scholarly journals Characterization and Remediation of Karst Collapse Columns for Mining Safety and Environmental Protection: A Case Study in Renlou Coal Mine, China

2018 ◽  
Vol 8 (2) ◽  
pp. 128
Author(s):  
Shuning Dong ◽  
Hao Wang ◽  
Wanfang Zhou
Keyword(s):  
Coal Mining ◽  
Coal Mine ◽  
Water Inrush ◽  
Economic Losses ◽  
Karst Collapse ◽  
Directional Drilling ◽  
Hydrogeological Characteristics ◽  
Geophysical Surveys ◽  
Underground Workings ◽  
Water Plug

Karst collapse columns are unique collapse structures in karst terranes. Coal mining in China has exposed numerous such features of tens of meters in diameter and hundreds of meters in height. Hydraulically conductive collapses functioned as groundwater pathways between underground workings and aquifers, resulting in water inrushes during coal mining. Over the last 60 years, water inrushes through these collapses have caused fatalities, economic losses, and degradation in the environment. Determination of locations and hydrogeological characteristics of the karst collapse columns are essential in preventing water inrush incidents through them. Advanced geophysical prospecting, directional drilling, aquifer testing and accompanied dye tracing are effective approaches to detecting and characterizing these structures. Five geophysical techniques consisting of both surface and underground geophysical surveys and directional drilling of three exploratory boreholes up to 986 m deep identified a concealed collapse feature of more than 135 m high in Renlou Coal Mine, China. The roof of the collapse feature was at approximately 785 m deep, and there was an open void of 1.5 - 2 m high at the top. Geotechnical properties, results from packer testing and tracer testing, monitoring of potentiometric pressures, and geochemical fingerprinting suggested that this collapse column was hydraulically conductive and still actively developing. Water in the confined thin-bedded limestone and Ordovician limestone aquifer that either overlies or underlie coal seams could flow into the underground working areas if this feature were not identified in advance but encountered during mining. A grouting program was designed and implemented to construct a water plug in the collapse that effectively cut off the hydraulic connections from the aquifers to the underground workings. Successful construction of the water plug in the collapse was confirmed by performance monitoring of the aquifers.

scholarly journals Risk Assessments of Water Inrush from Coal Seam Floor during Deep Mining Using a Data Fusion Approach Based on Grey System Theory

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yaru Guo ◽  
Shuning Dong ◽  
Yonghong Hao ◽  
Zaibin Liu ◽  
Tian-Chyi Jim Yeh ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Coal Mine ◽  
Drilling Fluid ◽  
Water Pressure ◽  
Water Inrush ◽  
Grey System Theory ◽  
Directional Drilling ◽  
Grey System ◽  
Highly Correlated

With the increase in depth of coal mining, the hydrogeological complexity largely increases and water inrush accidents happen more frequently. For the safety of coal mining, horizontal directional drilling and grouting techniques have been implemented to detect and plug the fractures and conduits that deliver high-pressure groundwater to coal mine. Taking the grouting engineering performed at Xingdong coal mine at 980 m below sea level as an example, we collected the data of grouting quantity, the loss of drilling fluid, gamma value, water temperature, average water absorption, distance between grouting loss points, water pressure on coal seam floor, and aquifuge thickness at 90 boreholes in the mine to conduct grey relational analysis, first. The analysis showed that the grouting quantity was highly correlated with all other factors. Subsequently, grey system evaluation was used to evaluate the risk of water inrush from the coal seam floor. The results of risk analysis illustrated that three water inrushes from Ordovician limestone occurred in mining face 2127, 2125, and 2222 in the study area were all located in the area with a risk score higher than 65. Through grouting, the identified cracks were effectively blocked and waterproof layers beneath the coal seam floors were constructed to reduce the threat of water inrush. By comparing the risk assessment results with three water inrush cases before grouting operation, we found that water inrush areas were consistent with the area of higher risk.

scholarly journals Hydrological Characteristics of Ordovician Karst Top in a Deep Region and Evaluation of Its Threat to Coal Mining: A Case Study for the Weibei Coalfield in Shaanxi Province, China

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Tao Li ◽  
Jiarui Zhang ◽  
Ying Gao ◽  
Xinqi Cao ◽  
Hongyang Liu ◽  
...  
Keyword(s):  
Coal Mining ◽  
North China ◽  
Water Pressure ◽  
Water Inrush ◽  
Drainage Water ◽  
Shaanxi Province ◽  
Water Drainage ◽  
Mining Areas ◽  
Hydrogeological Characteristics ◽  
In Situ Experiments

