Excavation of High-Stressed Hard Rock with Roadheader

2011 ◽  
Vol 52-54 ◽  
pp. 905-908 ◽  
Author(s):  
Zi Long Zhou ◽  
Xi Bing Li ◽  
Guo Yan Zhao ◽  
Zhi Xiang Liu ◽  
Guang Ju Xu
Keyword(s):  
Hard Rock ◽  
Deep Level ◽  
High Stress ◽  
Structural Instability ◽  
Positive Role ◽  
Particle Aggregate ◽  
Ground Stress ◽  
And Performance ◽  
Drill And Blast ◽  
Stress Work

Drill and blast method becomes unfavorable for deep mining of hard rock. Mechanical excavation with roadheader EBZ160TY was trialed at work face with hard rock and high ground stress. Work procedure and performance of the roadheader were recorded and analyzed. The results showed that, roadheader EBZ160TY, with designed excavating strength of 80 MPa, presented amazingly good performance in hard rock with strength of 148 MPa and consumed less cost compared to drill and blast method. High stress was found to play positive role in improving its working ability. Under the gentle disturbance of roadheader excavation, the high ground stress brings the surrounding rock mass to deform into yield and lets the stress/strain energy transform into fracture energy of rock fragmentation. With the push and rotation of roadheader, structural instability of confined high-stressed particle aggregate other than rock failure by mechanical wearing happens. The results show a good application prospect for roadheader in hard rock excavation especially at deep level.

Recovery-Stress States of Professional Ballet Dancers During Different Phases of a Ballet Season

2021 ◽  
Author(s):  
Jana S. De Wet ◽  
Eileen Africa ◽  
Ranel Venter
Keyword(s):  
Mixed Model ◽  
High Stress ◽  
Recovery Stress ◽  
Total Recovery ◽  
Ballet Dancers ◽  
Training Adaptations ◽  
Stress States ◽  
Classical Ballet ◽  
And Performance ◽  
Negative Training

Ballet dancers are exposed to chronic high training and performance demands that are associated with overtraining syndrome and injury. Balancing high training loads with recovery to reduce the risk of negative training adaptations is critical. Moreover, the recovery-stress states of professional ballet dancers during training phases of a season are largely unknown. Professional dancers (n = 27) from one classical ballet company in South Africa were monitored for two 8-week phases of a ballet season. A recovery-stress questionnaire for Athletes (RESTQ-76 Sport) was completed weekly during the rehearsal phase (P1) and the performance phase (P2), which took place at the start and the end of the ballet season, respectively. Comparisons were calculated between phases, sexes, and levels of performance with a mixed-model ANOVA and between demographic variables with a one-way ANOVA. The performance phase was signified by lower total recovery (TR, p < 0.01) and higher total stress (TS, p < 0.01) for the group. Female dancers had significantly lower recovery scores than male dancers during P2 (p < 0.01). No differences between levels of performance were found. Subscales previously associated with overreaching and injury were identified in certain groups during P2. In conclusion, P2 was a critical period where dancers, especially females, experienced high stress and low recovery. This could increase the risk for injury and negative training adaptations.

Study of Supercapacitors Based on Nanomaterial’s of Novel Architectures

2015 ◽  
Vol 733 ◽  
pp. 680-683
Author(s):  
Ya Rong He
Keyword(s):  
Energy Source ◽  
Electrode Materials ◽  
Discharge Rate ◽  
Structural Instability ◽  
Storage Device ◽  
Design Synthesis ◽  
Energy Devices ◽  
New Energy ◽  
And Performance ◽  
Performance Research

Sustainable exploration and use of energy source depend on discovery of new energy source and development of novel energy devices. As a kind of energy storage device, supercapacitors have many advantages over conventional batteries: high power density, long cycling stability, fast charge-discharge rate and being environment friendly. However, common problems involved with nanomaterials such as bad structural continuity, conglomeration and structural instability have restricted their application in supercapacitors. We have conducted the design, synthesis and performance research of the electrode materials containing. We demonstrate the above composite materials have wide prospect for application in the supercapacitors as well as other similar fields.

The Effect of EDZ on the Migration of Radionuclides in a KBS-3 Type Repository

2003 ◽  
Vol 807 ◽  
Author(s):  
Jorma Autio ◽  
Thomas Hjerpe ◽  
Marja Siitari-Kauppi
Keyword(s):  
Spent Nuclear Fuel ◽  
Hard Rock ◽  
State Of The Art ◽  
Migration Route ◽  
Excavation Damaged Zone ◽  
Tunnel Floor ◽  
Damaged Zone ◽  
Hydraulic Gradients ◽  
Drill And Blast

ABSTRACTThe role of excavation damaged zone (EDZ) in a KBS-3 type repository for spent nuclear fuel depends significantly on the design of the engineered barrier systems such as tunnel backfill since one obvious function of the backfill is to prevent the growth of EDZ. Main results of EDZ studies based on using 14C-PMMA method carried out at Äspö Hard Rock Laboratory in Sweden, and at Research Tunnel at Olkiluoto in Finland by Posiva and SKB in co-operation are presented. The significance of the results is evaluated quantitatively and qualitatively. The EDZ around the deposition hole on migration of radionuclides diffusing out of a waste canister was found unlikely to be a significant migration route in the absence of large hydraulic gradients. According to the study the EDZ caused by state-of-the-art drill and blast excavation adjacent to walls and roof of deposition tunnels was found negligible, however the EDZ adjacent to deposition tunnel floor is evidently more extensive and more significant.

