Ting Ren

University of Wollongong | UOW · School of Civil Mining and Environmental Engineering

Moisture content of rock/coal can change its mechanical properties and absorption capacities, which can directly affect gas diffusivity, change the stress distribution and hence cause significant impacts on the overall gas or coal extraction process. Observation of the water penetration process and water distribution in the coal matrix will be bene...

Long-term exposure to respirable coal and silica dust during underground tunnelling operations has gained increasing attention in recent years. The solution to effective mitigation of dust exposure depends not only on higher-order engineering controls, but also on administrative controls for frontline workers. However, there is a disconnect between...

When a longwall face approaches the finish-off line, 1 month is normally required to relocate the longwall equipment and seal the longwall panel, during which time the goaf gas atmosphere changes and the risk of spontaneous combustion and gas explosion considerably increases. To minimise the occurrence of these hazards, an improved insight into gas...

The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO 2 composition exceeds 90%. The fast direct desor...

Spontaneous heating of coal continues to present a health and safety hazard in underground coal mines. The influence of seam gas composition on gas flow dynamics and distribution characteristics in the active longwall goaf has not been studied in-depth, and corresponding effective proactive goaf inertization strategies for preventing potential spon...

Affected by an insufficient understanding of oxidation characteristics and the CO production mechanism in low-rank coal goaf, the safety management of coal spontaneous combustion (CSC) faces severe challenges. In this study, in-depth research was conducted using ambient temperature oxidation (ATO), temperature-programmed, in situ FTIR experiments a...

Microscopic pores significantly impact the coalbed methane (CBM) storage, hence gas energy recovery and gas-related problems mitigation. However, the quantitative relationship between microscopic pore properties and CBM storage dictated by gas adsorption capacity remains unclear. In this study, high-pressure isothermal gas adsorption experiments we...

Spontaneous combustion of coal occurs in the longwall (LW) goaf during mining cycles due to coal oxidation at low temperatures and air ingress. Coal seam orientations, dictated by the elevations of maingate (MG) and tailgate (TG) and the height of working face and starting-up line, significantly impact the gas distribution in the goaf. Despite this...

Well-developed pores and cracks in coal reservoirs are the main venues for gas storage and migration. To investigate the multi-scale pore fractal characteristics, six coal samples of different rankings were studied using high-pressure mercury injection (HPMI), low-pressure nitrogen adsorption (LPGA-N2), and scanning electron microscopy (SEM) test m...

Under the effects of complex geological and stress environments, burst hazards continue to be a major challenge for underground space utilization and deep resources exploration as its occurrence can lead to personnel causalities, equipment damage and structural collapse. Considering the stress path experienced by in-situ coal body, cyclic loading a...

Exposure to respirable coal dust and respirable crystalline silica dust in underground coal mines is increasingly becoming a concern as a result of the re-emergence of coal mine dust lung disease in New South Wales (NSW) and Queensland. A significant challenge in mitigating dust exposure lies in the better understanding of ventilation and dust beha...

To solve the problem of early warning of coal spontaneous combustion (CSC) caused by abnormal continuous CO overrun in the tailgate corner of low metamorphic coal seam, this paper takes 1306 working face of Dananhu No. 1 coal mine in Hami, Xinjiang as an example. Field measurement, experimental research and numerical simulation were used to study t...

Three stages of nitrogen (N2) injection enhanced gas drainage through underground in-seam boreholes were carried out in a coal mine located in the southern Sydney basin. Due to the high CO2 content and low permeability, hard-to-drain coals were encountered during the excavation process in this coal mine. Two parallel in-seam boreholes (the length o...

Coal and gas outbursts in underground mines are the result of dynamic rupture propagation along coal seams, starting from localized instability caused by the sudden release of gas and strain energies. Although physical simulations have facilitated quantitative studies of outbursts, and rupture processes have been investigated both experimentally an...

One of the major goals of mining science is to develop models that connect monitoring signals with the dynamics accompanying hazards. Whether the triggering process of an outburst produces observable signatures is a fundamental question related to the potential for outburst early warning realization and probabilistic forecasting. Inspired by a rece...

Computational fluid dynamics (CFD) is an effective methodology that has been widely used for decades to solve engineering problems involving spontaneous combustion and abnormal gas emissions. However, most of the previous CFD modelling focused on qualitative rather than quantitative analysis, and the factors influencing spontaneous combustion contr...

Every catastrophic coal and gas outburst begins as a tiny coal failure at almost a point, followed by violent ejection of enormous amounts of gas and pulverized coal. Whether the initial rupture of a large outburst produces observable signatures different from those of smaller events is a fundamental question associated with the potential for outbu...

Every gigantic Coal and Gas Outburst begins as a tiny, localized coal failure. This point of failure leads to a rupture of the coal seam, resulting in a violent ejection of enormous amounts of gas and pulverized coal. Whether the size of an outburst is predictable and whether a large-scale outburst requires unique conditions different from smaller...

Coal and gas outburst remains one of the most severe dynamic hazards to many underground coal mining operations worldwide, posing great threats to mine safety and productivity. To understand the influence of gas composition on coal and gas outburst propensity, bulk coal samples were collected from underground coal mine sites in NSW and QLD, and sub...

Coal and gas outburst is tightly related to the existence of tectonic coal. Because large blocks of tectonic coals are difficult to be collected, reconstituted coal specimens are often used to study the mechanical properties. In this study, reconstituted coal specimens were prepared under different external forces. Then, triaxial compression tests...

Spontaneous heating in the active goaf area during normal mining processes poses increased threats to mine productivity and safety, as evidenced in events induced by spontaneous combustion of coal. To control and mitigate this engineering problem, there is a need to gain critical knowledge of spontaneous combustion in the longwall goaf area, which...

Based on the particle size evolution of tectonic coal in formation process, the differences between tectonic coal and intact coal in pore structure and initial gas desorption characteristics were studied. Then, the influences of particle size reduction on pore structure and initial gas desorption characteristics were investigated; and the initial g...

The fragmentation of coal produces abundant coal gases and is presumed to be the defining characteristic of coal and gas outbursts. Knowing the mechanism of these catastrophic hazards is one of the most important breakthroughs in mining geology. In the outburst process, coal spallation represents a unique failure type and typically leaves behind a...

Geostress is the natural stress that has not been disturbed by engineering actions affecting strata. The geostress is also known as the initial stress of the rock mass, absolute stress, or the original rock stress.

Gas drainage technologies are the main means of lowering the gas content of coal seams and eliminating the gas hazard of coalmines. As China has a huge reservoir of coalbed methane (CBM) resources, the extraction and utilization of coal seam gas resources can realize the significant triple benefits of ensuring the safe mining of coal resources, pro...

The basic concept of force in coal mechanics consists of external force and stress. The external force is generated from the outside of coal seam and can be further divided into two types, surface force and body force. Surface force is applied to the coal surface, such as gas pressure, coal support force and the contact forces between different coa...

Coal strength plays a significant role in various mining related engineering activities, including the evaluation of coal and gas outburst dangers, pillar design, hydraulic fracturing design (involving enhanced gas drainage), coalface support, coal seam CO2 sequestration, and other activities.

Moisture, ash content, volatiles, density and hardness of coal. Pore, fracture structures of coal and characterization methods. Coal matrix and its scale features

Coal and gas outbursts are geological failures that occur in underground drainage or mining, and consist of the ejection of thousands of coal/rock pieces and a considerable amount of gas into a limited working space within a short period.

The form of gas migration in coal seams is either diffusion or seepage, and is closely related to the fracture scale and pore size distribution. However, the characteristic of inhomogeneous pore structure exists in natural coal seams, and has been simplified by some researchers on the basis of the primary and secondary effects of seepage and diffus...

