The toxicity of asbestos has been constantly an active research topic.Although asbestos has lots of advantages owing to its stable physicochemical properties and economic characteristics,nations enforce policies prohi...The toxicity of asbestos has been constantly an active research topic.Although asbestos has lots of advantages owing to its stable physicochemical properties and economic characteristics,nations enforce policies prohibiting or limiting its use because of its critical impact on human health.Especially in Korea 96% of imported asbestos are slate construction materials and with the influence of Saemaul movement,thatched roofs have been drastically replaced with slate roofs.Efforts to know the distribution characteristics of extensively used asbestos cement slates and to find out the removal method that suits the distribution characteristics are still in an insufficient state.The purpose of this work was to probe into the distribution of asbestos cement slate buildings in Korea and provide basic data of distribution characteristics for policy making in which consideration of the differences between rural and urban regions is necessary based on findings of the studies so far.It is considered helpful in many ways to solving asbestos cement slate related problems in countries where asbestos usage is increasing even after the 2000s including China.展开更多
High geothermal temperatures appear to be unfavorable for the construction of tunnels in slate rocks with high overburden. To investigate the mechanical characteristics of slates at various levels of geothermal temper...High geothermal temperatures appear to be unfavorable for the construction of tunnels in slate rocks with high overburden. To investigate the mechanical characteristics of slates at various levels of geothermal temperature, conventional triaxial compression tests at different levels of confining stress were carried out at 4 different temperatures from 20℃ to 120℃. The obtained results show high confining pressures weaken the thermal effects on rock mechanical characteristics while higher temperatures enhance the effect of confining pressure.At higher levels of confining stress the thermal effects on the rock strength characteristics decrease. The higher the temperature, the larger is the effect of confining pressure on the mechanical characteristics of the slate. Increase of temperature leads to a decrease of the peak strength but increases the deformability and ductility of the slate, the thermo effect on the peak strength and Poisson's ratio is larger than on the elastic modulus. Higher temperatures reduce the shear strength of slate, the decrease is mainly caused by a decrease of the cohesion. In general, the slate samples fail in shear failure.展开更多
Rock is subjected to impact loading during tunnel and subsurface engineering.For understanding the damage evolution of rock under dynamic impact, mechanical research was performed on the carboniferous slate surroundin...Rock is subjected to impact loading during tunnel and subsurface engineering.For understanding the damage evolution of rock under dynamic impact, mechanical research was performed on the carboniferous slate surrounding the Muzhailing tunnel under different influencing factors based on the Split Hopkinson Pressure Bar(SHPB)experimental system. The results show that:(1)carbonaceous slate exhibits a continuous failure process, which develops more rapidly in the presence of joints;simultaneously, a negative correlation was found between the joint density and the dynamic strength of rock;(2) under different impact velocities and wavelengths, the method of using incident energy to represent the dynamic damage threshold of carbonaceous slate under high in situ stress was proposed based on the kinetic energy theorem, and the damage threshold of carbonaceous slate was calculated to be 53 J;(3) impact times is the most critical core variable and negatively correlated with peak strength and positively correlated with strain rate, maximum strain, and cumulative damage. The carbonaceous slate is subjected to repeated load impacts, which is followed by accumulation of damage, continuous strength attenuation, and internal dominant fracture expansion. In particular,when the samples break, there is only one main rupture surface, which is the most significant difference from the single impact rupture form.展开更多
In numerical modelling,selection of the constitutive model is a critical factor in predicting the actual response of a geomaterial.The use of oversimplified or inadequate models may not be sufficient to reproduce the ...In numerical modelling,selection of the constitutive model is a critical factor in predicting the actual response of a geomaterial.The use of oversimplified or inadequate models may not be sufficient to reproduce the actual geomaterial behaviour.That selection is especially relevant in the case of aniso-tropic rocks,and particularly for shales and slates,whose behaviour may be affected,e.g.well stability in geothermal or oil and gas production operations.In this paper,an alternative anisotropic constitutive model has been implemented in the finite element method software CODE_BRIGHT,which is able to account for the anisotropy of shales and slates in terms of both deformability and strength.For this purpose,a transversely isotropic version of the generalised Hooke’s law is adopted to represent the stiffness anisotropy,while a nonuniform scaling of the stress tensor is introduced in the plastic model to represent the strength anisotropy.Furthermore,a detailed approach has been proposed to determine the model parameters based on the stressestrain results of laboratory tests.Moreover,numerical analyses are performed to model uniaxial and triaxial tests on Vaca Muerta shale,Bossier shale and slate from the northwest of Spain(NW Spain slate).The experimental data have been recovered from the literature in the case of the shale and,in the case of the slate,performed by the authors in terms of stress-strain curves and strengths.A good agreement can be generally observed between numerical and experi-mental results,hence showing the potential applicability of the approach to actual case studies.Therefore,the presented constitutive model may be a promising approach for analysing the anisotropic behaviour of rocks and its impact on well stability or other relevant geomechanical problems in aniso-tropic rocks.展开更多
