DYNA Numerical Experiment on Long-Term Stability of Strip Pillar in Deep Mine

2011 ◽  
Vol 217-218 ◽  
pp. 1520-1524
Author(s):  
Chun Qiu Wang ◽  
Shi Bin Gu ◽  
Zhong Ju Wei ◽  
Bo Li ◽  
Shao Jie Chen
Keyword(s):  
Stable State ◽  
Support Effect ◽  
Test Results ◽  
Deep Mine ◽  
Long Term Stability ◽  
Creep Stress ◽  
Working Face ◽  
Stress And Deformation ◽  
Overlying Strata

The creep test of the No. 3 coal seam of Daizhuang Coal Mine is carried. Based on the experiment results, the creep support effect of deep pillar is analyzed with LS-DYNA. The results show that the circumferential initial creep stress of the tested coal is 3.061MPa and the circumferential initial creep stress is far below the axial initial creep stress which is 7.020MPa. In addition, the creep strength is 9.3266MPa and the creep coefficient is 0.6472. According to the test results, the creep support effect of deep strip pillar can be simulated excellently with LS-DYNA. Stress and deformation in simulated strip pillar show evident rheology. Many changes will take place in the stable situation of pillar after the working face mining. Under the effect of the overlying strata, this pillar turns into steady creep state after 15~16 months, then the pillar is able to maintain long-term stable state.

scholarly journals Novel Application of the Roof-Cutting-Type Gob-Side Entry Retaining in Coal Mine

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Jiong Wang ◽  
Wenfei Li ◽  
Daoyong Zhu ◽  
Weili Gong ◽  
Yi Su
Keyword(s):  
Stable State ◽  
Stress Evolution ◽  
Coal Seams ◽  
Working Face ◽  
Mining Conditions ◽  
Support Resistance ◽  
Stress And Deformation ◽  
Cutting Height ◽  
Roof Deformation ◽  
Overlying Strata

In this study, the roof-cutting-type gob-side entry retaining is introduced, and its application in medium-thickness coal seams is studied. Based on the analysis of the construction procedure and principle, the mechanical model of the retained roadway structure and cantilever beam formed by roof cutting was established, and the support resistance and roof deformation were obtained. In addition, through technological design analysis and numerical simulation, the parameters of roof cutting were determined. The roof-cutting height and angle were designed to be 9 m and 15°, respectively. Flac3 D was used to analyze the stress evolution law under different mining conditions. The stress on the integrated coal side and roof subsidence was lower when the roof-cutting height was 8∼10 m and the cutting angle was 15°. Through field monitoring, the roof pressure, gob-side lateral gangue retaining pressure, anchor cable stress, and deformation of the surrounding rock eventually reached a stable state. This indicates that the roof cutting can effectively cut down the overlying strata over the gob and form a stable entry structure to meet the requirements of the next working face.

The Selection and Application of Filling Material Based on Long-Term Strength of Backfill Body

2011 ◽  
Vol 239-242 ◽  
pp. 3156-3160
Author(s):  
Bao Jie Fu ◽  
Min Tu
Keyword(s):  
High Stress ◽  
Filling Material ◽  
Term Strength ◽  
Exponential Relationship ◽  
Rock Body ◽  
Deep Mine ◽  
Long Term Stability ◽  
Working Face ◽  
Support Resistance

High stress makes backfill body present the rheological properties in deep mine. This paper first uses RRTS-ⅢA to carry on creep test of specimen in different proportion, according to ε-t curves under different load levels to determine the specimen’s long-term strength, based on the exponential relationship of rock block and rock body, the long-term compressive strength is derived, combining with concrete parameters of working face, mixture ratios of filling material which meet long-term stability are selected, while analyzing the support resistance of backfill body. The results show that this design can effectively avoid the rheological instability of backfill body.

