Publications
78 results found
Zhao R, Tao M, Zhao H, et al., 2023, Theoretical study on dynamic stress redistribution around circular tunnel with different unloading paths, COMPUTERS AND GEOTECHNICS, Vol: 163, ISSN: 0266-352X
Agrawal H, Durucan S, Cao W, et al., 2023, Rockburst and gas outburst forecasting using a probabilistic risk assessment framework in longwall top coal caving faces, Rock Mechanics and Rock Engineering, Vol: 56, Pages: 6929-6958, ISSN: 0723-2632
A probabilistic risk assessment framework was developed to mathematically represent the complex engineering phenomena of rock bursts and gas outbursts for a heterogeneous coal seam. An innovative object-based non-conditional simulation approach was used to distribute lithological heterogeneity present in the coal seam to respect their geological origin. The changing mining conditions during longwall top coal caving mining (LTCC) were extracted from a coupled numerical model to provide statistically sufficient data for probabilistic analysis. The complex interdependencies among abutment stress, pore pressure, the volume of total gas emission and incremental energy release rate, their stochastic variations and uncertainty were realistically implemented in the GoldSim software, and 100,000 equally likely scenarios were simulated using the Monte Carlo method to determine the probability of rock bursts and gas outbursts. The results obtained from the analysis incorporate the variability in mechanical, elastic and reservoir properties of coal due to lithological heterogeneity and result in the probability of the occurrence of rock bursts, coal and gas outbursts, and safe mining conditions. The framework realistically represents the complex mining environment, is resilient and results are reliable. The framework is generic and can be suitably modified to be used in different underground mining scenarios, overcoming the limitations of earlier empirical indices used.
Zhao R, Tao M, Cao W, et al., 2023, Strength and failure characteristics of marble spheres subjected to paired point loads, Journal of Rock Mechanics and Geotechnical Engineering, Vol: 15, Pages: 2280-2290, ISSN: 1674-7755
Failure of irregular rock samples may provide implications in the rapid estimation of rock strength, which is imperative in rock engineering practice. In this work, analytical, experimental and numerical investigations were carried out to study the mechanical properties and failure characteristics of rock spheres under paired point loads. Analytical solutions indicted that with the increase in sample size (contact angle) and decrease in Poisson's ratio, the uneven tensile stress in theta direction decreased. Then laboratory experiments were carried out to investigate the load characteristics and failure mode of spherical marble samples with different sizes subjected to a pair of diametral point loads. The discrete element method (DEM) was adopted to study the failure process of rock spheres. The effect of the sphere diameter on the point load contact angle was examined in terms of peak load, crushed zone distribution and energy dissipation. Experimental and numerical results showed that the samples primarily fail in tension, with crushed zones formed at both loading points. With increase in the sample size, the contact angle, crushed area and total work increase. As the specimen diameter increases from 30 mm to 50 mm, the peak load on the specimen increases from 3.6 kN to 8.8 kN, and the percentage of crushed zone (ratio of crushing zone to sample radius, d/r) increased from 0.191 to 0.262. The results of the study have implications for understanding the failure of irregular rock specimens under point loading conditions and their size effects.