The Muzhailing extra-long highway tunnel and corresponding inclined shafts in Lanzhou,Gansu Province,China passes through structurally complex carbonaceous slate that is under high ground stress.Rationally-designed an...The Muzhailing extra-long highway tunnel and corresponding inclined shafts in Lanzhou,Gansu Province,China passes through structurally complex carbonaceous slate that is under high ground stress.Rationally-designed and effective support is of high importance for achieving safe and efficient tunnel construction.The No.2 inclined shaft of Muzhailing Tunnel was taken as the engineering background prototype,for which,a similar model test was conducted to evaluate the effect of highly pretightened constant resistance(NPR,Negative Poisson’s Ratio)anchor cable support provision to the geologically complex carbonaceous slate at different depths.Two schemes were proposed during testing:one scheme was without support and the second was with asymmetric support from highly pre-tightened constant resistance anchor cable.Digital speckle displacement analysis system and micro-groundstress sensors were employed to measure the deformation and shear stress distribution of the tunnel.The results demonstrated that through the second support scheme,the deformation of the surrounding rock could be effectively ameliorated,while this support scheme was applied on the project site of the No.2 inclined shaft,to explore the rationality of the scheme through field engineering tests.On-site monitoring indicated that the deformation of the surrounding rock was within the reasonable design range and the problem of severe tunnel deformation was effectively controlled.The research methods and related conclusions can be used as a reference for the treatment of large deformation problems in deep-buried soft rock tunnels.展开更多
Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconventional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is we...Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconventional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is well understood but strictly isotropic rocks are rarely found in nature. This study aims at the examination of fracture initiation and propagation processes in a highly anisotropic rock, specifically slate. We performed a series of tensile fracturing laboratory experiments under uniaxial as well as triaxial loading. Cubic specimens with edge lengths of 150 mm and a central borehole with a diameter of13 mm were prepared from Fredeburg slate. An experiment using the rather isotropic Bebertal sandstone as a rather isotropic rock was also performed for comparison. Tensile fractures were generated using the sleeve fracturing technique, in which a polymer tube placed inside the borehole is pressurized to generate tensile fractures emanating from the borehole. In the uniaxial test series, the loading was varied in order to observe the transition from strength-dominated fracture propagation at low loading magnitudes to stress-dominated fracture propagation at high loading magnitudes.展开更多
In Internet of Things(IoT), the devices or terminals are connected with each other, which can be very diverse over the wireless networks. Unfortunately, the current devices are not designed to communicate with the col...In Internet of Things(IoT), the devices or terminals are connected with each other, which can be very diverse over the wireless networks. Unfortunately, the current devices are not designed to communicate with the collocated devices which employ different communication technologies. Consequently, the communication between these devices will be realized only by using the gateway nodes. This will cause the inefficient use of wireless resources. Therefore, in this paper, a smart service system(SSS) architecture is proposed, which consists of smart service terminal(SST), and smart service network(SSN), to realize the Io T in a general environment with diverse communication networks, devices, and services. The proposed architecture has the following advantages: i) the devices in this architecture cover multiple types of terminals and sensor-actuator devices; ii) the communications network therein is a converged network, and will coordinate multiple kinds of existing and emerging networks. This converged network offers ubiquitous access for various sensors and terminals; iii) the architecture has services and applications covering all smart service areas. It also provides theadaptability to new services and applications. A SSS architecture-based smart campus system was developed and deployed. Evaluation experiments of the proposed smart campus system demonstrate the SSS's advantages over the existing counterparts, and verify the effectiveness of the proposed architecture.展开更多
