ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
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2 MINING SUBSIDENCE AND ITS PROPERTIES
As a typical damage to landscape and environment, mining
subsidence has many important features, and those are the
basis of further studies. In order to simulate and represent the
shape and features of mining subsidence, its dynamic process
and properties should be understood firstly.
2.1 The dynamic of mining subsidence
Mining subsidence is a typical spatio-temporal dynamic process.
The mining activities were conducted underground and brought
damage to rock directly, and then the stress change would
spread in vertical and horizontal directions, finally, land over
working space and goaf would subside and create other
problems, and this procedure can be demonstrated by Fig. 1.
1 ►
Advancing direction
Fig. 1 The relationship of mining and subsidence
From Fig. 1 we can describe the dynamic process as follows: (1)
before coal was mined, underground rock and ground surface is
stable. (2) After mining begins, the balance of underground
stress would be damaged and the force would spread to ground
surface, but before point 1 was mined, no impact was created to
point A on ground surface. (3) When 1 was mined, point A began
to move at a low speed and with acceleration. (4) When point 2
was mined, point A would subside with biggest values and begin
decrease, but continue to move. (5) After point 2 was mined,
point A would continue to move with a lower speed until it
reaches a stable situation. So we can know that this process is
complex and dynamic.
We also can describe the procedure by Fig.2. From Fig.2, It can
be known that the area of subsiding land is much larger than
underground goaf by mining, and it looks like a basin, so it is
called subsiding basin.
2.2 The properties of mining subsidence
It is well known that GIS applications should be based on the
properties of geo-phenomena and its demands, so we would
give discussions on them.
Fig.2 The shape of subsiding basin and mining
(1) Mining subsidence is a three dimensional (3D) dynamic
process, so if we want to express and analyze it in GIS,
multi-dimensional and dynamic model and methods are
necessary.
(2) It is influenced by several factors, including thickness of coal
seam, mining depth, properties of rock and its force features,
mining methods and others. When it is analyzed in GIS, different
factor should be represent in different layer with different
patterns, and the information should be easy to get and
organize.
(3) The subsiding land can be expressed by different land use
and land cover, and it can be identified by spatial and attribute
information. So it should be represented by spatial and attribute
information with different methods, such as shapes, DLM,
images and other forms.
(4) It is a non-linear and non-even process, so the simulation
can't be realized by GIS solely, and it should be based on the
combination of spatial analyzing model and GIS. How to
establish the model is a key issue, especially to non-linear and
non-even process, the modeling methods based on statistics,
experience, mechanism and rule should be used.
(5) It obeys some laws and can be forecasted, so GIS can be
used to simulate and forecast the land subsiding situation, but
how to realize it is a important and difficult problem, especially
how to represent the laws by GIS.
(6) It will cause some further damages and problems, including
water and soil loss, damage of construction, impact on water
resource and land pollution. In GIS, mining subsidence would be
integration with other problems, and it should be open to other
field. Then, the data, information and model should obey certain
standard and rules.
From above properties, we can know that if we want to study
subsidence in GIS, several key issues should be given more
discussions, and in this paper emphasis would be paid on the
spatial information collection and 3D representation of subsiding
