scholarly journals Failure Mechanisms of Rheological Coal Roadway

2020 ◽  
Vol 12 (7) ◽  
pp. 2885 ◽  
Author(s):  
Yuantian Sun ◽  
Guichen Li ◽  
Junfei Zhang ◽  
Jiahui Xu
Keyword(s):  
Failure Mechanism ◽  
Coal Mass ◽  
Soft Coal ◽  
Coal Roadway ◽  
Roadway Stability ◽  
Deformation Properties ◽  
Underground Coal Mines ◽  
Negative Effect ◽  
Deep Underground

The roadway instability in deep underground conditions has attracted constant concerns in recent years, as it seriously affects the efficiency of coal mining and the safety of personnel. The large rheological deformations normally occur in deep roadway with soft coal mass. However, the failure mechanism of such roadways is still not clear. In this study, based on a typical soft coal roadway in the field, the in-situ measurements and rock mass properties were obtained. The rheological deformation of that roadway was revealed. Then a time-dependent 3D numerical model was established and verified. Based on the verified model, the deformation properties and evolutionary failure mechanism of deep coal roadway were investigated in detail. The results showed that the deformation of the soft coal roadway demonstrated rheological behavior and the applied support structures failed completely. After roadway excavation, the maximum and minimum stresses around the roadway deteriorated gradually with the increase of time. The failure zones in soft coal mass expanded increasingly over time, which had a negative effect on roadway stability in the long-term. According to the findings, helpful suggestions were further presented to control the rheological deformation in the roadway. This research systematically reveals the instability mechanism of the deep coal roadway and provides some strategies for maintaining roadway stability, which can significantly promote the sustainability of mining in deep underground coal mines.

scholarly journals Experiment and Application of Coalcrete on Roadway Stability: A Comparative Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Guichen Li ◽  
Yuantian Sun ◽  
Junfei Zhang ◽  
Qianjin Zhang ◽  
Changlun Sun ◽  
...  
Keyword(s):  
Coal Mass ◽  
Underground Mines ◽  
Support Structures ◽  
Tunnel Excavation ◽  
Deformation And Failure ◽  
Soft Coal ◽  
Jet Grouting ◽  
Roadway Stability ◽  
Deep Underground ◽  
The Stability

Improving roadway stability in deep underground mines is quite challenging, as the conventional support structures easily fail. Roadway collapse and large deformation occur just several months after tunnel excavation. In this study, a relatively new prereinforcement technique, the jet grouting (JG), is introduced to improve roadway stability. A field test was performed for evaluating the practicability and applicability of JG in soft coal mass. A series of laboratory tests were conducted to assess the properties of coalcrete (coal-grout after JG treatment). A two-dimensional numerical model was established for validating the input parameters. Based on the verified model, three JG support cases for roadway were modeled and compared with a conventional support case, namely, the currently used support in this mine “rock bolts + U-shaped steel set + shotcrete.” The results show that the proposed prereinforced JG support structures can considerably control the deformation and failure zone of the roadway and improve the bearing capacity of coal mass. The mechanism of maintaining roadway stability using JG techniques is further revealed. Some suggestions are further presented to improve the stability of the jet-grouted roadway.

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 Study on the Failure Mechanism for Coal Roadway Stability in Jointed Rock Mass Due to the Excavation Unloading Effect

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2515 ◽  
Author(s):  
Eryu Wang ◽  
Guangbo Chen ◽  
Xiaojie Yang ◽  
Guofeng Zhang ◽  
Wenbin Guo
Keyword(s):  
Rock Mass ◽  
Numerical Model ◽  
Crack Propagation ◽  
Failure Mechanism ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Coal Roadway ◽  
Roadway Stability ◽  
Rock Structure

Aiming at the large deformation instability problem caused by the excavation unloading of a coal roadway in deep-buried slowly inclined jointed rock mass, the geomechanical parameters and deformation failure characteristics of an engineering geomechanical model were investigated. The in-situ stress state of the model was measured with the stress relief method. The geological and mechanical properties of roadway surrounding rock were described. The surrounding rock structure was revealed with the electron microscopy scanning method, micro-fractures and randomly distributed joints highly developed in roadway surrounding rock. Field investigation and monitoring indicated the cross-section of roadway surrounding rock shrank continuously and the deformation distribution was obviously asymmetric. Shotcrete spalling and cable broken failures frequently occurred in the middle and ride side of roof and right rib. Based on the geomechanical conditions of the coal roadway, a discrete element numerical model of coal roadway in gently inclined jointed rock mass was established. The parameters of rock mass in the numerical model were calibrated. The model ran in unsupported condition to restore the evolution process of stress, crack propagation and deformation in roadway surrounding rock due to gradual deviatoric stress release caused by excavation. On this basis, the space-time evolution characteristics and law of stress, crack propagation and deformation were obtained and then the asymmetric large fragmentation and dilatation deformation failure mechanism of roadway surrounding rock in deep-buried slowly inclined jointed rock mass was revealed. The failure reasons of the support structure were analyzed, and the relevant support principles were proposed. The research results can provide scientific references for the stability control of roadways excavated in jointed rock mass.