Schultz RA, Heinemann N, Horváth B, et al., 2023, An overview of underground energy-related product storage and sequestration, Geological Society, London, Special Publications, Vol: 528, Pages: 15-35, ISSN: 0305-8719
<jats:title>Abstract</jats:title> <jats:p> Storage of energy-related products in the geological subsurface provides reserve capacity, resilience, and security to the energy supply chain. Sequestration of energy-related products ensures long-term isolation from the environment and, for CO <jats:sub>2</jats:sub> , a reduction in atmospheric emissions. Both porous-rock media and engineered caverns can provide the large storage volumes needed for energy security and supply-chain resilience today and in the future. Methods for site characterization and modelling, monitoring, and inventory verification have been developed and deployed to identify and mitigate geological threats and hazards such as induced seismicity and loss of containment. Broader considerations such as life-cycle analysis, environment, social and governance (ESG) impact and effective engagement with stakeholders can reduce project uncertainty and cost while promoting sustainability during the ongoing energy transition toward net-zero or low-carbon economies. </jats:p>
Schultz RA, Williams-Stroud S, Horváth B, et al., 2023, Underground energy-related product storage and sequestration: site characterization, risk analysis and monitoring, Geological Society, London, Special Publications, Vol: 528, Pages: 37-59, ISSN: 0305-8719
<jats:title>Abstract</jats:title> <jats:p>This paper presents a high-level overview of site characterization, risk analysis and monitoring priorities for underground energy-related product storage or sequestration facilities. The siting of an underground storage or sequestration facility depends on several important factors beginning with the area of review. Collection of all existing and available records and data from within the rock volume, including potential vulnerabilities such as prior containment issues, proximity to infrastructure and/or population centres, must be evaluated. Baselining of natural processes before storage or sequestration operations begin provides the basis for assessing the effects of storage or sequestration on the surroundings. These initial investigations include geological, geophysical and geochemical analyses of the suitability of the geological host rock and environs for storage or sequestration. A risk analysis identifies and evaluates threats and hazards, the potential impact should they develop into unwanted circumstances or events and the consequences to the facility should any of them occur. This forms the basis for framing effective mitigation measures. A comprehensive monitoring programme that may include downhole well surveillance, observation wells, geochemical sampling and well testing ensures that the facility operates as designed and that unforeseen issues, such as product migration or loss of integrity, can be identified and mitigated. In addition to these technical issues, human factors and public perception of a project are a critical part of the site characterization, construction and operational phases of a project. Despite differences between underground storage and sequestration, the characterization, risk analysis and monitoring approaches that were developed for underground natural gas storage or for carbon dioxide sequestration could be used for underground storage or sequestration of
Gu H, Lai X, Tao M, et al., 2023, The role of porosity in the dynamic disturbance resistance of water-saturated coal, INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, Vol: 166, ISSN: 1365-1609
- Author Web Link
- Cite
- Citations: 5
Dong L, Cao W, Hermas T, 2023, Editorial: Geomechanics and induced seismicity for underground energy and resources exploitation, FRONTIERS IN EARTH SCIENCE, Vol: 11
Tao M, Zhao H, Momeni A, et al., 2023, Dynamic failure behavior and damage evolution process of holed sandstone under impact loads, INTERNATIONAL JOURNAL OF DAMAGE MECHANICS, Vol: 32, Pages: 28-49, ISSN: 1056-7895
- Author Web Link
- Cite
- Citations: 3
Zhao H, Tao M, Li X, et al., 2022, Experimental investigation on dynamic mechanical properties and fracture evolution behavior of the underground openings with excavation damaged zones, INTERNATIONAL JOURNAL OF DAMAGE MECHANICS, Vol: 31, Pages: 1533-1561, ISSN: 1056-7895
- Author Web Link
- Cite
- Citations: 6
Cao W, Durucan S, Shi J-Q, et al., 2022, Induced seismicity associated with geothermal fluids re-injection: Poroelastic stressing, thermoelastic stressing, or transient cooling-induced permeability enhancement?, Geothermics, Vol: 102, Pages: 1-18, ISSN: 0375-6505
