Stone Column Equipment Work

OMS Vibroflot Utilized for Stone Column Project

OMS Vibroflot equipment was successfully utilized in the Nghi Son II BOT Thermal Power Plant Project located in Thanh Hoa Province, Vietnam. The project involved ground improvement works for coal stock house foundations built on soft soil conditions.

Thermal Power Plant Project – Nghi Son / Vietnam

The Nghi Son II BOT Thermal Power Plant project consists of two turbines with a total capacity of 600 MW. Four large coal stock houses were constructed on soft ground to store coal used as the primary fuel source for the power plant operation. The coal stock houses were designed to contain dry coal loads reaching heights of 12 meters.

The entire construction area was located on soft soil layers varying between 1.5 meters and 9 meters in depth. To prevent excessive settlement during coal loading operations, a stone column ground improvement solution was designed using:

• 9-meter stone column depth
• 800 mm column diameter
• 2.2 m × 2.2 m spacing in center areas
• 2.5 m × 2.5 m spacing at shoulder sections of coal masses

Significant Cost Savings Through Stone Column Method

Initially, the general contractor selected the Cement Deep Mixing (CDM) method for soft soil improvement. However, FECON successfully convinced DVN to replace the CDM method with the stone column dry bottom feed method.

This engineering decision enabled the project owner to save millions of USD in ground improvement costs while also ensuring the project was completed on schedule.

OMS Vibroflotation Equipment Performance

FECON S&C carried out the project using OMS vibroflotation equipment and the bottom feed method with three vibroflotation systems consisting of one electric motor unit and two hydraulic motor units.

Within the scope of the project:

• A total of 12,940 stone columns were installed
• All installation works were completed within 120 days
• The project satisfied both quality and schedule requirements of the project owner
• The work was completed 10 days earlier than the contractual schedule

FECON stated that they were highly satisfied with the technical support provided by OMS throughout the project implementation process.

Project Status

At the time of publication, the project had progressed to the concrete floor construction phase on the ground sections treated with stone columns. The Nghi Son II BOT Thermal Power Plant project was expected to be completed in July 2022.