scholarly journals Diffraction Characteristics of Small Fault ahead of tunnel face in coal roadway

2017 ◽  
Vol 21 (2) ◽  
pp. 95-99 ◽  
Author(s):  
Bo Wang ◽  
Shengdong Liu ◽  
Fubao Zhou ◽  
Jun Zhang ◽  
Fangkun Zheng
Keyword(s):  
Acoustic Wave ◽  
Coal Seam ◽  
Fault Prediction ◽  
P Wave ◽  
Mine Safety ◽  
Observation System ◽  
Tunnel Face ◽  
Coal Roadway ◽  
Small Fault ◽  
Channel Wave

Small fault ahead of the tunnel face in coal roadway is the important hidden hazard factor of coal and gas outburst accidents. The study of small fault prediction has important practical significance, which is the urgent demand of coal mine safety production. The diffraction of breakpoint can be used to identify the fault. However, unlike surface seismic exploration, the diffraction is with approximately horizontal incidence when the advanced detection is carried out in the roadway. The common advanced detection system is mainly as the reference of traffic tunnel, without considering the influence of low-velocity coal seam. Considering the influence of an acoustic wave of the roadway cavity and channel wave of the coal seam, the advanced detection model of small fault ahead of tunnel face is established. Diffraction advanced observation system in which sources located in front of tunnel face is constructed, and the numerical calculation of the high-order staggered-grid finite difference is carried out. The simulation results show that: Compared with the data collected by reflection observation system, in seismic records acquired by diffraction observation system, the suppression effect of acoustic wave is appeared. The diffracted P-wave of the breakpoint of component X is clear with strong energy and short-wave group. Multiple diffractions of the breakpoint are not found, but the multiple diffraction of tunnel face endpoint is obvious. The difference between breakpoint diffraction and multiple diffractions of the endpoint is clear, and diffracted P-wave of the breakpoint is easy to identify. The multiple reflected channel wave between the fault and the tunnel face is very obvious, and the reflected channel wave of small fault is so hard to identify. Migration results show that the imaging resolution of diffracted P-wave of small fault is higher than the reflected channel wave, and breakpoint location of imaging is consistent with the actual model.

Wave Field Characteristics of Small Faults around the Loose Circle of Rock Surrounding a Coal Roadway

2020 ◽  
Vol 25 (2) ◽  
pp. 245-254 ◽  
Author(s):  
Bo Wang ◽  
Huachao Sun ◽  
Lanying Huang ◽  
Shengdong Liu ◽  
Biao Jin ◽  
...  
Keyword(s):  
Coal Seam ◽  
Wave Field ◽  
Love Wave ◽  
The Body ◽  
Body Waves ◽  
Seismic Record ◽  
Coal Roadway ◽  
Geological Conditions ◽  
Small Fault ◽  
Channel Wave

The geological conditions of coal roadway excavation are complicated. Seismic advanced detection is strongly influenced by the loose circle of fractured rock surrounding the competent coal seam. However, the three-dimensional wave field characteristics of small fault advanced detection in the condition of the loose circle of coal roadway have not examined. In this paper, numerical modeling and field tests were conducted to address this knowledge gap. The results indicate that when a seismic source near the tunnel face is excited, the body waves and a Love channel wave propagate in the tunneling direction toward the small fault, then produces reflected body waves whose amplitude is relatively weak, and a reflected Love channel wave whose amplitude is relatively strong. When reflected body waves and the reflected Love channel wave enter the loose circle of surrounding rock, the former's signal is unrecognizable in seismic record; but the latter converts to a Love wave whose amplitude is strong in the loose circle of coal seam. The Love wave which has a large interval from other wave trains in the time domain is easily recognizable in seismic record, which makes it suitable for advanced detection of small fault. The signal-to-noise ratio of seismic record of X component is higher than those of Y component and Z component.

scholarly journals A comparative experimental study on advance geological prediction between TETSP and TSP303