Infrastructure mortgage in Russia: Opportunities and prospects

2019 ◽  
pp. 114-133
Author(s):  
G. I. Idrisov ◽  
Y. Yu. Ponomarev
Keyword(s):  
Federal Government ◽  
Public Debt ◽  
Budget Deficit ◽  
Expert Assessment ◽  
Inflation Expectations ◽  
Direct Impact ◽  
Long Run ◽  
Gdp Growth Rate ◽  
Negative Effect

The article shows that depending on the goals pursued by the federal government and the available interbudgetary tools a different design of infrastructure mortgage is preferable. Three variants of such mortgage in Russia are proposed, each of which is better suited for certain types of projects and uses different forms of subsidies. According to our expert assessment the active use of infrastructure mortgage in Russia can increase the average annual GDP growth rate by 0.5 p. p. on the horizon of 5—7 years. In the long run the growth of infrastructure financing through the use of infrastructure mortgage could increase long-term economic growth by 0.9 p. p., which in 20—30 years can add 20—30% of GDP to the economy. However, the change in the structure of budget expenditures in the absence of an increase in the budget deficit and public debt will cause no direct impact on monetary policy. The increase in the deficit and the build-up of public debt will have a negative effect on inflation expectations, which will require monetary tightening for a longer time to stabilize them.

The depressing (negative) effect of oestradiol benzoate on the in vitro secretion of LH and FSH by the pituitary gland of the LRH-pretreated long-term ovariectomized rat changes into the augmentative (positive) effect after discontinuation of the LRH-pretreatment

1985 ◽  
Vol 110 (3) ◽  
pp. 329-337 ◽  
Author(s):  
G. A. Schuiling ◽  
H. Moes ◽  
T. R. Koiter
Keyword(s):  
Depressing Effect ◽  
Ovx Rats ◽  
Gonadotrophin Secretion ◽  
Oestradiol Benzoate ◽  
Negative Effect ◽  
Positive Effect ◽  
Perifusion System

Abstract. The effect of pretreatment in vivo with oestradiol benzoate on in vitro secretion of LH and FSH was studied in long-term ovariectomized (OVX) rats both at the end of a 5-day continuous in vivo pretreatment with LRH and 4-days after cessation of such LRH pretreatment. Rats were on day 0 sc implanted with osmotic minipumps which released LRH at the rate of 250 ng/h. Control rats were implanted with a piece of silicone elastomer with the dimensions of a minipump. On days 2 and 4 the rats were injected with either 3 μg EB or with oil. On day 5 part of the rats were decapitated and the in vitro autonomous (i.e. non-LRH-stimulated) and 'supra-maximally' LRHstimulated release of LH and FSH was studied using a perifusion system. From other rats the minipumps were removed on day 5 and perifusion was performed on day 9. On the 5th day of the in vivo LRH pretreatment the pituitary LH/FSH stores were partially depleted; the pituitaries of the EB-treated rats more so than those of the oil-injected rats. EB alone had no significant effect on the content of the pituitary LH- and FSH stores. On day 9, i.e. 4 days after removal of the minipumps, the pituitary LH and FSH contents had increased in both the oil- and the EB injected rats, but had not yet recovered to control values. In rats not subjected to the 5-days pretreatment with LRH EB had a positive effect on the supra-maximally LRH-stimulated secretion of LH and FSH as well as on the non-stimulated secretion of LH. EB had no effect on the non-stimulated secretion of FSH. After 5 days of in vivo pretreatment with LRH only, the in vitro non-stimulated and supra-maximally LRH-stimulated secretion of both LH and FSH were strongly impaired, the effect correlating well with the LRH-induced depletion of the pituitary LH/FSH stores. In such LRH-pretreated rats EB had on day 5 a negative effect on the (already depressed) LRH-stimulated secretion of LH (not on that of FSH). EB had no effect on the non-stimulated LH/FSH secretion. It could be demonstrated that the negative effect of the combined LRH/EB pretreatment was mainly due to the depressing effect of this treatment on the pituitary LH and FSH stores: the effect of oestradiol on the pituitary LRH-responsiveness (release as related to pituitary gonadotrophin content) remained positive. In LRH-pretreated rats, however, this positive effect of EB was smaller than in rats not pretreated with LRH. Four days after removal of the minipumps there was again a positive effect of EB on the LRH-stimulated secretion of LH and FSH as well as on the non-stimulated secretion of LH. The positive effect of EB on the pituitary LRH-responsiveness was as strong as in rats which had not been exposed to exogenous LRH. The non-stimulated secretion of FSH was again not affected by EB. The results demonstrate that the effect of EB on the oestrogen-sensitive components of gonadotrophin secretion consists of two components: an effect on the pituitary LRH-responsiveness proper, and an effect on the pituitary LH/FSH stores. The magnitude of the effect of EB on the LRH-responsiveness is LRH dependent: it is very weak (almost zero) in LRH-pretreated rats, but strong in rats not exposed to LRH as well as in rats of which the LRH-pretreatment was stopped 4 days previously. Similarly, the effect of EB on the pituitary LH and FSH stores is LRH-dependent: in the absence of LRH, EB has no influence on the contents of these stores, but EB can potentiate the depleting effect of LRH on the LH/FSH-stores. Also this effect disappear after cessation of the LRH-pretreatment.

