On February 12, the Chongqing Donghuan Project Department carried out the over-consumption treatment for the over-consumption problem of the tunnels under construction (i.e. from January to December 2022). According to the statistics on the reduction of concrete in each tunnel, it is concluded that in 2022, the tunnel consumption of the project department will be reduced by about 2500 cubic meters, and the loss rate of shotcrete in each tunnel will be reduced compared with the previous one.
Through calculation, the minimum monthly over-consumption coefficient of Zhaojiaping, Zhujiawan and Nanshancun tunnels is 69%, and the total over-consumption rate is 101%; the minimum monthly over-consumption coefficient of Zhujiawan tunnel is 76%, and the total over-consumption rate is 100%; The monthly minimum over-consumption coefficient of Nanshan Village Tunnel is 79% and the total over-consumption rate is 103%, which are lower than requirements of China Railway First Bureau for the loss rate of shotcrete in IV and V surrounding rock tunnels. From November 1 to 30,
2021, the project department collected and counted the shotcrete data of Zhaojiaping, Zhujiawan and Nanshancun tunnels under construction, which showed that the average shotcrete overconsumption of the three tunnels under construction was 112%, 103% and 114%, respectively. All of them are higher than company's requirement that the loss coefficient of shotcrete should not exceed 100%.
In order to strengthen cost control, improve economic efficiency, promote large business management, and help the company develop with high quality, Chongqing Donghuan Project Department set up a QC team to establish the project "Reducing the loss coefficient of tunnel shotcrete", and the QC team was headed by the project leader. The technical backbones of each department and office shall act as the team members, regularly track, inspect, analyze and demonstrate the tunnel construction process, and confirm according to the inspection results, and summarize the main reasons for the high over-consumption coefficient of the tunnel shotcrete. Through the analysis of the causes of excessive consumption in the early stage, the
project department has formulated seven measures to seek breakthroughs from the aspects of personnel, management, technology, mechanical equipment and surrounding rock grade: First, training and education for management personnel and construction personnel, regular technical disclosure meetings, and the sense of responsibility and operation level of construction personnel have been significantly improved. The second is to strengthen the management of survey and test work, carry out personnel training, formulate reward and punishment measures, and effectively control the phenomenon of tunnel over-excavation and concrete quality problems. Third, learn advanced construction technology and operation procedures, invite experts and experienced personnel to give on-site guidance, and simultaneously implement video education, organize visits to adjacent units, and further standardize the operation procedures of on-site personnel. Fourth, formulate mechanical maintenance and repair system, implement responsible persons, eliminate old products, introduce new equipment, and increase work efficiency. Fifthly, divide the bad geological layer of the tunnel face into areas, adjust the blasting parameters reasonably according to local conditions, adjust the blasting area and hole spacing in time according to the surrounding rock conditions, and use machinery to break the under-excavated part after blasting, so as to achieve precise control. Sixthly, strictly control the distance between the peripheral holes, the angle and the distance from the excavation contour line on site, and timely adjust the technical measures such as the distance between the peripheral holes and the angle according to the over-excavation and under-excavation of the excavation contour after blasting. Seventh, regularly invite the leaders and colleagues of the company's industrial management department to the site to give guidance to the on-site technicians, correct deviations, solve doubts, and formulate the goals and directions for the next stage.
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