Driven by the increasing supply of heavy oils with deteriorating quality,a high nickel-resistant catalyst for catalytic cracking of inferior crude oils was developed by the Research Institute of Petroleum Processing(R...Driven by the increasing supply of heavy oils with deteriorating quality,a high nickel-resistant catalyst for catalytic cracking of inferior crude oils was developed by the Research Institute of Petroleum Processing(RIPP).Catalyst performance was evaluated in a laboratory fixed fluidized bed reactor.The test results showed that the high nickel resistance catalyst exhibited good bottoms crackability,good nickel resistance,and good adaptability to changes in operating parameters,which had no adverse effect on the product distribution,indicating to a most promising prospect for application of this catalyst in catalytic cracking of inferior crude oil.展开更多
Lightweight aggregates are increasingly used in concrete construction. They reduce concrete selfweight furnishing a structural advantage. In contrast, the mechanical properties and durability of lightweight concrete c...Lightweight aggregates are increasingly used in concrete construction. They reduce concrete selfweight furnishing a structural advantage. In contrast, the mechanical properties and durability of lightweight concrete can become the governing factor on lightweight aggregate replacement ratios. Alkali-Silica Reactison (ASR) and compressive strength of mortar samples with expanded slate, expanded glass or perlite, covering the spectrum of internal porosity and weight of lightweight aggregates, were evaluated. Scanning electron microscopy was utilized to evaluate the contribution of the aggregates’ porosity and chemical composition in inhibiting ASR. Perlite, owing to its highly porous microstructure and lower matter excelled in ASR expansion while chemical composition and denser microstructure of the heavier expanded slate resulted in more signified late ASR expansion and higher compressive strength. An attempt in visual inspection of ASR attack of alkali metal ions on silica-rich expanded glass using an ultra-accelerated exposure to sodium hydroxide solution was made</span></span><span style="font-family:Verdana;">.展开更多
Water-and-mud inrush disasters have become a major challenge in underground engineering for the construction of tunnels in sandstone and slate interbedded Presinian strata.Disaster prediction and prevention rely in pa...Water-and-mud inrush disasters have become a major challenge in underground engineering for the construction of tunnels in sandstone and slate interbedded Presinian strata.Disaster prediction and prevention rely in part on realistic modeling and observation of the disaster process,as well as the identification and examination of the underlying mechanisms.Based on the geological conditions and the historical records of the Xinping Tunnel on the China–Laos Railway,an engineering geological model of the water-and-mud inrush was established.A physical model test that accurately reproduced water-and-mud inrush during tunnel excavation in sandstone and slate interbedded strata was also carried out.Then,testing was conducted that examined the stress and strain,seepage pressure,and high-leakage flow of the surrounding rock.The results indicated that the water-and-mud inrush proceeded through three stages:seepage stage,high-leakage flow stage,and attenuation stage.In essence,the disaster was a catastrophic process,during which the water-resistant stratum was reduced to a critical safety thickness,a water-inrush channel formed,and the water-resistant stratum gradually failed under the influence of excavation unloading and in situ stress–seepage coupling.Parameters such as the stress and strain,seepage pressure,and flow of the surrounding rock had evident stage-related features during water-and-mud inrush,and their variation indicated the formation,development,and evolution of the disaster.As the tunnel face advanced,the trend of the stress–strain curve of the surrounding rock shifted from sluggish to rapid in its speed of increase.The characteristics of strain energy density revealed the erosion and weakening effect of groundwater on the surrounding rock.The seepage pressure and the thickness of the water-resistant stratum had a positive linear relationship,and the flow and thickness a negative linear relationship.There was a pivotal point at which the seepage pressure changed from high to low and the flow shifted from low to high.The thickness of the water-resistant stratum corresponding to the pivotal point was deemed the critical safety thickness.展开更多
基金Funded by a grant(12High-tech C20)from High-tech Urban Development Program from by Ministry of Land,Transport and Maritime Affairs of Korea
文摘The toxicity of asbestos has been constantly an active research topic.Although asbestos has lots of advantages owing to its stable physicochemical properties and economic characteristics,nations enforce policies prohibiting or limiting its use because of its critical impact on human health.Especially in Korea 96% of imported asbestos are slate construction materials and with the influence of Saemaul movement,thatched roofs have been drastically replaced with slate roofs.Efforts to know the distribution characteristics of extensively used asbestos cement slates and to find out the removal method that suits the distribution characteristics are still in an insufficient state.The purpose of this work was to probe into the distribution of asbestos cement slate buildings in Korea and provide basic data of distribution characteristics for policy making in which consideration of the differences between rural and urban regions is necessary based on findings of the studies so far.It is considered helpful in many ways to solving asbestos cement slate related problems in countries where asbestos usage is increasing even after the 2000s including China.
