Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars （CECGWEP）. However, retained entryways located in deep...Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars （CECGWEP）. However, retained entryways located in deep coal mines are hard to maintain, especially for constructing boreholes in confined spaces, owing to major deformations. Consequently, it is difficult to drill boreholes and maintain their stability, which therefore cannot guarantee the effectiveness of gas drainage. This paper presents three measures for conducting CECGWEP in deep mines on the basis of effective space in retained entryways for gas drainage, They are combinations of retaining roadways and face-lagging inclined boreholes, retaining roadways and face-advancing inclined boreholes, and retaining roadways and high return airway inclined boreholes. Several essential techniques are suggested to improve the maintenance of retained entryways and the stabilization of boreholes. For the particular cases considered in this study, two field trials have verified the latter two measures from the results obtained from the faces 1111（1） and 11112（1） in the Zhuji Mine. The results indicate that these models can effectively solve the problems in deep mines. The maximum gas drainage flow for a single hole can reach 8.1 m^3/min and the effective drainage distance can be extended up to 150 m or more.展开更多
Underground coal mining activities in the Quangninh coal basin (in the North ofVietnam) have been carried out at a depth of-130 m to-150 m,and in the near future thismining depth will become-300 m and-500 m.Together w...Underground coal mining activities in the Quangninh coal basin (in the North ofVietnam) have been carried out at a depth of-130 m to-150 m,and in the near future thismining depth will become-300 m and-500 m.Together with the increasing coal output,the quantity of methane and other mine gases emitted from coal beds during mining activitieswill grow bigger and bigger.According to the forecast of the coal mining industry,ifmines go deeper downward,all underground coal mines in the Quangninh basin will beclassified into the mine group with the dangerous level of methane bearings.Mine gascontrol and management operations with conventional ventilation are less effective andentail high expenses.One of the main solutions is to carry out short,medium and longboreholes for controlling and recovering methane and other mine gases from coal bedsbefore mining activities.Efficiency of drilling activities for methane gas recovery from coalseams with horizontal bore holes at underground coal mines depends on many factors includingthe mine gas draining borehole layout at the roadways,gas content in the coalbeds,technologies for mine gas draining boring activities,and so on.Methane gas existsin the coal beds under the adhesive state with stable physical and chemical bonds.In orderto recover these gases,it is necessary to carry out boreholes and create artificial joints(collecting pits) in coal beds with the impulse method (hydraulic separation method).展开更多
To determine reasonable distance of gas pre-drainage drillings in coal seams, a solid–gas coupling model that takes gas adsorption effect into account was constructed. In view of different adsorption constants,the pa...To determine reasonable distance of gas pre-drainage drillings in coal seams, a solid–gas coupling model that takes gas adsorption effect into account was constructed. In view of different adsorption constants,the paper conducted the numerical simulation of pre-drainage gas in drillings along coal seam, studied the relationship of adsorption constants and permeability, gas pressure, and effective drainage radius of coal seams, and applied the approach to the layout of pre-drainage gas drillings in coal seams. The results show that the permeability of coal seams is on the gradual increase with time, which is divided into three sections according to the increase rate: the drainage time 0–30 d is the sharp increase section;30–220 d is the gradual increase section; and the time above 200 d is the stable section. The permeability of coal seams is in negative linear and positive exponent relation with volume adsorption constant VLand pressure adsorption constant PL, respectively. The effective drainage radius is in negative linear relation with VLand in positive exponent relation with PL. Compared with the former design scheme, the engineering quantity of drilling could be reduced by 25%.展开更多