Coal formation, including coalification effect, peatization effect, diagenesis effect and metamorphism effect; Metamorphism types and maceral composition of coal; Generation of coal seam gas during coal metamorphism, basic composition of coal seam gas, and the existence forms of adsorbed gas and free gas. Controlling effect of magma intrusion on th...

Adsorption is a type of interfacial phenomena, which includes physical adsorption, chemical adsorption and absorption. The gas adsorption in coal belongs to physical adsorption, which means that the gas molecules concentrate in the surface of coal pores, i.e. the gas molecule concentration at the interface between gas and coal is larger than elsewh...

Most of the coal seams in China are characterized by high in-situ stress, high gas pressure, high gas content and low permeability, which makes the gas extraction rather difficult. This infrastructure not only limits CBM production but also presents considerable challenges to the safety and efficiency of coal mining in China.

This research reviewed the mechanics and gas desorption properties of intact coal, and tested the crushing work ratios of different intact coals, and then, studied the stress conditions for the failure or crushing of intact coal and the gas demand for the pulverization of intact coal particles. When a real-life outburst case is examined, the requir...

CO2 geo-sequestration in unminable coal seams is one promising method to mitigate greenhouse gas emissions and would be a means of cleaner production. At the same time, the injected CO2 can enhance coalbed methane recovery and offsets the economic cost for CO2 transportation and injection. However, this technology is still at its primary stage and...

Outburst energy is a major factor influencing coal and gas outbursts, albeit its estimation is difficult owing to the lack of amenable means for quantification of gas desorption. In the past decades, determining the mechanism of outbursts is one of the most challenging issues in rock mechanics. In this study, a triaxial coal and gas outburst simula...

This book focuses on the mechanical properties and permeability of coal, and the gas flow in coal seams. Based on coal permeability models, it establishes different models for coal seam gas, from the linear flow model to the gas–solid coupling flow model. It also provides the theoretical basis for the exploitation and safe production of coal as wel...

Protective seam mining is one kind of most effective measure to reduce coal and gas outburst risk. The pressure relief angles along inclination (δm) are key parameters for evaluating the effect of protective seam mining. However, the numerical relation between δm and coal seam dip (a) is defined by discrete data and is difficult to determine δm acc...

Coal and gas outbursts are small-scale geological disasters controlled by tectonic movement, and tectonic coal is widespread in outburst zones. In this study, we compare tectonic and intact coal specimens to examine the basic properties of tectonic coal. We estimate the different energies and limits of the crushing work ratio of coal from five typi...

Cellulose, hemicellulose and lignin are generally recognized as the main components of sawdust. In this paper, the spontaneous combustion mechanism of sawdust was studied from the aspect of these components. The thermogravimetry analysis and biochemical component analysis showed that the lignin decomposed evidently at the induction period of therma...

In this study, laboratory tests using six-cycles of nitrogen (N2) injection were carried out to investigate nitrogen flushing effect on coal seam gas recovery. In each test, N2 was injected for 200 min into a coal sample saturated with carbon dioxide (CO2), in a triaxial-loaded cell. Nitrogen injection was paused for about 20 h to allow gas desorpt...

Gas pressure changes during the process of coal mine gas drainage and CBM recovery. It is of great importance to understand the influence of sorption pressure on gas diffusion; however, the topic remains controversial in past studies. In this study, four samples with different coal ranks were collected and diffusion experiments were conducted under...

Respirable dust pollution at an underground heading face driven with continuous miner was detected during a ventilation survey. In order to obtain fundamental understandings of the airflow patterns and the respirable dust dispersion characteristics within the heading face, three dimensional Computational Fluid Dynamics (CFD) models were developed a...

Spontaneous combustion of coal has long been a thermal dynamic hazard during coal mining, storage, and transport, posing a great threat to coal mine safety. Especially coal spontaneous combustion in longwall goaf poses a great threat to underground working crew. To investigate such a mine safety issue with more insights and “what if” scenarios, thi...

