scholarly journals Study on the Formation Mechanism of Rock Burst Caused by Seam Floor Slip under an Ultrathick Conglomerate

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Zhiyong Ma ◽  
Wenkai Feng ◽  
Zhen Wang ◽  
Fujin Lin ◽  
Dayong Li
Keyword(s):  
Bearing Capacity ◽  
Rock Burst ◽  
Abutment Pressure ◽  
Microseismic Monitoring ◽  
Field Investigation ◽  
Ultimate Bearing Capacity ◽  
Estimation Model ◽  
Rock Bursts ◽  
High Level ◽  
And Control

A rock burst accident occurred on coalface 13230 of the Gengcun Coal Mine in Henan Province. Through a field investigation, theoretical analysis, and microseismic monitoring, we studied how the rock burst, which was caused by overall seam floor slip and instability, occurring under an ultrathick conglomerate. Because the overlying ultrathick conglomerate in the mined-out zone close to coalface 13230 had been inadequately mined, the leading section of the coalface was under a high level of stress. Combined with the tectonic stresses from the F16 faultage and the soft floor structure, these factors caused the floor of this coalface to trigger the overall slip-type rock burst. In this paper, an estimation model of the ultimate bearing capacity of a seam floor under an ultrathick conglomerate and the advancing abutment pressure on the coalface is presented. This model is used to show that the ultimate bearing capacity of the seam floor on coalface 13230 is 26.3 MPa, and the abutment pressure is far more than the floor bearing capacity. We also present pressure relief and reinforced supporting measures, which can effectively prevent floor slip-type rock bursts from occurring. The results of this study provide a reference for the prevention and control of floor slip-type rock bursts in coal mining under an ultrathick conglomerate.

Bearing Capacity Characteristic of Unsaturated Granular Soils

2011 ◽  
Vol 261-263 ◽  
pp. 989-993 ◽  
Author(s):  
Anuchit Uchaipichat ◽  
Ekachai Man Koksung
Keyword(s):  
Bearing Capacity ◽  
Matric Suction ◽  
Ultimate Bearing Capacity ◽  
Experimental Program ◽  
Granular Soils ◽  
Test Results ◽  
High Level ◽  
Unsaturated Granular Soils ◽  
Capacity Characteristic

An experimental program of laboratory bearing tests was performed to characterize the bearing capacity of foundation on unsaturated granular soils. All tests were performed by pushing a circular rod on the surface of compacted sand specimens with different values of matric suction until failure. The test results show an increase in ultimate bearing capacity with increasing matric suction at low suction value but a decrease in that at high level of suction. The comparisons between the test results and simulations using the expressions proposed in this paper are presented and discussed. Good agreements are achieved for all testing values of suction.

scholarly journals Controlling Mechanism of Rock Burst by CO2 Fracturing Blasting Based on Rock Burst System

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Tianwei Lan ◽  
Chaojun Fan ◽  
Jun Han ◽  
Hongwei Zhang ◽  
Jiawei Sun
Keyword(s):  
Coal Mining ◽  
Rock Burst ◽  
Coal Mine ◽  
Prevention And Control ◽  
Stress Measurement ◽  
Tectonic Stress ◽  
Microseismic Monitoring ◽  
Time Space ◽  
Controlling Mechanism ◽  
And Control

Rock burst induced by mining is one of the most serious dynamic disasters in the process of coal mining. The mechanism of a rock burst is similar to that of a natural earthquake. It is difficult to accurately predict the “time, space, and strength” of rock burst, but the possibility of rock burst can be predicted based on the results of microseismic monitoring. In this paper, the rock burst system under the tectonic stress field is established based on the practice of coal mining and the result of mine ground crustal stress measurement. According to the magnitude of microseismic monitoring, the amount of the energy and spatial position of the rock burst are determined. Based on the theory of explosion mechanics, aiming at the prevention and control of rock burst in the coal mine, the technique of liquid CO2 fracturing blasting is put forward. By the experiment of blasting mechanics, the blasting parameters are determined, and the controlling mechanism of rock burst of liquid CO2 fracturing blasting is revealed. The application of liquid CO2 fissure blasting technology in the prevention and control of rock burst in Jixian Coal Mine shows that CO2 fracturing blasting reduces the stress concentration of the rock burst system and transfers energy to the deeper part, and there is no open fire in the blasting. It is a new, safe, and efficient method to prevent and control rock burst, which can be applied widely.

