A Cascade Disaster Caused by Geological and Coupled Hydro-Mechanical Factors—Water Inrush Mechanism from Karst Collapse Column under Confining Pressure

A non-linear flow model that couples three flow types is built based on flow transition to investigate the flow behavior of water inrush induced by KCC.

Download Full-text

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

Geofluids ◽

10.1155/2019/1796965 ◽

2019 ◽

Vol 2019 ◽

pp. 1-15 ◽

Cited By ~ 6

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.

Download Full-text

Evolution Mechanism of Water-Conducting Channel of Collapse Column in Karst Mining Area of Southwest China

Geofluids ◽

10.1155/2021/6630462 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Zhengzheng Cao ◽

Yulou Ren ◽

Qinting Wang ◽

Banghua Yao ◽

Xinchao Zhang

Keyword(s):

Coal Seam ◽

Southwest China ◽

Water Inrush ◽

Mining Area ◽

Karst Collapse ◽

Coal Field ◽

Conducting Channel ◽

Evolution Mechanism ◽

Working Face ◽

Collapse Column

There are many karst collapse columns in coal seam roof in the southern coal field in China, which are different from those in coal seam floor in the northern coal field, due to the stratum characteristics. The karst collapse column in coal seam roof tends to reactivate and conduct water and induce the serious water inrush disaster, when the karst collapse column communicates with the overlying aquifer. In order to reveal the evolution mechanism of water-conducting channel of collapse column in karst mining area of southwest China, the aquifers and water inflow rule in 1908 working face in Qianjin coal mine are analyzed. Besides, the particle size distribution and mineral component of collapse column are researched by the X-ray diffraction test and the screening method, which are the basis for researching the water inrush mechanism in karst collapse column. On this basis, the water inrush of roof collapse column under the influence of mining is researched by establishing the numerical calculation model with the UDEC numerical software. The results show that the water flowing into the 1908 working face comes from the Changxing formation aquifer and Yulongshan formation aquifer above the coal seam, and the proportion of coarse particles and fine particles in collapse column is 89.86% and 10.14%, respectively. With the advance of working face, the water-conducting channel connected the working face with the aquifer, or the surface is formed by collapse pits, karst caves, and collapse column. The research results can be treated as an important basis for the water-preserved mining in southern coal field in China.

Download Full-text

Seepage Property of Crushed Mudstone Rock in Collapse Column

Advances in Civil Engineering ◽

10.1155/2020/8866697 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10 ◽

Cited By ~ 1

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.

Download Full-text

Analysis and Application of the Mechanical Properties of the Karst Collapse Column Fillings

Shock and Vibration ◽

10.1155/2021/5519048 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Zhibin Lin ◽

Boyang Zhang ◽

Xiaofei Gong ◽

Limin Sun ◽

Wenzhen Wang ◽

...

Keyword(s):

Tensile Strength ◽

Compressive Strength ◽

Moisture Content ◽

Water Inrush ◽

Friction Angle ◽

Karst Collapse ◽

Filling Material ◽

Cohesive Stress ◽

Consolidation Pressure ◽

Collapse Column

The filling material of the karst collapse column (KCC) is easy to be activated by mining. During this process, the mechanical properties of KCC fillings change, and its water resisting capacity constantly deteriorates and thus often leads to water inrush disaster. In this study, the samples of KCC fillings were taken on-site and then were remolded by the consolidation drainage method. The variation laws of the compressive strength, tensile strength, cohesive stress, internal friction angle, and permeability of the filling samples with respect to the consolidation pressure and moisture content were tested and analyzed. Based on an engineering example, the yield and activation and particle loss of the filling material of the KCC are analyzed. A mechanism for the lagging water inrush of KCC in the process of mining is proposed. The main results of the present study can be concluded concisely as follows. (1) The KCC fillings show obvious soft rock characteristics in the process of uniaxial compression and Brazilian split. The ratio of the uniaxial compressive strength to splitting tensile strength is between 12 : 1 and 8 : 1. The larger the consolidation pressure or the smaller the moisture content, the larger the ratio. (2) With the increase of consolidation pressure or the decrease of moisture content, the uniaxial compressive strength, elastic modulus, splitting tensile strength, cohesive stress, and internal friction angle of the filling material of the KCC increase linearly, while its permeability increases exponentially. (3) When the crack field of the surrounding rocks of the stope is connected with the KCC, its filling material will continue to yield, activate, and migrate under the fluid-solid coupling effect and finally result in the lagging water inrush from the KCC.

