Karst water is one of the major water hazards in China coalmines, causing frequent mine flooding and sever human casualties. This article, starting out on the spatial relation between mining facility and karst aquifer, extensively illustrates the techniques to identify water burst risks in karst aquifer and field testing methods of key parameters; primary water hazards control techniques for specific mining conditions and hydrogeological properties, such as retaining water-resistant safety rock pillar, water draining and depressurizing, bottom aquifuge consolidation grouting and revamp. All achievements can be of reference to other coal-producing countries confronted with karst water hazards.

INTRODUCTION

China has the largest coal production in the world. The total annual output has maintained at 3 billion tons since 2014 and recorded at 3.68 billion tons in 2015, almost twice the total of US, India, and Australia, which are 900 million, 550 million, and 451 million tons respectively.

In China, the over 500,000 km2 of coal-bearing area is divided into six regions, namely North China Carboniferous-Permian, northeast and northwest Jurassic, South China late Permian, Tibet-West Yunnan Mesozoic, and Taiwan Paleogene (Fan 2003). The complicated hydrogeological conditions are inherent with over 30 common types of water hazards.

China has a territory area of over 9.6 million km2, in which limestone is present as much as 2 million km2 or 20.83%. About 60% of the coal-bearing region in China, containing millions of tons of coal reservation, is affected by limestone karst water. Looking at the frequency and severity of water-related coalmine disasters in China, karst water has become one of the major water hazards threatening mining safety in China especially in North China and South China region. The frequent occurrence of mine flooding and human casualties caused by the large volumes of highly pressurized karst water is catastrophic to safe production in coalmines (Table 1) (Wu et al. 2013).

Table 1

Notorious karst water disasters in China

SN Date Coalmine Pit Max. water volume (m3/h) Water source Severity 
May 13, 1935 Zibo, Shandong Beida 26,580 Ordovician karst water Pit flood, 538 deaths 
June 04, 1960 Xinwen, Shandong Panxi 10,640 Ordovician karst water Pit flood 
June 05, 1971 Lianshao, Hunan Qiaotouhe 27,000 Permian karst water Pit flood 
Aug. 06, 1976 Hancheng, Shaanxi Magouqu 12,000 Ordovician karst water Pit flood 
June 02, 1984 Kailuan, Hebei Fan'ge zhuang 123,180 Ordovician karst water Pit flood, 11 deaths 
May 18, 1985 Jiaozuo, Henan Yanma zhuang 19,200 Carboniferous karst water Pit flood 
Jan. 05, 1993 Feicheng, Shandong Guozhuang 32,970 Ordovician karst water Pit flood 
Dec. 03, 1995 Fengfeng, Hebei Wutong zhuang 34,000 Ordovician karst water Pit flood, 17 deaths 
Oct. 20, 2004 Handan, Hebei Desheng 7,000 Ordovician karst water Pit flood, 29 deaths 
10 Feb. 03, 2013 Huaibei, Anhui Taoyuan 29,000 Ordovician karst water Pit flood, 1 death 
SN Date Coalmine Pit Max. water volume (m3/h) Water source Severity 
May 13, 1935 Zibo, Shandong Beida 26,580 Ordovician karst water Pit flood, 538 deaths 
June 04, 1960 Xinwen, Shandong Panxi 10,640 Ordovician karst water Pit flood 
June 05, 1971 Lianshao, Hunan Qiaotouhe 27,000 Permian karst water Pit flood 
Aug. 06, 1976 Hancheng, Shaanxi Magouqu 12,000 Ordovician karst water Pit flood 
June 02, 1984 Kailuan, Hebei Fan'ge zhuang 123,180 Ordovician karst water Pit flood, 11 deaths 
May 18, 1985 Jiaozuo, Henan Yanma zhuang 19,200 Carboniferous karst water Pit flood 
Jan. 05, 1993 Feicheng, Shandong Guozhuang 32,970 Ordovician karst water Pit flood 
Dec. 03, 1995 Fengfeng, Hebei Wutong zhuang 34,000 Ordovician karst water Pit flood, 17 deaths 
Oct. 20, 2004 Handan, Hebei Desheng 7,000 Ordovician karst water Pit flood, 29 deaths 
10 Feb. 03, 2013 Huaibei, Anhui Taoyuan 29,000 Ordovician karst water Pit flood, 1 death 

The China coal industry has accumulated rich achievements in karst water control and treatment, which will be of value and relevance to other countries facing similar threats from karst water in coalmines.

