The requirement of reinforcement effect of subgrade is stricter for railway than for highway. Cast-in-place concrete large-diameter pipe piles (PCC piles) are firstly applied to railway subgrade of connect-line of Nanjing south railway station. In order to explore the characteristics of railway subgrade reinforced by PCC piles

the field tests of quality inspections and performance tests are carried out

including low strain test

static load test

excavation test

and the monitoring of the stress of pile and soil

surface settlement of embankment

layered settlement of foundation

tensor force of geogrid

pore water pressure test. The quality inspections results indicate that PCC piles have good quality

and meet the requirement of bearing capacity design of railway subgrade. The performance tests confirm that the settlement is steady in 3 months after finishing construction of embankment; and the maximum lateral displacement is only 13 mm. As the settlement is steady quickly and small lateral displacement is strictly controlled; it indicates that railway subgrade reinforced by PCC piles can meet the requirement of control settlement with fast construction speed. It is expected to provide guidance for design and application of PCC piles reinforcing railway subgrade.