scholarly journals Influence of the Undercut Anchor Head Angle on the Propagation of the Failure Zone of the Rock Medium

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2371
Author(s):  
Józef Jonak ◽  
Robert Karpiński ◽  
Andrzej Wójcik
Keyword(s):  
Rock Mass ◽  
Rock Surface ◽  
Failure Zone ◽  
Constant Depth ◽  
Pull Out ◽  
A Value ◽  
Initial Stage ◽  
Failure Propagation ◽  
Rock Mass Failure ◽  
The Impact

The paper presents the results of a numerical analysis (FEM) describing the effect of the undercutting head angle on the formation of the rock mass failure zone during the initial stages of failure propagation. The research was carried out in the context of developing a technology for rock extraction by controlled pull-out of undercut anchors installed in the rock mass. The focus was on the initial stage of crack propagation and its trajectory for anchors embedded at an assumed constant depth and a value of the friction coefficient of the rock against the anchor head. It is shown that smaller angles favor smaller stripping angles and an increased radial impact of the head on the rock material (in the plane perpendicular to the head axis), while the impact of heads with larger angles is found to favor larger fracture penetration angles and faster penetration towards the free rock surface.

scholarly journals Numerical analysis of undercut anchor effect on rock

2021 ◽  
Vol 2130 (1) ◽  
pp. 012011
Author(s):  
J Jonak ◽  
R Karpiński ◽  
A Wójcik
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Rock Mass ◽  
Numerical Analysis ◽  
Coulomb Friction ◽  
Rock Surface ◽  
Failure Zone ◽  
Anchor Effect ◽  
The Finite Element Method ◽  
Pull Out

Abstract The paper presents the results of a numerical analysis using the Finite Element Method (FEM) of the friction issue in the contact between the undercut anchor head and rock during anchor pull-out. Formation of failure zone of rock medium was analysed assuming different Coulomb friction coefficients in the contact zone of conical anchor head with a rock. The problem is interesting as regards practical aspects of rock mass loosening during anchor pull-out. The analysis revealed a significant effect of the friction coefficient on the propagation and extent of the failure zone. Increasing the friction factor significantly decreases the extent of the failure zone measured on a free rock surface.

scholarly journals Numerical analysis of the effect of embedment depth on the geometry of the cone failure

2021 ◽  
Vol 2130 (1) ◽  
pp. 012012
Author(s):  
J Jonak ◽  
R Karpiński ◽  
A Wójcik
Keyword(s):  
Rock Mass ◽  
Fem Analysis ◽  
Potential Interaction ◽  
The Other ◽  
Rock Surface ◽  
Embedment Depth ◽  
Failure Zone ◽  
Pull Out ◽  
Failure Angle ◽  
Anchor Systems

Abstract This paper presents the results of a numerical FEM analysis of the effect of embedment depth on the extent of the failure zone (cone failure) under the effect of an undercut anchor. For the establishment of the other affecting quantities, the formation of the value of the cone failure angle of the rock medium depending on the embedment depth was analysed. The problem is interesting as regards aspects of rock mass loosening during pull-out of undercut anchors. As a result of the analysis, a significant effect of embedment depth on propagation and the extent of cone failure has been found. The increasing value of embedment depth significantly decreases the extent of the failure zone measured on a free rock surface. The increasing value of cone failure angle limits the potential interaction of failure zones in multi-anchor systems.

