At the construction site of the Phase III project of Xi'an Metro Line 1 in Shaanxi, the hardened road surface is clean and tidy, fog cannon machines and sprinkler systems automatically spray, and dust and noise monitoring equipment monitor in real time... Bidding farewell to the stereotype of being "dusty and dirty," the project site is bustling with activity, clean and orderly.


　　"The Phase III project of Xi'an Metro Line 1 connects the urban area of Xianyang and Fengxi New City of Xixian New Area, with 7 stations and a total length of 10.61 kilometers," introduced Wen Shaopeng, General Manager of PowerChina (Xi'an) Rail Transit Construction Co., Ltd. As the first rail transit line connecting Xi'an and Xixian New Area, Xi'an Metro Line 1 is an important transportation artery between Xi'an and Xianyang. With the continuous extension of Xi'an Metro Line 1, it will further promote the integrated development of Xi'an and Xianyang, alleviate urban traffic congestion, optimize urban spatial layout, and achieve the city's overall planning goals.

　　Overcoming Difficulties with Double Underpasses

　　The Phase III project of Xi'an Metro Line 1 is entrusted by the Xianyang Municipal Government to Xi'an Rail Transit Group Co., Ltd. for construction management and operation. It promotes "administrative integration" through "transportation integration" and drives the integrated development of Xi'an and Xianyang. As a rare cross-regional project jointly built by two cities, there are many coordination interfaces and a large workload of coordination during construction. "In addition to coordination work, the main difficulties in construction lie in the shield tunneling sections passing under rivers such as the Wei River and existing railway lines such as the Zhengzhou-Xi'an High-Speed Railway, with high technical requirements and construction risks," said the relevant person in charge of the project owner.


　　The underpass of the railway line mentioned by the project owner refers to the shield tunneling section from Qindu Station to Baoquan Road Station of the Phase III project of Xi'an Metro Line 1 passing under the Xuzhou-Lanzhou High-Speed Railway, the Longhai Railway, and the subgrade section of the Xianyang West Freight Yard. The shield tunneling under the Xuzhou-Lanzhou High-Speed Railway is the first time a metro has underpassed a ballastless track subgrade section of a high-speed railway. During shield construction, controlling the settlement of the high-speed railway subgrade is key to ensuring the operational safety of the high-speed railway and the safety of metro construction. For the shield tunneling under the high-speed railway, the owner organized design, construction, monitoring units, and research institutions to conduct research, strictly reviewed the construction plan for the shield underpass, and organized experts to repeatedly demonstrate the plan.

　　The shield tunneling section from Zhonghua West Road Station to Angu Road Station of the Phase III project of Xi'an Metro Line 1 passes under the Wei River. After multiple expert reviews, Xi'an Rail Transit Group determined to use a slurry balance shield machine for construction, which is also the first time a slurry balance shield machine has been used in metro engineering in Shaanxi. "The slurry shield method is suitable for underpassing large rivers or lakes. Compared with traditional methods, slurry shield technology is more difficult. The shield section crosses the Wei River channel, underpassing the Wei River for about 600 meters. The shield machine is about 15 meters from the river bottom and about 5.5 meters from the lowest scour line. The tunnel body mainly passes through medium sand with local coarse sand layers, posing high safety risks," said Wen Shaopeng. To ensure the smooth construction of the shield underpassing the Wei River, before shield construction, based on geological conditions and the engineering characteristics of the underpass operation, the construction party organized all participating parties to carry out technical analysis of shield machine adaptability. By optimizing the cutterhead, grouting and grease system design, and strengthening the tail brush sealing design, the safety assurance of slurry shield construction was increased. "Slurry shield tunneling balances the earth pressure and water pressure on the excavation face by sending slurry into the slurry chamber to maintain the stability of the excavation face. The excavated soil and sand are transported to the surface in the form of slurry, separated by slurry treatment equipment, and recycled. During shield construction, construction will be organized strictly according to the plan, deformation monitoring of the Wei River will be strengthened, and the surrounding environment will be protected," said the relevant person in charge at the project site.

　　"Smart" Supervision Ensures Project Safety

　　"Safety management starts as soon as workers enter the site," introduced Chen Kangrong, Director of the Safety and Environment Department of PowerChina (Xi'an) Rail Transit Construction Co., Ltd. The project department, in cooperation with Hangzhou Pinming Security Control Information Technology Co., Ltd. (hereinafter referred to as "Pinming Co., Ltd."), developed a smart construction site cloud platform integrated with the labor real-name system. When workers enter the site, information is collected, shared, and used to reduce the risk of labor disputes; through intelligent identification of safety helmet and reflective clothing wearing, management of special work areas is strengthened, the wearing rate of protective equipment is improved, and safe construction behavior on site is standardized; through intelligent identification of employee boundary crossing and intrusion by outsiders, safety management of construction areas is standardized, site safety is ensured, and strong support is provided for on-site management.

　　"In the construction of mined tunnels, we adopted multiple systems for superimposed management, including real-name access management, video surveillance, personnel positioning, and intelligent tunnel control systems. The data of the entire system is connected to the construction site management cloud platform, allowing real-time data and historical statistical records of the tunnel face to be viewed in the cloud, and alarm notifications to be received via mobile phones, with support for data export and threshold setting," said the relevant person in charge at the project site. Currently, the project has achieved real-time communication between above-ground and underground, collection of underground image data, comprehensive and accurate grasp of dynamic information of underground workers and mechanical equipment in space and time, and optimization of construction organization.

　　In addition, the project uses a combination of fixed cameras and dome cameras to set up a full-coverage, no-blind-spot video surveillance system at the construction site and office area, achieving full-process monitoring and full-process linkage, precisely controlling the site context, shortening management radius, and ensuring project safety.

　　"We adopted the tower crane monitoring system provided by Pinming Co., Ltd. to collect data throughout the operation of tower cranes. The anti-collision algorithm has reached 196 types and supports flat-jib, luffing-jib, and rail-mounted tower cranes, ranking among the top in the market," said the relevant person in charge at the project site. The system supports data analysis of tower crane operation and can provide detailed efficiency reports, further improving the project's construction progress. In addition, the project has installed online monitoring systems for large equipment such as tower cranes to monitor operation data in real time and ensure safe operation.

　　"To address problems such as 'difficult inspection, difficult rectification, and difficult management' in engineering projects, the project department adopted a hidden danger investigation system," introduced Chen Kangrong. This system can directly upload safety and quality issues via mobile phones and conduct data analysis and rectification, presenting the entire inspection and rectification process with responsibility assigned to individuals. In addition, based on the distribution and trend of problems, it can intelligently analyze problem trends and completion status, automatically classify and statistically analyze safety and quality problems, and intelligently generate various reports. High-incidence areas are clear at a glance, facilitating timely and effective rectification.

　　Undoubtedly, the comprehensive monitoring and analysis of people, machines, materials, methods, and environment at the construction site by the smart platform provides strong support for project management decisions. In Wen Shaopeng's view, informatization development is the general trend. "In the future, we hope to integrate urban planning, rail transit, municipal facilities, water system management, and other fields into a BIM (Building Information Modeling)-based rail transit full life cycle platform through system integration, thereby achieving more systematic and scientific planning of urban areas and better serving urban construction."