Research conclusions: ( 1 )Through the comparison of CFG pile raft，bored pile plate and pre - stressed pipe pile raft scheme，using pile raft for reinforcement multi line subgrade has obvious technical，economic and shorter work - period of comprehensive advantages. (2) By using the pile raft foundation，the amount of cushion compression,pile and the stab deformation of the piles can be ignored in the calculation of the settlement calculation of compositefoundation， the amount of compression of the substratum under the pile is only counted，calculation accuracy meets the requirements. (3) Using static pressure method for prestressed pipe pile construction,in case there are thick dense sand stratum，using high pressure water flushing with static pressure construction methods to traverse can meet the design pile depth. (4)Through observation and evaluation ol subgrade settlement，it is recognized that using the pile raft foundation without preloading meet the standard of settlement after construction. (5 ) The research results can provide reference for the foundation reinforcement of the multi line subgrade of passenger dedicated railway line.