding significant damage to homes,
business facilities and roads, while also minimising the risk to human
safety.
Pay attention to these potential warning signs:
-
Cracks forming in the ground outside
-
Unexplained depressions or dips in the ground
-
Trees or fence posts that tilt or fall
-
Rapid appearance of a hole in the ground
Comprehensive and affordable remediation solutions
When remediating the Lane Cove residential complex, Mainmark’s versatile Terefil® was an ideal solution, rapidly filling the void without placing undue pressure on existing drainage or perimeter walls. View this time lapse video to see Terefil in action, filling the underground void in Lane Cove.
Terefil is a lightweight cementitious fill used for a variety of complex
geotechnical applications, which includes filling and sealing large
underground voids and sinkholes. The comprehensive solution is
exceptionally lightweight, while also providing superior load bearing
capacity to the ground above.
It is also highly flowable meaning it can be pumped across long
distances so that it can be applied at sites even when access is
limited. This makes the application of Terefil quick and efficient,
causing minimal disruption to home and business owners. When used to
fill voids that have formed beneath roads or highways, there is little
or no effect on traffic.
Always seek expert guidance
If signs of underground voids or
sinkholes appear, consult structural and geotechnical engineers or
ground engineering experts.
For more information and advice about ground issues and remediation
solutions, contact Mainmark on 1800 623 312 in Australia, on 0800 873
835 in NZ, or visit
mainmark.com.
--ENDS--
Source: Mainmark - www.mainmark.com
Contact: 1800 623 312 in Australia, on 0800 873 835 in NZ, or visit mainmark.com
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