基金supported by National Natural Science Foundation of China(Grant No.41230635)Projects of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Grant No.SKLGP2013Z004)+1 种基金The Cultivating programme of middle-aged backbone teachers of Chengdu University of Technology(Grant No.JXGG201703)Key Projects of Education Department of Sichuan Province(Grant No.16ZA0095)
文摘High geothermal temperatures appear to be unfavorable for the construction of tunnels in slate rocks with high overburden. To investigate the mechanical characteristics of slates at various levels of geothermal temperature, conventional triaxial compression tests at different levels of confining stress were carried out at 4 different temperatures from 20℃ to 120℃. The obtained results show high confining pressures weaken the thermal effects on rock mechanical characteristics while higher temperatures enhance the effect of confining pressure.At higher levels of confining stress the thermal effects on the rock strength characteristics decrease. The higher the temperature, the larger is the effect of confining pressure on the mechanical characteristics of the slate. Increase of temperature leads to a decrease of the peak strength but increases the deformability and ductility of the slate, the thermo effect on the peak strength and Poisson's ratio is larger than on the elastic modulus. Higher temperatures reduce the shear strength of slate, the decrease is mainly caused by a decrease of the cohesion. In general, the slate samples fail in shear failure.
基金the financial support from the Key Special Project of the National Natural Science Foundation of China(Grant No.41941018)the Special Fund of Yueqi Scholars(Grant No.800015Z1207)。
文摘Rock is subjected to impact loading during tunnel and subsurface engineering.For understanding the damage evolution of rock under dynamic impact, mechanical research was performed on the carboniferous slate surrounding the Muzhailing tunnel under different influencing factors based on the Split Hopkinson Pressure Bar(SHPB)experimental system. The results show that:(1)carbonaceous slate exhibits a continuous failure process, which develops more rapidly in the presence of joints;simultaneously, a negative correlation was found between the joint density and the dynamic strength of rock;(2) under different impact velocities and wavelengths, the method of using incident energy to represent the dynamic damage threshold of carbonaceous slate under high in situ stress was proposed based on the kinetic energy theorem, and the damage threshold of carbonaceous slate was calculated to be 53 J;(3) impact times is the most critical core variable and negatively correlated with peak strength and positively correlated with strain rate, maximum strain, and cumulative damage. The carbonaceous slate is subjected to repeated load impacts, which is followed by accumulation of damage, continuous strength attenuation, and internal dominant fracture expansion. In particular,when the samples break, there is only one main rupture surface, which is the most significant difference from the single impact rupture form.