SPATIAL RELATION BETWEEN MINING FACILITY AND KARST AQUIFER

Taking North China coal-bearing region as an example, the strata development, from new to old, are Quaternary, Neogene (partially Paleogene), Permian, Carboniferous, and Ordovician. The Permian strata are the main coal seam, under the threat from karst aquifer in Carboniferous Taiyuan formation and Ordovician limestone.

The spatial relation between the mining facility (including excavation roadway and coal mining face) and karst aquifer are critical to the design and implementation of water hazards control and treatment. If faults do not exert an impact, the spatial relation between the mining facility and karst aquifer can be one of the following types (Gui & Hu 1997; Deng et al. 2011).
  • (1) Mining facility above karst aquifer (Figure 1). When karst aquifer is in horizontal or near-horizontal position (rock strata inclination is smaller than 15 °), and above which lies the coal roadway or coal mining face, water pressure distributes evenly over the bottom aquifuge. In this scenario, the dimensions of the mining facility, thickness and strength of bottom aquifuge, and water head pressure over karst aquifer are the major contributors to water burst from karst aquifer.

  • (2) Mining facility on the side of karst aquifer (Figure 2). When karst aquifer is in tilted position, to whose side stands the coal roadway or coal mining face, water pressure distributes unevenly over the bottom aquifuge. In this scenario, the major contributors to water burst are aquifer water pressure, strength of bottom aquifuge and coal (rock) pillar, etc.

Figure 1

Mining facility above karst aquifer. (a) Coal roadway above karst aquifer. (b) coal mining face above karst aquifer.

Figure 1

Mining facility above karst aquifer. (a) Coal roadway above karst aquifer. (b) coal mining face above karst aquifer.

Figure 2

Mining facility on the side of karst aquifer. (a) Coal roadway on one side of karst aquifer. (b) coal mining face on one side of karst aquifer.

Figure 2

Mining facility on the side of karst aquifer. (a) Coal roadway on one side of karst aquifer. (b) coal mining face on one side of karst aquifer.

WATER HAZARDS CONTROL IN EXCAVATION ROADWAY

Determining the safety water pressure

Mining activities break the natural stress balance between the hydrostatic pressure in pressure-bearing karst aquifer (Hre), weight of bottom aquifuge (γM0) and its strength (kp), causing stresses to concentrate around the mining facility. Such stress concentration, if exceeds the tolerance of the bottom coal seam, will result in water burst disaster (Gui & Sun 1999; Pan 2014; Wang 2015). The stresses on the bottom plate resemble a girder which is fixated on the two ends with uniformly distributed load. In the case of Figure 1(a), the scholar from the former Soviet Union, в.д. Slisalif, had derived the following formula based on the girder and the theory of strength: 
formula
1
In the formula:
  • Hth – theoretical safety water pressure bearable to the bottom aquifuge in the coal roadway (Mpa);

  • kp – average tensile strength of the bottom aquifuge in the coal roadway (Mpa);

  • γ – average weight of the bottom aquifuge in the coal roadway (MN/m3);

  • M0—average thickness of the bottom aquifuge in the coal roadway (m);

  • l – bottom width of coal roadway (m).

If the actual water head pressure in karst aquifer Hre is smaller than the value of Hth in formula (1), then the roadway is safe. If Hre > Hth, water will break the bottom plate and burst. As a countermeasure, it is mandatory to drain water to lower water head pressure by △H so that Hre-△H < Hth.

