With Shanghai-Nanjing intercity railway CFG pile-net composite foundation and Beijing-Shanghai high speed railway sand pile-net composite foundation of Kunshan test section, in order to get variation law of properties of composite foundations ,monitoring components, such as the soil pressure boxes, the settlement gauges and the pore water pressure gauges, etc, were put into the field test sections, to monitor and obtain the magnitude of ground settlements(post construction), pile tops soil pressure and soil pressures between piles , pore water pressures and other field test data. The settlement control effect of two different pile types (CFG pile-net and sand pile-net) was comparatively analyzed with field test during construction period and post construction settlement. The results show that both ground improve-ment method,i.e. CFG pile-net and sand pile-net preloading, can meet the settlement control requirement of ballastless track of High-speed Railway Post-construction Settlement (less than 15mm) with different preloading periods according to the field tests. The total settlements and settlement velocity of CFG pile-net foundation are smaller than that of sand pile-net foundation. The convergence speed of CFG pile-net foundation is faster, which means it requires a less period of time for preloading. But there is a big differ-ence affected by the pile stiffness on the law of stress of pile and soil. The stress ratio of pile and soil in CFG pile-net foundation is increases with the increasing of the filling of the embankment and eventually stabilized, while that of sand pile-net foundation decreases with the increasing of load first, presenting the wave shape change. And the dissipation rate of excess pore water pressure in CFG pile-net foundation is far less than the latter. In the case of short construction period, compared with the sand pile-net composite foundation, the settlement control effect of CFG pile-net composite foundation is more efficiently.
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