2021 ◽  
Vol 252 ◽  
pp. 01034
Author(s):  
Yue Liu ◽  
Jun-jie Li
Keyword(s):  
Rock Mass ◽  
Seismic Reflection ◽  
Imaging System ◽  
P Wave ◽  
Observation System ◽  
S Wave ◽  
Low Velocity ◽  
Long Distance ◽  
Tunnel Face ◽  
Significant Difference

We introduce a new tunnel long distance prediction seismic reflection imaging system called TETSP. We use TETSP and the latest generation TSP303 to advance geological comparison detection in Zhangcun tunnel in Thousand Island Lake-Hangzhou water transfer project. Firstly, we introduce the layout of TETSP observation system and data processing flow. Secondly, we expound the differences between TETSP and TSP303 in aspect of geophone coupling and acoustic interference suppression. Lastly, we analyze the characteristics of reflection anomalies in the karst cave zone of the rock mass. The actual tunnel excavation results verify the reliability of the TSP303 and TETSP prediction. Several conclusions are drawn as follow. Firstly, two kinds of seismic reflection technology both can detect whose wave impedance interface exist significant difference in front of tunnel face, but the TSP303 is more accurate. Secondly, the poor integrity of the rock mass is corresponding to the low velocity of P-wave and S-wave.

scholarly journals Geophysical and analytical determination of overstressed zones in exploited coal seam: a case study

2021 ◽  
Author(s):  
Dariusz Chlebowski ◽  
Zbigniew Burtan
Keyword(s):  
Coal Seam ◽  
Wave Velocity ◽  
Seismic Tomography ◽  
Analytical Modeling ◽  
Coal Mines ◽  
Vertical Stress ◽  
P Wave ◽  
Rockburst Hazard ◽  
State Of Stress ◽  
P Wave Velocity

AbstractA variety of geophysical methods and analytical modeling are applied to determine the rockburst hazard in Polish coal mines. In particularly unfavorable local conditions, seismic profiling, active/passive seismic tomography, as well as analytical state of stress calculating methods are recommended. They are helpful in verifying the reliability of rockburst hazard forecasts. In the article, the combined analysis of the state of stress determined by active seismic tomography and analytical modeling was conducted taking into account the relationship between the location of stress concentration zones and the level of rockburst hazard. A longwall panel in the coal seam 501 at a depth of ca.700 m in one of the hard coal mines operating in the Upper Silesian Coal Basin was a subject of the analysis. The seismic tomography was applied for the reconstruction of P-wave velocity fields. The analytical modeling was used to calculate the vertical stress states basing on classical solutions offered by rock mechanics. The variability of the P-wave velocity field and location of seismic anomaly in the coal seam in relation to the calculated vertical stress field arising in the mined coal seam served to assess of rockburst hazard. The applied methods partially proved their adequacy in practical applications, providing valuable information on the design and performance of mining operations.

scholarly journals Application of Comprehensive Geophysical Prospecting Method in Water Accumulation Exploration of Multilayer Goaf in Integrated Mine

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Lei Zhang ◽  
Lin Xu ◽  
Yong Xiao ◽  
NingBo Zhang
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Comprehensive Analysis ◽  
High Density ◽  
Electromagnetic Method ◽  
Mine Safety ◽  
Practical Significance ◽  
Time Base ◽  
Transient Electromagnetic Method ◽  
Transient Electromagnetic

A coal mine in Datong is an integrated mine. At present, there is goaf in the upper and lower part of the mining coal seam. There is a lot of ponding in the goaf, which has great potential safety hazards for production. In order to find out the scope and location of ponding in goaf, the comprehensive geophysical exploration method combining transient electromagnetic method and high-density resistivity method is used to carry out the research. Firstly, the time-base, turn-off time, receiving delay, current, superposition times, and other parameters of the instrument are tested on the surface of known goaf to obtain the best instrument parameters, and the parameters are used to verify the feasibility of the research scheme; then, the transient electromagnetic method is used for large-area exploration on the surface of the mine, the suspected goaf ponding area is found through comprehensive analysis, and the high-density resistivity exploration is arranged in the suspected goaf ponding area. According to the obtained results, the scope and location of the goaf ponding area are accurately located through comprehensive analysis. The results show that there are two goaf ponding areas in the exploration area, which are located above the 8# coal seam currently mined; the range and location of goaf ponding area can be accurately obtained by using the comprehensive geophysical method of high-density electrical method and transient electromagnetic method. This method can provide reference for mine water prevention and control in Datong area and has great practical significance to ensure coal mine safety production.