This paper presents the results of an evaluation study of gas drainability in the Bulli seam in the Southern Coalfield of the Sydney Basin, NSW, Australia, where the coal seam gas (CSG) contains a high proportion of carbon dioxide (CO 2 ). Historically the gas drainability in some particular areas of this coal seam was found to be particularly poor...

Coal mine dust continues to be a health and safety issue in underground coal mines. Coal seam water infusion was developed and widely applied in European coal mines for dust control, and was also a common practice in most Chinese coal mines. This method typically involves the infusion of water into the coal seam to increase its moisture content, an...

Spontaneous combustion of coal in underground coal mine is a long-standing thermal dynamic hazard. The hazard is harmful in diverse aspects: causing loss of coal resource, raising safety concerns, and giving off noxious/greenhouse effect gases. Detection and trending analysis of a few particular gaseous products liberated during coal oxidation is t...

Sawdust is a common by-product of wood processing industry. Spontaneous combustion would even take place under unfavorable conditions of storage and transportation. In this study, self-heating substances test experiments, Thermogravimetry (TG) experiments and Frank-Kamenetskii (FK) theory were used to compare the spontaneous combustion risk of thre...

Mine ventilation has always been critical for underground mining operations to ensure operational efficiency and compliance with safety and health statutory requirements. To obtain a thorough understanding of the ventilation flow characteristics on a longwall face, innovative three dimensional (3D) models, incorporating key features of the longwall...

Dust management at longwall faces has always been a concern for mine operators. Recent respirable dust monitoring at a longwall top coal caving (LTCC) face indicated that extremely high dust exposure levels have been experienced at the face. Dust contamination from intake ventilation and the incorrect use of ventilation arrangements (i.e. curtains)...

As the one of the most catastrophic hazards in underground mining, coal and gas outburst seriously threatens the safe mining of collieries. To understand the formation and transport mechanism of outburst coal-gas flow in roadway as well as evaluate the effects of gas desorption on its development, a new apparatus was developed to conduct simulated...

The performance of pre-gas drainage in low permeable seams especially in CO2 abundant coal seams is not satisfactory. Due to the high affinity of coal to CO2, much lead time is needed for gas drainage boreholes to reduce the coal seam gas content below the threshold limit value (TLV), thus meeting the demand of the scheduled mining activities. In t...

In the theory of spontaneous combustion, identifying the critical value of the Frank-Kamenetskii parameter corresponds to solving a bifurcation point problem. There are two different numerical methods used to solve this problem—the direct and indirect numerical methods. The latter finds the bifurcation point by solving a partial differential equati...

Nitrocellulose was an extremely dangerous explosive substance which would decompose at relatively low temperature. This paper studied the thermal properties transformed from thermal decomposition to thermal explosion for a less violent nitrocellulose sample (nitrogen content: 10.92%). Four experiments were implemented: XPS analysis and SEM analysis...

Seam gas pre-drainage, is widely used as an effective method to control gas and coal outburst in underground coal mines. However, in CO 2 abundant low permeable seams, this technology seems to be less efficient due to the CO 2 sorption characteristics and the lower safe mining threshold limit for CO 2 applied in many outburst risk management plans....

Spontaneous combustion of residual coal in longwall goaf is a long standing hazard. Airflow leakage into goaf is a major driver to the hazard and this issue deteriorates where longwalls are operating in multiple seams and shallow covers because mining-induced cracks are very likely to draw fresh airflow into goaf due to presence of pressure differe...

Gas management at longwall faces has always been a challenging issue to mine operators. Along a longwall face of an Australian colliery where CO2 is the dominant coal seam gas, frequent power trip off occurred due to the high goaf gas (CO2) emission, which significantly affected the normal longwall production and brought about safety threats to the...

Carbon dioxide (CO2) enhanced coalbed methane (ECBM) is an effective method to improve methane (CH4) production and this technology has already been used to increase gas production in several field trials worldwide. One major problem is the injection drop in the later period due to permeability decrease caused by coal matrix swelling induced by CO2...