Both field injectivity and induced seismicity were reported to be inversely correlated with the temperature of re-injected fluids at the Hellisheiði geothermal field in Iceland. This observation has led to a hypothesis that transient cooling-induced permeability enhancement is a novel mechanism for induced seismicity, in addition to elevated fluid pressure, poroelastic stressing, and thermoelastic stressing in geothermal environments. In this work, a 3D calibrated coupled THM model was developed to model the colder fluids re-injection process over a 1-year period and evaluate the potential for induced seismicity in terms of Coulomb stress changes at the Hellisheiði geothermal field. Three modelling scenarios taking into account respectively the poroelastic effect, thermoporoelastic effect, and thermoporoelastic effect with permeability enhancement, were examined and compared to identify the dominant mechanism for the recorded seismicity and examine the contribution from each individual mechanism. Results have shown that, under normal fluid re-injection pressure and temperature conditions, the permeability enhancement effect is the dominant mechanism for induced seismicity at the Hellisheiði geothermal field. Specifically, the contribution to Coulomb stress changes from the permeability enhancement effect is almost twice of that from the thermoelastic stressing, which is in turn two orders of magnitude larger than that from the poroelastic stressing. It has also been noted that, when reducing temperature of re-injected fluids from 120°C to 20°C, the temperature change is increased by 2.1 times at 1,000 m depth, while the amount of mass flow by around 4 times. Thus, the amount of heat transferred can be increased 8.4 times by lowering temperature of the injected fluids, which explains the high sensitivity of induced seismicity to temperature. Outcomes of this work suggest temperature control of injected fluids as a feasible regulation method to mit
Cao W, Verdon J, Ming T, 2022, Coupled poroelastic modelling of hydraulic fracturing-induced seismicity: Implications for understanding the post shut-in ML 2.9 earthquake at the Preston New Road, UK, Journal of Geophysical Research. Solid Earth, Vol: 127, Pages: 1-24, ISSN: 2169-9356
Post-injection seismicity associated with hydraulic stimulation has posed great challenges to hydraulic fracturing operations. This work aims to identify the causal mechanism of the post shut-in ML 2.9 earthquake in August 2019 at the Preston New Road, UK, amongst three plausible mechanisms, that is, the post shut-in pore pressure diffusion, poroelastic stressing on a non-overpressurized fault, and poroelastic stressing on an overpressurized fault. A 3D fully coupled poroelastic model that considers the poroelastic solid deformation, fluid flow in both porous rocks and fracture structures, and hydrofracturing-induced pressure perturbations was developed to simulate the hydromechanical response of the shale reservoir formation to hydraulic fracturing operations at the site. Based on the model results, Coulomb stress changes and seismicity rate were further evaluated on the PNR-2 fault responsible for the earthquake. Model results have shown that increased pore pressure plays a dominant role in triggering the fault slippage, although the poroelastic stress may have acted to promote the slippage. Amongst the three plausible mechanisms, the post shut-in pore pressure diffusion is the most favored in terms of Coulomb stress change, seismicity rate, timing of fault slippage and rupture area. The coupled modeling results suggested that the occurrence of the post shut-in ML 2.9 earthquake was a three-staged process, involving first propagation of fracture tips that stimulated surrounding reservoir formations, then hydraulic connection with and subsequent pore pressure diffusion to the conductive PNR-2 fault, and eventually fault activation primarily under the direct impact of increased pore pressure.
Tao M, Wang J, Zhao H, et al., 2022, The influence of acid corrosion on dynamic properties and microscopic mechanism of marble, GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES, Vol: 8, ISSN: 2363-8419
Tao M, Cheng W, Nie K, et al., 2022, Life cycle assessment of underground coal mining in China, SCIENCE OF THE TOTAL ENVIRONMENT, Vol: 805, ISSN: 0048-9697
- Author Web Link
- Cite
- Citations: 26
Cao W, Durucan S, Shi JQ, et al., 2022, Coupled THM modelling of induced seismicity associated with geothermal fluids re-injection: the role of transient cooling-induced permeability enhancement
Seismicity induced by injection of energy depleted geothermal fluid, as well as field injectivity, has been observed to be inversely correlated with the temperature of re-injected fluids at the Hellisheiði geothermal field, Iceland. Using the Hellisheiði field injection data, transient cooling-induced permeability enhancement as a distinctive mechanism for induced seismicity in geothermal reservoirs was investigated. A 3D coupled THM model was developed to model the colder fluids re-injection process over a 1-year period and evaluate the potential for induced seismicity at Hellisheiði. Three modelling scenarios considering respectively the poroelastic effect, thermoporoelastic effect, and thermoporoelastic effect with permeability enhancement, were examined and compared to identify the dominant mechanism for induced seismicity and examine the contribution from each individual mechanism. Results have shown that, under normal fluid re-injection pressure and temperature conditions, the permeability enhancement effect is the dominant mechanism for induced seismicity at Hellisheiði. In addition, by reducing temperature of re-injected fluids from 120 °C to 20 °C, the amount of heat transferred can be increased by 8.4 times, which explains the high sensitivity of induced seismicity to temperature. The findings of this work suggest that temperature control of injected fluids can be a feasible regulation method to mitigate injection-induced seismic risk.
Cao W, Verdon JP, Tao M, 2021, Coupled poroelastic modelling of hydraulic fracturing-induced seismicity: Implications for understanding the post shut-in ML 2.9 earthquake at the Preston New Road, UK, Publisher: ESSOAr
Post-injection seismicity associated with hydraulic stimulation has posed great challenges to hydraulic fracturing operations. This work aims to identify the causal mechanism of the post shut-in ML 2.9 earthquake in August 2019 at the Preston New Road, UK, amongst three plausible mechanisms, i.e., the post shut-in pore pressure diffusion, poroelastic stressing on a non-overpressurised fault, and poroelastic stressing on an overpressurised fault. A 3D fully-coupled poroelastic model that considers the poroelastic solid deformation, fluid flow in both porous rocks and fracture structures, and hydraulic fracture propagation was developed to simulate the hydromechanical response of the shale reservoir formation to hydraulic fracturing operations at the site. Based on the model results, Coulomb stress changes and seismicity rate were further evaluated on the PNR-2 fault responsible for the earthquake. Model results have shown that increased pore pressure plays a dominant role in triggering the fault slippage, although the poroelastic stress may have acted to promote the slippage. Amongst the three plausible mechanisms, the post shut-in pore pressure diffusion is the most favoured in terms of Coulomb stress change, seismicity rate, timing of fault slippage and rupture area. The coupled modelling results suggested that the occurrence of the post shut-in ML 2.9 earthquake was a three-staged process, involving first propagation of fracture tips that stimulated surrounding reservoir formations, then hydraulic connection with and subsequent pore pressure diffusion to the partially-sealing PNR-2 fault, and eventually fault activation primarily under the direct impact of increased pore pressure.
Cao W, Lei Q, Cai W, 2021, Stress-Dependent Deformation and Permeability of a Fractured Coal Subject to Excavation-Related Loading Paths, ROCK MECHANICS AND ROCK ENGINEERING, Vol: 54, Pages: 4299-4320, ISSN: 0723-2632
- Author Web Link
- Cite
- Citations: 7
Cao W, Shi J-Q, Durucan S, et al., 2021, Evaluation of shear slip stress transfer mechanism for induced microseismicity at In Salah CO2 storage site, International Journal of Greenhouse Gas Control, Vol: 107, Pages: 1-20, ISSN: 1750-5836
Stress transfer caused by injection-induced fault reactivation plays a significant role in triggering induced seismicity. This work aims to investigate to which extent the shear slip stress transfer mechanism might have contributed to a 4-month period of heightened microseismicity around one of the horizontal injection wells (KB-502) at the In Salah CO2 storage site. Building upon previous reservoir modelling and history matching work by the authors, coupled geomechanical and reservoir modelling of CO2 injection at KB-502 was carried out, featuring the explicit simulation of injection-induced fault reactivation and stress transfer, and the implementation of a strain-dependent permeability model to represent the fault hydrological behaviour. This approach allows a much-improved overall match to the field bottomhole pressures at KB-502 over the previous results, where fault zone reactivation and associated dynamic permeability behaviour were not considered, especially over the 4-month period of interest. Based upon the coupled modelling results, Coulomb stress changes were used to evaluate the potential for enhanced microseismicity related to CO2 injection-induced fault reactivation at KB-502. Analyses on the potential for microseismicity have shown that seismic events are likely to take place in both hydraulically connected regions and stress transfer influenced regions. The variation of computed Coulomb stress changes in near-fault areas compares favourably with the heightened field recorded seismicity during the period modelled. The integrated interpretation of microseismic monitoring and coupled geomechanics and reservoir modelling have suggested that the shear slip stress transfer mechanism was active and contributed to the occurrence of induced seismicity at In Salah.