scholarly journals Study on Rib Sloughage Prevention Based on Geological Structure Exploration and Deep Borehole Grouting in Front Abutment Zones

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Cheng Wang ◽  
Zuqiang Xiong ◽  
Chun Wang ◽  
Yuli Wang ◽  
Yaohui Zhang
Keyword(s):  
Coal Seam ◽  
Tectonic Stress ◽  
Geological Structure ◽  
Longwall Face ◽  
Mine Safety ◽  
Shanxi Province ◽  
Thick Coal Seam ◽  
Plastic Failure ◽  
Mining Conditions ◽  
Roof Strata

This research presents the grouting method of preventing rib sloughage which severely impacts mine safety and longwall retreat speed in thick coal seam with numerical simulation and laboratory tests. Based on the analysis of the plastic failure mode of five types of coal seam, roof strata ahead of the longwall face, and fractures developed in the coal seam, the following results are drawn, the range and degree of plastic failure generated in the coal seam and roof strata ahead of the longwall face gradually decreased as the coal mass strength increased; the grouting boreholes are essentially laid out within the coal rib instead of the roof. For a particular case of a coal mine in Shanxi province, a novel cement-based material was grouted, which fulfilled the reinforcement requirements under the tectonic stress regions and front abutment zones. Besides, the grouting borehole construction requested predrilled boreholes, full borehole intubation, lengthened hole sealing, and multiple-step drilling and grouting. This study can provide a theoretical framework of a design overview and practical basis for similar mining conditions in other coalfields.

Prediction of upper limit position of bedding separation overlying a coal roadway within an extra-thick coal seam

2018 ◽  
Vol 25 (2) ◽  
pp. 448-460 ◽  
Author(s):  
Hong Yan ◽  
Ji-xiong Zhang ◽  
Lin-yue Li ◽  
Rui-min Feng ◽  
Tian-tong Li
Keyword(s):  
Coal Seam ◽  
Thick Coal Seam ◽  
Coal Roadway ◽  
Upper Limit ◽  
Limit Position

THE 3-C ACOUSTIC PROCESS—A NEW APPROACH TO PREDICTING ACOUSTIC WAVE PERFORMANCE IN SEDIMENTS

2000 ◽  
Vol 40 (1) ◽  
pp. 367
Author(s):  
M.J. Wiltshire ◽  
L.M. Huggard
Keyword(s):  
Acoustic Wave ◽  
Management Practices ◽  
Wave Theory ◽  
Field Studies ◽  
Acoustic Properties ◽  
P Wave ◽  
Performance Modelling ◽  
Seismic Attribute ◽  
Log Data

Acoustic wave performance modelling is of considerable interest to seismic interpreters. Conventional interpretative models employ continuous density log data to compute theoretical acoustic data. Their dependence on high quality density log data limits the application of these techniques to areas where good logs have been acquired. Such techniques are therefore commonly used in field studies, but are generally not used in exploration.This paper details a newly developed method of predicting acoustic compression wave performance, based on sequence compaction theory, elastic wave theory and established petrophysical relationships. This allows extension of the existing density log based p-wave velocity prediction methods into areas where log data are minimal and log quality is marginal.Applications of the technique include:improvements to the quality of acquired sonic data;improved velocity control, resulting in better quality synthetic seismograms and more precise control of time-depth conversion; andimproved seismic attribute mapping, offering possibilities of better drilling target selection.With application of the technique, many wells can now be used in which poor log data quality or absence of key logs previously prevented their use as well-to-seismic control points in basin modelling. The technique can be allied to MWD resistivity logging technology to allow continuous computation of acoustic properties and realtime correlation of drilling data to seismic. This results in better location of casing and logging points, and the design of more efficient logging programs, with benefits to both drilling safety and economics.The technique allows improvement in the quality of acquired data and acquisition economics, better utilisation of old data, and better engineering and geologic management practices in current exploration drilling. It has considerable potential for overcoming sonic log acquisition problems associated with poorly compacted rocks, and has application in many areas of sequence and basin studies.