Designing Light Alloys for Fatigue Crack Growth Resistance

2011 ◽  
Vol 690 ◽  
pp. 393-396
Author(s):  
Anastasios G. Gavras ◽  
Diana A. Lados
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
High Stress ◽  
Compact Tension ◽  
Fatigue Crack Growth Resistance ◽  
Reduction Strategies ◽  
Stress Ratios ◽  
And Performance ◽  
Wrought Aluminum

Fatigue crack growthresistance is critical to the design and performance of structural components.This study focuses on understanding the microstructural mechanisms of fatigue crack propagation in commonly used structural materials, cast and wrought aluminum and titanium alloys, with various microstructures resulting from changes in chemistry or heat treatment (A535-F, 6061-T6, and mill- and b-annealed Ti-6Al-4V).Stress ratio effects were evaluated by conducting fatigue crack growth tests on compact tension specimens at low, intermediate, and high stress ratios, R=0.1, 0.5, and 0.7, respectively. Initial flaw size effects were also studied by performing small crack growth tests at R=0.1. Data reduction strategies compensating for closure and Kmax effects on crack growth and design curves will be presented.

scholarly journals Effects of Pairing on the Relationships between Motivation and Task Performance in an Interactive Task

2019 ◽  
Vol 7 (4) ◽  
pp. p451
Author(s):  
Katsuyuki Konno ◽  
Tsutomu Koga ◽  
Atsumi Yamaguchi
Keyword(s):  
Task Performance ◽  
First Year ◽  
Positive Role ◽  
Task Motivation ◽  
Computer Mediated ◽  
Interactive Task ◽  
And Performance ◽  
First Year University ◽  
Pair Work

This study investigates how learners’ own motivational variables are related to task performance and how learners’ task performance is influenced by their partners’ motivational variables in an interactive task. A total of 28 Japanese first year university students engaged in a computer mediated, decision making task, and the number of words produced and turns taken during the task was counted as their task performance. Questionnaires were administered to measure eight motivational dispositions related to the task. Correlation analyses were used to examine the relationships between task motivation and performance. The results showed that (a) learners’ task motivation was positively correlated with task performance, suggesting a positive role of task motivation in performing a task and (b) learners’ task performance was negatively correlated with the interlocutors’ task motivation, except for the highly motivated pairs, which implied limited effects of pair work. This study finally provides some pedagogical and future implications.

scholarly journals Study on stress among software professionals in Madhapur area of Hyderabad, Telangana

2019 ◽  
Vol 6 (9) ◽  
pp. 4062
Author(s):  
Vimala Thomas ◽  
Y. Sai Krishna ◽  
K. J. Kishore Kumar
Keyword(s):  
Perceived Stress ◽  
High Stress ◽  
Working Hours ◽  
Cross Sectional Study ◽  
Perceived Stress Scale ◽  
Cross Sectional ◽  
Stress Scale ◽  
Software Professionals ◽  
Study Participants ◽  
Stress Work

Background: Stress is inescapable part of modern life, where workplace is becoming a volatile stress factory for most employees. Occupational stress/work stress/job stress can occur when there is discrepancy between the demands of the environment/workplace and an individual’s ability to carry out and complete these demands. There is paramount need to address the factors which are leading to stress at the earliest since they are increasing rapidly. The objectives of the study were to determine the levels of stress among software professionals and to determine its association with key socio-demographic variables and with working environment.Methods: A cross sectional study was conducted among software professionals working in Madhapur area of Hyderabad using self-administered, pre-designed and pre-tested questionnaire after taking informed consent. Data was analyzed using MS Excel and Epi Info software.Results: Among the study participants, 71.5% were males and 28.5% were females. Mean age of the study participants was 34.04±7.52 years. Around 45.25% were having low stress, 33.5% moderate stress and only 21.25% had high stress according to perceived stress scale. Significant association was found between stress and age, type of family, marital status, gender and working hours per day.Conclusions: In the study, most of them were having low stress according to perceived stress scale. Females were having high stress compared to males. Software professionals have to be educated on factors which are leading to stress to prevent its adverse effects. 

Prevention Logic of Rock Burst for Brittle Rock under High Geo-Stress

2011 ◽  
Vol 261-263 ◽  
pp. 1484-1488
Author(s):  
Guo Qing Chen ◽  
Guo Shao Su ◽  
Tian Bin Li
Keyword(s):  
Rock Burst ◽  
Prevention And Control ◽  
Hard Rock ◽  
Deep Tunnel ◽  
Working Face ◽  
Numerical Software ◽  
Released Energy ◽  
Ground Stress ◽  
And Control ◽  
Good Agreement

Rock burst hazard is the main problem of hard rock deep tunnel under high ground stress conditions. The prevention logic of prevention and control of rock burst is proposed by combining local energy release rate index based on the brittle Hoek-Brown model. Stress releasing holes are adopted to lead some energy to release actively and eliminate burst potential of rock burst. Supporting opportunity and parameters were studied by contrasting the magnitude of released energy in FLAC3D numerical software, and then the prevention logic of rock burst is presented. Stress releasing holes relieve stress concentration of the working face, transfer the stress to the deep and reduce the risk of rock burst near the working face. At last, the prevention and control of rock burst for sinping II Hydropower tunnel was analyzed, the results are in good agreement with the actual situations. The proposed method could benefit other deep tunnel projects which have brittle failure.

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