Download Full-text

A method for prevent water inrush from karst collapse column: a case study from Sima mine, China

Environmental Earth Sciences ◽

10.1007/s12665-017-6831-2 ◽

2017 ◽

Vol 76 (14) ◽

Cited By ~ 7

Author(s):

Hao Li ◽

Haibo Bai ◽

Jianjun Wu ◽

Huiming Zhao ◽

Kai Ma

Keyword(s):

Water Inrush ◽

Karst Collapse ◽

Collapse Column

Download Full-text

Geological Structure Exploration of Karst Collapse Column and Evaluation of Water Insulation Properties of the Mud Part

Geofluids ◽

10.1155/2021/2071333 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Shijian Yu ◽

Jiyang Liu ◽

Peng Bai ◽

Hongtao Xu ◽

Runshan He ◽

...

Keyword(s):

Water Inrush ◽

Splitting Method ◽

Geological Structure ◽

Karst Collapse ◽

Electrical Characteristics ◽

X Ray Diffraction ◽

Working Face ◽

Mineral Compositions ◽

Collapse Column ◽

Brazilian Splitting

In this study, the X5 KCC in Shiquan Coal Mine was investigated by means of controlled source audio magnetotelluric exploration and borehole television. In this way, the subsection geological structure of the KCC was obtained. Next, the geological and electrical characteristics of each part were analyzed, and it is concluded that the development status of the mud part under coal seam floor is the key part to judging whether water inrush will occur during working face recovery under aquifer pressure. Furthermore, the mineral compositions of purplish-red mudstone and lime mudstone were obtained by performing an X-ray diffraction experiment on the KCC interstitial materials. On this basis, the water insulation properties of the mud part were qualitatively evaluated. Finally, the tensile strength of the mud part was obtained by the Brazilian splitting method, and the water insulation ability of the mud part at the periods when the tunneling roadway and the working face passed the KCC was calculated, respectively. The research results boast guiding significance for safe recovery of the working face passing KCCs under aquifer pressure.

Download Full-text

Damage Characteristics and Mechanism of a 2010 Disastrous Groundwater Inrush Occurred at the Luotuoshan Coalmine in Wuhai, Inner Mongolia, China

Water ◽

10.3390/w12030655 ◽

2020 ◽

Vol 12 (3) ◽

pp. 655 ◽

Cited By ~ 1

Author(s):

Fangpeng Cui ◽

Qiang Wu ◽

Chen Xiong ◽

Xiang Chen ◽

Fanlan Meng ◽

...

Keyword(s):

Coal Seam ◽

Inner Mongolia ◽

In Situ Stress ◽

Economic Losses ◽

Karst Collapse ◽

Great Effort ◽

Groundwater Inrush ◽

Collapse Column ◽

Great Damage

On 1 March 2010, a disastrous groundwater inrush occurred at the Luotuoshan coalmine in Wuhai (Inner Mongolia, China). Great effort was taken during the post-accident rescue. However, triggered by a large amount of groundwater rushed in from the Ordovician limestone aquifer underlying the No.16 coal seam through the fractured sandy claystone and the karst collapse column, it caused great damage, including 32 deaths and direct economic losses of over 48 million yuan. The groundwater inrush originated from the floor heave in the air return gallery of the No.16 coal seam. The peak inflow rate was 60,036 m3/h. The gallery excavation under conditions caused by the incompletely recognized hydrogeological environment induced the accident. The unidentified spatial distribution of the karst collapse column triggered the accident directly. The high-pressure groundwater accumulated in the collapse column and the gallery excavation, which caused the redistribution of the in situ stress, contributing to progressive fractures in the floor of the No. 16 coal seam. Eventually, an intensive water-conductive passage consisting of the fractured floor and the karst collapse column formed. Administratively/technically, that mandatory regulations on gallery excavation were not carried out which contributed the accident. Moreover, the poor awareness about groundwater inrush recognition and quick remediation also contoirbuted to the disastrous extent of the accident.

