Surface drilling was performed at the Luling Coal Mine,in Huaibei,to shorten the period required for gas draining.The experimental study was designed to reduce the cost of gas control by efficiently draining gas from ...Surface drilling was performed at the Luling Coal Mine,in Huaibei,to shorten the period required for gas draining.The experimental study was designed to reduce the cost of gas control by efficiently draining gas from the upper protected layer.The structural arraignment and technical principles of pressure relief via surface drilling are discussed.Results from the trial showed that gas drained from the surface system over a period of 10 months.The total amount of collected gas was 248.4 million m^3.The gas draining occurred in three stages：a growth period;a period of maximum gas production;and an attenuation period.The period of maximum gas production lasted for 4 months.During this time the methane concentration ranged from 60%to 90%and the average draining rate was 10.6 m^3/min.Combined with other methods of draining it was possible to drain 70.6%of the gas from middle coal seam groups.The amount of residual gas dropped to 5.2 m^3/ton,and the pressure of the residual gas fell to 0.53 MPa, thereby eliminating the outburst danger in the middle coal seam groups.The factors affecting pressure relief gas draining by surface drilling were analysed.展开更多
Composite borehole profiling combined with trenching is an effective way to acquire evidence of past ruptures of buffed active faults. In this study, three composite borehole profiles and a large-scale trench excavati...Composite borehole profiling combined with trenching is an effective way to acquire evidence of past ruptures of buffed active faults. In this study, three composite borehole profiles and a large-scale trench excavation were carded out across the surface rupture zone of the 1976 Ms7.8 Tangshan earthquake. The following three major conclusions have been reached. （1） The surface rupture zone of the 1976 earthquake extends more than 47 km long to the south of Tangshan city, passing to the west of Sunjialou, to Daodi town in Fengnan County, to Xihe in Fengnan County. （2） The surface rupture zone is divided into south and north branches. The north branch has mainly fight-lateral strike-slip motion, and the vertical displacement of the surface is up on the west and down on the east. On the other hand, the vertical displacement of the south branch is up on the east and down on the west, accompanied by some right-lateral slip. Such a faulting style cannot be explained by the movement of a single normal or reverse fault, but is consistent with the vertical displacement field induced by the fight-lateral strike-slip of the fault belt. The drilling and trenching data from this study verify that such activity continued through the Late Quaternary on the Tangshan Fault. （3） The fault planes exhumed by trenching and the dislocations of strata revealed by the boreholes indicate that multiple faulting events occurred on the Tangshan Fault in the Late Quaternary. The timing of three ruptures prior to the 1976 earthquake was 7.61-8.13, 〉14.57, and 24.21-26.57 ka BP. Counting the earthquake of 1976, the recurrence interval of the four strong events is about 6.7 to 10.8 ka. On one of the three borehole profiles, the Niumaku profile, nine faulting events were detected since 75.18 ka BP with an average interval of 8.4 ka. In addition, this paper also discusses the difference between the Late Quaternary sedimentary environments to the north and south of Tangshan city based on stratum dating.展开更多
基金supported by the Key Project of the Natural Science Foundation of China(No.70533050 and 51004106)the Fundamental Research Funds for the Central Universities (No.2010QNB02)
文摘Surface drilling was performed at the Luling Coal Mine,in Huaibei,to shorten the period required for gas draining.The experimental study was designed to reduce the cost of gas control by efficiently draining gas from the upper protected layer.The structural arraignment and technical principles of pressure relief via surface drilling are discussed.Results from the trial showed that gas drained from the surface system over a period of 10 months.The total amount of collected gas was 248.4 million m^3.The gas draining occurred in three stages：a growth period;a period of maximum gas production;and an attenuation period.The period of maximum gas production lasted for 4 months.During this time the methane concentration ranged from 60%to 90%and the average draining rate was 10.6 m^3/min.Combined with other methods of draining it was possible to drain 70.6%of the gas from middle coal seam groups.The amount of residual gas dropped to 5.2 m^3/ton,and the pressure of the residual gas fell to 0.53 MPa, thereby eliminating the outburst danger in the middle coal seam groups.The factors affecting pressure relief gas draining by surface drilling were analysed.
基金supported by the Fundamental Research Funds of Institute of Crustal Dynamics,China Earthquake Adminishtration (Grant No. ZDJ2007-1)
文摘Composite borehole profiling combined with trenching is an effective way to acquire evidence of past ruptures of buffed active faults. In this study, three composite borehole profiles and a large-scale trench excavation were carded out across the surface rupture zone of the 1976 Ms7.8 Tangshan earthquake. The following three major conclusions have been reached. （1） The surface rupture zone of the 1976 earthquake extends more than 47 km long to the south of Tangshan city, passing to the west of Sunjialou, to Daodi town in Fengnan County, to Xihe in Fengnan County. （2） The surface rupture zone is divided into south and north branches. The north branch has mainly fight-lateral strike-slip motion, and the vertical displacement of the surface is up on the west and down on the east. On the other hand, the vertical displacement of the south branch is up on the east and down on the west, accompanied by some right-lateral slip. Such a faulting style cannot be explained by the movement of a single normal or reverse fault, but is consistent with the vertical displacement field induced by the fight-lateral strike-slip of the fault belt. The drilling and trenching data from this study verify that such activity continued through the Late Quaternary on the Tangshan Fault. （3） The fault planes exhumed by trenching and the dislocations of strata revealed by the boreholes indicate that multiple faulting events occurred on the Tangshan Fault in the Late Quaternary. The timing of three ruptures prior to the 1976 earthquake was 7.61-8.13, 〉14.57, and 24.21-26.57 ka BP. Counting the earthquake of 1976, the recurrence interval of the four strong events is about 6.7 to 10.8 ka. On one of the three borehole profiles, the Niumaku profile, nine faulting events were detected since 75.18 ka BP with an average interval of 8.4 ka. In addition, this paper also discusses the difference between the Late Quaternary sedimentary environments to the north and south of Tangshan city based on stratum dating.
