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.

scholarly journals Study on Stress Relief of Hard Roof Based on Presplitting and Deep Hole Blasting

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Peng Gong ◽  
Yongheng Chen ◽  
Zhanguo Ma ◽  
Shixing Cheng
Keyword(s):  
Stress Distribution ◽  
Coal Mine ◽  
Coal Pillar ◽  
Deep Hole ◽  
Hard Roof ◽  
Formation Conditions ◽  
Coal Pillars ◽  
Mining Coal ◽  
The Impact ◽  
Pillar Size

For the problem that the hard roof causes wider end-mining coal pillar, and the roadway is greatly affected by mining, this paper took Shanxi Luning Coal Mine as the engineering background; based on the stress distribution characteristics of the coal pillar, the calculation method of the limit end-mining coal pillar size was given; considering the formation conditions and transmission forms of the advanced abutment stress, a method combining presplitting and deep hole blasting was proposed to weaken the advanced abutment stress. The numerical simulation was used to analyze the stress distribution of coal pillars, which was verified by on-site industrial tests. The results showed that the presplitting can achieve the blocking of stress. The closer it is to the peak of the abutment stress, the better the blocking effect. Deep hole blasting can weaken the source of the advanced abutment stress and reduce the peak of abutment stress. With the combination of the two blasting methods, the end-mining coal pillar size of Luning Coal Mine can be reduced to 60 m. The method combining presplitting and deep hole blasting can effectively reduce the end-mining coal pillar size and reduce the impact of mining on the deformation of the dip roadway.

scholarly journals Determination of fracture location of double-sided directional fracturing pressure relief for hard roof of large upper goaf-side coal pillars

2019 ◽  
Vol 38 (1) ◽  
pp. 111-136 ◽  
Author(s):  
Jiangwei Liu ◽  
Changyou Liu ◽  
Xuehua Li
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Mine ◽  
High Stress ◽  
Coal Pillar ◽  
Local Stress ◽  
Pressure Relief ◽  
Directional Hydraulic Fracturing ◽  
Fracture Location ◽  
Hard Roof ◽  
Coal Pillars

After mining the upper-goaf side, large coal pillars and part of hard roof exposed above the pillars remain. The hard roof can significantly deform the roadway by transferring high stress through coal pillars to the roadway. This paper reports the use of hydraulic fracturing technology to cut the hard roof on both sides (i.e. the broken roof slides to the goaf) to relieve the pressure. The position of the roof fracture is the key to controlling the pressure relief. The bearing characteristics of the large coal pillars and hard roof are analyzed to establish a mechanical model of the broken-roof sliding instability after directional fracturing and determine the width of the coal pillars that can collapse under maximum overburden load on coal pillars as a reasonable hydraulic fracturing position. The results show that the distance from the mine gateway to the fracture location increases with increasing hard-roof length, coal pillar depth, coal pillar thickness (mining height), and goaf width. In addition, the distance to the mine gateway decreases with increasing coal strength, support of the coal pillar by the anchor rod, cohesive force, and internal friction angle of the coal–rock interface. Engineering tests were applied in coal roadway 5107 of coal seam 5# of the Baidong Coal Mine of the Datong Coal Mine Group. Given the site conditions, a reasonable fracturing length of 8.8 m was obtained. Next, directional hydraulic fracturing was implemented. The comparison of the roof deformation before and after fracturing suggests that this method reduces the local stress concentration in coal pillars, which allows the surrounding rock deformation in roadway 5107 to be controlled.

scholarly journals Design a Reasonable Width of Coal Pillar Using a Numerical Model. A case study of Khe Cham basin, Vietnam

2020 ◽  
Vol 174 ◽  
pp. 01043
Author(s):  
Phuc Le Quang ◽  
Vladimir Zubov ◽  
Thang Pham Duc
Keyword(s):  
Numerical Simulation ◽  
Coal Pillar ◽  
Linear Increase ◽  
Underground Mines ◽  
Support Pressure ◽  
Efficient Production ◽  
Mining System ◽  
Geological Conditions ◽  
Coal Pillars ◽  
Roadway Deformation

