1
24-006
Additional Damage to Buildings and Infrastructure Induced by
Long-Term Surface Movements Above Longwall Mining
André Vervoort
KU Leuven, Belgium
ABSTRACT
After the systematic closure of Europe’s coalfields in the late
twentieth century, the emphasis is now clearly on industry’s
environmental legacy. One aspect of the latter is the long-
term surface movement above abandoned coal mines. The
analysis of satellite data shows that the subsidence lasts lon-
ger than generally assumed. However, a few years after the
flooding of the abandoned underground coal mines, a new
phenomenon was observed, i.e., the direction of the surface
movement was reversed. The phase of upsidence has already
lasted for several decades, and only future measurements
will tell how long it continues. A key conclusion is that the
regions with maximum subsidence do not necessarily cor-
respond to the greatest upsidence. In other words, buildings
and infrastructure are subjected to a different loading from
this upsidence than during the subsidence phase. The long-
term surface movements have an impact on vulnerable struc-
tures in the densely populated regions of the former deep
coal mining areas in Europe. These movements create addi-
tional damage. This new knowledge is also relevant for mines
that are still in operation or future mines that are planned.
INTRODUCTION
At the end of the twentieth century, entire coal fields in
Europe were closed. In Belgium (Campine coal basin),
the five remaining underground coal mines were closed
between 1988 and 1992. Coal production in these mines
began between 1917 and 1930. These mines applied the
longwall mining method (with goaf), and most panels were
situated between 500 to 1000 m depth. The average min-
ing height per coal seam was relatively low, i.e., between
1.0 and 1.5 m. The Campine coal basin is characterized
by numerous faults, causing a high degree of compartmen-
talization. This combined with past tectonic movements
along these faults resulted in complex mining geometries,
i.e., the position of the various longwall panels and their
shape. In other words, mining did not follow a regular pat-
tern. Below a given location, the total mining interval cov-
ered several hundred meters, and more than 5 seams were
mined (even, sometimes more than 10). At both sides of
the panels, single gateroads were excavated.
At the end of the coal mine’s lifespan, the underground
pumping installations were dismantled, and the vertical
shafts were sealed. This meant that after the closure, the
open tunnels, the collapsed goaf volumes and the surround-
ing rock mass or strata started to be filled with ground-
water and the hydraulic gradient started to evolve towards
the original hydraulic gradient. It is generally accepted that
after closing the underground access, the surface move-
ments are reversed, i.e., from a downward subsidence to an
upward movement (uplift or upsidence). Examples can be
found in the reference list in Vervoort 2021a. The link with
the flooding of these mines was clearly established by other
research (Baglikow 2011 Bekendam and Pöttgens 1995
Caro Cuenca et al. 2013 Samsonov et al. 2013). Although
the direction of the additional movements has reversed,
the cumulative amount of movements remains downward
in comparison to the situation before the start of mining.
(Further, an example is presented.) Recently, an analytical
framework was successfully presented to better understand
the different mechanisms and processes involved (Vervoort
2021b Vervoort 2022a). Good correlation was observed
between the measured and the calculated upsidence values
along north-south transects. The crucial aspect for a good
match between the two is to take into account the expan-
sion of the goaf material when the water level is increased,
but, as important, to also include in the calculations the
expansion of all the strata between the excavated panels and
around the mined area. It is believed that the strata layers
are also drained during mining and that the pore pressure
values are increased towards their original values before
the mining began. A good fit with the measurements was
24-006
Additional Damage to Buildings and Infrastructure Induced by
Long-Term Surface Movements Above Longwall Mining
André Vervoort
KU Leuven, Belgium
ABSTRACT
After the systematic closure of Europe’s coalfields in the late
twentieth century, the emphasis is now clearly on industry’s
environmental legacy. One aspect of the latter is the long-
term surface movement above abandoned coal mines. The
analysis of satellite data shows that the subsidence lasts lon-
ger than generally assumed. However, a few years after the
flooding of the abandoned underground coal mines, a new
phenomenon was observed, i.e., the direction of the surface
movement was reversed. The phase of upsidence has already
lasted for several decades, and only future measurements
will tell how long it continues. A key conclusion is that the
regions with maximum subsidence do not necessarily cor-
respond to the greatest upsidence. In other words, buildings
and infrastructure are subjected to a different loading from
this upsidence than during the subsidence phase. The long-
term surface movements have an impact on vulnerable struc-
tures in the densely populated regions of the former deep
coal mining areas in Europe. These movements create addi-
tional damage. This new knowledge is also relevant for mines
that are still in operation or future mines that are planned.
INTRODUCTION
At the end of the twentieth century, entire coal fields in
Europe were closed. In Belgium (Campine coal basin),
the five remaining underground coal mines were closed
between 1988 and 1992. Coal production in these mines
began between 1917 and 1930. These mines applied the
longwall mining method (with goaf), and most panels were
situated between 500 to 1000 m depth. The average min-
ing height per coal seam was relatively low, i.e., between
1.0 and 1.5 m. The Campine coal basin is characterized
by numerous faults, causing a high degree of compartmen-
talization. This combined with past tectonic movements
along these faults resulted in complex mining geometries,
i.e., the position of the various longwall panels and their
shape. In other words, mining did not follow a regular pat-
tern. Below a given location, the total mining interval cov-
ered several hundred meters, and more than 5 seams were
mined (even, sometimes more than 10). At both sides of
the panels, single gateroads were excavated.
At the end of the coal mine’s lifespan, the underground
pumping installations were dismantled, and the vertical
shafts were sealed. This meant that after the closure, the
open tunnels, the collapsed goaf volumes and the surround-
ing rock mass or strata started to be filled with ground-
water and the hydraulic gradient started to evolve towards
the original hydraulic gradient. It is generally accepted that
after closing the underground access, the surface move-
ments are reversed, i.e., from a downward subsidence to an
upward movement (uplift or upsidence). Examples can be
found in the reference list in Vervoort 2021a. The link with
the flooding of these mines was clearly established by other
research (Baglikow 2011 Bekendam and Pöttgens 1995
Caro Cuenca et al. 2013 Samsonov et al. 2013). Although
the direction of the additional movements has reversed,
the cumulative amount of movements remains downward
in comparison to the situation before the start of mining.
(Further, an example is presented.) Recently, an analytical
framework was successfully presented to better understand
the different mechanisms and processes involved (Vervoort
2021b Vervoort 2022a). Good correlation was observed
between the measured and the calculated upsidence values
along north-south transects. The crucial aspect for a good
match between the two is to take into account the expan-
sion of the goaf material when the water level is increased,
but, as important, to also include in the calculations the
expansion of all the strata between the excavated panels and
around the mined area. It is believed that the strata layers
are also drained during mining and that the pore pressure
values are increased towards their original values before
the mining began. A good fit with the measurements was