By establishing the numerical model in the vertical plane and the similar model in the horizontal plane of gas flow in goaf, the influence of high drainage roadway or drilling on the gas seepage field was analyzed, an...By establishing the numerical model in the vertical plane and the similar model in the horizontal plane of gas flow in goaf, the influence of high drainage roadway or drilling on the gas seepage field was analyzed, and the extraction mechanism was clarified. On this basis, the academic thought of directional long drilling group instead of high drainage roadway was put forward. And then using complex function theory, the permeation mechanical model of drilling group with circle distribution in the mining-induced fracture zone was established to explore the coupling relationship between the drilling quantity, extraction volume and the equivalent extraction rate of single drilling. Finally, combined with the concrete geological production conditions, the main parameters of directional long drilling group were determined. The distance between the drilling group center and the air-return roadway is 24 m, the height is 18 m, and the three drillings are in an approximate equilateral triangle distribution with a space of 8 m. The equivalent extraction square is 4.15 m2. It is shown that the effect of directional long drilling group is evident. The gas content in the upper comer is controlled below 0.95%, the content in the tail roadway is kept below the alarm value, and the content is over 50% in the drill, realizing the secure and effective extraction of coal and gas.展开更多
Objective： of chronic subdural hematoma The surgical management （CSDH） is still a controversial issue, and a standard therapy has not been established because of the unclear pathogenic mechanisms in CSDH. The inten...Objective： of chronic subdural hematoma The surgical management （CSDH） is still a controversial issue, and a standard therapy has not been established because of the unclear pathogenic mechanisms in CSDH. The intention of this paper is to find a simple and efficient surgical procedure for CSDH. Methods： A retrospective study of 448 patients with CSDH by surgical treatment during 2005 to 2009 was conducted in order to compare the efficiency between two diferent primary surgical methods, i.e. twist-drill drainage without irrigation in Group A （n-178） and one burr-hole with irrigation in Group B （n=270）. The results were statistically analyzed. Results： The reoperation rates in Group A and Group B were 7.9% and 11.9% respectively. The good outcome rate was 88.8% and 73.5%, the complicatiGn was 7.9% and 20.7% in Group A and Group B, respectively. Conclusions： The burr-hole drainage with irrigation of the hematoma cavity is not beneficial to the outcome and prognosis. Irrigation is not important in the surgical treatmerit for CSDH. Thus in initial treatment, twist-drill drainage without irrigation of the hematoma cavity is recommended because it is relatively safe, time-saving and cost-effective.展开更多
基金Acknowledgments The research was supported by Program for Changjiang Scholars and Innovative Research Team in University （IRT_I4R55）, and the National Natural Science Foundation of China under Grant No. NSFC-51274193.
文摘Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars （CECGWEP）. However, retained entryways located in deep coal mines are hard to maintain, especially for constructing boreholes in confined spaces, owing to major deformations. Consequently, it is difficult to drill boreholes and maintain their stability, which therefore cannot guarantee the effectiveness of gas drainage. This paper presents three measures for conducting CECGWEP in deep mines on the basis of effective space in retained entryways for gas drainage, They are combinations of retaining roadways and face-lagging inclined boreholes, retaining roadways and face-advancing inclined boreholes, and retaining roadways and high return airway inclined boreholes. Several essential techniques are suggested to improve the maintenance of retained entryways and the stabilization of boreholes. For the particular cases considered in this study, two field trials have verified the latter two measures from the results obtained from the faces 1111（1） and 11112（1） in the Zhuji Mine. The results indicate that these models can effectively solve the problems in deep mines. The maximum gas drainage flow for a single hole can reach 8.1 m^3/min and the effective drainage distance can be extended up to 150 m or more.
文摘Underground coal mining activities in the Quangninh coal basin (in the North ofVietnam) have been carried out at a depth of-130 m to-150 m,and in the near future thismining depth will become-300 m and-500 m.Together with the increasing coal output,the quantity of methane and other mine gases emitted from coal beds during mining activitieswill grow bigger and bigger.According to the forecast of the coal mining industry,ifmines go deeper downward,all underground coal mines in the Quangninh basin will beclassified into the mine group with the dangerous level of methane bearings.Mine gascontrol and management operations with conventional ventilation are less effective andentail high expenses.One of the main solutions is to carry out short,medium and longboreholes for controlling and recovering methane and other mine gases from coal bedsbefore mining activities.Efficiency of drilling activities for methane gas recovery from coalseams with horizontal bore holes at underground coal mines depends on many factors includingthe mine gas draining borehole layout at the roadways,gas content in the coalbeds,technologies for mine gas draining boring activities,and so on.Methane gas existsin the coal beds under the adhesive state with stable physical and chemical bonds.In orderto recover these gases,it is necessary to carry out boreholes and create artificial joints(collecting pits) in coal beds with the impulse method (hydraulic separation method).
