On January 16, the Chongqing municipal key project, the Lijiatuo Double-Line Bridge North Approach Project, achieved new progress. As a beam of light shone into the three-lane tunnel of the Jiulongpo double-line tunnel, the tunnel was broken through, marking the full completion of the Jiulongpo double-line tunnel.

The Lijiatuo Double-Line Bridge North Approach Project is located in Jiulongpo District, starting from Qinglongzui Interchange in the north and ending at Lijiatuo Bridge, with a total length of about 2.65 kilometers. The entire line is designed to urban expressway standards and includes one medium tunnel, one main-line elevated bridge, and one interchange.

"The Jiulongpo double-line tunnel is divided into a two-lane tunnel on the left line and a three-lane tunnel on the right line. The two-lane tunnel on the left line was successfully completed in August last year, and today both tubes are officially completed," said Zou Tao, technical director of the Lijiatuo Double-Line Bridge North Approach Project of China Railway 11th Bureau Group. The Jiulongpo double-line tunnel passes beneath schools and residential buildings and is close to a military area. Some sections of the tunnel were originally designed for blasting excavation, but since blasting produces vibration and noise, it would have a significant impact on nearby buildings and the daily lives of nearby residents. To reduce disturbance and create a harmonious environment, the excavation method for the entire tunnel was changed to mechanical excavation.

"Mechanical excavation produces little vibration and causes little disturbance to nearby residents, achieving harmonious construction."

Zou Tao said that the Jiulongpo double-line tunnel also passes beneath a power school and residential buildings, with shallow cover at the tunnel crown, the shallowest being only 7.6 meters, imposing high requirements for the protection of existing buildings and structures. In addition, the tunnel is a small-clearance tunnel; after excavation, the thin rock wall in the middle bears relatively high pressure, and the side wall pressure of the left and right tubes is also relatively high, so construction of the later tube can easily cause damage and collapse to the earlier tube. To ensure the stability of ground structures and safety during construction, in addition to adopting mechanical excavation, the project adhered to the principles of "advance pipe roof, short advance, strong support, early closure, and frequent measurement," and strengthened initial support and advance support during construction, while closely carrying out in-tunnel monitoring and measurement and surface observation, effectively ensuring that all work proceeded safely.

Wu Jianming, on-site project manager of Chongqing Chengtou Infrastructure Construction Co., Ltd., said that since the project team entered the site in August 2021, the company has organized all participating parties to overcome difficulties and carried out management in safety, green construction, harmony, and quality to ensure the tunnel was completed on schedule. During tunnel construction, the project applied standardization, intelligentization, and other means to improve construction management quality and build a premium project.

The Lijiatuo Double-Line Bridge North Approach Project is part of the Fourth Vertical Line of the expressway network. After completion, the project will further improve the urban expressway network framework of the central urban area, strengthen the rapid connection between Banan District and Jiulongpo District, alleviate traffic pressure on adjacent river-crossing channels, and be of great significance to promoting Chongqing's economic development.