Quality Control of the TNF Construction Method

Quality control is carried out in accordance with our “TNF Construction Method Construction Management Standards.”

1. Laboratory Mix Design Test

Before construction, laboratory mix design tests are conducted using soil samples collected from trial excavation at the site to determine the appropriate amount of stabilizing agent to be added.

2. Hexavalent Chromium Leaching Test

After the mix design test, we confirm that the amount of hexavalent chromium leached from the improved soil—produced using on-site soil and the planned stabilizing agent—falls within the soil environmental standard limits.

This test is conducted in accordance with the leaching test specified in Environmental Agency Notification No. 46 (Test Method 1), performed at the mix design stage.

3. On-Site Unconfined Compressive Strength Test

During ground improvement construction, unconfined compressive strength tests (JIS A 1216) are conducted after 7 and 28 days to verify that the strength meets or exceeds the design criteria.