scholarly journals Experimental Study of Hysteresis Characteristics of Water-Sediment Mixture Seepage in Rock Fractures

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Lili Cao ◽  
Pu Zhang ◽  
Jiazhi Zhang ◽  
Gang Lin ◽  
Izhar Mithal Jiskani ◽  
...  
Keyword(s):  
Particle Size ◽  
Coal Mine ◽  
Mass Concentration ◽  
Water Inrush ◽  
Sand Particle ◽  
Rock Fractures ◽  
Fracture Opening ◽  
Sediment Mixture ◽  
And Control ◽  
Hysteresis Characteristics

The hysteresis of water-sediment mixture seepage in rock fractures is one of the critical factors which affect the determination of the timing of coal mine water inrush disasters prevention and control. In this paper, a mechanical model was established to study the hysteresis whose criteria were also put forward. The area of the hysteresis loop and the maximum pressure gradient were selected as characterization parameters of hysteresis. On this basis, an experimental system was established to study influences of different sand particle size, sand mass concentration, and fracture opening on water-sediment mixture seepage in rock fractures. The results indicated that the increase in the sand particle size and sand mass concentration could effectively enhance hysteresis characteristics of specimen fractures. While hysteresis characteristics decreased significantly with the increase of fracture opening. The research results are useful to prevent and control water inrush disasters of coal mine.

scholarly journals Experimental Investigation of Water-Inrush Risk Based on Permeability Evolution in Coal Mine and Backfill Prevention Discussion

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Meng Li ◽  
Jixiong Zhang ◽  
Weiqing Zhang ◽  
Ailing Li ◽  
Wei Yin
Keyword(s):  
Experimental Investigation ◽  
Coal Mine ◽  
Strain Softening ◽  
Water Inrush ◽  
Rock Fractures ◽  
Permeability Evolution ◽  
Testing Laboratories ◽  
Fracture Development ◽  
Confining Pressures ◽  
Maximum Permeability

Induced by coal mining, the fractures constantly occur in geologic strata until failure occurs, which provide channels for water flow. Therefore, it is essential to investigate the permeability evolution of rocks under load. Borehole sampling was conducted in a bedrock layer beneath an aquifer, and the permeability evolution of sandstone specimens under different confining pressures was tested in rock mechanics testing laboratories. The results indicated that the permeability gradually decreases with the increasing confining pressures, while the peak strength increases with the increase of confining pressures. The minimum and maximum permeabilities occurred in the sandstone specimens that were subjected to elastic deformation and strain-softening stages, respectively. The failure, and maximum permeability, of these sandstone specimens did not occur simultaneously. To prevent the flow channel being formed due to the development and failure of rock fractures, a method of backfill gob was proposed and also the influence of backfill on fracture development was discussed.

scholarly journals An Approach to Dynamic Disaster Prevention in Strong Rock Burst Coal Seam under Multi-Aquifers: A Case Study of Tingnan Coal Mine

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7287
Author(s):  
Xinxin Zhou ◽  
Zhenhua Ouyang ◽  
Ranran Zhou ◽  
Zhenxing Ji ◽  
Haiyang Yi ◽  
...  
Keyword(s):  
Rock Burst ◽  
Coal Mine ◽  
Water Inrush ◽  
Coal Seams ◽  
High Position ◽  
Integrated Method ◽  
Working Face ◽  
Strong Rock ◽  
And Control

In order to prevent the multi-dynamic disasters induced by rock burst and roof water inrush in strong rock burst coal seams under multi-aquifers, such as is the case with the 207 working face in the Tingnan coal mine considered in this study, the exhibited characteristics of two types of dynamic disasters, namely rock burst and water inrush, were analyzed. Based on the lithology and predicted caving height of the roof, the contradiction between rock burst and water inrush was analyzed. In light of these analyses, an integrated method, roof pre-splitting at a high position and shattering at a low position, was proposed. According to the results of numerical modelling, pre-crack blasting at higher rock layers enables a cantilever roof cave in time, thereby reducing the risk of rock burst, and pre-crack blasting at underlying rock layers helps increase the crushing degree of the rock, which is beneficial for decreasing the caving height of rock layers above goaf, thereby preventing the occurrence of water inrush. Finally, the proposed method was applied in an engineering case, and the effectiveness of this method for prevention and control of multi-dynamics disasters was evaluated by field observations of the caving height of rock layers and micro-seismic monitoring. As a result, the proposed method works well integrally to prevent and control rock burst and water inrush.

