Abstract. A set of nozzle and water dispersion devices were designed to obtain a desirable jet breakup and save water from an impact sprinkler (IS) at low pressure conditions. Comparative performance indicators were obtained for the commercial LP and IS sprinkler heads. Results show that under the same working conditions, the IS produced a large spray range and the water distribution in the middle of the spray range (R) was better than the LP. The best simulated uniformity from the IS was obtained for the combined spacing factor of 1.4*R and the combined uniformity was 4% larger than the LP. Considering the middle position of the spray range, the number and diameter of the droplets from the IS were larger than the droplets from the LP. However, in the end position of the spray range, the droplet diameters from the IS were quite smaller than the LP. Velocities from IS ranged between 0.2 and 6.4 m/s, while that from LP sprinkler were slightly higher ranging from 0.15 to 7.7 m/s at 150 kPa. Overall, introduction of the fixed dispersion device with a pointed tip profile combined with the 6 mm nozzle offered some advantages for the IS over the LP sprinkler at low-pressure conditions. Keywords: Dispersion device, Droplet distribution, Impact sprinkler, Low pressure sprinkler, Nozzle, Spray range, Uniformity.

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In order to research the influence of the shear capacity of reinforced concrete beam with the incorporation of basalt fiber, four basalt fiber reinforced concrete beams with parameters of length and volume ratio were designed and made. The fiber lengths were 12mm and 30mm, and the volume ratios were 1‰ and 2‰. The test data of basalt fiber reinforced concrete was obtained through the shear experiments and comparison with the common reinforced concrete beam. The results of the experiment show that the cracking load of the basalt fiber reinforced concrete beam increase obviously with the growing of fiber characteristic parameters, and effectively reduce the diagonal crack width.

Combined with the current research situation of construction of tunnels with small clear spacing, the key technology of design and construction of tunnels with small clear spacing is summarized, which primarily consists of rational clear interval of tunnels with small clear spacing, advanced support, construction methods and clip rock reinforcement. The passage describes various methods of key technologies currently in use and the selecting rule under the condition of various categories of surrounding rocks, which has some significance on the safe construction of tunnels with small clear spacing.