Journal of University of Science and Technology Beijing
Volume 14, Number 6, December 2007, Page 1
Corresponding author: Qingxiang Huang, E-mail: hqx363@hotmail.com Also available online at www.sciencedirect.com
Mineral
Experimental research of overburden movement and subsurface
Experimental research of overburden movement and subsurface
Qingxiang Huang
1,2)
1) School of Energy and Resource, Xi’an University of Science and Technology, Xi’an 710054, China
2) Department of Mining, College of Engineering and mineral resource, West Virginia University, Morgantown, WV 26501, USA
(Received 2006-06-16)
Abstract: Shallow seam coal field has the largest coal reserve in China. Mining in shallow depth causes serious problems, and sub-
surface dewatering is a major issue. In this paper, the physical simulating models were prepared to study overburden movement and
aquiclude stability in the shallow seam mining of Yushuwan coal field, China. According to the characteristic of clay aquiclude and
bedrock in the overburden, the proper simulation materials for simulating the plastic clay aquiclude layers and brittle bedrock layers
were determined by the stress-strain tests and hydrophilic tests. The physical simulating models of solid medium and two phases of
solid-liquid medium were carried out to simulate the failure and caving process of the roof and overburden, as well as the subsurface
water seeping. Based on the simulation, it was found that the movement of clay aquiclude follows the movement of the underlying
bedrock layers. The stability of aquiclude is mainly affected by cracks in fracture zone. The tests also showed that the best way to
control the stability of aquiclude is to reduce the subsiding gradient, and there is a possibility of ground water conservation under
longwall mining in Yushuwan mine. This research provides a foundation for further study on mining dewatering and water conserva-
tion.
Key words: physical simulation; aquiclude; crack; mining dewatering; shallow seam mining
[This work was financially supported by the National Natural Science Foundation of China (No.50574074), the Key Program of
Science and Technology of the Ministry of Education of China (No.204183), and the Program for New Century Excellent Talents in
University of China (NCET-04-0971).]
1. Introduction
There is a vast shallow seam coal field under the
southern edge of Maowusu Desert in northwest China,
called the Shenfu Coalfield. It has the largest reserve
and best quality of coal in China. Its proven reserve is
223600 Mt and the estimate reserve is 60001000 Gt.
The coal is low in ash, sulfur, and phosphor contents,
but has a high heating value. The geological condition
is also simple, being flat and shallow in depth [1].
Since the coal seams are shallow and the surface is
covered with thick sandy soils, water is stored at the
bottom of the sandy layer that is underlaid by the clay
layer. Therefore, the clay layer acts as an aquiclude for
the ground water, and its stability is important for
preserving the ground water, which sustains the local
population. As underground mining expands, a large
amount of surface water seeps down in some mining
areas, depleting surface water and speeding up deser-
tification in sandy soil areas.
Yushuwan coal mine is the largest coal mine in the
Yulin area of Shenfu Coalfield. The coal is to be used
for coal liquefaction in the future. Its coal production
is estimated as 10 Mt/a in the initial stage, and in-
creased to 20 Mt/a at the second stage. It is planned as
a model mine for clean utilization of coal and
post-mining water protection, the so-called green coal
mine [2]. When constructed, it will be the standard for
coalmine construction in China.
Currently the basic requirement to protect
post-mining water resources is to understand the sta-
bility of the clay aquiclude. To study the failure me-
chanisms of the aquiclude during mining and deter-
mine the dewatering mechanism is the basis for de-
veloping a new method to avoid surface dewatering
while mining. Mining dewatering is usually studied by
numerical method in western country, but it is hard to
get the caving mechanism [3].
The simulating model of mining dewatering in-
volves the two-phase medium. The simulating method
for the two-phase medium is in the exploration stage.
At present, solid phase material model test is mainly