Horizontal roof gap of backfill hydraulic support

For the backfill hydraulic support as the key equipment for achieving integration of backfilling and coal mining simultaneously in the practical process, its characteristics will directly influence the backfill body's compression ratio. Horizontal roof gap, as a key parameter of backfilling characteristics, may impact the backfilling effect from the aspects of control of roof subsidence in advance, support stress, backfilling process and the support design. Firstly, the reason why horizontal roof gap exists was analyzed and its definition, causes and connotation were introduced, then adopting the Pro/E 3D simulation software, three typical 3D entity models of backfill hydraulic supports were built, based on the influence of horizontal roof gap on backfilling effect, and influence rules of four factors, i.e. support height, suspension height, suspension angle and tamping angle, were emphatically analyzed on horizontal roof gap. The results indicate that, the four factors all have significant impacts on horizontal roof gap, but show differences in influence trend and degree, showing negative linear correlation, positive linear correlation, positive semi-parabolic correlation and negative semi-parabolic correlation, respectively. Four legs type is the most adaptive to the four factors, while six legs(II) type has the poorest adaptability, and the horizontal roof gap is small under large support height, small suspension height, small suspension angle and large tamping angle situation. By means of optimizing structure components and their positional relation and suspension height of backfill scrape conveyor in the process of support design and through controlling working face deployment, roof subsidence in advance, mining height and backfilling during engineering application, the horizontal roof gap is optimized. The research results can be served as theoretical basis for support design and guidance for backfill support to have better performance in backfilling.

Effect of Support Height on Microstructure and Mechanical Properties of Selective Laser Melting Ti-15Mo Alloy

In this research,for the first time,the Ti-15Mo alloy generated via selective laser melting(SLM)with many different support heights was examined.With the increase of the support height,the risks of forming microcracks and small holes increase while the ductility of the sample decreases.The grain sizes of the samples decrease with an increase in support height because of the more efficient heat dissipation rate during the SLM process.The average grain sizes of the samples are 36.95±0.7μm(5 mm-sample I),35.24±0.7μm(10 mm-sample II)and 33.91±0.7μm(15 mm-sample III),respectively.As the support height increases,the intensity of(111)texture increases and the misorientation angles gradually decrease.The ultimate tensile strength,yield strength and ductility of the three samples are 970±13 MPa,769±12 MPa and 9.78%±1.5%(sample I),1051±11 MPa,932±11 MPa and 7.17%±2%(sample II),1123±14 MPa,1089±9 MPa and 5.4%±1.4%(sample III),respectively.The decrease in grain size,increase in dislocation density and enhancement of the(111)texture are all conducive to achieving the higher strength.