The definition of "residual gas" can be found in different scenarios, such as the "fast" and "slow" desorption methods of measuring gas content and the sorption hysteresis test and gas management of coal mines, however, its meaning varies a lot in different contexts. The main aim of this paper is to discuss the existence of truly undesorbable resid...

Abstract Sodium dithionite and thiourea dioxide are two typical reducing agents commonly used in industry. This paper compared the thermal hazards of sodium dithionite and thiourea dioxide based on DSC-TG (Differential Scanning Calorimetry and Thermogravimetry) thermal analysis, small-scale self-heating experiments and FTIR smoke gas analysis. From...

In the aspect of numerical methods for incompressible flow problems, there are two different algorithms: semi-implicit method for pressure-linked equations (SIMPLE) series algorithms and the pressure Poisson algorithm. This paper introduced a new discretized pressure Poisson algorithm for the steady incompressible flow based on a nonstaggered grid....

Determining gas diffusion coefficient from experimental data is a key step of reproducing and predicting the diffusion process in coal. Previously analytical solution, including the unipore diffusion model and the bidisperse diffusion model, has been used extensively to estimate the gas diffusion coefficient(s) in coal. The utilization of analytica...

Gas flow in coal seam consists of laminar flow through coal cleat and diffusion through pores of coal matrix. Previous studies on the prediction of CBM production mostly focused on the impact of permeability change while the gas exchange between matrix and cleat was assumed to obey unipore diffusion assumption with a single diffusion coefficient. H...

To further understand methane flow characteristics on a longwall face, this study focuses on the investigation of methane flow behaviour under six different operating and mining conditions, namely, the impact of ventilation in terms of both flow rate and the ventilation scheme, coal seam gas content, adjacent gas bearing strata, drum sprays and the...

The management of methane gas has always been a challenging issue for longwall operations. To improve the understanding of methane dispersion and flow characteristics on a longwall face, Computational Fluid Dynamics (CFD) modelling studies were conducted employing the longwall models developed recently. As a prerequisite of the CFD study, the metha...

This paper presents a mechanical model for cone bolts by analysing the cone anchorage function as a wedge-style mechanical anchor. Analytical and numerical methods were employed. The failure of a cone bolt commences with a series of partial shear failure through the grout around the cone, followed by bolt slipping as the actual bearing angle of the...

Cotton is a flammable material and some cottons would decompose or even self-ignite at bad storage and transport conditions. This paper studied the spontaneous combustion of cotton from the aspect of thermal decomposition temperature (TDT) and critical ambient temperature (CAT). From Fourier transform infrared spectroscopy analysis and chromatograp...

Self-heating or even spontaneous combustion of stockpiled coal, which is likely to outbreak under favourable circumstances during its transport, process, and storage, is a long-standing thermal dynamic hazard. This hazard is harmful in diverse aspects: causing loss of coal resource and caking property, raising safety concerns upon occurrence of ope...

In order to understand the physical mechanism of coal seam methane replacement by injecting CO2/N2, this paper analyses the flow mechanisms of methane and injected gas during replacement and the corresponding controlling factors. Based on Langmuir model, Langmuir-like sorption swelling model, P&M permeability model and variable Klinkenberg coeffici...

Self-heating or even spontaneous combustion of stockpiled coal, which is likely to outbreak under favourable circumstances during its transport, process, and storage, is a long-standing thermal dynamic hazard. This hazard is harmful in diverse aspects: causing loss of coal resource and caking property, raising safety concerns upon occurrence of ope...

Spontaneous heating of coal stockpile has long been a thermal dynamic hazard during coal storage, processing, and transport. A transient non-equilibrium thermal CFD model has been developed to study the low-temperature self-heating behaviour of coal in multiple stockpiles under different prevailing wind conditions. Modelling results from the initia...

Coal seams that are prone to strong outbursts have low strength and cause heavy structural damage to the seam. Their outburst risk is highly related to the release of the adsorbed coalbed gas, which is controlled by the gas desorption and diffusion characteristics of coal. In the Haizi Coal Mine, China, an extremely high gas outburst risk was detec...