In order to the solve the problem of high rebound rate of shotcrete during underground support in drifts, Jinchuan Project conducted tests on shotcreting process with liquid accelerator at 1350mL. Through repeated tests and comparisons of different results, it was noticed that liquid accelerator could significantly reduce rebound rate and save shotcrete material, which further generate economic benefits for the project.
The comparison was done between Line 48 single-rail haulage way and Line 53 single-rail haulage way both at 1350mL, and mainly targeted at secondary support. The test material consist of PC32.5 cement, aggregates, powder accelerator and liquid accelerator. Material ratio with powder accelerator is per usual, and with liquid accelerator as 2%. Before apply shotcrete, measurement and survey of tunnel were carried in order to differentiate area for comparison, and to evaluate shotcrete amount.Upon the completion of shotcreting process, the measurement and analysis were done which indicated that the average rebound rate was 25% using powder accelerator, while below 10% using liquid accelerator, 15% decrease achieved.
In summary, it was proven that using liquid accelerator could significantly decrease rebound rate. We will conduct further test to determine the best material ratio and promote the application in all our projects, hence to achieve cost-reduction and efficiency-enhancement goals.
