Evolution and application of in-seam drilling for gas drainage

The presence of seam gas in the form of methane or carbon dioxide presents a hazard to underground coal mining operations.In-seam drilling has been undertaken for the past three decades for gas drainage to reduce the risk of gas outburst and lower the concentrations of seam gas in the underground ventilation.The drilling practices have reflected the standards of the times and have evolved with the development of technology and equipment and the needs to provide a safe mining environment underground.Early practice was to adapt equipment from other felds,with rotary drilling being the only form of drilling available.This form of drainage allowed various levels of gas drainage coverage but with changing emphasis,research and development within the coal industry has created specifc equipment,technology and practices to accurately place in-seam boreholes to provide effcient and effective gas drainage.Research into gas content determination established a standard for the process and safe levels for mining operations to continue.Surveying technology improved from the wire-line,single-shot Eastman survey instruments which was time-dependent on borehole depth to electronic instruments located in the drill string which transmitted accurate survey data to the drilling crew without time delays.This allowed improved directional control and increased drilling rates.Directional drilling technology has now been established as the industry standard to provide effective gas drainage drilling.Exploration was identifed as an additional beneft with directional drilling as it has the ability to provide exploration data from long boreholes.The ability of the technology to provide safe and reliable means to investigate the need for inrush protection and water drainage ahead of mining has been established.Directional drilling technology has now been introduced to the Chinese coal industry for gas drainage through a practice of auditing,design,supply,training and ongoing support.Experienced drilling crews can offer site specifc gas drainage drilling services utilising the latest equipment and technology.

Microscopic properties and sealing performance of new gas drainage drilling sealing material

The geological condition of Chinese coal mines are complex and high gassy,which account for ffty percent to seventy percent.Because of the abundant pores and cracks around the drainage drilling hole,the gas concentration attenuates rapidly,and the effective gas drainage period is short.The traditional sealing materials of yellow mud and cement-sand grout will readily shrink after the drilling hole is sealed,the sealing length is short and the sealing quality is not satisfactory.Currently widely used polyurethane material will shrink when it comes into contact with water,and the price is also very high.In this study,taking cement as a base material,a novel composite sealing material mixed by expansion admixture,additive,and fbrin and coupling agent was developed and the sealing performance and expansion property of the material were also studied and analyzed.The FEI Quanta TM 250 environmental scanning electron microscope was used to investigate the microstructure of material.The results revealed that the new composite sealing material had a desirable expansion performance and a defnite fluidity convenient for grouting.The solidifed material,combining closely with the drilling wall,possessed an adequate strength and was not easy to shrink.Compared to the conventional polyurethane,the gas drainage concentration by drilling sealing exceeded 40 percent,and the sealing capacity improves5 times,the sealing effect increases signifcantly.

Relationship between different surgical methods,hemorrhage position,hemorrhage volume,surgical timing,and treatment outcome of hypertensive intracerebral hemorrhage

BACKGROUND:The present study aimed to explore the relationship between surgical methods,hemorrhage position,hemorrhage volume,surgical timing and treatment outcome of hypertensive intracerebral hemorrhage(HICH).METHODS:A total of 1 310 patients,who had been admitted to six hospitals from January 2004 to January 2008,were divided into six groups according to different surgical methods:craniotomy through bone fl ap(group A),craniotomy through a small bone window(group B),stereotactic drilling drainage(group C1 and group C2),neuron-endoscopy operation(group D) and external ventricular drainage(group E) in consideration of hemorrhage position,hemorrhage volume and clinical practice. A retrospective analysis was made of surgical timing and curative effect of the surgical methods.RESULTS:The effectiveness rate of the methods was 74.12% for 1 310 patients after onemonth follow-up. In this series,the disability rate was 44.82% 3–6 months after the operation. Among the 1 310 patients,241(18.40%) patients died after the operation. If hematoma volume was >80 mL and the operation was performed within 3 hours,the mortality rate of group A was signifi cantly lower than that of groups B,C,D,and E(P<0.05). If hematoma volume was 50–80 mL and the operation was performed within 6–12 hours,the mortality rate of groups B and D was lower than that of groups A,C and E(P<0.05). If hematoma volume was 20–50 mL and the operation was performed within 6–24 hours,the mortality rate of group C was lower than that of groups A,B and D(P<0.05).CONCLUSIONS:Craniotomy through a bone f lap is suitable for patients with a large hematoma and hernia of the brain. Stereotactic drilling drainage is suggested for patients with hematoma volume less than 80 mL. The curative effect of HICH individualized treatment would be improved via the suitable selection of operation time and surgical method according to the position and volume of hemorrhage.