Widely distributed in North China, Ordovician karst is characterized by having high thickness, nonuniform aquosity, and significant water pressure-bearing properties. Deep mining in North China is threatened by associated water hazards; hence, research on the hydrogeological characteristics of deep Ordovician karst is needed. In this study, the Weibei coalfield in Shaanxi Province, China, was selected as the study area, especially mines in the Hancheng and Chenghe mining areas. In situ experiments, including water pumping, water drainage, water injecting and water pressure, and laboratory experiments, were conducted to study the hydrogeological characteristics of the Ordovician karst top in the study area. A comprehensive analysis was conducted on controlling factors for the development of the Ordovician karst top in the study area, and a method for evaluating the water inrush risk in coal mining areas based on karst hydrogeological characteristics was proposed. The research results indicated that the Ordovician karst top in the study area was characterized by heterogeneity, vertical zonation, and partially filled properties, which were mainly controlled by two factors: sedimentation and tectonism. The hydrogeological conditions of the Ordovician karst could be divided into three types: nonfilled and nonsignificant tectonism, filled and nonsignificant tectonism, and significant tectonism. Among them, the filled and nonsignificant tectonism type Ordovician karst top type had a filling thickness of 20 m. Based on karst hydrogeological characteristics, the methods were proposed to evaluate the water inrush risk in the coal mining floor. The practical tests verified the methods.

scholarly journals Application of Directional Borehole Grouting Technology to Structural Complex Foor Reinforcement in Deep Underground Coal Mine

2018 ◽  
Author(s):  
Qiqing Wang ◽  
Wenping Li
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Water Conservation ◽  
Water Inrush ◽  
Geological Structure ◽  
Directional Drilling ◽  
Rock Stratum ◽  
Factors Affecting ◽  
Mining Depth ◽  
Complex Structural

Water inrush from coal floor constitutes one of the main disasters in mine construction and mine production, which always brings high risks and losses to the coal mine safe production. As the mining depth of coal fields in North China gradually increased, especially in the complicated structural region, the threat posed by limestone karstic water of coal floor to the safe stoping of mines has become increasingly prominent. In this paper, the Taoyuan coalmine was taken as an example, for which, the directional borehole grouting technology was utilized to reinforce the coal seam floor prior to mining. Also, the factors affecting the grouting effect were analyzed. These were the geological structure, the crustal stress and the range of slurry diffusion. The layout principle of grouting drilling was put forward and the directional drilling structure was designed. The water level observations in the end hole indicated that the target stratum was accurate and reliable. The effect of grouting was validated through the audio frequency electric perspective method and the holedrilling in the track trough. The results demonstrated that the effect of grouting in third limestone and the rock stratum above the third limestone of coal seam floor was apparent. Simultaneously, no water inrush occurred following the actual mining of the working face, which further demonstrated that the grouting reinforcement effect was apparent. The research findings were of high significance for the prevention and control of floor water disaster and water conservation in deep complex structural areas.

scholarly journals Modeling Rock Fracture Propagation and Water Inrush Mechanisms in Underground Coal Mine

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Shichuan Zhang ◽  
Baotang Shen ◽  
Yangyang Li ◽  
Shengfan Zhou
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Rock Fracture ◽  
Water Inrush ◽  
Water Channel ◽  
Karst Collapse ◽  
Mining Equipment ◽  
Geological Conditions ◽  
Fracturing Process ◽  
Collapse Column

Water inrush in underground mines is a major safety threat for mining personnel, and it can also cause major damage to mining equipment and result in severe production losses. Water inrush can be attributed to the coalescence of rock fractures and the formation of water channel in rock mass due to the interaction of fractures, hydraulic flow, and stress field. Hence, predicting the fracturing process is the key for investigating the water inrush mechanisms for safe mining. A new coupling method is designed in FRACOD to investigate the mechanisms of water inrush disaster (known as “Luotuoshan accident”) which occurred in China in 2010 in which 32 people died. In order to investigate the evolution processes and mechanisms of water inrush accident in Luotuoshan coal mine, this study applies the recently developed fracture-hydraulic (F-H) flow coupling function to FRACOD and focuses on the rock fracturing processes in a karst collapse column which is a geologically altered zone linking several rock strata vertically formed by the long-term dissolution of the flowing groundwater. The numerical simulation of water inrush is conducted based on the actual geological conditions of Luotuoshan mining area, and various materials with actual geological characteristics were used to simulate the rocks surrounding the coal seam. The influences of several key factors, such as in situ stresses, fractures on the formation, and development of water inrush channels, are investigated. The results indicate that the water inrush source is the Ordovician limestone aquifer, which is connected by the karst collapse column to No. 16 coal seam; the fracturing zone that led to a water inrush occurs in front of the roadway excavation face where new fractures coalesced with the main fractured zone in the karst collapse column.

