Abstract: The wet shotcreting technology has been gradually applied to roadway support of fractured rock mass in extremely cold mining areas, and the temperature is critical to the strength development of wet shotcreting. This paper has introduced the low strength of spray layer, likely cracking and other problems occurred to wet shotcreting support in cold regions of Jinying Gold Mine, studied the rules of influence of temperature, cement content and water-cement ratio on the strength of spray layer, and adopted SEM to observe the microstructure of wet shotcreting. The results show that the initial strength of wet shotcreting reduces significantly when the temperature is below 10 °C, and the temperature above 16 °C is quite beneficial to the long-term strength increase; there is a critical range of cement content, and when the cement content is greater than the threshold, the strength of wet shotcreting increases significantly; the different water-cement ratios have a complementary effect on the strength development of different ages, because the low water-cement ratio helps increase the initial strength, while the high ratio helps increase the long-term strength; the temperature plays an essential role in the microstructure of wet shotcreting, and inner initial porosity and aggregate interface bonding strength cracking directly affects the macro-mechanical properties of wet shotcreting; when the temperature is lower than 10 °C, the aggregate interface intends to have microcracks due to different coefficients of thermal expansion; the daily spray amount has reached 40 m3 and the repair rate of wet shotcreting support reduced by 80% in Jinying Gold Mine by improving mixture ratio and technology.

Key words: wet shotcrete, mine in cold region, compressive strength, microstructure, roadway supporting