PCC桩加固铁路软土地基现场试验研究

铁路相对于公路对承载力和沉降控制都提出了更高的要求。现浇混凝土大直径管桩（PCC桩）技术首次在南京南站联络线铁路工程中应用，为了研究PCC桩加固铁路路基的工作特性，开展了PCC桩加固铁路软土地基的现场检测与监测试验研究。现场检测包含静载试验、低应变检测和开挖检测。现场监测内容为：桩土应力、地基和路堤水平位移、表面沉降、分层沉降、土工格栅张力、孔隙水压力等。质量检测结果表明，PCC桩施工质量良好，承载力达到铁路地基设计要求。现场监测表明，地基沉降在填土结束后3个月稳定，最大水平位移为13 mm，路基沉降稳定快，水平位移小，路堤稳定性高，能满足铁路严格控制沉降和快速施工的要求。研究成果对PCC桩复合地基加固铁路地基的设计和应用提供了依据。

Field test of railway soft clay subgrade reinforced by PCC piles

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.