When mining extra-thick coal seams,the main cause of strong ground pressure are the high-level thick and hard strata,but as yet there is no active and effective control technology.This paper proposes the method of sub...When mining extra-thick coal seams,the main cause of strong ground pressure are the high-level thick and hard strata,but as yet there is no active and effective control technology.This paper proposes the method of subjecting hard roofs to ground fracturing,and physical simulation is used to study the control effect of ground fracturing on the strata structure and energy release.The results show that ground fracturing changes the structural characteristics of the strata and reduces the energy release intensity and the spatial extent of overburden movement,thereby exerting significant control on the ground pressure.The Datong mining area in China is selected as the engineering background.An engineering test was conducted on site by ground horizontal well fracturing,and a 20-m-thick hard rock layer located 110 m vertically above the coal seam was targeted as the fracturing layer.On-site microseismic monitoring shows that the crack propagation length is up to 216 m and the height is up to 50 m.On-site mine pressure monitoring shows that(1)the roadway deformation is reduced to 100 mm,(2)the periodic weighting characteristics of the hydraulic supports are not obvious,and(3)the ground pressure in the working face is controlled significantly,thereby showing that the ground fracturing is successful.Ground fracturing changed the breaking characteristics of the high-level hard strata,thereby helping to ameliorate the stress concentration in the stope and providing an effective control approach for hard rock.展开更多
Field experiments were conducted for two consecutive years(2013-2014 and 2014-2015)to study the effects of straw mulching on microclimate characteristics,energy flux,soil evaporation(Es)and evapotranspiration of winte...Field experiments were conducted for two consecutive years(2013-2014 and 2014-2015)to study the effects of straw mulching on microclimate characteristics,energy flux,soil evaporation(Es)and evapotranspiration of winter wheat(Triticum aestivum L.)under adequate drip irrigation in North China Plain(NCP).The results revealed that straw mulching affected air temperature(T_(a))and dew point temperature(T_(d))near the soil surface but had little effect on relative humidity(RH)compared with non-mulched fields.Straw mulching increased the turbulent exchange coefficient(K),and K within the canopy was higher than that above the canopy.Straw mulching clearly increased the sensible heat flux(H)distribution in April-June,and part of the energy needed for evapotranspiration was provided by transfer from the warmer air aloft.There was a linear functional relationship between H and T_(a)measured above and within the canopy.The straw mulching decreased Es but increased crop transpiration(T).Mulched treatment(TM)can decrease the total irrigation amount by about 7%-15%compared with the non-mulched treatment(TN).There were no significant differences(p>0.05)in cumulative crop evapotranspiration(ETc)between TM and TN treatments under adequate drip irrigation,and the use of mulch may need to be combined with an optimal deficit drip irrigation schedule for managing the declining water table in NCP.展开更多
基金This work was supported by the State Key Research Development Program of China(Grant No.2018YFC0604500,2018YFC0604506)by the China Postdoctoral Science Foundation(Grant No.2019M651080)+3 种基金as an applied basic research Project of Shanxi Province(Grant No.201901D211030)by the Scientific,Technological Innovation Programs of Higher Education Institutions in Shanxi(STIP)(Grant No.2019L0208)as a Major Program in Shanxi Province(Grant No.20191101015)as a Distinguished Youth Funds of National Natural Science Foundation of China(No.51925402).
文摘When mining extra-thick coal seams,the main cause of strong ground pressure are the high-level thick and hard strata,but as yet there is no active and effective control technology.This paper proposes the method of subjecting hard roofs to ground fracturing,and physical simulation is used to study the control effect of ground fracturing on the strata structure and energy release.The results show that ground fracturing changes the structural characteristics of the strata and reduces the energy release intensity and the spatial extent of overburden movement,thereby exerting significant control on the ground pressure.The Datong mining area in China is selected as the engineering background.An engineering test was conducted on site by ground horizontal well fracturing,and a 20-m-thick hard rock layer located 110 m vertically above the coal seam was targeted as the fracturing layer.On-site microseismic monitoring shows that the crack propagation length is up to 216 m and the height is up to 50 m.On-site mine pressure monitoring shows that(1)the roadway deformation is reduced to 100 mm,(2)the periodic weighting characteristics of the hydraulic supports are not obvious,and(3)the ground pressure in the working face is controlled significantly,thereby showing that the ground fracturing is successful.Ground fracturing changed the breaking characteristics of the high-level hard strata,thereby helping to ameliorate the stress concentration in the stope and providing an effective control approach for hard rock.
基金supported by the National“12th Five-Year Plan”Scientific and Technological Project of China(2014BAD12B05)the IWHR Innovative Team Project(ID0145B602017).
文摘Field experiments were conducted for two consecutive years(2013-2014 and 2014-2015)to study the effects of straw mulching on microclimate characteristics,energy flux,soil evaporation(Es)and evapotranspiration of winter wheat(Triticum aestivum L.)under adequate drip irrigation in North China Plain(NCP).The results revealed that straw mulching affected air temperature(T_(a))and dew point temperature(T_(d))near the soil surface but had little effect on relative humidity(RH)compared with non-mulched fields.Straw mulching increased the turbulent exchange coefficient(K),and K within the canopy was higher than that above the canopy.Straw mulching clearly increased the sensible heat flux(H)distribution in April-June,and part of the energy needed for evapotranspiration was provided by transfer from the warmer air aloft.There was a linear functional relationship between H and T_(a)measured above and within the canopy.The straw mulching decreased Es but increased crop transpiration(T).Mulched treatment(TM)can decrease the total irrigation amount by about 7%-15%compared with the non-mulched treatment(TN).There were no significant differences(p>0.05)in cumulative crop evapotranspiration(ETc)between TM and TN treatments under adequate drip irrigation,and the use of mulch may need to be combined with an optimal deficit drip irrigation schedule for managing the declining water table in NCP.