Stability Analysis of Jinghua Gypsum Mine Golf in Jingmen City

2014 ◽  
Vol 580-583 ◽  
pp. 324-328
Author(s):  
Cong Xin Chen ◽  
Kai Zong Xia ◽  
Yuan Bin Dong ◽  
Xiu Min Liu ◽  
Ping Lu Huang
Keyword(s):  
Large Range ◽  
Underground Mining ◽  
Stable State ◽  
Long Term Stability ◽  
Covering Layer ◽  
Small Column ◽  
Short Period ◽  
The Stability ◽  
Overlying Strata

According to golf’s distribution and occurrence situation of Jinghua Gypsum Mine circumstances in Jingmen city, The golf is divided into general golf, filling golf, then the stability of column and covering layer of the two kinds of golf are analysed. It is shown that: For the general golf, A large range of column is stable within a relatively short period of time in the process of underground mining. it will be unstable for local small column because of it was bore weight of overlying strata. After the column was soaked, its strength will be greatly reduced, and the long term stability of column will not be guarantee. Complementary, the covering layer is basically critical stable state; For the filling golf, A large range of column is stable, and the covering layer is also basically critical stable state. It can promote the control of mining disaster and the protection of ecological environment and similar engineering with a high theoretical and practical value.

scholarly journals Evaluating Long-Term Strength and Time to Failure of Sandstone with Different Initial Damage

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Rongbin Hou ◽  
Yanke Shi ◽  
Leige Xu ◽  
Jinwei Fu ◽  
Kai Zhang
Keyword(s):  
Failure Time ◽  
Term Strength ◽  
Steady Creep ◽  
Creep Failure ◽  
Damage State ◽  
Term Stability ◽  
Long Term Stability ◽  
Creep Stress ◽  
Initial Damage

Long-term strength (LTS) of rock materials is important for the long-term stability analysis and the failure prediction of structures in rock engineering. Numerous studies have been carried out on the LTS for various kinds of rock; however, the effects of initial damage on the LTS and creep failure time of rock have not been conducted. In the present study, the creep experiment with controllable initial damage state of rock was designed. Then, the LTS of rock specimens with different initial damage was determined by four methods (i.e., the isochronous stress-strain curve method, the steady creep discriminated method, the volumetric strain inflexion point determined method, and the intersection of the steady creep rate method). The results show that, with the increase in the initial damage, the LTS of rock decreases and the relationship between the initial damage and the LTS of rock can be described as a linear function. Finally, an evaluation method for predicting the creep failure time of rock under a single stress level was proposed. In addition, the creep failure time of rock with different initial damage under different creep stress levels was obtained by the method. The results indicate that both the initial damage and the creep stress levels have a great influence on creep failure time, i.e., greater initial damage or creep stress leads to a shorter period for rock failure. Thus, for analyzing the long-term stability of rock mass structure, not only the influence of in situ stress but also the initial damage state of the surrounding rock should be considered.

Long-term stability study of drug products and out-of-specification test results

2011 ◽  
Vol 16 (12) ◽  
pp. 615-622 ◽  
Author(s):  
Ilya Kuselman ◽  
Ilana Schumacher ◽  
Francesca Pennecchi ◽  
Cathy Burns ◽  
Aleš Fajgelj ◽  
...  
Keyword(s):  
Stability Study ◽  
Test Results ◽  
Specification Test ◽  
Term Stability ◽  
Drug Products ◽  
Long Term Stability

Improve Stability of Dicalcium Silicate/Zirconia Composite Coatings by Post-Spraying Heat Treatment

2005 ◽  
Vol 107 ◽  
pp. 141-144 ◽  
Author(s):  
Youtao Xie ◽  
Paul K. Chu ◽  
Xuan Yong Liu ◽  
Chuan Xian Ding
Keyword(s):  
Heat Treatment ◽  
Composite Coatings ◽  
Immersion Test ◽  
Dicalcium Silicate ◽  
Test Results ◽  
Long Term Stability ◽  
The Stability ◽  
Plasma Sprayed ◽  
Sprayed Coatings

The long-term stability of plasma-sprayed dicalcium silicate (C2S) composite coatings is determined by the phase composition, crystallinity, and other properties. Zirconia reinforcement and post-spraying heat treatment are applied to C2S coatings simultaneously in this work. The stability of the coating increases evidently by reinforcement with 70wt% zirconia and heat treatment at 800oC for 4 hours. SEM reveals that the smooth glassy surface of the as-sprayed coatings is replaced by randomly dispersed crystals. Tris-HCl immersion test results show that the dissolution rate of the composite coatings decreases after the heat treatment.