Problems in surrounding rock displacement, roadway deformation and complex support are the hallmarks of the long wall mining system. Such problems seriously affect the safety and efficient production of coal mines. To control the deformation of the rocks around the roadway next to the goaf, to reduce the support pressure, in Vietnamese underground mines often leave supporting coal pillars. Identification of a reasonable design for roadway supporting pillars by a numerical simulation study was conducted under the geological and technical foundation of I-10- 2 working faces at the Khe Cham coal mine, Vietnam . The characteristics of stress and pressure distribution of roof layers on coal pillars are modeled under different pillar widths. The results show a great linear increase of the vertical stress on the narrow coal pillar and as the width of the coal pillar increases, the area of the elastic core area also increases and the level of stress increase tends to be stable without any apparent uptrend. Coal pillar deformation decreases with increasing coal pillar width, but it leads to large coal loss and waste of resources. Therefore, with the current supporting solutions to increase the stability of the coal pillar, the size range of a coal pillar is determined to be 6-8 m through numerical simulation. The conclusions obtained may provide a certain reference number to choose the logical location of the furnace lines under similar geological conditions.

Hazards for Construction Workers

2017 ◽  
Author(s):  
Gavin H. West ◽  
Laura S. Welch
Keyword(s):  
Heavy Metals ◽  
Prevention And Control ◽  
Respiratory Diseases ◽  
Noise Exposure ◽  
Engineered Nanomaterials ◽  
Construction Workers ◽  
Chronic Obstructive ◽  
Obstructive Pulmonary Disease ◽  
And Control ◽  
The Impact

This chapter describes the hazards for construction workers, with a particular focus on injuries as well as exposures to hazardous chemicals and dusts. A section describes hazardous exposures to lead and other heavy metals. Another section describes noise exposure. The impact of musculoskeletal disorders among construction workers is then discussed. A section on respiratory diseases focuses on asbestosis, silicosis, chronic obstructive pulmonary disease, and asthma. Exposures known to cause dermatitis and cancer are reviewed. There is a discussion of engineered nanomaterials as a potential emerging hazard. Various approaches to prevention and control, including regulations and health services, are described.

Numerical Simulation of Blasting-Induced Damage in Grouting Curtain of Sandstone Aquifer for Vertical Shaft

2015 ◽  
Vol 723 ◽  
pp. 271-278
Author(s):  
Yu Liang Zhou ◽  
Dong Feng Yuan ◽  
Jun Zheng ◽  
Hua Wang
Keyword(s):  
Numerical Simulation ◽  
Prevention And Control ◽  
Damage Zone ◽  
Surrounding Rock ◽  
Damage Effect ◽  
Vertical Shaft ◽  
Control Methods ◽  
Sandstone Aquifer ◽  
And Control ◽  
Dynamic Damage

To provide a theoretical basis for water prevention and control methods and reasonable supporting techniques for vertical shaft, and to ensure the shaft construction to pass the sandstone aquifer safely and rapidly, numerical simulation using dynamic damage constitutive model, which was a user-defined constitutive modules in FLAC3D, a lagrangian analysis code in three dimensions, has been applied to investigate the dynamic damage effect in the surrounding rock of the grouting curtain near the driving working face for vertical shaft excavated by blasting. The results indicate that the distribution of the damage zone in the surrounding rock of the shaft, which decreases the effective thickness of the grouting curtain, was like a ellip-se, and that the depth of the damage zone in the surrounding rock of the shaft grouting curtain is fewer than that of the driving face floor. It can be concluded that the centre part of the driving face floor, especially the cutting hole zones, and the shaft wall in the greater horizontal stress side are the " key parts " for shaft water prevention and control methods.

scholarly journals The Impact of COVID-19 on Pedestrian Flow Patterns in Urban POIs—An Example from Beijing

2021 ◽  
Vol 10 (7) ◽  
pp. 479
Author(s):  
Yihang Li ◽  
Liyan Xu
Keyword(s):  
Prevention And Control ◽  
Control Period ◽  
Flow Patterns ◽  
Control Measures ◽  
Pedestrian Flow ◽  
Prevention Measures ◽  
Government Control ◽  
Functional Categories ◽  
And Control ◽  
The Impact