Mechanism Analysis on Concrete Column’s Recovery Strengthening

2014 ◽  
Vol 941-944 ◽  
pp. 707-711
Author(s):  
Zhi Peng Lai ◽  
Shao Hua Guo
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Concrete Columns ◽  
Ultimate Bearing Capacity ◽  
Theoretical Research ◽  
Concrete Column ◽  
Mechanism Analysis ◽  
Axial Deformation ◽  
Element Simulation ◽  
And Control

This paper deals with the behavior of concrete columns actuated by SMA wires winding around the column’s cylindrical surface, when the concrete column are constrained and driven in circumferential direction by the SMA wires, the column’s ultimate bearing capacity and axial deformation are mainly studied. Both theoretical research and finite element simulation are carried out. The results indicate that, the SMA’s limited recovery in reverse transformation by heating can generate circumferential prestress, which will improve the concrete column’s ultimate bearing capacity and control its deformation, so as to realize the concrete column’s recovery strengthening.

scholarly journals Experimental Investigation on the Influence of Regional Concrete Spalling on Shield Tunnel Segments

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Shimin Wang ◽  
Chuankun Liu ◽  
Gaoyu Ma ◽  
Songyu Cao ◽  
Junbo Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Bearing Capacity ◽  
Reduction Rate ◽  
Internal Force ◽  
Field Investigation ◽  
Ultimate Bearing Capacity ◽  
Shield Tunnel ◽  
Damage And Failure ◽  
Lining Structure ◽  
Critical Instability

Based on the field investigation and analysis, the mechanical characteristics of segment structure in shield tunnels are compared and analyzed under the circumstances of different concrete spalling region by the method of similarity model experiment. Through data analysis of acoustic emission, the results for displacement and internal force of shield tunnel segments are clarified on the segment lining, the influential rule of load bearing capacity is also determined, and the deformation and stress for the different concrete spalling region are described as well. The corresponding research results indicate that range for elastic bearing stage is enlarged while it is narrowed for plastic bearing stage, the convergence and deformation and the accumulated event numbers for acoustic emission on critical instability point are obviously increasing, and the process of damage and failure tends to be sudden for segment lining structure. The ultimate bearing capacity of the damaged segment lining obviously decreases due to regional concrete spalling; to be more specific, the reduction rate for ultimate bearing capacity becomes 6%, 6%, and 13%, respectively, when the range of concrete spalling reaches 45°, 60°, and 75°.

Production of asari (Manila) clams, Ruditapes philippinarum, during the period of harvest decrease in the 2000s in the Banzu tidal area, Tokyo Bay

2020 ◽  
Vol 33 ◽  
pp. 14
Author(s):  
Mitsuharu Toba ◽  
Jun Kakino ◽  
Kazuo Tada ◽  
Yutaka Kobayashi ◽  
Hideharu Tsuchie
Keyword(s):  
Field Investigation ◽  
Ruditapes Philippinarum ◽  
Management Style ◽  
Seed Stock ◽  
Tokyo Bay ◽  
Yearly Variation ◽  
Culture Area ◽  
Stock Biomass ◽  
Tidal Area ◽  
High Level