Numerical Simulation Study on Setting Stopping Line of Working Face in Shuguang Mine

2014 ◽  
Vol 580-583 ◽  
pp. 2554-2557
Author(s):  
Hua Jun Xue ◽  
Jun Chen ◽  
Bo Liu ◽  
Jie Kong ◽  
Zhi Jun Hao
Keyword(s):  
Numerical Simulation ◽  
Recovery Rate ◽  
Coal Pillar ◽  
Economic Benefits ◽  
Surrounding Rock ◽  
Long Term Stability ◽  
Rock Stability ◽  
Working Face ◽  
Stopping Line

The surrounding rock deformation of pedestrian roadway was serious under the influence of the working face. And it has affected the safety and normal use of roadway. To ensure the long-term stability of the pedestrian roadway surrounding rock and increase the coal recovery rate of working face, the paper studied the position of stopping line of 1203 working face by numerical simulation. The results show that setting 115m wide of security coal pillar between 1203 working face and pedestrian roadway that the area of stress concentration near the working face has less effect on the pedestrian roadway could better control the surrounding rock stability of the pedestrian roadway and meet the need of the long-term normal production use. It narrows the width of security coal pillar, increase the coal resources recovery rate and achieve the better economic benefits.

Analysis on Key Strata’s Subsidence in Paste-Like Filling Face

2012 ◽  
Vol 524-527 ◽  
pp. 525-530
Author(s):  
Jian Hao ◽  
Yong Kui Shi ◽  
Kuan Liu
Keyword(s):  
Lower Layer ◽  
Early Stage ◽  
Stable State ◽  
Key Strata ◽  
Primary Stress ◽  
Ground Pressure ◽  
Working Face ◽  
High Layer ◽  
Supporting Force ◽  
Overlying Strata

Using theoretical analysis and actually test research to analyze stress condition of filling body and average subsidence of the key strata, analysis shows that the average vertical stress in filling body was about 15Mpa when entering into stable state, which is equal to the primary stress, 13.75Mpa. The filling body could tighten the roof well and the filling body can support full weight of the overlying strata. The limestone, thickness of 5.3m, above the 81006 working face is the key strata of mining stope. On the interaction between ground pressure and the supporting force of filling body, the whole key strata subsided about 98.64mm on average theoretically, as the height meter monitored, the subsidence value of key strata was 108mm on average, conforms to the theoretical value, which proves the filling effect was good. At the early stage after filling, the roof subsided relatively faster as the filling body had not coagulated completely and the strength was lower. At this stage the roof was not tightened enough with the filling body, it subsided relatively faster in some certain limited space. After a while, the limestone, the key strata of mining stope, became stable for a short term, and then it would continue to subside until being stable under the disturbance of the high layer, because the movement of lower layer created some space for high layer.

scholarly journals N-cadherin mediates plasticity-induced long-term spine stabilization

2010 ◽  
Vol 189 (3) ◽  
pp. 589-600 ◽  
Author(s):  
Pablo Mendez ◽  
Mathias De Roo ◽  
Lorenzo Poglia ◽  
Paul Klauser ◽  
Dominique Muller
Keyword(s):  
Molecular Mechanisms ◽  
Stable State ◽  
Long Term Potentiation ◽  
Excitatory Synapses ◽  
Loss Of Function ◽  
Long Term Stability ◽  
Spine Stabilization ◽  
Term Potentiation ◽  
Dynamic Structures

Excitatory synapses on dendritic spines are dynamic structures whose stability can vary from hours to years. However, the molecular mechanisms regulating spine persistence remain essentially unknown. In this study, we combined repetitive imaging and a gain and loss of function approach to test the role of N-cadherin (NCad) on spine stability. Expression of mutant but not wild-type NCad promotes spine turnover and formation of immature spines and interferes with the stabilization of new spines. Similarly, the long-term stability of preexisting spines is reduced when mutant NCad is expressed but enhanced in spines expressing NCad-EGFP clusters. Activity and long-term potentiation (LTP) induction selectively promote formation of NCad clusters in stimulated spines. Although activity-mediated expression of NCad-EGFP switches synapses to a highly stable state, expression of mutant NCad or short hairpin RNA–mediated knockdown of NCad prevents LTP-induced long-term stabilization of synapses. These results identify NCad as a key molecular component regulating long-term synapse persistence.

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