March/April 2022 - 83

Deep Soil Mixing Use in Poland
FEATURE ARTICLE
Deep Mixing Series: This article is the
second keynote highlighted from DFI's virtual
Deep Mixing Conference in 2021, for which
Topolnicki served as a committeee co-chair.
Polish applications of deep soil mixing
(DSM) technology occupy a leading
position in Europe. That includes use for
road and railway embankments,
bridges, residential and industrial buildings,
silos, commercial centers, slabs, car
parks and storage yards, excavation
supports and cut-off walls. In fact, more
than 350 road and railway viaducts and
200 wind turbines have been founded
nationally on DSM columns, which are
firsts on an international scale. This
represents more than 1,200 implementations
by the Polish geotechnical
industry. Considering the need to update
DSM design recommendations, this
article will attempt to summarize the
best practices of wet DSM design and
implementation, in particular. It draws
on 20 years of experience and will highlight
the properties and principles of the
design of stabilized soil and lessons
learned. Case studies are included to further
understanding of the careful considerations
needed with this technology.
Historical Use
Considering the DSM market's development
elsewhere can be interesting for
countries where soil mixing is still in
early application stages. A patent for a
method to seal and strengthen the
ground and the device for it was filed in
Poland as early as 1966 and only 10
years later than in the U.S., ahead of
DSM studies and application in Japan
and Scandinavia. However, the invented
device was never constructed, and in
1995, dry soil mixing was introduced in
Poland by a Swedish contractor, with the
first major work on a motorway. The use
of wet DSM started in 1999, with the first
major project comprising construction
of cut-off walls inside levees of the
Vistula River in Cracow. Wet technology
quickly dominated Poland's market and
found its place among other ground
improvement (GI) methods. At Keller
Poland, this soil treatment approach
gained a considerable market share by
2005, reaching up to 33%.
The market reaction came quickly,
but with mixed outcomes. While appreciating
the growing number of DSM
applications and the simple tools
involved, some companies underestimated
the demands of soil mixing.
As a result, problems with the quality of
DSM works appeared. The antidote was
a quick implementation of design,
execution and QC/QA standards; this
was helped by a book published in 2004
that preceded the Eurocode.
This situation did not last long, and
current practices of the more than 20
specialty contractors in Poland and
AUTHORS Michał Topolnicki, Prof., Ph.D., D.Sc., Keller Polska
DEEP FOUNDATIONS * MAR/APR 2022 * 83
equipment used meet world standards.
In use are single, double and triple
mixing tools, trenchers, rotary heads for
mass mixing, cutters and very efficient
batching plants. Modern electronic
systems sometimes support the execution
process, although most of the
works involve manual control.
About half the companies in Poland
likely provide DSM on a regular basis,
the next five from time to time, and the
remainder offer the possibility of doing
such works. Of six companies that
responded to a 2018 survey from the
Polish Federation of Foundation Contractors,
we learned that two to three
new DSM projects are launched nationally
every week, and the estimated value
of this market is currently around $35
million (€30.9 million).
Applications mostly involve use of
the wet method and column-type
mixing, with the productivity and quality
of DSM works having significantly
improved over time. In part, the ability to
do large diameter columns (8 ft or 2.4 m)
has increased productivity threefold,
while trench mixing offers capacities of
2
Mixing Process Considerations
As observed when soil samples are
mixed in the laboratory, mixing the
same volume of grout with a soil
produces di fferent compressive
up to 10,764 ft (1,000 m2) a day.
March/April 2022

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