Rock Movement in Tectonic Zones. Mining Activities and Rock Pressure Management in the Norilsk-Kharaelakh Fault Area

2020 ◽  
pp. 148-151
Author(s):  
S.G. Kirillov ◽  
Z.G. Ufatova ◽  
I.F. Khrushchev ◽  
K.A. Bashirov
Keyword(s):  
Rock Mass ◽  
High Mobility ◽  
Mining Operations ◽  
Profile Line ◽  
Initial Stage ◽  
Tectonic Zones ◽  
Rock Movement ◽  
Hazard Level ◽  
And Control ◽  
The Impact

The article describes the rock mass state within the boundaries of the Skalistiy mining allotment. The ore mass within the mine field was found to preserve its rock-bump hazard and show high mobility in the impact zone of the Norilsk-Kharaelakh Fault and the associated high failure potential manifested as roof cavings. Based on the monitoring results along underground profile lines, it was concluded that the displacement process is currently at its initial stage. Moreover, the maximum subsidence in the central part of the profile line is about 3 times higher (up to 35 mm) than in other areas. This is caused by immediate proximity of this zone to the Norilsk-Kharaelakh Fault. Assessment of the bump hazard level of this rock mass with the help of the Prognoz-2 instrument that was performed by the rock-bump forecasting and control teams of the mine and the Norilskshakhtstroy company, showed the 'Not Hazardous' category in all cases. However, the progress of mining operations towards the Norilsk-Kharaelakh Fault may lead to deterioration in the condition of mine workings. This can be manifested through rock exfoliation from the walls of the advance workings of the safety layer in highly and extremely faulted rocks. In addition, permanent workings, which are one of the most critical structures of the production level and which will be used until the development of the deposit area adjacent to the Norilsk-Kharaelakh Fault is completed, will be maintained in increasingly difficult conditions. The article describes recommendations for mining operations in the fault area with account for the current mining and geomechanical situation and the potential for its change.

scholarly journals The Impact of Multiple Seam Mining Exploitations on Seismic Activity and State of Stress

2017 ◽  
Vol 39 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Tadeusz Majcherczyk ◽  
Zbigniew Niedbalski
Keyword(s):  
Rock Mass ◽  
Seismic Activity ◽  
Vertical Stress ◽  
Hard Coal ◽  
Variable Degree ◽  
Concentration Coefficient ◽  
A Value ◽  
State Of Stress ◽  
Seam Mining ◽  
The Impact

Abstract The paper presents an analysis of seismic activity for selected areas of hard coal mine executing exploitation in a rock mass with a variable degree of rock disturbance, i.e., also with a varied number of previous mined-out seams. A distribution of vertical stress and a value of vertical stress concentration coefficient were also determined in the strata of immediate roof of the seams planned for mining. In the analyzed case, despite the lack of thick and solid strata of sandstones in the roof, the rock mass emits seismic activity, where the energy largely depends upon an impact of exploitation edges and tectonic disturbance.

scholarly journals Influence of the Undercut Anchor Head Angle on the Propagation of the Failure Zone of the Rock Medium—Part II

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3880
Author(s):  
Józef Jonak ◽  
Robert Karpiński ◽  
Andrzej Wójcik
Keyword(s):  
Surface Friction ◽  
Geometric Parameters ◽  
Rock Surface ◽  
Failure Zone ◽  
Conical Part ◽  
Rock Masses ◽  
Numerical Investigations ◽  
Initial Stage ◽  
Special Cases

Problems concerning the influence of the geometric parameters of an undercutting anchor on the range of the failure zone of rock medium during the pulling out of the anchor constitute one of the aspects that arouse the interest of authors due to attempts to use undercutting anchors in the process of rock lump separation. This method is considered an alternative to the existing methods of separation, especially in special cases of mining technologies. This article presents the results of numerical investigations into the effect of changes in the head geometry that occur as a result of wear on the conical part of the undercutting anchor and the extent of failure of the rock medium during its pulling out. This is an extension of considerations presented in previous work, where special attention was paid to the influence of potential errors in anchor installation, leading to changes in head geometry and, consequently, to changes in the extent of the failure zone of the rock medium. As a result, significant changes in the volume of the detached rock masses are observed. This study shows that the increasing surface friction of the stripping anchor head leads to a decrease in the angle of the undercutting head. As a result, the extent of the failure zone measured on the free rock surface increases, the value of the angle of the failure cone at the initial stage of the stripping decreases, and the deformation of rock in the plane perpendicular to the anchor axis increases.

