The friction characteristics of rock damage plane have important impact on the stability of block structure formed after the stratum is broken. The mechanics properties of rock damage plane are described by parameters...The friction characteristics of rock damage plane have important impact on the stability of block structure formed after the stratum is broken. The mechanics properties of rock damage plane are described by parameters such as roughness coefficient, wall compress strength and basic friction angle. These three coefficients for fine grain sandstone and medium granular sandstone and grit sandstone are test. The friction stress is researched at the condition of different normal compressive stress acting on the tension damage plane. The friction law of tension damage plane of sandstone abided by is summed up. This law will provide scientific basis for block structure stability judging in basic roof stratum and roof pressure intensity calculating.展开更多
In real world applications the supply, the demand and the transportation cost per unit of the quantities in a transportation problem are hardly specified precisely because of the changing economic and environmental co...In real world applications the supply, the demand and the transportation cost per unit of the quantities in a transportation problem are hardly specified precisely because of the changing economic and environmental conditions. It is also important that the time required for transportation should be minimum. In this paper a method has been proposed for the minimization of transportation costs. Supply and transportation costs per unit of the quantities are also determined. The present study was carried out to evaluate the quality of gravel to know its suitability for aggregate (raw material for concrete and road). The samples of gravel were analyzed for petrographic, physical, mechanical and chemical properties. Samples were categorized as quartzite group and carbonate group according to ASTM standard 295. Among these, samples of quartzite group were found dominant. The petrography examination of gravels which was carried out constituted of opal, tridymite, chalcedony, crystobalite and alkali carbonates rocks. Those minerals react with alkalis in cement leading to expansion and cracking of concrete. Other components such as sulfides, sulfates, halites, iron oxides, clay minerals and anhydrites are examined, which might be present as coating and impurities. The present study indicated that all samples are suitable for concrete making and obtain the optimum solution for transporting these materials from quarries to cities with minimum cost according to Egyptian Code.展开更多
The mathematical model and the numerical simulation for the transfer of coal bed methane were established based on the combination of the porous flow theory and elastic plastic mechanics theory and the numerical solut...The mathematical model and the numerical simulation for the transfer of coal bed methane were established based on the combination of the porous flow theory and elastic plastic mechanics theory and the numerical solution was given, together with the consideration of the fluid solid interaction between the coal bed gas and coal framework. Then the dispersion for the equation of gas porous flow and coal seam distortion was carried out and the functional analysis equation was obtained. Finally, the coupling solution was educed and calculated by finite element method(FEM) on a model example.展开更多
The Port Harcourt Enugu expressway is part of a national road grid that links parts of southern and northern Nigeria. The severe pavement failure between Umuahia and Okigwe section of the expressway covering a distanc...The Port Harcourt Enugu expressway is part of a national road grid that links parts of southern and northern Nigeria. The severe pavement failure between Umuahia and Okigwe section of the expressway covering a distance of about 30 km was investigated by geotechnical and mineralogical assessment of disturbed and undisturbed samples of the underlying soils. Also vertical electrical sounding was performed at the failed sections. Results indicate that the section is underlain by shales of the Imo Formation, and soils are composed of 27% and 74% sand and fines respectively. The Atterberg limit values are moderate to high, with liquid limit in the range of 49-54%, plasticity index 11.1-24.4% and linear shrinkage 17.86-23.57% respectively. Abrasion test results of 0.58 to 16% indicate shales of low durability. The 24 hour free swell tests results range from 33-70% implying soils of moderate to high hydro-affinity and volume change. These data corroborate the X-ray diffraction analyses results which show montmorillonite and kaolinite as the main clay minerals present in the soils. Undrained cohesion range from 9 to 54 kPa and frictional angle from 13° to 29°. High settlement amounts and field observation of intense failure correlated well with the engineering properties and the clay minerals. The soils indicate mainly MI-MH and A-7-5 soils on the USC and AASHTO classification system respectively, implying poor quality soils as subgrade materials. stabilisation. Result of the study will be useful in remedial works areas underlain by the shales. The engineering properties may be modified and upgraded by on the failed sections of the road and future pavement design in展开更多
文摘The friction characteristics of rock damage plane have important impact on the stability of block structure formed after the stratum is broken. The mechanics properties of rock damage plane are described by parameters such as roughness coefficient, wall compress strength and basic friction angle. These three coefficients for fine grain sandstone and medium granular sandstone and grit sandstone are test. The friction stress is researched at the condition of different normal compressive stress acting on the tension damage plane. The friction law of tension damage plane of sandstone abided by is summed up. This law will provide scientific basis for block structure stability judging in basic roof stratum and roof pressure intensity calculating.
文摘In real world applications the supply, the demand and the transportation cost per unit of the quantities in a transportation problem are hardly specified precisely because of the changing economic and environmental conditions. It is also important that the time required for transportation should be minimum. In this paper a method has been proposed for the minimization of transportation costs. Supply and transportation costs per unit of the quantities are also determined. The present study was carried out to evaluate the quality of gravel to know its suitability for aggregate (raw material for concrete and road). The samples of gravel were analyzed for petrographic, physical, mechanical and chemical properties. Samples were categorized as quartzite group and carbonate group according to ASTM standard 295. Among these, samples of quartzite group were found dominant. The petrography examination of gravels which was carried out constituted of opal, tridymite, chalcedony, crystobalite and alkali carbonates rocks. Those minerals react with alkalis in cement leading to expansion and cracking of concrete. Other components such as sulfides, sulfates, halites, iron oxides, clay minerals and anhydrites are examined, which might be present as coating and impurities. The present study indicated that all samples are suitable for concrete making and obtain the optimum solution for transporting these materials from quarries to cities with minimum cost according to Egyptian Code.
文摘The mathematical model and the numerical simulation for the transfer of coal bed methane were established based on the combination of the porous flow theory and elastic plastic mechanics theory and the numerical solution was given, together with the consideration of the fluid solid interaction between the coal bed gas and coal framework. Then the dispersion for the equation of gas porous flow and coal seam distortion was carried out and the functional analysis equation was obtained. Finally, the coupling solution was educed and calculated by finite element method(FEM) on a model example.
文摘The Port Harcourt Enugu expressway is part of a national road grid that links parts of southern and northern Nigeria. The severe pavement failure between Umuahia and Okigwe section of the expressway covering a distance of about 30 km was investigated by geotechnical and mineralogical assessment of disturbed and undisturbed samples of the underlying soils. Also vertical electrical sounding was performed at the failed sections. Results indicate that the section is underlain by shales of the Imo Formation, and soils are composed of 27% and 74% sand and fines respectively. The Atterberg limit values are moderate to high, with liquid limit in the range of 49-54%, plasticity index 11.1-24.4% and linear shrinkage 17.86-23.57% respectively. Abrasion test results of 0.58 to 16% indicate shales of low durability. The 24 hour free swell tests results range from 33-70% implying soils of moderate to high hydro-affinity and volume change. These data corroborate the X-ray diffraction analyses results which show montmorillonite and kaolinite as the main clay minerals present in the soils. Undrained cohesion range from 9 to 54 kPa and frictional angle from 13° to 29°. High settlement amounts and field observation of intense failure correlated well with the engineering properties and the clay minerals. The soils indicate mainly MI-MH and A-7-5 soils on the USC and AASHTO classification system respectively, implying poor quality soils as subgrade materials. stabilisation. Result of the study will be useful in remedial works areas underlain by the shales. The engineering properties may be modified and upgraded by on the failed sections of the road and future pavement design in
