These days, SCI workers at Nam Theun 1 Hydropower Plant Project were consolidating the cofferdam in order for its completion right next week.
The shift starts at 21h15
From 21h00, more than 50 Engineers and workers were presented at the site. Said by the Engineer Nguyen Van Thuong – QC executive on his shift, because of the rushing schedule and taking advantage of the dry weather, the shift transfer was done directly on site. Also stated by Thuong, today, this item was serviced by 30 helpers, 10 drivers, 3 M&E workers, 3 shuttering capenters and 3 field technicians. After hearing the site safety regulations within 15 minutes, they started their work immediately.
The Namtheun 1’s cofferdam construction, having the concrete volume of around 140.000m2 and the elevation range from 123-173 started from the river foundation inclusive of the downstream cofferdam, was completed at the level 150 while the upstream cofferdam was under construction at the level 167. According to Engineer Pham Quang Anh – RCC concerete item site manager, the upstream cofferdam would be finished in 5 – 6 days if the weather was favourable.
A variety of bulldozers, vibrators, scrapers, vacuum machines, mortar machines were 'live-transfered' from the present shift to the next shift at 9:15 PM with the desire to take advantage of the nonstop performance of machines. Although the stages of roller compacted concrete RCC at the cofferdam were so familiar, the field QC Engineer and technicians were very meticulous and detailed in the new construction. Starting from grouting on the scorched surface, then the concrete was compacted by a 15T vibrator (in which 01 turn of compaction was done by the static vibriator and three times of compaction by the vibrator).
Revelea by Engineer Thuong, the 20cm minimum overlap compact was done for keeping all of the RCC ranges in strong compaction. Afterthat, the concrete placing layer was checked by the surveyor who controlled the tilt layer by a laser meter. The following work was leveling of RCC in which the width of each pouring strip range was around 12-15 m (depending on the width of each slant strip) and the thickness of each layer was 35cm (30cm after it was compacted). Due to two consecutive dumping strips, the concrete placement should be spaced about 10-15m apart with flattened RCC conditions without stratification. After finishing 10-15m leveling, the contiguous areas of rock formations, stone roofs, and pre-set details will be flattened manually.
This process was kept going together in the enthusiasm of each driver, every laborer who seemed not pay attention to the break time until the horn signalling the break when all workers were invited to stop their work and use bread and milk for calming down their hunger. And then, the site was bustling with vibrators, mortar spreaders, concrete graders with the workers’laught as if they had never been tired.
The breaktime was out of the workers’ concern
Said by Engineer Pham Quang Anh, this is the first time SCI had implemented RCC compacted concreting - the advanced construction method in hydropower construction that was very popular today. Not only that, this is the first RCC dam in the world that doese use the downstream formwork but use a vibrator to create a downstream roof – although the construction techniques were very difficult, SCI has done it sucessfully. Therefore, SCI is highly evaluated by JV general contractor (including consortium of CMC contractor (Italy) - Italian Thai (Thailand) - Song Da (Vietnam).
Thanks to the SCI workers’ efforts, the upstream cofferdam will be completed in the near future that absolutely helps the SCI brand more and more be trusted for the big projects like the sun which is dispelling the fog. One shift nigh is finished quickly and welcome the new working day of the next 50 workers and engineers.
Some night shift photos on site:
