Research On Appliaction Of CFG Pile Composite Foundation In The Wanggang Segment Of Hada High-speed Railway

With the qualities of increased transport capability, higher speed in traveling,improved passenger comfort and reduced maintenance work, high-speed railwayshave been the trend of the railway development in China. The post-constructionsettlement of the high-speed railway is strictly demanded, and the bearingcapability as well as the ground settlement is critical to the foundation tre atment ofhigh-speed railway construction. The CFG pile composite foundation, havingshorter construction period, higher bearing capability and less lateral deformation,can meet the requirements of the high-speed railway foundation treatment. Theextensive application of CFG pile to construction engineering has obtained goodeconomic benefits. However, the usage of CFG piles on high-speed railway is justat the starting stage, and either the engineering application of CFG pile or thetheory research on it is less. Yet, there has not been any domestic experience inhigh-speed railway construction in the cold areas of northeast China.The Harbin-Dalian high-speed railway is the first high-speed railway example inwhich the ballast-less track is used in the domestic northeast areas. Based on theCFG-piled composite foundation treatment technique applied to the Wanggangsegment of the Harbin-Dalian Passenger Dedicated Line in Harbin, this paper isusing the methods of field testing and numerical analysis to do some research on thebearing capability and settlement characteristic of the CFG pile.At first，the concept, composition, mechanism of CFG pile composite foundationand the cushion storey are described, and the methods for calculating the bearingcapability, the settlement and the post-construction settlement of the foundation isintroduced. Moreover, the method for settlement prediction is illustrated. Then, thispaper describes the application of CFG pile composite foundation to the Wanggang segment of the Harbin-Dalian Passenger Dedicated Line in Harbin, including theconstruction technique and quality control measures for spirally-drilled pile withpumped concrete, burying of foundation settlement observation elements, theobserving method, data collection and analysis of the foundation settlement and theoperation steps of the single-pile composite foundation net load testing. Here，thebearing capability characteristic value and the ultimate bearing capability will beestimated by using the p-s curve.At last, the single-pile composite foundation net load testing is numericallysimulated by using the finite difference method code-FLAC3D. Based on the7-metre high embankment and1.5-metre-far pile spacing, the simulation simulatesthe influence of different pile lengths and different cushion thickness on the CFGpile composite foundation’ s pile-soil stress ratio and settlement, in order to find therules of such influence on CFG pile bearing capability and the foundationsettlement.