The COVID-19 pandemic is a major challenge for society as a whole, and analyzing the impact of the spread of the epidemic and government control measures on the travel patterns of urban residents can provide powerful help for city managers to designate top-level epidemic prevention policies and specific epidemic prevention measures. This study investigates whether it is more appropriate to use groups of POIs with similar pedestrian flow patterns as the unit of study rather than functional categories of POIs. In this study, we analyzed the hour-by-hour pedestrian flow data of key locations in Beijing before, during, and after the strict epidemic prevention and control period, and we found that the pedestrian flow patterns differed greatly in different periods by using a composite clustering index; we interpreted the clustering results from two perspectives: groups of pedestrian flow patterns and functional categories. The results show that depending on the specific stage of epidemic prevention and control, the number of unique pedestrian flow patterns decreased from four before the epidemic to two during the strict control stage and then increased to six during the initial resumption of work. The restrictions on movement are correlated with most of the visitations, and the release of restrictions led to an increase in the variety of unique pedestrian flow patterns compared to that in the pre-restriction period, even though the overall number of visitations decreased, indicating that social restrictions led to differences in the flow patterns of POIs and increased social distance.

scholarly journals Stability Control of Deep Coal Roadway under the Pressure Relief Effect of Adjacent Roadway with Large Deformation: A Case Study

2021 ◽  
Vol 13 (8) ◽  
pp. 4412
Author(s):  
Houqiang Yang ◽  
Nong Zhang ◽  
Changliang Han ◽  
Changlun Sun ◽  
Guanghui Song ◽  
...  
Keyword(s):  
Large Deformation ◽  
Coal Mine ◽  
High Stress ◽  
Surrounding Rock ◽  
Western China ◽  
Engineering Practice ◽  
Pressure Relief ◽  
Coal Roadway ◽  
And Control ◽  
Relief Effect

High-efficiency maintenance and control of the deep coal roadway surrounding rock stability is a reliable guarantee for sustainable development of a coal mine. However, it is difficult to control the stability of a roadway that locates near a roadway with large deformation. With return air roadway 21201 (RAR 21201) in Hulusu coal mine as the research background, in situ investigation, theoretical analysis, numerical simulation, and engineering practice were carried out to study pressure relief effect on the surrounding rock after the severe deformation of the roadway. Besides, the feasibility of excavating a new roadway near this damaged one by means of pressure relief effect is also discussed. Results showed that after the strong mining roadway suffered huge loose deformation, the space inside shrank so violently that surrounding rock released high stress to a large extent, which formed certain pressure relief effect on the rock. Through excavating a new roadway near this deformed one, the new roadway could obtain a relative low stress environment with the help of the pressure relief effect, which is beneficial for maintenance and control of itself. Equal row spacing double-bearing ring support technology is proposed and carried out. Engineering practice indicates that the new excavated roadway escaped from possible separation fracture in the roof anchoring range, and the surrounding rock deformation of the new roadway is well controlled, which verifies the pressure relief effect mentioned. This paper provides a reference for scientific mining under the condition of deep buried and high stress mining in western China.

scholarly journals The experience of European hospital-based health care workers on following infection prevention and control procedures for COVID-19

2020 ◽  
Author(s):  
Denise van Hout ◽  
Paul Hutchinson ◽  
Marta Wanat ◽  
Caitlin Pilbeam ◽  
Herman Goossens ◽  
...  
Keyword(s):  
Health Care ◽  
Health Care Workers ◽  
Prevention And Control ◽  
Infection Prevention ◽  
Infection Risk ◽  
Infection Prevention And Control ◽  
Emotional Wellbeing ◽  
Care Workers ◽  
And Control ◽  
The Impact

