The "enlarged compaction pile by tamping deep layer of bored hole" had been used on treatment of foundations with large thickness of loess, mixed earthfill, liquefied soil, different kinds of weak soft soil, swelling loess, etc. Their effective mechanism, design calculating methods, test and examinations arc introduced in this paper. This method can eliminate the swelling property of loess effectively and raise the strength of the foundation. At the same time, a large amount of architectural and industry residues are used for tamping and filling materials. There are good economic and social benefits due to convert residues to the useful materials.