Research on the Economic Organization Environmental Impact

2017 ◽  
Vol 68 (3) ◽  
pp. 599-601
Author(s):  
Dan Paul Stefanescu ◽  
Oana Roxana Chivu ◽  
Claudiu Babis ◽  
Augustin Semenescu ◽  
Alina Gligor
Keyword(s):  
Economic Activity ◽  
Economic Organization ◽  
Economic Activities ◽  
Environmental Implications ◽  
Minimal Impact ◽  
Wide Range ◽  
Material Environment ◽  
Negative Effect ◽  
Harmful Effects

Any economic activity carried out by an organization, can generate a wide range of environmental implications. Particularly important, must be considered the activities that have a significant negative effect on the environment, meaning those which pollute. Being known the harmful effects of pollution on the human health, the paper presents two models of utmost importance, one of the material environment-economy interactions balance and the other of the material flows between environmental factors and socio-economic activities. The study of these models enable specific conditions that must be satisfied for the economic processes friendly coexist to the environment for long term, meaning to have a minimal impact in that the residues resulting from the economic activity of the organization to be as less harmful to the environment.

scholarly journals Long-Term Cryopreservation Does Not Affect Quality of Peripheral Blood Stem Cell Grafts: A Comparative Study of Native, Short-Term and Long-Term Cryopreserved Haematopoietic Stem Cells

2021 ◽  
Vol 30 ◽  
pp. 096368972110360
Author(s):  
Daniel Lysak ◽  
Michaela Brychtová ◽  
Martin Leba ◽  
Miroslava Čedíková ◽  
Daniel Georgiev ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Statistical Significance ◽  
Extended Period ◽  
High Dose ◽  
Atp Production ◽  
Cd34 Cells ◽  
Negative Effect

Cryopreserved haematopoietic progenitor cells are used to restore autologous haematopoiesis after high dose chemotherapy. Although the cells are routinely stored for a long period, concerns remain about the maximum storage time and the possible negative effect of storage on their potency. We evaluated the effect of cryopreservation on the quality of peripheral stem cell grafts stored for a short (3 months) and a long (10 years) period and we compared it to native products.The viability of CD34+ cells remained unaffected during storage, the apoptotic cells were represented up to 10% and did not differ between groups. The clonogenic activity measured by ATP production has decreased with the length of storage (ATP/cell 1.28 nM in native vs. 0.63 in long term stored products, P < 0.05). Only borderline changes without statistical significance were detected when examining mitochondrial and aldehyde dehydrogenase metabolic activity and intracellular pH, showing their good preservation during cell storage. Our experience demonstrates that cryostorage has no major negative effect on stem cell quality and potency, and therefore autologous stem cells can be stored safely for an extended period of at least 10 years. On the other hand, long term storage for 10 years and longer may lead to mild reduction of clonogenic capacity. When a sufficient dose of stem cells is infused, these changes will not have a clinical impact. However, in products stored beyond 10 years, especially when a low number of CD34+ cells is available, the quality of stem cell graft should be verified before infusion using the appropriate potency assays.

scholarly journals Long-term subjective memory after electroconvulsive therapy

BJPsych Open ◽  
2020 ◽  
Vol 6 (2) ◽  
Author(s):  
Robert Sigström ◽  
Axel Nordenskjöld ◽  
Anders Juréus ◽  
Caitlin Clements ◽  
Erik Joas ◽  
...  
Keyword(s):  
Electroconvulsive Therapy ◽  
Memory Impairment ◽  
Rating Scale ◽  
Final Analysis ◽  
Negative Effects ◽  
Subjective Memory ◽  
Subjective Memory Impairment ◽  
Negative Effect ◽  
Negative Expectations

Background There have been reports of long-term subjective memory worsening after electroconvulsive therapy (ECT). Aims To study the prevalence and risk factors of long-term subjective memory worsening among patients receiving ECT in routine clinical practice. Method Patients (n = 535, of whom 277 were included in the final analysis) were recruited from eight Swedish hospitals. Participants' subjective memory impairment was assessed before ECT and a median of 73 days after ECT using the memory item from the Comprehensive Psychopathological Rating Scale. Participants also rated their pre-ECT expectations and post-ECT evaluations of the effect of ECT on memory on a 7-point scale. We used ordinal regression to identify variables associated with subjective memory worsening and negative evaluations of the effect of ECT on memory. Results Comparisons of pre- and post-ECT assessments showed that subjective memory worsened in 16.2% of participants, remained unchanged in 52.3% and improved in 31.4%. By contrast, when asked to evaluate the effect of ECT on memory after treatment 54.6% reported a negative effect. Subjective memory worsening was associated with negative expectations before ECT, younger age and shorter duration of follow-up. Conclusions Although subjective memory improved more often than it worsened when assessed before and after ECT, a majority of patients reported that ECT had negative effects on their memory when retrospectively asked how ECT had affected it. This might suggest that some patients attribute pre-existing subjective memory impairment to ECT. Clinicians should be aware that negative expectations are associated with subjective worsening of memory after ECT.

scholarly journals Can communication with social robots influence how children develop empathy? Best-evidence synthesis

AI & Society ◽  
2021 ◽  
Author(s):  
Ekaterina Pashevich
Keyword(s):  
Emotional Development ◽  
Evidence Synthesis ◽  
Social Robots ◽  
Human Robot Interaction ◽  
Emotional Engagement ◽  
Social And Emotional Development ◽  
Social And Emotional ◽  
Best Evidence Synthesis ◽  
Negative Effect

AbstractSocial robots are gradually entering children’s lives in a period when children learn about social relationships and exercise prosocial behaviors with parents, peers, and teachers. Designed for long-term emotional engagement and to take the roles of friends, teachers, and babysitters, such robots have the potential to influence how children develop empathy. This article presents a review of the literature (2010–2020) in the fields of human–robot interaction (HRI), psychology, neuropsychology, and roboethics, discussing the potential impact of communication with social robots on children’s social and emotional development. The critical analysis of evidence behind these discussions shows that, although robots theoretically have high chances of influencing the development of empathy in children, depending on their design, intensity, and context of use, there is no certainty about the kind of effect they might have. Most of the analyzed studies, which showed the ability of robots to improve empathy levels in children, were not longitudinal, while the studies observing and arguing for the negative effect of robots on children’s empathy were either purely theoretical or dependent on the specific design of the robot and the situation. Therefore, there is a need for studies investigating the effects on children’s social and emotional development of long-term regular and consistent communication with robots of various designs and in different situations.

scholarly journals Examining Eurozone Crisis and Unemployment Relationship Using Var Models

2013 ◽  
Vol 60 (2) ◽  
pp. 85-92
Author(s):  
Dimitrios Dapontas
Keyword(s):  
Government Spending ◽  
Eurozone Crisis ◽  
Var Models ◽  
Monthly Data ◽  
Distributed Lag ◽  
Distributed Lag Model ◽  
Negative Effect ◽  
Lag Model ◽  
The Relationship

Abstract This work examines the relationship between the Eurozone crisis and unemployment. We deploy distributed lag model using two binary (Crisis and crisis in another country) along with three (Government spending to GDP, Labor freedom, and urbanization) variables working as a long term factors applied on a six countries set (Cyprus, Greece, Ireland, Italy, Portugal and Spain respectively) spanning the period January1995-May 2012 in order to explain the unemployment change using VAR models on monthly data in contrast to longer frequency analyses. This innovative approach is determining the optimal lag length between unemployment and crises determining the time between turbulence and its effect to unemployment. The results show that optimal lag varies among two and eight months. Two variables seem to have negative effect on unemployment (Government spending to GDP, labor freedom) and one positive (urbanization).

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