Influence of social networks on business processes’ development

2020 ◽  
Vol 19 (12) ◽  
pp. 2225-2252
Author(s):  
E.V. Popov ◽  
V.L. Simonova ◽  
O.V. Komarova ◽  
S.S. Kaigorodova
Keyword(s):  
Social Networks ◽  
Social Media ◽  
Business Models ◽  
Business Processes ◽  
Digital Economy ◽  
Theoretical Understanding ◽  
Sales Channels ◽  
A Value ◽  
The Impact

Subject. The emergence of new ways of interaction between sellers and buyers, the formation of new sales channels and product promotion based on the use of digital economy tools is at the heart of improving the business processes. Social networks became a tool for development; their rapid growth necessitates theoretical understanding and identification of potential application in enterprise's business process digitalization. Objectives. We explore the role of social media in the digitalization of business processes, systematize the impact of social networks on business processes of enterprises in the digital economy. Methods. The theoretical and methodological analysis of social networks as a tool for digitalization of company's business processes rests on the content analysis of domestic and foreign scientific studies, comparison, generalization and systematization. Results. We highlight the key effects of the impact of social networks on the business processes of the company; show that the digitalization of business processes should be considered in the context of a value-based approach, aimed at creating a value through the algorithmization of company operations. We determine that social networks are one of the most important tools for digitalization of company's business processes, as they have a high organizational and management potential. We also systematize the effects of social media on company's business processes. Conclusions. We present theoretical provisions of the impact of social networks on business processes of enterprises, which will enable to model and organize ideas about the development of digital ecosystems and the formation of business models.

scholarly journals Determining the Role of Acidity, Fate and Formation of IEPOX-Derived SOA in CMAQ

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 707
Author(s):  
Petros Vasilakos ◽  
Yongtao Hu ◽  
Armistead Russell ◽  
Athanasios Nenes
Keyword(s):  
Significant Influence ◽  
Organic Aerosol ◽  
Liquid Water Content ◽  
Anthropogenic Emissions ◽  
So2 Emissions ◽  
Aerosol Acidity ◽  
A Value ◽  
Future Emission ◽  
The Impact

Formation of aerosol from biogenic hydrocarbons relies heavily on anthropogenic emissions since they control the availability of species such as sulfate and nitrate, and through them, aerosol acidity (pH). To elucidate the role that acidity and emissions play in regulating Secondary Organic Aerosol (SOA), we utilize the 2013 Southern Oxidant and Aerosol Study (SOAS) dataset to enhance the extensive mechanism of isoprene epoxydiol (IEPOX)-mediated SOA formation implemented in the Community Multiscale Air Quality (CMAQ) model (Pye et al., 2013), which was then used to investigate the impact of potential future emission controls on IEPOX OA. We found that the Henry’s law coefficient for IEPOX was the most impactful parameter that controls aqueous isoprene OA products, and a value of 1.9 × 107 M atm−1 provides the best agreement with measurements. Non-volatile cations (NVCs) were found in higher-than-expected quantities in CMAQ and exerted a significant influence on IEPOX OA by reducing its production by as much as 30% when present. Consistent with previous literature, a strong correlation of isoprene OA with sulfate, and little correlation with acidity or liquid water content, was found. Future reductions in SO2 emissions are found to not affect this correlation and generally act to increase the sensitivity of IEPOX OA to sulfate, even in extreme cases.

scholarly journals The impact of drilling and slitting construction on damage field: evolution characteristics in low-permeability coal seam

2021 ◽  
Vol 37 ◽  
pp. 205-215
Author(s):  
Heng Chen ◽  
Hongmei Cheng ◽  
Aibin Xu ◽  
Yi Xue ◽  
Weihong Peng
Keyword(s):  
Finite Element ◽  
Rock Mass ◽  
Damage Mechanics ◽  
Effective Strain ◽  
Secondary Development ◽  
Distribution Area ◽  
Finite Element Program ◽  
Element Program ◽  
Mining Face ◽  
The Impact