Li C, Zhou J, Armaghani DJ, et al., 2021, Stochastic assessment of hard rock pillar stability based on the geological strength index system, GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES, Vol: 7, ISSN: 2363-8419
- Author Web Link
- Cite
- Citations: 20
Agrawal H, Durucan S, Cao W, et al., 2021, Probabilistic Risk Assessment of Rock Bursts and Excessive Gas Emissions in Longwall Top Coal Caving Mining
Despite many years of research, rock bursts and excessive gas emissions remain a longstanding cause for concern and a major hazard in underground coal mining. There are several traditional approaches to forecast rock bursts in underground mining, but it is difficult to use a single criterion for this purpose due to variations in mining conditions worldwide. This paper presents a generic probabilistic risk assessment (PRA) framework developed to estimate the probability of rock bursts and excessive gas emissions by incorporating the inherent uncertainty involved in a typical longwall coal mining scenario. The vertical stress, total volume of gas emission, and incremental energy release rate (ERR) were determined from a coupled geomechanical and gas flow model to represent longwall top coal caving mining practiced at Coal Mine Velenje. The values were fed into the PRA framework and the probability of rock bursts, gas emissions and safe mining conditions were estimated. The probability of rock burst occurrence was calculated to be 0.138, excessive gas emission to be 0.353 and safe mining conditions to be 0.565. This paper offers a new approach to overcome the limitations of traditional approaches for rock burst and excessive gas emissions forecasting.
Cai W, Durucan S, Cao W, et al., 2021, Seismic Response to Fluid Injection in Faulted Geothermal Reservoirs: A Case Example from Iceland
Seismic response to fluid injection at the Húsmúli area within the Hellisheiði geothermal field in Iceland was investigated by correlating induced seismicity with fault structures and fluid injection rates. Induced seismicity recorded around five injection wells over a half-year fluid injection period was first analysed using the k-means clustering model, which identified two clusters associated with the injection wells studied. Based on the clustered seismic events, the geometry of the injected fluid flow was estimated using the spatial density of seismic events. A statistical approach, using locations of three seismic events to identify one fracture plane, was utilised to identify the dominant fault structures, which spatially correlate well with local fault structures dominating the fluid flow. In the temporal domain, the fluid injection rate and wellhead pressure for the five wells were separately analysed against the seismic response, which shows that the seismic frequency and the b value increased along with local fluctuations of injection rate and pressure in the controlling system. It can be concluded that the integrated analysis of induced seismicity, fault structures and fluid injection in spatial-temporal domains is crucial to understand the seismic response to fluid injection in faulted/fractured geothermal reservoirs.
Gu H, Tao M, Li X, et al., 2021, Dynamic response and meso-deterioration mechanism of water-saturated sandstone under different porosities, MEASUREMENT, Vol: 167, ISSN: 0263-2241
- Author Web Link
- Cite
- Citations: 14
Cao W, Durucan S, Cai W, et al., 2021, Combining Microseismic Observations and Reservoir Simulation to Interpret Fracture Criticality in Faults at the Hellisheiði Geothermal Field, Iceland, Pages: 418-427
Fault reactivation and associated microseismicity induced by fluid injection into the subsurface pose a potential threat in geothermal power generation. In this research, the gradient of critical pore pressure change to trigger seismicity (Δpc/h), referred to as the fracture criticality, has been proposed to represent the critical state of subsurface fractures. The fracture criticality is subjected to variability due to heterogeneous fracture attributes and rock properties. The statistics of fracture criticality could be applied to the probabilistic evaluation of fluid injection-induced seismic risk, which considers the injection-driven pore pressure increase, the variability of fracture criticality, and local fracture density. The seismic risk evaluation based on statistics of fracture criticality was applied to the Hellisheiði geothermal site, where microseismic observations and reservoir simulation over a half-year fluid injection period were integrated to achieve the probabilistic distribution of fracture criticality and evaluate the injection-induced seismic risk in both fault and off-fault zones. It has been found that the fracture criticality within both fault and off-fault zones shows natural variability (mostly ranging between 0-1.0 bar/km), and the values estimated roughly follow Gaussian distributions. Relatively high probability of seismic event occurrence was estimated for fault zones around five geothermal fluid re-injection wells at the site, which were consistent with seismically-active areas over the microseismic monitoring period.