In Tokyo Bay, the harvestable quantity of asari (Manila) clams Ruditapes philippinarum has been decreasing since the late 1990s. We conducted a field investigation on clam density in the Banzu culture area from April 1988 to December 2014 and collected records spanning January 1986 to September 2017 from relevant fisheries cooperative associations to clarify the relationship between the temporal variation in stock abundance and the production activities of fishermen. The yearly variation in clam abundance over the study period was marked by larger decreases in the numbers of larger clams. A large quantity of juvenile clams, beyond the biological productivity of the culture area, may have been introduced as seed stock in the late 1980s despite the high level of harvestable stock. The declines in harvested quantity began in the late 1990s and may have been caused by decreases in harvestable stock despite the continuous addition of seed stock clams. The harvested quantity is likely to be significantly dependent upon the wild clam population, even within the culture area, as the harvestable quantity was not correlated with the quantity of seed stock introduced during the study period. These declines in harvested quantity may have resulted from a decreasing number of operating harvesters due to the low level of harvestable stock and consequently reduced profitability. Two findings were emphasized. A certain management style, based on predictions of the contributions of wild and introduced clams to future stock biomass, is essential for economically-feasible culturing. In areas with less harvestable stock, actions should be taken to maintain the incomes of harvesters while avoiding overexploitation, even if the total harvest quantity decreases.

Non-Communicable Diseases and Global Health Politics

2019 ◽  
pp. 626-659
Author(s):  
Roger Magnusson
Keyword(s):  
Respiratory Diseases ◽  
Communicable Diseases ◽  
World Health ◽  
Global Response ◽  
Non Communicable Diseases ◽  
Health Politics ◽  
Chronic Respiratory Diseases ◽  
Health Organization ◽  
High Level ◽  
And Control

Non-communicable diseases (NCDs), including cardiovascular disease, cancer, chronic respiratory diseases, and diabetes, are responsible for around 70 percent of global deaths each year. This chapter describes how NCDs have become prevalent and critically evaluates global efforts to address NCDs and their risk factors, with a particular focus on the World Health Organization (WHO) and United Nations (UN) system. It explores the factors that have prevented those addressing NCDs from achieving access to resources and a priority commensurate with their impact on people’s lives. The chapter evaluates the global response to NCDs both prior to and since the UN High-Level Meeting on Prevention and Control of Non-communicable Diseases, held in 2011, and considers opportunities for strengthening that response in future.

scholarly journals Boundaryless working hours and recovery in Germany

2021 ◽  
Author(s):  
Laura Vieten ◽  
Anne Marit Wöhrmann ◽  
Alexandra Michel
Keyword(s):  
Working Hours ◽  
Working Time ◽  
Overtime Work ◽  
Psychological Detachment ◽  
Representative Study ◽  
Flexible Working ◽  
Recovery Experiences ◽  
High Level ◽  
And Control ◽  
Extended Work

Abstract Objective Due to recent trends such as globalization and digitalization, more and more employees tend to have flexible working time arrangements, including boundaryless working hours. The aim of this study was to investigate the relationships of various aspects of boundaryless working hours (overtime, Sunday work, and extended work availability) with employees’ state of recovery. Besides, we examined the mediating and moderating role of recovery experiences (psychological detachment, relaxation, mastery, and control) in these relationships. Methods We used data from 8586 employees (48% women; average age of 48 years) who took part in the 2017 BAuA-Working Time Survey, a representative study of the German working population. Regression analyses were conducted to test main effects as well as mediation and moderation. Results Overtime work, Sunday work, and extended work availability were negatively related to state of recovery. Psychological detachment mediated these relationships. Furthermore, we found that relaxation and control mediated the association between extended work availability and state of recovery. However, no relevant moderating effects were found. Conclusions Altogether, our findings indicate that various aspects of boundaryless working hours pose a risk to employees’ state of recovery and that especially psychological detachment is a potential mechanism in these relationships. In addition, the results suggest that a high level of recovery experiences cannot attenuate these negative relationships in leisure time. Therefore, employers and employees alike should try to avoid or minimize boundaryless working hours.

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