Download Full-text

Investigation on the Fracturing Permeability Characteristics of Cracked Specimens and the Formation Mechanism of Inrush Channel from Floor

Shock and Vibration ◽

10.1155/2021/8858733 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Jianning Wang ◽

Weitao Liu ◽

Jianjun Shen

Keyword(s):

Crack Initiation ◽

Crack Propagation ◽

Formation Mechanism ◽

Water Pressure ◽

Water Inrush ◽

Confining Pressure ◽

Crack Initiation And Propagation ◽

Initiation And Propagation ◽

Final Failure ◽

Cracked Specimens

To study the fracture characteristics and the permeability change law of the cracked specimens during the complete stress-strain process, a mechanical model was constructed, from which different types of crack initiation angles were obtained. The crack inclination angles under uniaxial compression, confining compression, and confining tension, and the influence of confining pressure and pore water pressure on the crack propagation and permeability of rock mass were investigated and simulated with RFPA-Flow software using prefabricated crack models with crack initiation angles of 30°, 45°, and 60°. Furthermore, the formation mechanism of inrush channel from floor was qualitatively analyzed. The results indicated that the theoretical initiation angles of wing cracks, secondary coplanar cracks, and secondary inclined antiwing cracks were found to be 70.53°, 0°, and 123.8°, which were consistent with the simulation results. The crack propagation was mainly concentrated at the postpeak stage of the complete stress-strain curve, causing the peak of seepage velocity to lag behind the stress peak. For the case with a constant confining pressure, the rate of crack initiation and propagation to final failure was positively correlated with the internal pore pressure. For the case with a constant water pressure, the speed of crack initiation and propagation to final failure decreased first and then increased as the confining pressure increased. In addition, the longitudinal propagation of wing cracks and the increase in permeability were prone to occur in the low confining pressure zone, which induced the formation of water inrush channels. The research result provides an improved understanding for predicting and preventing water inrush disasters.

Download Full-text

Research on the Development Mechanism of Postpeak Cracks in Sandstone under Different Confining Pressures

Mathematical Problems in Engineering ◽

10.1155/2019/6208207 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10

Author(s):

Jihua Zhang ◽

Lianguo Wang ◽

Yun Dong ◽

Yadong Chen ◽

Yang Jiang ◽

...

Keyword(s):

Probability Density ◽

Water Inrush ◽

Confining Pressure ◽

Ct Images ◽

Surrounding Rock ◽

Internal Crack ◽

Geometrical Parameters ◽

Stress Levels ◽

Confining Pressures ◽

Development Mechanism

Water inrush happens occasionally during deeper roadways excavation. It is mainly due to the lack of understanding in the formation and development mechanism of cracks and its spatial distribution pattern under ground stress. In view of this, this paper used different stress levels to represent the fracture state of different parts of the surrounding rock of the deep roadway; CT detection technique is used to scan the fractured sandstone in the postpeak state; and the CT images under different confining pressures are thus obtained. The geometrical parameters such as area, length, and width of the crack are used to describe the distribution patterns based on CT images processing technique and statistical principle. These patterns are then analyzed under varying postpeak stress levels and confining pressures. The result shows that, as the area, length, and width of the cracks get larger, number of cracks increases with decreasing stress level; at different stress levels, sandstone crack area probability density, crack length probability density, and crack width probability density form exceptional, linear, and Gaussian distribution, respectively. The amount of confining pressure affects the size of cracks and the extent of expansion. This means that the higher the confining pressure is, the easier the internal crack will be penetrated and expanded and the bigger the cracks are, and the number of cracks gets lesser. Such research results can be used to describe the propagation and evolution law of cracks under different stress states of postpeak rock, which also provide an important basis for further analysis of its permeability and the stability of roadway surrounding rock.

Download Full-text