Cao W, Durucan S, Cai W, et al., 2020, A physics-based probabilistic forecasting methodology for hazardous microseismicity associated with longwall coal mining, International Journal of Coal Geology, Vol: 232, Pages: 1-14, ISSN: 0166-5162
Mining-induced microseismicity is widely considered as a result of slippage of pre-existing critically stressed fractures caused by stress perturbations around an advancing face. An in-depth analysis of the recorded microseismicity associated with longwall top coal caving mining at Coal Mine Velenje in Slovenia has been previously carried out and reported by the authors. It has been concluded that while microseismic event rate is affected by mining intensity (longwall face daily advance rate) as well as local abundance of pre-existing fractures, spatial and magnitude characteristics of microseismicity are predominantly influenced by the latter. Based upon this improved understanding of fracture-slip seismic-generation mechanism, the current work aimed at establishing a data-driven yet physics-based probabilistic forecasting methodology for hazardous microseismicity using microseismic monitoring data with concurrent face advance records. Through performing statistical analyses and probability distribution fitting for temporal, magnitude and spatial characteristics of microseismicity within a time window, a short-term forecasting model is developed to estimate the probability of potentially hazardous microseismicity over the next time interval in the form of a joint probability. The real time forecasting of hazardous microseismicity during longwall coal mining is realised through regularly updating the statistical model using the most recent microseismic sequence datasets and face advance records. This forecasting methodology is featured by the physical basis which provides a good explicability of forecasting results, and the probabilistic perspective which accounts for the stochastic nature of mining-induced microseismicity. This model has been employed to make time-varying forecasts of hazardous microseismicity around two longwall panels over a one-year coal production period at Coal Mine Velenje, and satisfactory results at both panels were achieved. In addition, t
Cai W, Bai X, Si G, et al., 2020, A Monitoring Investigation into Rock Burst Mechanism Based on the Coupled Theory of Static and Dynamic Stresses, ROCK MECHANICS AND ROCK ENGINEERING, Vol: 53, Pages: 5451-5471, ISSN: 0723-2632
- Author Web Link
- Cite
- Citations: 52
Cao W, Yildirim B, Durucan S, et al., 2020, Fracture behaviour and seismic response of naturally fractured coal subjected to true triaxial stresses and hydraulic fracturing, Fuel: the science and technology of fuel and energy, Vol: 288, Pages: 1-15, ISSN: 0016-2361
Hydraulic fracturing of coalbed methane wells has been widely practised as an effective method to increase drainage efficiency in low-permeability, low-pressure and low-saturated coal seams. To investigate hydraulic fracture performance and associated seismic response in coal, hydraulic fracturing experiments were carried out on two cubic coal blocks containing a host of natural fractures using a true triaxial rock testing machine equipped with loading, injection and acoustic systems. The acoustic system uses transducers with active sources to repetitively generate and receive ultrasonic P/S wave pulses for characterising mechanical properties of the coal blocks and revealing fracture growth. Silicon oil was injected into the middle of coal blocks to create hydraulic fractures under deviatoric stress conditions, and the stress and displacement, borehole pressure and volume, and seismic response were recorded over the injection process. X-ray computed tomography (CT) was conducted before and after the experiments to identify the location and geometry of hydraulic and natural fractures. Results have shown that the fracturing behaviour, the drawdown period of borehole pressure and the intrusion of fracturing fluid are dominated by the complexity and insulation offered by internal natural fracture networks of coal blocks. In addition, seismic spectrograms captured both fracture initiation and its subsequent interaction with natural fractures, which indicates that the induced fracture and fracturing fluid interfere with the propagation of seismic waves and influence ultrasonic seismic characteristics. Seismic velocity tomography of ultrasonic acoustic signals recorded also provided the spatial information of fractures, such as approximate locations of pre-existing fractures and injection-disturbed regions.
