1
25-098
Using Foam as a Transportation Medium for Backfilling
Underground Voids with Liquid-Sand
Nico Sutmoller
Aerix Industries, Golden, CO
Rich Palladino
Aerix Industries, Golden, CO
ABSTRACT
Underground voids present a unique geotechnical engi-
neering challenge. This paper will address materials and
transportation mediums that are typically used for backfill-
ing underground voids with native material. After review-
ing traditional backfill and transportation methods, this
paper will explore the advancing technology of foam trans-
portation and the advantages of using this technology for
transporting fill materials into underground voids to back-
fill them with Liquid-Sand. The paper will also review the
benefits that Liquid-Sand brings to these applications and
highlight specific case studies in which foam transportation
has proven effective and provided cost-effective, environ-
mental benefits.
INTRODUCTION
Underground voids, resulting from both historic and active
mining operations, occur frequently. When these voids
are created, surface subsidence often occurs as these mines
begin to collapse, which leaves these underground voids
inaccessible. This means that the backfilling of these voids
must be conducted remotely with the use of boreholes
drilled from the surface.
Historically, traditional backfilling methods for these
types of applications included hydraulic backfilling and
grouting. These two applications are often expensive and
not necessarily environmentally conscious.
The advance of foam transportation technology offers
an effective, cost-efficient, and environmentally stable alter-
native to these traditional backfilling methods. Traditional
backfilling methods have utilized water as the transporta-
tion medium. Using foam as the transportation medium
drastically reduces the amount of water used for a project,
eliminates the need for fill materials like Portland cement
or fly ash, and reduces the amount of pumping equipment
needed on a project, minimizing costs and saving energy.
This paper will review this foam transportation technol-
ogy and highlight real-world applications in which it has
proven to be an effective, environmentally safe alternative
to traditional methods in backfilling underground voids.
BENEFITS OF FOAM TRANSPORTATION
TECHNOLOGY
While traditional methods of material transportation for
backfilling use large amounts of water to transport solid
materials into void fill areas, foam transportation technol-
ogy utilizes foam composed of macroscopic air bubbles.
This technology provides a number of environmental and
cost-saving advantages for backfill projects.
Environmental Benefits
Because air bubbles replace the water that is typically used
for material transportation, foam transportation technology
can drastically reduce the amount of water used for a back-
filling project. In a typical hydraulic backfilling project, the
slurry is 30% solids and 70% water, by weight, although
this can vary depending on the project. Using these propor-
tions as an example, 100 gallons of water would be necessary
to transport 360 pounds of sand. In field-scale quantities,
720 gallons of water would be required to transport one
cubic yard of backfill sand. In contrast, in Liquid-Sand,
which is made up of approximately 50% foam and 50%
solid material by volume, only about eight gallons of water
would be used to transport that same cubic yard volume of
25-098
Using Foam as a Transportation Medium for Backfilling
Underground Voids with Liquid-Sand
Nico Sutmoller
Aerix Industries, Golden, CO
Rich Palladino
Aerix Industries, Golden, CO
ABSTRACT
Underground voids present a unique geotechnical engi-
neering challenge. This paper will address materials and
transportation mediums that are typically used for backfill-
ing underground voids with native material. After review-
ing traditional backfill and transportation methods, this
paper will explore the advancing technology of foam trans-
portation and the advantages of using this technology for
transporting fill materials into underground voids to back-
fill them with Liquid-Sand. The paper will also review the
benefits that Liquid-Sand brings to these applications and
highlight specific case studies in which foam transportation
has proven effective and provided cost-effective, environ-
mental benefits.
INTRODUCTION
Underground voids, resulting from both historic and active
mining operations, occur frequently. When these voids
are created, surface subsidence often occurs as these mines
begin to collapse, which leaves these underground voids
inaccessible. This means that the backfilling of these voids
must be conducted remotely with the use of boreholes
drilled from the surface.
Historically, traditional backfilling methods for these
types of applications included hydraulic backfilling and
grouting. These two applications are often expensive and
not necessarily environmentally conscious.
The advance of foam transportation technology offers
an effective, cost-efficient, and environmentally stable alter-
native to these traditional backfilling methods. Traditional
backfilling methods have utilized water as the transporta-
tion medium. Using foam as the transportation medium
drastically reduces the amount of water used for a project,
eliminates the need for fill materials like Portland cement
or fly ash, and reduces the amount of pumping equipment
needed on a project, minimizing costs and saving energy.
This paper will review this foam transportation technol-
ogy and highlight real-world applications in which it has
proven to be an effective, environmentally safe alternative
to traditional methods in backfilling underground voids.
BENEFITS OF FOAM TRANSPORTATION
TECHNOLOGY
While traditional methods of material transportation for
backfilling use large amounts of water to transport solid
materials into void fill areas, foam transportation technol-
ogy utilizes foam composed of macroscopic air bubbles.
This technology provides a number of environmental and
cost-saving advantages for backfill projects.
Environmental Benefits
Because air bubbles replace the water that is typically used
for material transportation, foam transportation technology
can drastically reduce the amount of water used for a back-
filling project. In a typical hydraulic backfilling project, the
slurry is 30% solids and 70% water, by weight, although
this can vary depending on the project. Using these propor-
tions as an example, 100 gallons of water would be necessary
to transport 360 pounds of sand. In field-scale quantities,
720 gallons of water would be required to transport one
cubic yard of backfill sand. In contrast, in Liquid-Sand,
which is made up of approximately 50% foam and 50%
solid material by volume, only about eight gallons of water
would be used to transport that same cubic yard volume of