文摘In numerical modelling,selection of the constitutive model is a critical factor in predicting the actual response of a geomaterial.The use of oversimplified or inadequate models may not be sufficient to reproduce the actual geomaterial behaviour.That selection is especially relevant in the case of aniso-tropic rocks,and particularly for shales and slates,whose behaviour may be affected,e.g.well stability in geothermal or oil and gas production operations.In this paper,an alternative anisotropic constitutive model has been implemented in the finite element method software CODE_BRIGHT,which is able to account for the anisotropy of shales and slates in terms of both deformability and strength.For this purpose,a transversely isotropic version of the generalised Hooke’s law is adopted to represent the stiffness anisotropy,while a nonuniform scaling of the stress tensor is introduced in the plastic model to represent the strength anisotropy.Furthermore,a detailed approach has been proposed to determine the model parameters based on the stressestrain results of laboratory tests.Moreover,numerical analyses are performed to model uniaxial and triaxial tests on Vaca Muerta shale,Bossier shale and slate from the northwest of Spain(NW Spain slate).The experimental data have been recovered from the literature in the case of the shale and,in the case of the slate,performed by the authors in terms of stress-strain curves and strengths.A good agreement can be generally observed between numerical and experi-mental results,hence showing the potential applicability of the approach to actual case studies.Therefore,the presented constitutive model may be a promising approach for analysing the anisotropic behaviour of rocks and its impact on well stability or other relevant geomechanical problems in aniso-tropic rocks.
基金supported by the National Key Research and Development Program of China(No.2016YFC0600901)the Fundamental Research Funds for the Central Universities(No.2015QB02)。
文摘The Muzhailing extra-long highway tunnel and corresponding inclined shafts in Lanzhou,Gansu Province,China passes through structurally complex carbonaceous slate that is under high ground stress.Rationally-designed and effective support is of high importance for achieving safe and efficient tunnel construction.The No.2 inclined shaft of Muzhailing Tunnel was taken as the engineering background prototype,for which,a similar model test was conducted to evaluate the effect of highly pretightened constant resistance(NPR,Negative Poisson’s Ratio)anchor cable support provision to the geologically complex carbonaceous slate at different depths.Two schemes were proposed during testing:one scheme was without support and the second was with asymmetric support from highly pre-tightened constant resistance anchor cable.Digital speckle displacement analysis system and micro-groundstress sensors were employed to measure the deformation and shear stress distribution of the tunnel.The results demonstrated that through the second support scheme,the deformation of the surrounding rock could be effectively ameliorated,while this support scheme was applied on the project site of the No.2 inclined shaft,to explore the rationality of the scheme through field engineering tests.On-site monitoring indicated that the deformation of the surrounding rock was within the reasonable design range and the problem of severe tunnel deformation was effectively controlled.The research methods and related conclusions can be used as a reference for the treatment of large deformation problems in deep-buried soft rock tunnels.
基金funded by the German Federal Ministry for Economic Affairs(FKZ 0325279B)
文摘Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconventional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is well understood but strictly isotropic rocks are rarely found in nature. This study aims at the examination of fracture initiation and propagation processes in a highly anisotropic rock, specifically slate. We performed a series of tensile fracturing laboratory experiments under uniaxial as well as triaxial loading. Cubic specimens with edge lengths of 150 mm and a central borehole with a diameter of13 mm were prepared from Fredeburg slate. An experiment using the rather isotropic Bebertal sandstone as a rather isotropic rock was also performed for comparison. Tensile fractures were generated using the sleeve fracturing technique, in which a polymer tube placed inside the borehole is pressurized to generate tensile fractures emanating from the borehole. In the uniaxial test series, the loading was varied in order to observe the transition from strength-dominated fracture propagation at low loading magnitudes to stress-dominated fracture propagation at high loading magnitudes.