Zhao R, Tao M, Zhao H, et al., 2020, Dynamics fracture characteristics of cylindrically-bored granodiorite rocks under different hole size and initial stress state, THEORETICAL AND APPLIED FRACTURE MECHANICS, Vol: 109, ISSN: 0167-8442
- Author Web Link
- Cite
- Citations: 15
Cao W, Durucan S, Cai W, et al., 2020, The role of mining intensity and pre-existing fracture attributes on spatial, temporal and magnitude characteristics of microseismicity in longwall coal mining, Rock Mechanics and Rock Engineering, Vol: 53, Pages: 4139-4162, ISSN: 0723-2632
Knowledge regarding microseismic characteristics associated with longwall coal mining is crucial in evaluating the potential for underground mining hazards. Although microseismicity is induced by mining activities, it still remains uncertain as to what extent mining activities influence the spatial, temporal, and magnitude characteristics of microseismicity. To establish a thorough understanding of the relationship between microseismic characteristics and mining activities, a 27-month long microseismic monitoring campaign was conducted around a highly stressed coal zone and eight producing longwall panels at Coal Mine Velenje in Slovenia. Each microseismic event was classified to be associated with the producing longwall panel that triggered it, and the microseismic response to multi-panel longwall top coal caving face advance was analysed. Monitoring data have shown that locations of microseismic events coincided with stress concentrated regions. It was established that both seismic count and energy-intensive regions associated with coal mining in different panels are spatially connected, but they do not fully overlap with mined-out or stress concentrated areas. In addition, microseismic event counts frequency was found to be well correlated with mining intensity, while seismic energy magnitude and spatial distribution are poorly correlated with the same. Therefore, microseismic characteristics could not be explained solely by the mining-induced stress transfer and mining intensity, but are believed to be dominated by pre-existing natural fractures throughout the coal seam. Analyses of these observations helped the development of a conceptual seismic-generation model, which provides new insights into the causes of microseismicity in coal mining.
Gu H, Tao M, Li X, et al., 2020, Dynamic tests and mechanical model for water-saturated soft coal with various particle gradations, INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, Vol: 132, ISSN: 1365-1609
- Author Web Link
- Cite
- Citations: 16
Luo R, Li G-Y, Chen L, et al., 2020, Ground subsidence induced by pillar deterioration in abandoned mine districts, JOURNAL OF CENTRAL SOUTH UNIVERSITY, Vol: 27, Pages: 2160-2172, ISSN: 2095-2899
- Author Web Link
- Cite
- Citations: 4
Cao W, Shi J-Q, Durucan S, et al., 2020, Gas-driven rapid fracture propagation under unloading conditions in coal and gas outbursts, International Journal of Rock Mechanics and Mining Sciences, Vol: 130, ISSN: 1365-1609
Coal and gas outbursts have long posed a serious risk to safe and efficient production in coal mines. It is recognised that coal and gas outbursts are triggered by excavation unloading followed by gas-driven rapid propagation of a system of pre-existing or mining-induced fractures. Gas-filled fractures parallel to a working face are likely to experience opening first, then expansion and rapid propagation stages under unloading conditions. The fracture opening is driven by the effective stress inside the fracture, while the fracture expansion and rapid propagation is propelled by the pressure build-up of desorbed gas in the vicinity of the fracture. Based upon this understanding, this research aimed to identify the key factors affecting outburst initiation and its temporal evolution during roadway developments. Specifically, the response of pre-set fractures in a thin coal seam sandwiched between rock layers to roadway development is simulated using a geomechanical model coupled with fracture mechanics for fracture opening and propagation. In addition, kinetic gas desorption and its migration into open fractures is considered. During simulations outburst is deemed to occur when the fracture length exceeds the dimension of a host element. The findings of this research suggest that the simulated coal and gas outburst caused by roadway development may be considered as a dynamic gas desorption-driven fracture propagation process. The occurrence of coal and gas outbursts is found to be influenced mainly by the coal properties, fracture attributes, and initial gas pressure and the in situ stress conditions. Furthermore, the model predictions in terms of dome-shaped erupted-zone and layer-by-layer coal breakage are consistent with the field reports. In addition, the model results suggest that delayed occurrence of coal and gas outbursts, especially after sudden exposure of a coal seam or after blasting disturbance, reported in the literature may be related to the gas desorp
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.