Abstract: In order to research the reasonable controlling critical technical problem of ground treatment and remnant collapse in the area of dead weight collapse loess with great thickness, a large area and deep level immersion load test was made for pile ground by using different treatment depths. The test results indicate that the foundation treated by the pile ground would have the occurrence of different degrees of foundation collapse settlement after deep immersion in the range of 6-12 m. The remnant collapse of foundation treatment in the depth of 15 m is more than 200 mm; and the foundation’s whole subsidence is relatively small. This phenomenon indicates that the current regulation, Code for Building Construction in Collapsible Loess Regions, is too strict about the minimum depth of treatment for class B and class C building foundations; and it dose not agree with the current standards of economy and technology. It is suggested that the 12-15 m could regard as the foundation treatment rational depth for class B and class C buildings in the area of dead weight collapse loess with great thickness. In light of unreasonable regulations about the remnant collapse of class B and class C buildings in current code, this article puts forward the concept of “remnant collapse reduction factor” and its recommended value, so as to give a reference for the same kind of construction projects and code revision.

Key words: dead weight collapse loess with great thickness, pile ground, deep level immersion, remnant collapse, treatment rational depth, remnant collapse reduction factor