The tunnel length of the project is 2,583m. Project started in 2017 and completed in 2020. This is a 2-lane road tunnel using the drill and blast method of construction.
Shimizu is the first company to employ liquid accelerator solution for a tunnelling project in Japan. Japan has always used powder accelerator for wet sprayed concrete. Rebound ratees was around 20 to 30%, dust were high and sprayed concrete output coud not exceed more than 12 - 14 m3/hr. Normet and our marketing partner in Japan, Sandvik proposed the Normet's solution and we were chosen as the solution provider. We had to reach the performance specifications using liquid accelerator as below (this is essentially the specifications for powder accelerator):
|3 hr Strength
|> 2 MPa
|1 Day Strength
|> 10 MPa
|28 Day Core Strength
|> 36 MPa
|Max. Aggregate Size
|OPC Content / m3
Normet team made the mix design and conducted successful test sprays on site to proof that we can meet the project specifications.
Shimizu had completed the tunnelling works ahead of schedule. Operators of Spraymec 8100 VC could spray up to 24m3/hr with an average of 8.2% rebound. Refer to table on the right, reference is from Shimizu's report on rebound with different spray concrete output.
Shimizu had made studies and the following data were collected from their engineers on site; Shimizu had made a report and published a paper on this stating that their first project with liquid accelerator was successful in reducing cycle time, rebound and dust.
Based on the data provided by Shimizu, the project achieved 25% reduction in cycle times as they managed to have a higher sprayed concrete output as compared to powder. Most significant success is seen in reduction of rebound, up to 49% when using Normet's liquid accelerator as compared to powder. In addition, dust emission was reduced by 55% and this provided a safer working environment for the operators.