'Smart' equipment bolsters China's subway construction

Builders in China are intensifying efforts to make more intelligent equipment in an effort to leapfrog from "manual construction" to "intelligent construction" and enhance workplace safety.

At the construction site for the No 01 section of Wuxi Metro Line 6 in Wuxi, Jiangsu province, builders from China Railway No 4 Engineering Group (CREC4) replaced the traditional manual vibration mode with side-wall intelligent vibration equipment on Nov 20, enhancing quality and saving on labor and cost.

Adopting a track-type design and equipped with a retractable mechanical arm to cover a height of 13 meters and a length of 50 meters, the new equipment includes a high-precision positioning sensing system and a multi-sensor integration composed of vibration sensors, cameras and sonar.

The device, jointly designed and developed by the CREC4 project department and a manufacturer, aims to inject new "intelligent energy" to urban rail transit construction, said Mei Yantao, chief engineer of the CREC4 project department for the metro work.

The fourth plenary session of the 20th Central Committee of the Communist Party of China issued a communique in Beijing on Oct 23 on the strengthening of China's manufacturing and transportation sector.

Mei said: "Previously, the concrete vibration of the side walls of subway stations in China mainly relied on manual labor.

"For a side wall generally reaching five to eight meters high, workers holding vibration rods have to endure high labor intensity and safety risks. Also, human factors can easily lead to missed vibration or over-vibration, resulting in defects such as honeycomb and rough surface on the concrete surface."

In addition, a single side wall — which is some 20 to 30 meters long — usually requires six to 12 builders to work for several hours at a time. Fatigue can impact construction quality, Mei said, stressing that traditional construction methods often face such challenges as redoing poor work or delays in project schedule.

All these factors led them to seek new intelligent vibration equipment to achieve technological breakthroughs, Mei said.

"Its vibration path can be automatically planned, and the frequency, duration, and insertion depth can be adjusted in real time to achieve 'adaptive vibration' and ensure that the concrete is compacted and unified," he added.

During operations, the device supports two modes — remote control and fully automatic, and one operator can monitor two devices simultaneously, saving on manpower.

Mei said the new device can achieve significant results in quality, efficiency, and cost: "In terms of quality, human construction defects are basically eliminated, and the first acceptance rate of concrete has reached over 99 percent, achieving 'solid inside and beautiful outside, no leakage or seepage'."

"In terms of efficiency, a single device can replace four to six workers, with continuous operation throughout the day, and in terms of cost, the construction of the main structure of a single station can be done for around 500,000 yuan ($70,420) less," Mei added.