When is sonic drilling the right solution?
19 December 2018
Mainmark:
Geotechnical engineers often specify the use
of deep drilling to assess soil conditions before commencing complex
construction projects. Choosing the right
drilling method is one of the
most important decisions and can directly impact project outcomes.
When deeper boreholes or high quality soil samples are required,
particularly in more difficult geological conditions,
sonic drilling can
be an ideal solution.
Sonic drilling uses high frequency resonant technology
that produces a very straight drill point which penetrates most ground
formations including cobbles, rock layers and boulders. It can be
undertaken in almost all types of soil and ground conditions, from
gravel and landfill, to softer formations such as sandstone, limestone
or weathered basalt.
The high vibration frequency causes a very thin layer of soil particles
directly surrounding the drill string and bit to lose structure and
temporarily behave like a fluid powder or paste. When retrieving the
drill, the suction and vibration enables the soil to reform.
While the
technology was originally developed to speed up the process of
digging oil wells, it was also found to have an outstanding ability to
take an accurate representation of a continuous core sample of almost
any material, even boulders and bedrock.
With extremely fast penetration speed, it is able to extract quality,
undisturbed samples with minimal impact to surrounding soil and less
environmental disturbance or contamination.
Deep core soil samples inform remediation solutions
In some cases, deep core soil
samples can help to better inform
remediation solutions. This was the
case when an elevated
railway bund at a
Queensland coal export
facility displayed signs of differential settlement just four
years after construction.
Sonic drilling was used to extract samples that could be analysed in
order to identify weak soil layers in the ground beneath the railway.
Using samples collected to a depth of 10m underneath the rail beam, an
appropriate solution was identified to help improve the soil density and
bearing capacity in weak layers beneath the rail while avoiding
contamination of adjacent coal stock.
Innovative placement technique solves the unsolvable
Sonic drilling also played a key
role in an Australian first
mine shaft rehabilitation project.
An abandoned mine shaft located beneath a motel carpark in regional
New
South Wales had collapsed and voids began to form, resulting in serious
subsidence affecting both the carpark and the motel building.
The technically and physically challenging remediation project had
already undergone prior failed attempts before Mainmark was engaged to
help resolve the issue, using a solution to plug the shaft at 30m
underwater, then cap, and seal the mineshaft.
The sonic drill rig was instrumental, enabling the Mainmark crew to
successfully remediate the site by combining bespoke cementitious grout
and an innovative placement technique.
During the carefully staged project, the sonic drill rig was used to
install three 76mm ID steel casings to a depth of 60m to provide access
for a temporary or ‘sacrificial’ plug, allowing technicians to implement
the required grouting solution in order to seal the mineshaft.
This unique approach resulted in Mainmark solving an extremely complex
problem that had previously been considered unsolvable.
--ENDS--
Source: Mainmark - www.mainmark.com
Contact: N/A
External Links:
https://mainmark.com/about/service-location/sonic-drill-geo-probe-quantum-imager/
https://mainmark.com/wp-content/uploads/2017/09/PP-N15W032-Mine-Shaft.pdf
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