Retaining safety water-resistant rock pillar

For scenario in Figure 2(a) where roadway is on the side of karst aquifer, the first step is to calculate width of the safety water-resistant rock pillar via в.д. Slisalif's formula: 
formula
2

In the formula:

  • Lp – width of the safety water-resistant rock pillar (m);

  • K – safety coefficient, ref. 2–5;

  • M – height of coal roadway (m);

  • Hre1 – actual water pressure at the contact point of coal roadway and top surface of karst aquifer (Mpa);

  • kp – average tensile strength of the rock strata in which the coal roadway passes through

Once Lp is obtained using formula (2), find spot A in Figure 2(a) (the boundary of coal roadway), then measure the minimum distance t from A to the top surface of karst aquifer (i.e., the water head pressure on spot C is Hre2), hereby (Gui & Hu 1997): 
formula
3

In the formula:

  • Hth – theoretical safety water pressure bearable to the bottom plate in the coal roadway (Mpa);

  • kp – average tensile strength of the bottom aquifuge in the coal roadway (Mpa);

  • γ – average weight of the bottom aquifuge in the coal roadway (MN/m3);

  • t – minimum distance from coal roadway boundary to top surface of karst aquifer (m);

  • l – bottom width of coal roadway (m);

  • α – inclination angle of rock strata (°).

If Hth > Hre2, the safety water-resistant rock pillar of width Lp is secure. If Hth < Hre2, the width of the safety water-resistant rock pillar is not secure and needs widening until Hth > Hre2.

WATER HAZARDS CONTROL IN WORKING PANEL

Technology for water burst identification

When mining proceeds into coal seam in peril of karst aquifer, the main contributors to water burst are (Li et al. 1987; Gui et al. 1999; Huang & Li 2008):

  • (1) Karst water head pressure on the bottom aquifuge (Pre). Pre is decided by the hydrogeological properties of the karst aquifer and can be directly measured by water level (pressure) observation port. When rock strata are in horizontal or near-horizontal position (Figure 1(b)), Pre is evenly distributed (and Pre = Hre). When rock strata are tilted (Figure 2(b)), Pre is unevenly distributed (it increases as it goes deeper), the water head pressure on the bottom plate at the mechanic roadway is higher than that at the airway by △P = Hred- Hreu = γwLsinα, in which γw represents the weight of water (MN/m3), L is the inclination length of the coal mining face (m), α the inclination angle of rock (coal) strata (°).

  • (2) The effective thickness (h2) and strength (kp) of bottom aquifuge. The destruction caused by mining in the bottom plate (the depth as h1) will decrease the effective aquifuge thickness to h2 (Figure 1(b) and Figure 2(b)). Therefore, h2 and kp are two critical parameters to evaluate the water-resistance of the bottom aquifuge.

The following commonly-used parameters to identify water burst from karst aquifer in China coalmines (Yin & Hu 2008; Zhang et al. 2015; Fan et al. 2016): 
formula
4
 
formula
5
 
formula
6

In the formulas, Ts is the water burst coefficient (Mpa/m), M0 is the thickness of the bottom aquifuge in coal seam (m), h1 is the destruction depth in bottom coal seam after mining (m), I is the critical indicator of water burst, σ3 is the minimum horizontal main stress on the rock mass in the bottom aquifuge (Mpa), Z is the water-resistance coefficient (Mpa/m), Pfis the stress that fractures the bottom plate in the hydraulic fracturing tests (Mpa), R is the extension radius of the fissures caused by hydraulic fracturing (ref. 40–50 m).

It can be seen that, in formula (4), (5) and (6), the values of Pre, M0 and R are known, the values of h1, σ3 and Pf have to be obtained through experiments.

In many China coalmines, h1 is measured in the field by (Jiang 2009; Wu et al. 2013; Chen et al. 2014; Zhang 2015): before stoping, drill in the airway, roadway, or open-off cuts slanting inwards the bottom aquifuge (and study the development pattern of the pre-existing fissures in bottom rock strata). After stoping, consolidation grouting by sections through the drilling holes using the ‘drill hole double-end leak stoppage device’ (Figure 3), and measuring water leakage in each section. By analyzing the leakage pattern to determine the destruction depth in the bottom plate h1. Formula (4) will then generate the water burst coefficient Ts to judge the risks of water burst.
Figure 3

Drill hole double-end leak stoppage device (Patent No.90225165.1).

Figure 3

Drill hole double-end leak stoppage device (Patent No.90225165.1).