scholarly journals Identification of Hydraulic Connection Points between Different Confined Aquifers in the Liyazhuang Coal Mine

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhenghe Liu ◽  
Peiyun Zhao ◽  
Lusheng Yang ◽  
Jingui Zhao ◽  
Hailong Ye ◽  
...  
Keyword(s):  
Flow Field ◽  
Coal Seam ◽  
Numerical Simulations ◽  
Water Level ◽  
Coal Mine ◽  
Prevention And Control ◽  
Water Inrush ◽  
Hydraulic Connection ◽  
Contact Points ◽  
And Control

Water inrush from coal seam floors is one major geological obstacle hindering safe and efficient production activities in mines. Determining the source of water inrush can facilitate its prediction and guide decisions regarding measures for prevention and control. The process of identifying the location of hidden hydraulic contact points in different confined aquifers forms the basis of hydrogeological explorations. It is also the basis for categorizing mine areas prone to water inrush and making qualitative decisions regarding the prevention and control of water inrush. In this study, the positions of hidden hydraulic contact points between the Ordovician Fengfeng and Shangmajiagou formations in the basement of the Liyazhuang coal mine were determined using numerical simulations of the flow fields. First, each node of the finite element grid was considered as a water inrush point to determine the water level at other nodes. Subsequently, the error between measured and simulated water levels, determined based on the flow fields, was determined using the least squares method. The node with the minimum error was then considered as the hidden hydraulic contact point. The simulation results for the flow field indicate a distance of 5000 m between the hydraulic connection and the water inrush points located between the peak formation and the Majiagou aquifer in the Liyazhuang coal mine. Furthermore, the hydraulic relationship between them is poor. Observational data of water inrush from the floor of the No. 2 coal seam and the water level of the confined aquifer in the Liyazhuang coal mine, including the water quality test data of different Ordovician ash aquifers, show that the source of water inrush from the floor of the No. 2 coal seam is the aquifer of the Fengfeng Formation. This finding is consistent with the results of the numerical simulations of the flow field. The results demonstrate that, in mining areas subjected to high pressures, numerical simulations of the flow field can serve as an effective tool for determining the location of hidden hydraulic contact points.

scholarly journals Experimental Study of the Water-Sediment Two-Phase Seepage Characteristics in Rock Fractures and the Influencing Factors

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Kui Di ◽  
Ming Li ◽  
Xianbiao Mao ◽  
Zhanqing Chen ◽  
Lianying Zhang ◽  
...  
Keyword(s):  
Particle Size ◽  
Pressure Gradient ◽  
Volume Fraction ◽  
Water Inrush ◽  
Experimental System ◽  
Sand Particle ◽  
Two Phase ◽  
Absolute Value ◽  
The Absolute ◽  
Seepage Characteristics

The water-sediment two-phase seepage in coarse fractures is one of the major factors to trigger mine water inrush disasters. Based on seepage mechanics theory, a mechanical model of the water-sediment two-phase seepage in coarse fractures was established. An experimental system was also developed to study the seepage characteristics under various conditions. The relationships between the absolute value of the pressure gradient and the seepage velocity were analyzed during the test process. The nonlinear characteristics of the seepage test were revealed. In addition, variation laws of the absolute value of the pressure gradient with the sand volume fraction and the sand particle size were illustrated, which were related to the loss of pressure during the particle movement. The impacts of the sand volume fraction and the sand particle size on the equivalent fluidity and β -factor of non-Darcy flow were discussed and analyzed. It was determined that the local turbulence was the main reason for the change of nonlinear variation characteristics of seepage parameters.

scholarly journals Permeability Characteristics of Water-Sand Seepage in Fracture by Experiment

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Yu Liu ◽  
Shuncai Li ◽  
Wei Li ◽  
Zhihao Luo ◽  
Liming Wu ◽  
...  
Keyword(s):  
Particle Size ◽  
Water Inrush ◽  
Great Influence ◽  
Side Wall ◽  
Hysteresis Curve ◽  
Sand Particle ◽  
Type I ◽  
Permeability Characteristics ◽  
Type Iv ◽  
Seepage Characteristics