基金supported by the national 973 project of China under Grants 2013CB329104the Natural Science Foundation of China under Grants 61372124, 61427801+1 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions (Grant No.13KJB520029)the Jiangsu Province colleges and universities graduate students scientific research and innovation program CXZZ13_0477,NUPTSF(Grant No.NY214033)
文摘In Internet of Things(IoT), the devices or terminals are connected with each other, which can be very diverse over the wireless networks. Unfortunately, the current devices are not designed to communicate with the collocated devices which employ different communication technologies. Consequently, the communication between these devices will be realized only by using the gateway nodes. This will cause the inefficient use of wireless resources. Therefore, in this paper, a smart service system(SSS) architecture is proposed, which consists of smart service terminal(SST), and smart service network(SSN), to realize the Io T in a general environment with diverse communication networks, devices, and services. The proposed architecture has the following advantages: i) the devices in this architecture cover multiple types of terminals and sensor-actuator devices; ii) the communications network therein is a converged network, and will coordinate multiple kinds of existing and emerging networks. This converged network offers ubiquitous access for various sensors and terminals; iii) the architecture has services and applications covering all smart service areas. It also provides theadaptability to new services and applications. A SSS architecture-based smart campus system was developed and deployed. Evaluation experiments of the proposed smart campus system demonstrate the SSS's advantages over the existing counterparts, and verify the effectiveness of the proposed architecture.
文摘Driven by the increasing supply of heavy oils with deteriorating quality,a high nickel-resistant catalyst for catalytic cracking of inferior crude oils was developed by the Research Institute of Petroleum Processing(RIPP).Catalyst performance was evaluated in a laboratory fixed fluidized bed reactor.The test results showed that the high nickel resistance catalyst exhibited good bottoms crackability,good nickel resistance,and good adaptability to changes in operating parameters,which had no adverse effect on the product distribution,indicating to a most promising prospect for application of this catalyst in catalytic cracking of inferior crude oil.
文摘Lightweight aggregates are increasingly used in concrete construction. They reduce concrete selfweight furnishing a structural advantage. In contrast, the mechanical properties and durability of lightweight concrete can become the governing factor on lightweight aggregate replacement ratios. Alkali-Silica Reactison (ASR) and compressive strength of mortar samples with expanded slate, expanded glass or perlite, covering the spectrum of internal porosity and weight of lightweight aggregates, were evaluated. Scanning electron microscopy was utilized to evaluate the contribution of the aggregates’ porosity and chemical composition in inhibiting ASR. Perlite, owing to its highly porous microstructure and lower matter excelled in ASR expansion while chemical composition and denser microstructure of the heavier expanded slate resulted in more signified late ASR expansion and higher compressive strength. An attempt in visual inspection of ASR attack of alkali metal ions on silica-rich expanded glass using an ultra-accelerated exposure to sodium hydroxide solution was made</span></span><span style="font-family:Verdana;">.
基金the National High-Speed Rail United Foundation of China(No.U1934213)。
文摘Water-and-mud inrush disasters have become a major challenge in underground engineering for the construction of tunnels in sandstone and slate interbedded Presinian strata.Disaster prediction and prevention rely in part on realistic modeling and observation of the disaster process,as well as the identification and examination of the underlying mechanisms.Based on the geological conditions and the historical records of the Xinping Tunnel on the China–Laos Railway,an engineering geological model of the water-and-mud inrush was established.A physical model test that accurately reproduced water-and-mud inrush during tunnel excavation in sandstone and slate interbedded strata was also carried out.Then,testing was conducted that examined the stress and strain,seepage pressure,and high-leakage flow of the surrounding rock.The results indicated that the water-and-mud inrush proceeded through three stages:seepage stage,high-leakage flow stage,and attenuation stage.In essence,the disaster was a catastrophic process,during which the water-resistant stratum was reduced to a critical safety thickness,a water-inrush channel formed,and the water-resistant stratum gradually failed under the influence of excavation unloading and in situ stress–seepage coupling.Parameters such as the stress and strain,seepage pressure,and flow of the surrounding rock had evident stage-related features during water-and-mud inrush,and their variation indicated the formation,development,and evolution of the disaster.As the tunnel face advanced,the trend of the stress–strain curve of the surrounding rock shifted from sluggish to rapid in its speed of increase.The characteristics of strain energy density revealed the erosion and weakening effect of groundwater on the surrounding rock.The seepage pressure and the thickness of the water-resistant stratum had a positive linear relationship,and the flow and thickness a negative linear relationship.There was a pivotal point at which the seepage pressure changed from high to low and the flow shifted from low to high.The thickness of the water-resistant stratum corresponding to the pivotal point was deemed the critical safety thickness.