The values of σ3 and Pf are measured onsite using ‘hydraulic fracturing’. The ‘testing system of tectonic stress in hydraulic fracturing’ is shown as in Figure 4 (Gidley et al. 1989; Dong 2010; Wang 2014). Hydraulic fracturing drilling in the bottom plate and partitioning n fracturing segments for different lithologic properties within the h2 (Figures 1(b) and Figure 2(b)) (length of each segments is li, i = 1,2,…,n, ∑lih2), fracturing segment by segment (each segment can be fractured 4–5 times) until reliable fracturing parameters are obtained: the maximum and the minimum main horizontal stress σ1i and σ3i and fracturing stress Pfi, etc.
Figure 4

Testing system of tectonic stress in hydraulic fracturing (Dong 2010).

Figure 4

Testing system of tectonic stress in hydraulic fracturing (Dong 2010).

If the water pressure on the bottom aquifer in the testing spot is Pre, formula (5) can be applied to get the value of Ii (=Pre/σ3i, i = 1,2,…,n). Risks of water burst are higher at segments where Ii > 1, precautious measures are demanded (Murdoch & Slac 2002; Liu et al. 2007; Xie et al. 2009).

Similarly, formula (6) can be applied to get the value of Zi(=Pfi/R, i = 1,2,…,n). Water burst is unlikely to happen if Pfi > Pre (i = 1,2,…,n) at all segments. If some segments generate Pfi < Pre (i = 1,2,…,m, m < n), then it is required to calculate the total water-resistance value ZT, if ZT > Pre, warnings about water burst can be neutralized, otherwise the risks are high (Huang & Li 2008; Liu 2014; Zhang et al. 2016). ZT can be derived by: 
formula
7

In the formula, is the weighted average thickness of water-resistance coefficient (Mpa/m).

Technology for water draining and depressurizing

When the tolerance of bottom aquifuge for water pressure (Prea) is smaller than the karst water pressure exerted on the aquifuge (Pre), draining is required to reduce the water head pressure in karst aquifer to below Prea. The preconditions for applying water draining and depressurizing are:

  • (1) Within mining boundaries, if water replenishment to the karst aquifer is poor, it is feasible to lower water pressure to safety values through limited and controlled draining.

  • (2) If the designed roadway must expose the karst aquifer, water must be drained to lower water pressure in the karst aquifer.

  • (3) If consolidation grouting and revamp cannot enhance the water-resistance of the bottom aquifuge, which cannot undertake both karst aquifer pressure and mine pressure, water draining must be taken properly to lower water pressure in the karst aquifer.

In most China coalmines, popular ways to drain water and depressurize are conducted on ground level, underground level, and dual-mode. For ground draining, big holes are drilled into the karst aquifer. Then use submerged pump to extract water from the karst aquifer. This method is reliable and simple to execute, commonly used for mines where coal seam is close to ground surface.

Underground draining (two scenarios: roadway draining and drill hole draining) is to either expose karst aquifer in the roadway or drill into the karst aquifer in roadway to lower water level. When in dual-mode, both ground and underground draining are utilized for mines where hydrogeological conditions are complicated.

When conducting underground draining, compatible equipment, including pumps, pipelines, water tanks, and power facilities, must be configured in place. Pumps include working pump, back-up pump, and maintenance pump. Working pump is required to ‘drain up normal mine water discharge of 24 h within 20 h’. Back-up pump capacity shall be no smaller than 70% of the working pump, while maintenance pump capacity no smaller than 25% of the working pump. The total capacity of back-up pump and maintenance pump shall ‘drain up the maximum mine water discharge of 24 h within 20 h’ (SACMS 2010).

No matter which draining method is chosen, implementation must take into considerations of prospecting facts. In addition, when draining high-pressured karst aquifer, drilling must be protected with back pressure and blow-out device. If water pressure in the drill holes surges or ‘resists’, drilling must pause immediately (without drawing out the drill pole) and resume after the site is technically conditioned (SACMS 2009) to avoid high-pressured water burst, which could evolve into fatal accidents.

