A solid foundation

Solution

Qing Li Wang, project manager for GEDI (Guangdong Electric Power Design Institute) at the Duyen Hai 1 power plant which is under construction on the coast of the Mekong Delta.
 

At the Duyen Hai power plant , the chinese company GEDI used the cement deep mixing (CDM) method to stabilize the soils. In CDM, deep holes – up to 30 meters in this case – are bored into the ground with a special drill. During the drilling process a cement slurry is injected resulting in a stabilization of the soil column. In this way a foundation of stabilized soil columns is created. It is a very effective approach, but requires just the right cement. After extensive testing, GEDI chose Holcim Stable Soils (HSS) for its job. HSS has been specially developed for CDM. Among other things, it offers better chemical compatibility to soft clay soils than regular cement, while delivering twice the strength. That means contractors need less cement per cubic meter of soil, reducing the number of piles required – and reducing the cost.

 

Qing Li Wang guides his visitors around the grounds of the Duyen Hai 1 power plant with a clear sense of pride. “Soon,” says the project manager with a smile, “we will generate electricity here for the first time – thanks in part to Holcim.”

Duyen Hai 1 is the first of three new plants being built by the Vietnamese government here on the Mekong Delta coast, near the city of Trà Vinh. While these projects are bringing much needed jobs as well as power to the rapidly developing area, construction has been anything but easy.

The plants are located on an alluvial plain between two of the Mekong’s major distributaries. It is a flat, watery land, dotted with rice paddies and shrimp farms, and fronted by the sea. “The soil here is wet and soft,” says Wang. “You cannot build large structures on it. Before doing anything else, we needed to stabilize the ground.”

That’s where Holcim comes in. Its Holcim Stable Soil (HSS) product has been designed expressly to shore up weak earth. As part of a method known as cement deep mixing (CDM), HSS can be used to create a foundation of stabilized soil columns under the ground – turning swampy mud into terra firma.

Wang works for Guangdong Electric Power Design Institute (GEDI), the Chinese contractor building Duyen Hai 1. He says HSS not only helped GEDI lay the foundation for the plant, it also allowed them to build other important below-ground structures, like the intake and outtake canals. “Holcim’s know-how and ability to deliver large quantities to the extremely remote location were key for us as well,” he adds.

 

Captain Doan Minh Sang steers the “Saigon”. The barge transports Holcim cement in a three-day trip over inland rivers and canals in the Mekong Delta to the construction side at Duyen Hai.

“Holcim’s know-how and ability to deliver large quantities to the extremely remote location were key for us as well”

Qing Li Wang
Project Manager at GEDI

For Holcim Vietnam, success on this major project required a concerted, firmwide effort. Its commercial team worked closely with GEDI on initial evaluations and the all-important trial mixes. Its consultants supported GEDI with technical advice. The production team ensured that volumes were increased to meet the project’s demands. And its supply-chain team tackled the complex delivery logistics.

This last was no mean feat, as Doan Minh Sang can attest. He is the captain of one of the tanker barges Holcim used to transport HSS from its Thi Vai cement grinding station to the site. Sang, who has been a captain for eight years, made the run regularly. That meant taking on product at the pier at Thi Vai and then making the 300-kilometer, three-day trip over inland rivers and canals to Duyen Hai, before returning for more. In this way, Sang and his colleagues delivered some 150,000 tonnes of HSS to the project, including over a crucial two-month period during the stabilization phase.

 

Because of the remote location of Duyen Hai, delivering the required amounts of cement was a challenge for all involved. To meet it, Holcim Vietnam developed a detailed logistics concept, which included a fleet of 16 barges. Eleven of the barges transported the cement in jumbo bags, each holding 1,000 kilos, and the other five were specially equipped tanker barges for bulk cement.

The Duyen Hai 1 coal-fired thermal power plant covers 50 hectares of coastal land between two of the distributary mouths of the Mekong River. At full capacity, it will generate 1,245 MW of power, contributing 7.5 to 8 billion kWh annually to the region. Owned by Electricity Vietnam (EVN), it is being built by Guangdong Electric Power Design Institute (GEDI), a Chinese contractor with headquarters in Guangzhou. Two other plants, Duyen Hai 2 and 3, are also under construction nearby. These too are relying on Holcim for soil stabilization.

 

Back at Duyen Hai, Wang explains. “We had planned four months for the stabilization but delays left us only two, which meant we needed a supply of more than 1,000 tonnes of HSS per day. In spite of the rainy season, Holcim delivered – on many days supplying nearly 1,300 tonnes from both Hon Chong and Thi Vai plants. In China, where I come from, Holcim is famous for its products and services. The company really lived up to its reputation on this job.”