scholarly journals A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

2020 ◽  
Vol 8 (4) ◽  
pp. 1120-1134 ◽  
Author(s):  
Binbin Qin ◽  
Guoying Wei ◽  
Zhen Lou ◽  
Zehua Wang ◽  
Fulian He ◽  
...  
Keyword(s):  
Coal Seam ◽  
Soft Layer ◽  
Coal Roadway ◽  
Coal And Gas Outbursts

Reasons and Control Countermeasures of Special Soft Coal Roadway Deformation in Liangbei Coal Mine

2013 ◽  
Vol 671-674 ◽  
pp. 1144-1149
Author(s):  
Le Tuan Cheng ◽  
Jia Lin Zhang ◽  
Zheng Sheng Zou ◽  
Qing Bo Li
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Mining Area ◽  
Gas Content ◽  
Deformation And Failure ◽  
Gas Outburst ◽  
Soft Coal ◽  
Coal Roadway ◽  
Roadway Stability ◽  
Roadway Deformation

B1 coal seam located at -550m level in Liangbei Coal Mine is a typical "three-soft" seam. The coal roadway with a depth of 610-750m lies under the critical softening depth of the roadway, and its support difficulty coefficient is 1.5-2.0. The coal has poor air permeability, high gas content and high gas pressure, so danger degree of the gas outburst is relatively strong. The coal seam was destroyed in a disastrous state by more than 100 boreholes for gas outburst prevention during the excavation. This results in the difficulty in the roadway support. Engineering geological characteristics of the coal roadway at 11 mining area are introduced. Based on the engineering geo-mechanics method, the reasons of deformation and failure of the coal roadway are analyzed. In view of problems in excavation and support, as well as the type of the coal roadway deformation mechanism, the borehole parameters are optimized for the gas outburst prevention, and bolt-net-cable coupling support with high convex steel-belt is used to control the coal roadway stability at 11 mining area. Practice shows that the effect is fine.

scholarly journals Coal Seam Roof: Lithology and Influence on the Enrichment of Coalbed Methane

2019 ◽  
Vol 23 (4) ◽  
pp. 359-364
Author(s):  
Yunlan He ◽  
Xikai Wang ◽  
Hongjie Sun ◽  
Zhenguo Xing ◽  
Shan Chong ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coalbed Methane ◽  
Low Frequency ◽  
Propagation Speed ◽  
Wave Impedance ◽  
P Wave ◽  
Borehole Data ◽  
Seismic Frequencies ◽  
Argillaceous Siltstone ◽  
Gas Bearing

To identify the lithology of coal seam roof and explore the influence of these roofs on the enrichment of coalbed methane, low-frequency rock petrophysics experiments, seismic analyses and gas-bearing trend analyses were performed. The results show that the sound wave propagation speed in rock at seismic frequencies was lower than that at ultrasound frequencies. Additionally, the P-wave velocities of gritstone, fine sandstone, argillaceous siltstone and mudstone were 1,651 m/s, 2,840 m/s, 3,191 m/s and 4,214 m/s, respectively. The surface properties of the coal seam roofs were extracted through 3D seismic wave impedance inversion. The theoretical P-wave impedance was calculated after the tested P-wave velocity was determined. By matching the theoretical P-wave impedance of the four types of rocks with that of the coal seam roofs, we identified the lithology of the roofs. By analyzing known borehole data, we found that the identified lithology was consistent with that revealed by the data. By comparing and analyzing the coal seam roof lithology and the gas-bearing trends in the study area, we discovered that the coal seam roof lithology was related to the enrichment of coalbed methane. In the study area, areas with high gas contents mainly coincided with roof zones composed of mudstone and argillaceous siltstone, and those with low gas contents were mainly associated with fine sandstone roof areas. Thus, highly compact areas of coal seam roof are favorable for the formation and preservation of coalbed methane. 

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