The overbroken rock mass of gob areas is made up of broken and accumulated rock blocks compressed to some extent by the overlying strata. The beating pressure of the gob can directly affect the safety of mining fields...The overbroken rock mass of gob areas is made up of broken and accumulated rock blocks compressed to some extent by the overlying strata. The beating pressure of the gob can directly affect the safety of mining fields, formarion of road retained along the next goaf and seepage of water and methane through the gob. In this paper, the software RFPA＇2000 is used to construct numerical models. Especially the Euler method of control volume is proposed to solve the simulation difficulty arising from plastically finite deformations. The results show that three characteristic regions occurred in the gob area： （1） a naturally accumulated region, 0-10 m away from unbroken surrounding rock walls, where the beating pressure is nearly zero; （2） an overcompacted region, 10-20 m away from unbroken walls, where the beating pressure results in the maximum value of the gob area; （3） a stable compaction region, more than 20 m away from unbroken walls and occupying absolutely most of the gob area, where the beating pressures show basically no differences. Such a characteristic can exolain the easy-seeoaged “O”-ring phenomena around mining fields very well.展开更多
Bump foil bearings without nominal radial clearance were analyzed. An air film thickness model and a bearing theoretical analytical model were developed accounting for air compressibility and foil deformation. To anal...Bump foil bearings without nominal radial clearance were analyzed. An air film thickness model and a bearing theoretical analytical model were developed accounting for air compressibility and foil deformation. To analyze hydrodynamic characteristics of bump foil bearings with different operating eccentricities, the air film thickness equation and Reynolds equation were coupled through pressure and solved by Newton-Raphson Method (NRM) and Finite Difference Method (FDM). The characteristics of an bump foil bearing model were discussed including load carrying capacity, film thickness and pressure distributions. The results of simulation show that bump foil bearing without nominal radial clearance can provide better stability and greater load capacity. This numerical analytical method also reveals a good convergence in numerical calculation.展开更多
In order to study the distribution of lateral floor abutment pressure at a working face,we first used elasticity theory to establish a distribution model of lateral floor abutment pressure and then analysed its distri...In order to study the distribution of lateral floor abutment pressure at a working face,we first used elasticity theory to establish a distribution model of lateral floor abutment pressure and then analysed its distribution.Second,we established a three-dimensional numerical simulation model of the Haizi Coal Mine No.86 mining area by using FLAC^（3D）（ITASCA Consulting Group） software.We investigated the distribution of lateral floor abutment pressure of a stope,which indicated that the position of abutment pressure peak varies at different floor depths.We then determined the rational reinforcement range of a floor roadway,based on the conclusion reached earlier.Finally,we used our conclusions in support of the No.86 mining area crossing-roadway.The supported crossing-roadway remained stable when mining the upper workface,which validates the accuracy of our numerical simulation and provides a future reference for the support of span-roadways under similar conditions.展开更多
Water shows anomalies different from most of other materials.Different sceniaros have been proposed to explain water anomalies,among which the liquid-liquid phase transition(LLPT)is the most discussed one.It attribute...Water shows anomalies different from most of other materials.Different sceniaros have been proposed to explain water anomalies,among which the liquid-liquid phase transition(LLPT)is the most discussed one.It attributes water anomalies to the existence of a hypothesized liquid-liquid critical point(LLCP)buried deep in the supercooled region.We briefly review the recent experimental and theoretical progresses on the study of the LLPT in water.These studies include the discussion on the existence of the first order LLPT in supercooled water and the detection of liquid-liquid critical point.Simulational results of different water models for LLPT and the experimental evidence in confined water are also discussed.展开更多
基金Projects 2005CB221502 supported by the Vital Foundational 973 Program of China, 50225414 by the National Outstanding Youth Foundation,20040350222 by China Postdoctoral Science FoundationBK 2004033 by Jiangsu Natural Science Foundation
文摘The overbroken rock mass of gob areas is made up of broken and accumulated rock blocks compressed to some extent by the overlying strata. The beating pressure of the gob can directly affect the safety of mining fields, formarion of road retained along the next goaf and seepage of water and methane through the gob. In this paper, the software RFPA＇2000 is used to construct numerical models. Especially the Euler method of control volume is proposed to solve the simulation difficulty arising from plastically finite deformations. The results show that three characteristic regions occurred in the gob area： （1） a naturally accumulated region, 0-10 m away from unbroken surrounding rock walls, where the beating pressure is nearly zero; （2） an overcompacted region, 10-20 m away from unbroken walls, where the beating pressure results in the maximum value of the gob area; （3） a stable compaction region, more than 20 m away from unbroken walls and occupying absolutely most of the gob area, where the beating pressures show basically no differences. Such a characteristic can exolain the easy-seeoaged “O”-ring phenomena around mining fields very well.
文摘Bump foil bearings without nominal radial clearance were analyzed. An air film thickness model and a bearing theoretical analytical model were developed accounting for air compressibility and foil deformation. To analyze hydrodynamic characteristics of bump foil bearings with different operating eccentricities, the air film thickness equation and Reynolds equation were coupled through pressure and solved by Newton-Raphson Method (NRM) and Finite Difference Method (FDM). The characteristics of an bump foil bearing model were discussed including load carrying capacity, film thickness and pressure distributions. The results of simulation show that bump foil bearing without nominal radial clearance can provide better stability and greater load capacity. This numerical analytical method also reveals a good convergence in numerical calculation.
基金supported by the National Basic Research Program of China(No.2010CB226805)the National Natural Science Foundation of China(Nos.50874103 and 50974115)+1 种基金the Natural Science Foundation of Jiangsu Province(No.KB2008135)the State Key Laboratory Fund(No.SKLGDUEK0905)
文摘In order to study the distribution of lateral floor abutment pressure at a working face,we first used elasticity theory to establish a distribution model of lateral floor abutment pressure and then analysed its distribution.Second,we established a three-dimensional numerical simulation model of the Haizi Coal Mine No.86 mining area by using FLAC^（3D）（ITASCA Consulting Group） software.We investigated the distribution of lateral floor abutment pressure of a stope,which indicated that the position of abutment pressure peak varies at different floor depths.We then determined the rational reinforcement range of a floor roadway,based on the conclusion reached earlier.Finally,we used our conclusions in support of the No.86 mining area crossing-roadway.The supported crossing-roadway remained stable when mining the upper workface,which validates the accuracy of our numerical simulation and provides a future reference for the support of span-roadways under similar conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.11290162/A040106,10974238,11274012,91021007and 11174006)the National Basic Research Program of China(GrantNo.2012CB921404)
文摘Water shows anomalies different from most of other materials.Different sceniaros have been proposed to explain water anomalies,among which the liquid-liquid phase transition(LLPT)is the most discussed one.It attributes water anomalies to the existence of a hypothesized liquid-liquid critical point(LLCP)buried deep in the supercooled region.We briefly review the recent experimental and theoretical progresses on the study of the LLPT in water.These studies include the discussion on the existence of the first order LLPT in supercooled water and the detection of liquid-liquid critical point.Simulational results of different water models for LLPT and the experimental evidence in confined water are also discussed.