Studies on the seepage characteristics of water-sand cracks are of great significance to reveal the mechanisms of water and sand inrush. Using a self-made water-sand fracture seepage test instrument, a water-sand seepage test was carried out, and the permeability of water and sand in the fracture was determined. The hysteresis characteristics of water-sand flow in the fracture were obtained after the required permeability was attained. The results show that the hysteresis curve changes from type I to type IV with the increase in sand particle size and concentration. The hysteresis parameters are described by the maximum hysteresis Gp ∗ and the hysteresis area S, both of which show an increasing trend with the increase in sand particle size and concentration; however, this increase is not synchronous. The average velocity and turbulent kinetic energy distribution of the water-sand fluid on the fracture cross section are greatly affected by the particle size and concentration of the volume of sand. This study can provide a reference for further study of water inrush from a shallow coal seam. Through simulation, it is found that the particle size has a great influence on the seepage velocity, and the influence near the side wall surface is greater than that in the middle position.

scholarly journals Review of Respirable Coal Mine Dust Characterization for Mass Concentration, Size Distribution and Chemical Composition

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 426
Author(s):  
Behrooz Abbasi ◽  
Xiaoliang Wang ◽  
Judith C. Chow ◽  
John G. Watson ◽  
Bijan Peik ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Particle Size ◽  
Real Time ◽  
Coal Mine ◽  
Energy Dispersive ◽  
Size Distributions ◽  
X Ray ◽  
Membrane Filters ◽  
Mine Dust ◽  
Mass Concentrations

Respirable coal mine dust (RCMD) exposure is associated with black lung and silicosis diseases in underground miners. Although only RCMD mass and silica concentrations are regulated, it is possible that particle size, surface area, and other chemical constituents also contribute to its adverse health effects. This review summarizes measurement technologies for RCMD mass concentrations, morphology, size distributions, and chemical compositions, with examples from published efforts where these methods have been applied. Some state-of-the-art technologies presented in this paper have not been certified as intrinsically safe, and caution should be exerted for their use in explosive environments. RCMD mass concentrations are most often obtained by filter sampling followed by gravimetric analysis, but recent requirements for real-time monitoring by continuous personal dust monitors (CPDM) enable quicker exposure risk assessments. Emerging low-cost photometers provide an opportunity for a wider deployment of real-time exposure assessment. Particle size distributions can be determined by microscopy, cascade impactors, aerodynamic spectrometers, optical particle counters, and electrical mobility analyzers, each with unique advantages and limitations. Different filter media are required to collect integrated samples over working shifts for comprehensive chemical analysis. Teflon membrane filters are used for mass by gravimetry, elements by energy dispersive X-ray fluorescence, rare-earth elements by inductively coupled plasma-mass spectrometry and mineralogy by X-ray diffraction. Quartz fiber filters are analyzed for organic, elemental, and brown carbon by thermal/optical methods and non-polar organics by thermal desorption-gas chromatography-mass spectrometry. Polycarbonate-membrane filters are analyzed for morphology and elements by scanning electron microscopy (SEM) with energy dispersive X-ray, and quartz content by Fourier-transform infrared spectroscopy and Raman spectroscopy.

scholarly journals A thermodynamic assessment of precipitation, growth, and control of MnS inclusion in U75V heavy rail steel

2021 ◽  
Vol 40 (1) ◽  
pp. 178-192
Author(s):  
Wen-Qiang Ren ◽  
Lu Wang ◽  
Zheng-Liang Xue ◽  
Cheng-Zhi Li ◽  
Hang-Yu Zhu ◽  
...  
Keyword(s):  
Particle Size ◽  
Rail Steel ◽  
Solidification Process ◽  
Segregation Ratio ◽  
Two Phase ◽  
Final Particle ◽  
Solid Liquid ◽  
And Control ◽  
Heavy Rail ◽  
Heavy Rail Steel

Abstract Thermodynamic analysis of the precipitation behavior, growth kinetic, and control mechanism of MnS inclusion in U75V heavy rail steel was conducted in this study. The results showed that solute element S had a much higher segregation ratio than that of Mn, and MnS would only precipitate in the solid–liquid (two-phase) regions at the late stage during the solidification process at the solid fraction of 0.9518. Increasing the cooling rate had no obvious influence on the precipitation time of MnS inclusion; however, its particle size would be decreased greatly. The results also suggested that increasing the concentration of Mn would lead to an earlier precipitation time of MnS, while it had little effect on the final particle size; as to S, it was found that increasing its concentration could not only make the precipitation time earlier but also make the particle size larger. Adding a certain amount of Ti additive could improve the mechanical properties of U75V heavy rail steel due to the formation of TiO x –MnS or MnS–TiS complex inclusions. The precipitation sequences of Ti3O5 → Ti2O3 → TiO2 → TiO → MnS → TiS for Ti treatment were determined based on the thermodynamic calculation.

Sign in / Sign up

Export Citation Format

Share Document