The quality of the backfill grout of shield tunnels by recycling incinerated sludge was investigated through laboratory tests and model tests. The laboratory mix tests led to a basic mix proportion to be satisfied with the quality required. The state of mixing material adhering to the inside wall of pressure tubes during grouting was also confirmed from the model tests. The test results showed that the quality of the backfill grout by recycling incinerated sludge could be maintained as the same level as the regular materials of the backfill grout.