ABSTRACTBackgroundWorking under pandemic conditions exposes health care workers (HCWs) to infection risk and psychological strain. Protecting the physical and psychological health of HCWs is a key priority. This study assessed the perceptions of European hospital HCWs of local infection prevention and control (IPC) procedures during the COVID-19 pandemic and the impact on their emotional wellbeing.MethodsWe performed two rounds of an international cross-sectional survey, between 31 March and 17 April 2020 via existing research networks (round 1), and between 14 May and 31 August 2020 via online convenience sampling (round 2). Main outcome measures were (1) behavioural determinants of HCW adherence with IPC procedures, (2) WHO-5 Well-Being Index, a validated scale of 0-100 reflecting emotional wellbeing. The WHO-5 was interpreted as a score below or above 50 points, a cut-off score used in previous literature to screen for depression.Results2,289 HCWs (round 1: n=190, round 2: n=2,099) from 40 countries in Europe participated. Mean age of respondents was 42 (±11) years, 66% were female, 47% and 39% were medical doctors and nurses, respectively. 74% (n=1699) of HCWs were directly treating patients with COVID-19, of which 32% (n=527) reported they were fearful of caring for these patients. HCWs reported high levels of concern about COVID-19 infection risk to themselves (71%) and their family (82%) as a result of their job. 40% of HCWs considered that getting infected with COVID-19 was not within their control. This was more common among junior than senior HCWs (46% versus 38%, P value <.01). Sufficient COVID-19-specific IPC training, confidence in PPE use and institutional trust were positively associated with the feeling that becoming infected with COVID-19 was within their control. Female HCWs were more likely than males to report a WHO-5 score below 50 points (aOR 1.5 (95% confidence interval (CI) 1.2-1.8).ConclusionsIn Europe, the COVID-19 pandemic has had a differential impact on those providing direct COVID-19 patient care, junior staff and women. Health facilities must be aware of these differential impacts, build trust and provide tailored support for this vital workforce during the current COVID-19 pandemic.

scholarly journals Impact of the Inflow Population From Outbreak Areas on the COVID-19 Epidemic in Yunnan Province and the Recommended Control Measures: A Preliminary Study

2020 ◽  
Vol 8 ◽  
Author(s):  
Zhong Sun ◽  
Guozhong He ◽  
Ninghao Huang ◽  
Hongyu Chen ◽  
Shuwei Zhang ◽  
...  
Keyword(s):  
Prevention And Control ◽  
Yunnan Province ◽  
Clinical Manifestations ◽  
Control Measures ◽  
Proper Management ◽  
Outbreak Areas ◽  
Prevention And Control Measures ◽  
And Gender ◽  
And Control ◽  
The Impact

Background: COVID-19 developed into a global pandemic in 2020 and poses challenges regarding the prevention and control capabilities of countries. A large number of inbound travelers from other regions could lead to a renewed outbreak of COVID-19 in the local regions. Globally, as a result of the imbalance in the control of the epidemic, all countries are facing the risk of a renewed COVID-19 outbreak brought about by travelers from epidemic areas. Therefore, studies on a proper management of the inbound travelers are urgent.Methods: We collected a total of 4,733,414 inbound travelers and 174 COVID-19 diagnosed patients in Yunnan province from 21 January 2020 to 20 February 2020. Data on place of origin, travel history, age, and gender, as well as whether they had suspected clinical manifestations for inbound travelers in Yunnan were collected. The impact of inbound travelers on the local epidemic was analyzed with a collinear statistical analysis and the effect of the control measures on the epidemic was evaluated with a sophisticated modeling approach.Results: Of the 174 COVID-19 patients, 60.9% were not from Yunnan, and 76.4% had a history of travel in Hubei. The amount of new daily cases in Yunnan was significant correlated with the number of inbound travelers from Hubei and suspected cases among them. Using Susceptible–Exposed–Infectious–Recovered (SEIR) model analysis, we found that the prevention and control measures dropped the local R0 down to 1.07 in Yunnan province.Conclusions: Our preliminary analysis showed that the proper management of inbound travelers from outbreak areas has a significantly positive effect on the prevention and control of the virus. In the process of resettlement, some effective measures taken by Yunnan province may provide an important reference for preventing the renewed COVID-19 outbreak in other regions.

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