scholarly journals Study of Characteristics of Surface Subsidence in Longwall Coal Mine under Poor Ground Conditions in Indonesia

2017 ◽  
Vol 6 (1) ◽  
pp. 129
Author(s):  
Phanthoudeth Pongpanya ◽  
Takashi Sasaoka ◽  
Hideki Shimada ◽  
Sugeng Wahyudi
Keyword(s):  
Numerical Simulation ◽  
Finite Difference ◽  
Coal Mine ◽  
Longwall Mining ◽  
Surface Subsidence ◽  
Maximum Surface ◽  
Mining Depth ◽  
Simulation Techniques ◽  
Ground Conditions ◽  
The Impact

This paper aims to study the characteristics of surface subsidence induced by longwall mining under poor ground conditions in Indonesia by means of numerical simulation techniques using finite difference code “FLAC3D”. The effect of mining depth in cases of single panel and multi-panel longwall mining, the influence of panel and pillar widths, and the impact of backfilling material, were incorporated into the FLAC3D software. The simulated results indicated that the angle of draw and maximum surface subsidence were significantly associated with the depth of mining, the number of extracted panels, the width of panel and pillar, and the type of backfill. In single panel mining, the largest maximum surface subsidence is observed in case of the shallowest mining depth, and it gradually decreases as the depth increases. In contrast, the angle of draw increases with increasing the mining depth. In multi-panel mining, the angle of draw and maximum surface subsidence increase as the mining depth increases. Moreover, the angle of draw and maximum surface subsidence decrease when the narrow panel and large pillar widths are adopted, and the backfilling materials are applied.

scholarly journals Control Technology of Surface Movement Scope with Directional Hydraulic Fracturing Technology in Longwall Mining: A Case Study

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3480 ◽  
Author(s):  
Zhanjie Feng ◽  
Wenbing Guo ◽  
Feiya Xu ◽  
Daming Yang ◽  
Weiqiang Yang
Keyword(s):  
Numerical Simulation ◽  
Hydraulic Fracturing ◽  
Longwall Mining ◽  
Numerical Models ◽  
Surface Subsidence ◽  
The Sustainable Development ◽  
Surface Movement ◽  
Directional Hydraulic Fracturing ◽  
Simulation Results ◽  
Overlying Strata

Mining-induced surface subsidence causes a series of environmental hazards and social problems, including farmland destruction, waterlogging and building damage in the subsidence area. To reduce mining damages, an innovative method of controlling the surface movement scope via artificial weak planes generated by hydraulic fracturing technology was proposed in this paper. Numerical models were built to analyze the influence of weak planes with different heights and dips on the overlying strata movement. The numerical simulation results showed that the weak planes structure cut off the development of the overlying strata displacement to the surface and affected the surface movement scope. When the weak planes’ dips were bigger than the angle of critical deformation, with the increase of the weak planes’ heights (0–120 m) the advance angle of influence changed from 53.61° to 59.15°, and the advance distance of influence changed from 173.31 m to 140.27 m which decreased by 30.04 m. In applications at Sihe coal mine in China, directional hydraulic fracturing technology was used in panel 5304 to form artificial weak planes in overlying strata. The measured surface subsidence and deformation value met the numerical simulation results and the mining-induced surface movement scope reduced. Moreover, no damage occurred to the surface buildings which were predicted to be in the affected area after extraction. This technology provided a new method to protect the surface structures from damages and had great benefits for the sustainable development of coal mines.

Modelling a helicopter rotor’s response to wake encounters

2004 ◽  
Vol 108 (1079) ◽  
pp. 15-26 ◽  
Author(s):  
G. R. Whitehouse ◽  
R. E. Brown
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Helicopter Rotor ◽  
Forward Speed ◽  
Transport Aircraft ◽  
Simulation Techniques ◽  
Airport Capacity ◽  
Aircraft Wake ◽  
The Impact ◽  
Rotary Wing

In recent years, various strategies for the concurrent operation of fixed-and rotary-wing aircraft have been proposed as a means of increasing airport capacity. Some of these strategies will increase the likelihood of encounters with the wakes of aircraft operating nearby. Several studies now exist where numerical simulations have been used to assess the impact of encounters with the wakes of large transport aircraft on the safety of helicopter operations under such conditions. This paper contrasts the predictions of several commonly-used numerical simulation techniques when each is used to model the dynamics of a helicopter rotor during the same idealised wake encounter. In most previous studies the mutually-induced distortion of the wakes of the rotor and the interacting aircraft has been neglected, yielding the so-called ‘frozen vortex’ assumption. This assumption is shown to be valid only when the helicopter encounters the aircraft wake at high forward speed. At the low forward speeds most relevant to near-airfield operations, however, injudicious use of the frozen vortex assumption may lead to significant errors in predicting the severity of a helicopter’s response to a wake encounter.

scholarly journals Controlling the Deformation of a Small Coal Pillar Retaining Roadway by Non-Penetrating Directional Pre-Splitting Blasting with a Deep Hole: A Case Study in Wangzhuang Coal Mine