基金Financial support for this work,provided by the National Natural Science Foundation of China(Nos.51327007,51104118 and51204134)Shaanxi Province Youth Science and Technology Star Project of China(2014KJXX69)
文摘To determine reasonable distance of gas pre-drainage drillings in coal seams, a solid–gas coupling model that takes gas adsorption effect into account was constructed. In view of different adsorption constants,the paper conducted the numerical simulation of pre-drainage gas in drillings along coal seam, studied the relationship of adsorption constants and permeability, gas pressure, and effective drainage radius of coal seams, and applied the approach to the layout of pre-drainage gas drillings in coal seams. The results show that the permeability of coal seams is on the gradual increase with time, which is divided into three sections according to the increase rate: the drainage time 0–30 d is the sharp increase section;30–220 d is the gradual increase section; and the time above 200 d is the stable section. The permeability of coal seams is in negative linear and positive exponent relation with volume adsorption constant VLand pressure adsorption constant PL, respectively. The effective drainage radius is in negative linear relation with VLand in positive exponent relation with PL. Compared with the former design scheme, the engineering quantity of drilling could be reduced by 25%.
基金Project(50834005) supported by the National Natural Science Foundation of ChinaProject(2010QZ06) supported by the Fundamental Research Funds for the Central Universities of China
文摘By establishing the numerical model in the vertical plane and the similar model in the horizontal plane of gas flow in goaf, the influence of high drainage roadway or drilling on the gas seepage field was analyzed, and the extraction mechanism was clarified. On this basis, the academic thought of directional long drilling group instead of high drainage roadway was put forward. And then using complex function theory, the permeation mechanical model of drilling group with circle distribution in the mining-induced fracture zone was established to explore the coupling relationship between the drilling quantity, extraction volume and the equivalent extraction rate of single drilling. Finally, combined with the concrete geological production conditions, the main parameters of directional long drilling group were determined. The distance between the drilling group center and the air-return roadway is 24 m, the height is 18 m, and the three drillings are in an approximate equilateral triangle distribution with a space of 8 m. The equivalent extraction square is 4.15 m2. It is shown that the effect of directional long drilling group is evident. The gas content in the upper comer is controlled below 0.95%, the content in the tail roadway is kept below the alarm value, and the content is over 50% in the drill, realizing the secure and effective extraction of coal and gas.
文摘Objective： of chronic subdural hematoma The surgical management （CSDH） is still a controversial issue, and a standard therapy has not been established because of the unclear pathogenic mechanisms in CSDH. The intention of this paper is to find a simple and efficient surgical procedure for CSDH. Methods： A retrospective study of 448 patients with CSDH by surgical treatment during 2005 to 2009 was conducted in order to compare the efficiency between two diferent primary surgical methods, i.e. twist-drill drainage without irrigation in Group A （n-178） and one burr-hole with irrigation in Group B （n=270）. The results were statistically analyzed. Results： The reoperation rates in Group A and Group B were 7.9% and 11.9% respectively. The good outcome rate was 88.8% and 73.5%, the complicatiGn was 7.9% and 20.7% in Group A and Group B, respectively. Conclusions： The burr-hole drainage with irrigation of the hematoma cavity is not beneficial to the outcome and prognosis. Irrigation is not important in the surgical treatmerit for CSDH. Thus in initial treatment, twist-drill drainage without irrigation of the hematoma cavity is recommended because it is relatively safe, time-saving and cost-effective.
