Research conclusions: ( 1) This paper adopts several in － situ testing methods such as double bridge cone penetration test，three bridge rotating penetration test，sample drilling，slab loading test，shear wave test． The three bridge rotating penetration test technology is a new species of in － situ test techniques which overcome the problem as conventional sounding can not penetrate the hard layer and the test depth inadequate，and its penetration depth can reach 60 m in this field． ( 2) This paper use the method of contrast analysis and mutual verification find out the cause of foundation soil era， lithologic features and its distribution law． ( 3) Thus improved the quality of exploration，shorten the cycle of survey and lower the cost，provides a reliable design parameters and practical foundation design suggestions for engineering design．