Technology for bottom aquifuge consolidation grouting and revamp

If the karst aquifer has sufficient water replenishment with high water yield and pressure, draining does not suffice to reduce water pressure. Moreover, the massive drainage workload is not only costly, but also may cause secondary disasters such as karst collapse at ground level. In this case, the countermeasure is to consolidate and revamp the bottom aquifuge to enhance its water-resistant capability. ‘Consolidation’ is to grout into the pre-existing fissures and faults in the bottom aquifuge so as to improve rock mass strength and resistance against karst water pressure. ‘Revamp’ is to convert the limestone strata, located in the shallow part of the karst aquifer where water yield is low, into aquifuge so as to increase actual aquifuge thickness and its water-resistance against karst water. In China coalmines, the mainstream techniques are underground drilling for local consolidation grouting and revamp (Xu & Li 2014; Xu & Yang 2014; Xu et al. 2014), ground targeted branch drilling for holistic consolidation grouting and revamp through sequential strata (Li et al. 2013; Shi et al. 2013; Shi 2014).

  • (1) Underground drilling for local consolidation grouting and revamp. As a first step, conduct geological prospecting to identify water yield anomaly in the bottom aquifuge and the shallow part in the karst aquifer. Then at coal mining face, drill in the airway, roadway, or open-off cuts slanting inwards the anomaly spots and grout. Lastly, observe and monitor grouting outcomes through drilling or prospecting (Hou 2013).

  • (2) Ground targeted branch drilling for holistic consolidation grouting and revamp through sequential strata. As underground workspace is narrow, leaving limited room for bottom aquifuge revamp, only certain sections (where water yield is abnormal) in one coal mining face can be grouted at a time. In recent years, the ground targeted branch drilling for holistic consolidation grouting and revamp through sequential strata is widely adopted in many China coalmines to consolidate and revamp bottom aquifuge in an extensive area (such as multiple coal mining face in one mine).

In the North China coal-bearing region, the minable coal seam in the lower part of Permian Shanxi formation is in the closest proximity to karst aquifer. The aquifuge between the two (i.e. the coal seam bottom aquifuge) has a thickness of 50–60 m (or as thick as 75 m), composed of mudstone, fine sandstone and siltstone with low water yield (Figure 5(a)). The Carboniferous Taiyuan formation strata have a thickness of 100–170 m (average 120 m), composed of thin limestone stratum mudstone, sandy mudstone, sandstone, and thin coal seam. The thin limestone stratum comprises of 10–12 layers, named from tom down are L1, L2, …, L12. L1 and L2 are thin limestone layers (5m±) and water-free. L3 and L4 are thicker limestone layers (12 m±) and evenly extended, whose high water yield is the direct water source to mining.
Figure 5

Bottom plate holistic consolidation grouting and revamp in 6# coal seam, Huaibei Zhuzhuang coalmine.

Figure 5

Bottom plate holistic consolidation grouting and revamp in 6# coal seam, Huaibei Zhuzhuang coalmine.

Ordovician limestone strata are below Carboniferous Taiyuan formation and its thickness is over 500 m with developed karst fissures, high water pressure (5.0–7.5Mpa), and high water yield. If there are water-conductive faults or karst collapse column, it will strengthen the hydraulic relations among the Ordovician limestone, Carboniferous Taiyuan formation, and coal seam, thus threatening mining safety.

Bottom aquifuge consolidation grouting and revamp is shown as in Figure 5(b). At ground level, first to drill vertically into the ground (the parent hole) and then, at certain depth of the parent hole, to drill branch holes along L3 limestone stratum and grout (the number of branch holes are determined by the dimensions of the bottom plate to be revamped and the grout spreading radius; drilling path is sophisticatedly controlled by the built-in measure and control system). L3 limestone stratum, once grouted into aquifuge, will add to the original aquifuge thickness by △M = 23 m (i.e. the distance between L1 top to L3 bottom), lowering water burst coefficient by 27%. This technique has been applied successfully in Huaibei Zhuzhuang coalmine and Huaibei Hengyuan coalmine in the North China coal-bearing region, gaining effective and cost-saving results in water hazards control. As it ensures mining safety without draining underground water from karst aquifer, it will be the primary technique in China coalmines to treat high-pressured karst water hazard with high water yield.

