Study on roadway layout and surrounding rock control of isolated island panel.

During the re-mining of historical residual coal resources, the stress environment is complex, the surrounding rock conditions are bad, the mining roadway is significantly affected by ground pressure, the layout is difficult, and the safety is poor. Taking the recovery of isolated island coal pillar in 4# coal seam as the research background, based on the difference in the distribution morphology of the goaf on both sides of the isolated island coal pillar, the stress and failure law of the isolated island panel boundary are studied by numerical simulation method. (1) The peak stress difference of multiple goaf boundaries on both sides of the isolated island coal pillar is between 0.18 and 4.51 MPa. The peak stress is affected by the change of the length of the roof "cantilever beam" at the stopping line of the goaf, so that the peak stress of the goaf boundary is periodic. (2) The high stress is mainly concentrated in the center of the pillar. The peak stress at the end of each pillar is 35-40 MPa. The coal pillar bears high stress, and the stress zone of the original rock moves to the end of the coal pillar. (3) There is a plastic zone of 8-20 m at the corner of the end of each coal pillar. On the basis of the stress zone and failure zone distribution of the goaf boundary on both sides of the isolated island panel, the roadway layout of the isolated island panel is determined, that is, the air-return roadway of the isolated island panel is arranged at random, and the width of the isolated island coal pillar d1 is selected as 10 m. The transport roadway is arranged straight, and the transport roadway of the isolated island panel is in the width section area of the goaf X4103. The width d1 of the isolated island coal pillar is selected to be 8 m, and the length d5-d7 of the mining roadway layout in the width of the coal pillar is 24 m. The roadway of isolated island panel is divided into 4 areas for support control, and the drilling pressure relief technology is proposed for high stress roadway. Through the field monitoring data, it can be seen that the mining roadway can meet the requirements of isolated island coal pillar recovery, which provides reference for the layout and control of abandoned coal roadway in this mine and other mines.

A validated method for the determination of quetiapine fumarate tablets in human plasma by UPLC-MS/MS and its application to a pharmacokinetic study in healthy Chinese subjects.

A rapid, highly specific and sensitive UPLC-MS/MS method was developed for the determination of Quetiapine Fumarate, a therapeutic drug for various psychiatric disorders, in human plasma. The samples were pretreated using a protein precipitation method, followed by chromatographic separation using a column (Kinetex C18, 2.6µm 50*2.1mm) equipped with an ESI source and MRM mode mass spectrometer. In the validation results of the method, the analyte quetiapine showed a peak at approximately 1.0 minute and exhibited good linearity within the concentration from 2.5 to 2000ng/mL. The intra- and inter-batch precision CV% were within the range of -1.3% to 7.7% and precision of intra- and inter-batch were below 15.0%. Furthermore, this method demonstrated low matrix effects and high recovery rates. The quetiapine plasma sample solution remained stable at room temperature for 25 hours and following 4 freeze-thaw cycles. The prepared samples remained stable in the autosampler (The temperature control of the autosampler was 5oC) for 185 hours and after four freeze-thaw cycles at -20oC and -70oC for 40 days. The present work effectively employed this approach to investigate the pharmacokinetics of orally administered quetiapine fumarate tablets in a cohort of healthy Chinese individuals, both in a fasting state and after a meal.

Influence of the ultra-fine fly ash dosages on the mechanical properties of the sulfoaluminate cement-based high water backfilling material.

To reduce the filling cost of high-water backfilling material (HWBM) in mining backfill and improve the recycling utilization of the industrial waste such as the coal fly ash. The ultra-fine fly ash (UFA) was added to the HWBM as a partial replacement in this work. Therefore, a series of experiments were performed to investigate the effect of UFA on the mechanical properties of the HWBM at the different curing conditions, then the hydration mechanism of the HWBM blended with UFA was analyzed by XRD and SEM method. The result indicates that the strength of the HWBM decreased with the increasing of UFA dosages, but the addition of UFA can improve the residual strength of the initial HWBM. Additionally, when the HWBM was cured at the laboratory air condition, its carbonation process was restrained obviously as the UFA dosages were less than 15% at the ages of 28 days, which indicates the UFA can improve the weathering resistance of the HWBM with the curing ages increasing effectively. The XRD and SEM results also shows that the degree of crystallinity of the HWBM increased when UFA dosages were less than 15% effectively, while there were few obvious changes on types of hydration products. It indicates that the main affects of UFA on the performance of HWBM is filler and dilution, which reduced the contact area between hydration products of HWBM and CO2 in the air, further improved the carbonation resistance of HWBM.

Height of overburden fracture based on key strata theory in longwall face.

Among the three overburden zones (the caving zone, the fracture zone, and the continuous deformation zone) in longwall coal mining, the continuous deformation zone is often considered to be continuous without cracks, so continuum mechanics can be used to calculate the subsidence of overburden strata. Longwall coal mining, however, will induce the generation of wide cracks in the surface and thus may cause the continuous deformation zone to fracture. In this paper, whether there are cracks in the continuous deformation zone as well as the height of overburden fracture in longwall face and the subsidence and deformation of strata of different fracture penetration ratios were studied by means of physical simulation, theoretical analysis and numerical simulation. The results show that: (1) Rock stratum starts to fracture as long as it has slightly subsided for only tens of millimeters, and the height of fracture development is the height of working face overburden. (2) With the increase of fracture penetration ratio, the subsidence of key strata remains basically unchanged; the surface deformation range and the maximum compression deformation decrease, while the maximum horizontal movement and maximum horizontal tensile deformation increase. Therefore, the subsidence of overburden strata which have fractured but have not broken can be calculated through the continuum mechanics method.