Sichuan-Tibet Railway Section 5 - Jiangsu ARIT new materials Co., LTD

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Name

Sichuan-Tibet Railway Section 5

BACKGROUND

The Sichuan-Tibet Railway (川藏铁路) is a major railway project in China, connecting Chengdu in Sichuan Province to Lhasa in the Tibet Autonomous Region. It is the second major railway line into Tibet after the Qinghai-Tibet Railway. The railway is divided into three sections: Chengdu-Ya'an, Ya'an-Nyingchi, and Nyingchi-Lhasa.The Ya'an-Nyingchi section, which started construction in November 2020, is considered one of the most challenging railway projects in the world due to its complex geological conditions, fragile environment, and extreme climate. It will traverse through the Sichuan Basin, the Yunnan-Guizhou Plateau, and the Qinghai-Tibet Plateau, with significant elevation changes and numerous natural hazards such as avalanches, landslides, and earthquakes.

PROJECT CHALLENGE

The tunnel has a large burial depth, with severe seepage at the working face. The shotcrete takes a relatively long time to set and harden, has poor adhesion, and there is a large area of rebound and block falling.

Solution from ARIT

The cement used on site is Yadong P.O42.5. The liquid finished product prepared with ART-HQ330 was tested for compatibility with the on-site cement. The test results are shown in Table 1. The use of ART-HQ330 allows for on-demand preparation. The mix proportion of C30 shotcrete is shown in Table 2.

Table 1 Comparison of Compatibility between Two Accelerators and Yadong Cement

Accelerators	Dosage/%	1d Strength/MPa	Cement	Initial Setting/min:s	Final Setting/min:s
ART-HQ330	7	8.9	Yadong	0.055555556	0.180555556
Original Accelerator	8	4.1		0.159722222	0.364583333

Table 2 Mix Proportion of Shotcrete C30

Cement	Sand	Gravel	Water	Reducer	Accelerator
(kg/m3)	(kg/m3)	(kg/m3)	(kg/m3)	(kg/m3)	(kg/m3)
480	847	785	172	5.6	37.6

Table 3 Comparison of Field Usage of Two Accelerators

Accelerators	Dosage/%	Rebound amount/%	Spraying flatness	Remarks
ART-HQ330	45815	45950	Good	Successful spraying at seepage areas
Original Accelerator	45878	＞ 40	Poor	Severe block dropping and large rebound during seepage spraying

Through trial spraying, the problems of severe block dropping and high rebound rate due to seepage on site were solved. The sprayed surface is smooth, and the spraying operation time was greatly reduced, effectively improving the construction progress. The usage effect was recognized by the tunnel construction team. Picture 1 below shows the construction site.