CONCLUSION

Following conclusions can be drawn based on the above analysis:

  • (1) The spatial relation between mining facility, including coal roadway and coal mining face, and karst aquifer is critical to the design and implementation of water hazards control and treatment. If faults do not exert an impact, the spatial relation can be generalized into two categories, the mining facility is either above or on the side of the karst aquifer.

  • (2) Identification of water burst from karst aquifer can be realized through water coefficient, critical indicator of water burst, and water-resistance coefficient, etc. The key parameters relevant to the above-mentioned coefficients can be obtained onsite through the drill hole double-end leak stoppage device and the testing system of tectonic stress in hydraulic fracturing, such as destruction depth in bottom mining plate (h1), the minimum main horizontal stress on the rock mass in the bottom aquifuge (σ3), and the stress that fractures rock mass in the bottom aquifuge (Pf).

  • (3) Technical solutions to contain karst water include retaining safety water-resistant rock pillar, water draining and depressurizing, and bottom aquifuge consolidation grouting and revamp, etc. Of all, the ground targeted branch drilling for holistic consolidation grouting and revamp through sequential strata is more effective and cost-saving. It will become the mainstream solution to contain high-pressured and abundant karst water hazard in China coalmines in the future.

ACKNOWLEDGEMENT

This article is funded by National Natural Science Foundation of China (41373095) and Anhui Science and Technology Breakthrough Project (1501zc04048).