CHANNEL WAVES AS A TOOL OF APPLIED GEOPHYSICS IN COAL MINING

Geophysics ◽  
1963 ◽  
Vol 28 (5) ◽  
pp. 701-714 ◽  
Author(s):  
Theodore C. Krey
Keyword(s):  
Coal Mining ◽  
Coal Mine ◽  
Low Velocity ◽  
The Earth ◽  
Applied Geophysics ◽  
Geophysical Surveys ◽  
Small Density

A well‐known difficulty in coal mining is the unexpected occurrence of minor faults, by which the seams are displaced by only one or a few meters. It is practically impossible to predict such faults from geophysical surveys on the surface of the earth. However, as coal normally has a very low velocity and, also, only a small density compared to the neighboring rocks, channel waves along the seams are theoretically possible as will be shown. Such channel waves have been successfully produced and recorded by underground seismic work within a German coal mine. Moreover, a reflection from a known minor fault could clearly be observed.

scholarly journals Seepage Property of Crushed Mudstone Rock in Collapse Column

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Bo-Yang Zhang ◽  
Zhi-Bin Lin
Keyword(s):  
Particle Size ◽  
Water Resource ◽  
Water Inrush ◽  
Underground Water ◽  
Economic Losses ◽  
Karst Collapse ◽  
Hydraulic Pressure ◽  
Water Flow Velocity ◽  
Collapse Column ◽  
Seepage Properties

The karst collapse column composed of crushed rocks and fine argillaceous or clay particles is easy to form the fissure channels between the coal seam working face and the confined limestone aquifer under mining and causes water inrush disasters with the loss of underground water resource, economic losses, and casualties. It is of great necessity to understand the seepage properties of crushed rock in karst collapse column for the prevention of water inrush and the protection of underground water resource. A self-developed seepage test system is used in this paper to conduct laboratory experiments on seepage properties of crushed mudstone specimens. The effects of the particle size distribution, the porosity (specimen height), and the hydraulic pressure on the water flow velocity and the permeability of crushed specimen are analyzed. The results indicate that the permeability of specimen increases with the particle size, porosity, and hydraulic pressure. It can be known from the comparative experiments of progressive hydraulic pressure on one specimen and variable hydraulic pressure on different specimens with constant particle size and porosity that more fine particles leak out from the specimen with repeated application of hydraulic pressure on one specimen. Therefore, the permeability of one specimen is bigger than that of different specimens under the condition of same hydraulic pressure.

scholarly journals Damage Characteristics and Mechanism of a Strong Water Inrush Disaster at the Wangjialing Coal Mine, Shanxi Province, China

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Cui Fangpeng ◽  
Wu Qiang ◽  
Zhang Shuai ◽  
Wu Ningan ◽  
Ji Yuan
Keyword(s):  
Coal Mine ◽  
Water Inrush ◽  
Groundwater Exploration ◽  
Shanxi Province ◽  
Economic Losses ◽  
Great Effort ◽  
Groundwater Inrush ◽  
Mining Face ◽  
Inrush Water ◽  
Great Damage

A serious groundwater inrush occurred at the Wangjialing coal mine on March 28, 2010. Great effort from all over the country was taken during the postaccident rescue. However, triggered by accumulated water in the upper abandoned tunnels and goafs of a nearby closed individually owned coal mine, it caused great damage, including 38 deaths and direct economic losses of over 49 million yuan. The inrush water was from the abandoned tunnels and goafs, which were filled subsequently by groundwater from the sandstone aquifer in the roof of the coal seam. The passage formed in the west roof of the heading face of the air return tunnel in the 20101 first mining face. Unidentified distribution and water-filled degree of the abandoned tunnels and goafs are critical bases for the accident. That important regulations for abundant groundwater exploration and release were not carried out thoroughly was another fatal cause leading to the accident. The poor awareness of water hazard controlling also contributed to the accident to a large extent.

scholarly journals Directional Hydraulic Fracturing (DHF) of the Roof, as an Element of Rock Burst Prevention in the Light of Underground Observations and Numerical Modelling

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 562
Author(s):  
Marek Jendryś ◽  
Andrzej Hadam ◽  
Mateusz Ćwiękała
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Coal Mining ◽  
Rock Burst ◽  
Coal Mine ◽  
Seismic Activity ◽  
Black Coal ◽  
Directional Hydraulic Fracturing ◽  
Before And After ◽  
The Face

The following article analyzes the effectiveness of directional hydraulic fracturing (DHF) as a method of rock burst prevention, used in black coal mining with a longwall system. In order to define changes in seismic activity due to DHF at the “Rydułtowy” Black Coal Mine (Upper Silesia, Poland), observations were made regarding the seismic activity of the rock mass during coal mining with a longwall system using roof layers collapse. The seismic activity was recorded in the area of the longwall itself, where, on a part of the runway, the rock mass was expanded before the face of the wall by interrupting the continuity of the rock layers using DHF. The following article presents measurements in the form of the number and the shock energy in the area of the observed longwall, which took place before and after the use of DHF. The second part of the article unveils the results of numerical modeling using the discrete element method, allowing to track the formation of goafs for the variant that does not take DHF into consideration, as well as with modeled fractures tracing DHF carried out in accordance with the technology used at “Rydułtowy” coal mine.

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