ABSTRACT The fracture field of coal and rock mass is the main channel for gas migration and accumulation. Exploring the evolution law of fracture field of coal and rock mass under the condition of drilling and slitting construction has important theoretical significance for guiding efficient gas drainage. The generation and evolution process of coal and rock fissures is also the development and accumulation process of its damage. Therefore, based on damage mechanics and finite element theory, the mathematical model is established. The damage variable of coal mass is defined by effective strain, the elastoplastic damage constitutive equation is established and the secondary development of finite element program is completed by FORTRAN language. Using this program, the numerical simulation of drilling and slitting construction of the 15-14120 mining face of Pingdingshan No. 8 Mine is carried out, and the effects of different single borehole diameters, different kerf widths and different kerf heights on the distribution area of surrounding coal fracture field and the degree of damage are studied quantitatively. These provide a theoretical basis for the reasonable determination of the slitting and drilling arrangement parameters at the engineering site.

The influence of Hanok experience on tourists’ attitude and behavioral intention: An interplay between experiences and a Value-Attitude-Behavior model

2021 ◽  
pp. 135676672110117
Author(s):  
Choong-Ki Lee ◽  
Yvette Reisinger ◽  
Muhammad Shakil Ahmad ◽  
Yae-Na Park ◽  
Choong-Won Kang
Keyword(s):  
Behavioral Intention ◽  
Sem Analysis ◽  
Experience Economy ◽  
A Value ◽  
Functional Value ◽  
Experienced Utility ◽  
Attitude Behavior ◽  
Tourism And Hospitality ◽  
The Impact ◽  
Value Functional

This study examines the impact of Hanok experience on tourists’ attitude and behavioral intention using the experience economy ( Pine and Gilmore, 1998 ) and the experienced utility theory ( Kahneman et al., 1997 ). Specifically, the study explores how tourists’ experiences are associated with a Value-Attitude-Behavior (VAB) model in the context of a heritage tourism attraction such as Jeonju Hanok Village in South Korea. A total of 323 responses were examined using SEM analysis. The results revealed that educational, entertainment, and escapism experiences significantly influenced functional value. Functional value had a significant relationship with attitude, which was positively related to behavioral intention. The results indicate the interplay of tourists’ experiences with the VAB model. The study provides theoretical and practical implications for tourism and hospitality academics and practitioners.

scholarly journals Monitoring of the Impact of Lithium Nitrate on the Alkali–aggregate Reaction Using Acoustic Emission Methods

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 20
Author(s):  
Justyna Zapała-Sławeta ◽  
Grzegorz Świt
Keyword(s):  
Acoustic Emission ◽  
Initial Reaction ◽  
Lithium Nitrate ◽  
Acoustic Emission Method ◽  
Emission Method ◽  
Acoustic Activity ◽  
Initial Stage ◽  
Chemical Admixture ◽  
Different Characteristics ◽  
The Impact

The study analyzed the possibility of using the acoustic emission method to analyse the reaction of alkali with aggregate in the presence of lithium nitrate. Lithium nitrate is a chemical admixture used to reduce adverse effects of corrosion. The tests were carried out using mortars with reactive opal aggregate, stored under the conditions defined by ASTM C227. The acoustic activity of mortars with a corrosion inhibitor was referred to linear changes and microstructure of specimens in the initial reaction stages. The study found a low acoustic activity of mortars with lithium nitrate. Analysis of characteristic parameters of acoustic emission signals, combined with the observation of changes in the microstructure, made it possible to describe the corrosion processes. As the reaction progressed, signals with different characteristics were recorded, indicating aggregate cracking at the initial stage of the reaction, followed by cracking of the cement paste. The results, which were referred to the acoustic activity of reference mortars, confirmed that the reaction of opal aggregate with alkali was mitigated in mortars with lithium nitrate, and the applied acoustic emission method enabled the detection and monitoring of ASR progress.

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