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3084
Author(s):  
Shixing Cheng ◽  
Zhanguo Ma ◽  
Peng Gong ◽  
Kelong Li ◽  
Ning Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Mine ◽  
High Efficiency ◽  
Longwall Mining ◽  
Coal Pillar ◽  
Field Application ◽  
Vertical Stress ◽  
Mine Pressure ◽  
Deep Hole ◽  
Fracture Length

In longwall mining of coal mines, the large deformation of small pillar retaining roadways creates difficulties for the safe and efficient retreating of the mining panel. Based on the engineering background of a small coal pillar retaining roadway in Wangzhuang coal mine, pressure relief technology for non-penetrating directional pre-splitting blasting with a deep hole ahead was proposed. The influence of the non-penetrating fracture length on the pre-splitting effect was studied by numerical simulation. The results showed that the vertical stress in the coal pillar center, the small pillar retaining roadway deformation, and the energy accumulation on the pillar decreased with an increase in the non-penetrating fracture length. The vertical stress at the working face end increased with an increase in the non-penetrating fracture length. The field application and monitoring results indicated that non-penetrating directional pre-splitting blasting could effectively control the deformation of small pillar retaining roadways. The roof-to-floor and rib-to-rib maximum convergences of the 6208 tail entry were reduced by 53.66% and 52.62%, respectively, compared to the results with no blasting. The roadway section met the demands of mining panel high-efficiency retreating, thereby demonstrating the rationality of the technical and numerical simulation results. The research results shed light on the improvement of small coal pillar retaining roadway maintenance theory and technology.

scholarly journals Experimental Methods of Validation for Numerical Simulation Results on Steel Flow through Tundish

2016 ◽  
Vol 61 (4) ◽  
pp. 2057-2060
Author(s):  
J. Pieprzyca ◽  
P. Warzecha ◽  
T. Merder ◽  
M. Warzecha
Keyword(s):  
Numerical Simulation ◽  
Liquid Steel ◽  
Flow Distribution ◽  
Physical Modelling ◽  
Simulation Techniques ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Steel Flow ◽  
Liquid Flows ◽  
The Impact

Abstract The article presents experimental results on the impact of tundish flow regulator influencing the liquid steel flow course. The research was conducted based on the hybrid modelling methods understood as a complementary use of Computational Fluid Dynamics (CFD) methods and physical modelling. Dynamic development of numerical simulation techniques and accessibility to highly advanced and specialized software causes the fact that these techniques are commonly used for solving problems related to liquid flows by using analytical methods. Whereas, physical modelling is an important cognitive tool in the field of empirical identification of these phenomena. This allows for peer review and specification of the researched problems. By exploiting these relationships, a comparison of the obtained results was performed in the form of residence time distribution (RTD) curves and visualization of particular types of liquid steel flow distribution zones in the investigated tundish.

Study on the Ground Settlement Regularity Caused by Deep Caving Method

2014 ◽  
Vol 670-671 ◽  
pp. 907-911
Author(s):  
Shu Xiang Wei ◽  
Yun Yong Wang ◽  
Chang Yu Jin ◽  
Long Bin Dong ◽  
Dong Liu
Keyword(s):  
Stress Distribution ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Rock Mechanics ◽  
Surface Subsidence ◽  
Ground Settlement ◽  
Deep Mining ◽  
Mining Depth ◽  
Displacement Angle ◽  
The Finite Difference Method

With the increase of mining depth, rock mechanics conditions become complicates. So the surface subsidence law caused by deep mining is different from the shallow. Based on the finite difference method and rock mechanics theory, the surface subsidence law cased by deep caving mining was studied, the strata movement rule and characteristics of stress distribution of different excavation stage was analyzed systematically. The results of the study can provide certain reference significance for the deep mining to confirm the displacement angle and range of surface subsidence.

scholarly journals Mechanism of Coal Burst and Prevention Practice in Deep Asymmetric Isolated Coal Pillar: A Case Study from YaoQiao Coal Mine

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Chengchun Xue ◽  
Anye Cao ◽  
Wenhao Guo ◽  
Songwei Wang ◽  
Yaoqi Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Mine ◽  
Prevention And Control ◽  
High Stress ◽  
Coal Pillar ◽  
Support Pressure ◽  
Mining District ◽  
Coal Pillars ◽  
And Control ◽  
The Impact

Coal pillar bursts continue to be a severe dynamic hazard. Understanding its mechanism is of paramount importance and crucial in preventing and controlling its occurrence. The extreme roadway deformations from the asymmetric isolated coal pillars in the central mining district of YaoQiao Coal Mine have responded with frequent intense tremors, with risky isolated coal pillar bursts. The theoretical analysis, numerical simulation, and field measurements were done to research the impact of spatial overburden structure and stress distribution characteristics on the isolated coal pillar area, aiming to reveal the mechanism of coal pillar burst leading to the practice of prevention and control in the asymmetric isolated coal pillar area. The study shows that the overburden structure of the asymmetric is an asymmetric “T” structure in the strike-profile, and the stress in the coal pillar is mostly asymmetric “saddle-shaped” distribution, with the peak stress in the east side of the coal pillar, and the coal pillar is a “high stress serrated isolated coal pillar.” Numerical simulation results showed that the support pressure in the isolated coal pillar area on the strike profile was asymmetrically “saddle-shaped” distribution. The peak vertical stress in the coal pillar area continued to rise and gradually shifted to the mining district's deep part. As a result, the response of the roadway sides to the dynamic load disturbance was more pronounced. They developed a coal burst prevention and control program of deep-hole blasting in the roof of asymmetrical isolated coal pillar roof and unloading pressure from coal seam borehole. Monitored data confirmed that the stress concentration was influential in the roadway’s surrounding rock in the asymmetric isolated coal pillar area, circumventing coal pillar burst accidents. The research outcomes reference the prevention and control of coal bursts at isolated working faces of coal pillars under similar conditions.

Analysis Based on FLAC3D of Surface Subsidence Caused by a Double-Tube Parallel Tunnel Excavation

2013 ◽  
Vol 395-396 ◽  
pp. 443-446
Author(s):  
Dong Liang Guo ◽  
De Shen Zhao
Keyword(s):  
Numerical Simulation ◽  
Finite Difference ◽  
Land Subsidence ◽  
Surface Subsidence ◽  
Ground Subsidence ◽  
Tunnel Construction ◽  
Tunnel Excavation ◽  
Spring Street ◽  
Practical Engineering ◽  
Parallel Tunnel

In the double-tube parallel tunnel excavation cross-range, it will result in a larger superimposed surface subsidence, and even induce land subsidence to cause the accident. This paper uses the finite difference FLAC3D software to have a numerical simulation on double-tube parallel tunnel excavation of Dalian Spring Street Station. The land subsidence law of a double-tube parallel tunnel excavation which is obtained by analyzing the vertical and longitudinal settlement curve can predictable similar ground subsidence caused by tunnel construction and guide the safety construction of practical engineering

Numerical simulation of seismic cone signals

2005 ◽  
Vol 42 (2) ◽  
pp. 574-586 ◽  
Author(s):  
John A Howie ◽  
Ali Amini
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Finite Difference ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Field Effect ◽  
Near Field ◽  
Ground Conditions ◽  
Near Field Effect

Numerical analysis can provide insight into the effect of ground conditions on seismic signals recorded in downhole seismic testing. As part of a study of the interpretation of seismic cone data in complex ground conditions, this paper deals with the cases of wave propagation in (i) homogeneous soil and (ii) soil of increasing stiffness with depth. The main purpose of this study was to assess the validity of the use of the finite difference program FLAC for the simulation of the downhole seismic test. For realistic assumptions of material stiffness and damping, the main characteristics of field seismic cone penetration test (SCPT) seismic data were reproduced in the simulated data. Both displayed the same general shape of signal, number of oscillations, signal attenuation, frequency content, compression wave component (near-field effect), signal widening, and shift of the peak of the frequency spectrum with depth. Damping was shown to cause signal widening and dispersion, and the shear wave velocity, Vs, interpreted from the simulated wave traces varied with the interval method used to determine it. For a case history of field data, it was found that Vs varied by about 3%, depending on the analysis method used. The results show that finite difference modeling of wave propagation can provide useful insights into the factors affecting the interpretation of downhole seismic tests.Key words: seismic cone testing, shear wave velocity, signal widening, near-field effect, numerical simulation, finite difference.

scholarly journals Three-Dimensional Analysis of Gate-Entry Stability in Multiple Seams Longwall Coal Mine Under Weak Rock Conditions

2020 ◽  
Vol 9 (1) ◽  
pp. 72
Author(s):  
Pisith Mao ◽  
Hideki Shimada ◽  
Akihiro Hamanaka ◽  
Sugeng Wahyudi ◽  
Jiro Oya ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Coal Mine ◽  
Longwall Mining ◽  
Three Dimensional ◽  
Weak Rock ◽  
Failure Zone ◽  
East Kalimantan ◽  
The Stability ◽  
Coal Reserves

A study of multiple seams longwall mining is proposed to investigate its applicability in Indonesia coal mine. The study area of this research is PT Gerbang Daya Mandiri (GDM) coal mine located in East Kalimantan Island. The study of seam interaction is crucial for developing multiple seams longwall mining especially when it comes to weak rock conditions which are usually found in most of the coal reserves in Indonesia. This paper will use numerical simulation to investigate the effect of the first mined-out seam on the development of the second coal seam gate-entry by considering a couple of key parameters including depth of the coal seam and interburden length. The simulation model consists of two main indicators for instability which include failure zone, the contour of safety factor. The results show that the effect of seam interaction on gate-entry has different intensity based on the thickness of the interburden and coal seam depth. This work also provided appropriate support configuration for maintaining the stability of gate-entry.

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