REFERENCES

REFERENCES
Chen
G. S.
Wang
X. Y.
Zhai
Y.
Sun
S. H.
2014
Exploration technology of coal floor mining damage depth
.
Mine Safety
45
(
4
),
96
98
.
Deng
Y. S.
Wang
H. Z.
Wen
G. C.
Hu
C.
Bie
Y. P.
2011
Informatization of Coalmine Water Hazards Control
.
China Coal Industry Publishing Home
,
Beijing
.
Dong
S. N.
2010
Integrated in-situ tests for water inrush possibility evaluation in coal seam floors
.
Journal of Engineering Geology
18
(
1
),
116
119
.
Fan
T. J.
2003
A Comprehensive Guidebook to Water Control in Coalmines
.
Jilin Audio-Visual Press
,
Changchun
.
Fan
Y. H.
Liu
W. L.
Cao
F. M.
2016
Application of modified water inrush coefficient method to evaluation of coal floor water inrush of Xianfeng open-pit coal mine
.
Coal Engineering
48
(
1
),
114
117
.
Gidley
J. L.
Holditch
S. A.
Nierode
D. E.
Ralph
W. V. J.
1989
Recent Advances in Hydraulic Fracture
.
Society Petroleum Engineering Monograph
, pp.
119
204
.
Gui
H. R.
Hu
Y. B.
1997
Calculation Methods of Stress Analysis for Reasonable Retainment of Water-Resisting Coal (Rock) Pillars
.
China Coal Industry Publishing Home
,
Beijing
.
Gui
H. R.
Sun
B. K.
1999
Study meaning and the core content of the control theory about water inrush from bed bottom in deep mining
.
Journal of Huainan Institute of Technology
19
(
3
),
1
4
.
Gui
H. R.
Gong
N. Q.
Sun
B. K.
1999
Study of control theory on water inrush from bed bottom in deep mining – basic study thinking and plan
.
Journal of Huainan Institute of Technology
19
(
4
),
1
4
.
Hou
J. S.
2013
Study and application of floor grouting reinforcement technology on the fully mechanized coal face of 21101
.
Coal Engineering
6
,
55
57
.
Huang
H.
Li
C.
2008
Forecast method of water inrush of floor over confined water body and its prevention and control measures
.
Metal Mine
6
,
126
129
.
Jiang
Q.
2009
Coal floor strata failure depth test of working face at big mining depth
.
Coal Geology & Exploration
37
(
4
),
30
33
.
Li
B. Y.
Shen
G. H.
Jing
Z. G.
Gao
H.
1987
Theory and practice to prevent water inrush in floor coal seam in mining panels
. In:
Conference Proceeding of the 22nd International Conference of Mining Safety
,
China Coal Industry Publishing Home
,
Beijing
, pp.
65
70
.
Li
Q. X.
Shi
Z. J.
Fang
J.
2013
Drilling technology and equipment for pre-grouting reinforcement directional borehole in coal floor
.
Metal Mine
9
,
126
131
.
Liu
Z. B.
2014
Rock Mass Fluid-Stress Coupling Process and Coal Seam Floor Water Inrush Mechanism Study
.
Dissertation
.
Xi'an Research Institute of China Coal Technology and Engineering Group Co.
,
Xi'an
,
China
.
Liu
Q. M.
Li
W. P.
Ji
Z. K.
Cheng
W.
Zeng
X. G.
Jiao
Y. L.
2007
The method of actual measurement coefficient of water-resisting to evaluate dangerousness of ordovician limestone water invasion
.
Coal Geology & Exploration
35
(
4
),
38
41
.
Murdoch
L. C.
Slac
W. W.
2002
Forms of hydraulic fractures in shallow fine-grained formation
.
Geotech. Geoenviron. Eng.
128
(
6
),
479
487
.
Pan
Y. G.
2014
Coalmine Water Hazards Control
.
China Coal Industry Publishing Home
,
Beijing
.
SACMS (State Administration of Coal Mine Safety)
2009
Regulations on Coalmine Water Control
.
China Coal Industry Publishing Home
, pp.
61
62
.
SACMS (State Administration of Coal Mine Safety)
2010
Coal Mine Safety Regulations
.
China Coal Industry Publishing Home
, pp.
152
153
.
Shi
H. Q.
2014
Application of measurement while directional drilling technology in preventing and controlling the water disasters in coalmine
.
Modern Mining
4
,
38
41
.
Shi
Z. J.
Wen
R.
Fang
J.
Li
Q. X.
Gao
J.
2013
Research and development on drilling measuring system of directional drilling in underground mine
.
Coal Science and Technology
41
(
3
),
16
20
.
Wang
Y.
2014
Effect of Hydraulic Fracturing on Stress Distribution in Multi-Seam Mining Condition
.
Dissertation
.
Xi'an University of Science and Technology
,
Xi'an
,
China
.
Wang
Y. M.
2015
Study on Water-inrush from Floor under Confined Water and Technique of Prevention and Control
.
Dissertation
.
China University of Mining &Technology
,
Xuzhou
,
China
.
Wu
Q.
Zhao
S. Q.
Dong
S. N.
Li
J. Z.
2013
Handbook to Coalmine Water Control
.
China Coal Industry Publishing Home
,
Beijing
.
Xie
X. H.
Su
B. Y.
Gao
Y. F.
Duan
X. B.
2009
Numerical study on water inrush above a confined aquifer in coal mining using hydro-fracturing
.
Chinese Journal of Rock Mechanics and Engineering
24
(
6
),
987
993
.
Xu
Y. C.
Li
J. B.
2014
‘Pore-fractured lifting type’ mechanical model for floor water inrush of the grouting enforcement working face
.
Journal of China University of Mining & Technology
43
(
1
),
49
55
.
Xu
Y. C.
Yang
Y.
2014
New progress on floor grouting reinforcement technology of water control in coal mining face
.
Coal Science and Technology
42
(
1
),
98
101
,
120
.
Xu
Y. C.
Li
J. H.
Liu
B. Z.
2014
Reinforcement of working face by grouting in floor in Jiaozuo coal mining area
.
Coal Geology & Exploration
42
(
4
),
50
54
.
Yin
S. X.
Hu
W. Y.
2008
Rocks’ water-resistance ability and natural progressive intrusion height
.
Coal Geology & Exploration
36
(
1
),
35
40
.
Zhang
P. Q.
2015
Detection on floor failure depth caused by mining disturbances based on ultrasonic technology
.
Coal Science and Technology
43
(
5
),
118
121
.
Zhang
J. J.
Song
Y.
Xi
F. Z.
2015
Application of analytic hierarchy process-entropy weight method in water burst evaluation of coal seam floor
.
Safety in Coal Mines
46
(
11
),
200
203
.
Zhang
F. D.
Shen
B. H.
Kang
Y. H.
2016
Water inrush failure mechanism of mining floor under unloading effect
.
Rock and Soil Mechanics
37
(
2
),
431
437
.