Ground subsidence induced by extraction of coal seam belowground brings about changes in surface environment leading to trough and pot-hole subsidence.Pot-hole subsidence is extremely hazardous and does not give any p...Ground subsidence induced by extraction of coal seam belowground brings about changes in surface environment leading to trough and pot-hole subsidence.Pot-hole subsidence is extremely hazardous and does not give any prior indication before its occurrence.In India,several pot-holes have occurred in the coal mines of South Eastern Coalfields Limited triggering the need for in-depth studies.In line with the requirement,literature review and field investigations were conducted to develop an in-depth understanding of various parameters influencing the occurrence of pot-holes.The critical parameters identified were rock to soil ratio,depth to height of extraction ratio,brittleness index of rock and rock density.Risk assessment of pot-hole subsidence has been done by developing an empirical rating approach named as pot-hole subsidence rating(PHSR),involving the critical parameters with suitable corrections for certain structural and mining conditions to obtain corrected PHSR(CPHSR).CPHSR was then applied for all the 34pot-holes studied and it was found that all the pot-holes fall under Class I and Class II category of risk representing a very high to high risk class.An effort was made for the estimation of pot-hole depth utilizing the developed CPHSR in both the development and depillaring cases.The developed approach was found to yield consistent results in pot-hole depth prediction.展开更多
移栽后注水能够缩短钵苗的生长周期,且能起到抗旱保苗效果。传统的灌溉方式需水量大,造成水资源浪费。以玉米钵苗为研究对象,通过玉米钵苗土槽试验,确定单株钵苗的注水量100 m L以上。结合单株钵苗的注水量与本课题组正在开发的旱田钵...移栽后注水能够缩短钵苗的生长周期,且能起到抗旱保苗效果。传统的灌溉方式需水量大,造成水资源浪费。以玉米钵苗为研究对象,通过玉米钵苗土槽试验,确定单株钵苗的注水量100 m L以上。结合单株钵苗的注水量与本课题组正在开发的旱田钵苗移栽机构特点,设计一种穴注水机构及其试验台,并对穴注水机构出水口的运动轨迹进行分析。该机构最突出的特点是内腔不动,外腔旋转,且内腔设计一个扇形槽口,使该机构能同时对准前后两个穴口注水。选取出水口内径、电机转速和水箱液面高度为主要影响因子,水量为考核指标,进行单因素试验和正交试验。结果表明,当出水口内径16 mm,电机转速288 r·min-1水箱液面高度32 cm,注水量最大为156 m L。研究结果可为旱田钵苗移栽穴注水装备的研制提供技术依据。展开更多
基金Financial support for this work is provided by M/s SECL,CIL,India
文摘Ground subsidence induced by extraction of coal seam belowground brings about changes in surface environment leading to trough and pot-hole subsidence.Pot-hole subsidence is extremely hazardous and does not give any prior indication before its occurrence.In India,several pot-holes have occurred in the coal mines of South Eastern Coalfields Limited triggering the need for in-depth studies.In line with the requirement,literature review and field investigations were conducted to develop an in-depth understanding of various parameters influencing the occurrence of pot-holes.The critical parameters identified were rock to soil ratio,depth to height of extraction ratio,brittleness index of rock and rock density.Risk assessment of pot-hole subsidence has been done by developing an empirical rating approach named as pot-hole subsidence rating(PHSR),involving the critical parameters with suitable corrections for certain structural and mining conditions to obtain corrected PHSR(CPHSR).CPHSR was then applied for all the 34pot-holes studied and it was found that all the pot-holes fall under Class I and Class II category of risk representing a very high to high risk class.An effort was made for the estimation of pot-hole depth utilizing the developed CPHSR in both the development and depillaring cases.The developed approach was found to yield consistent results in pot-hole depth prediction.
文摘移栽后注水能够缩短钵苗的生长周期,且能起到抗旱保苗效果。传统的灌溉方式需水量大,造成水资源浪费。以玉米钵苗为研究对象,通过玉米钵苗土槽试验,确定单株钵苗的注水量100 m L以上。结合单株钵苗的注水量与本课题组正在开发的旱田钵苗移栽机构特点,设计一种穴注水机构及其试验台,并对穴注水机构出水口的运动轨迹进行分析。该机构最突出的特点是内腔不动,外腔旋转,且内腔设计一个扇形槽口,使该机构能同时对准前后两个穴口注水。选取出水口内径、电机转速和水箱液面高度为主要影响因子,水量为考核指标,进行单因素试验和正交试验。结果表明,当出水口内径16 mm,电机转速288 r·min-1水箱液面高度32 cm,注水量最大为156 m L。研究结果可为旱田钵苗移栽穴注水装备的研制提供技术依据。
