In order to research on deformation

permeability regularity and optimum methods of foundation treatment in the area of dead-weight collapse loess with heavy section

large-scale soaking tests with observing points arranged and moisture meters buried

and collapsible loess treatment tests with down hole deep compaction(DDC) and (lime) soil compaction pile were carried out. Research results indicate that: in water infiltration process

soil with depth above 22.5-25.0 m is more vulnerable to collapse; and soil with depths below 22.5-25.0 m whose moisture content increases slowly so as to reach hardly collapsible starting moisture content

it is not easy to collapse; therefore

these depth 22.5-25.0 m

depth can be used as critical depths for on-site collapsibility evaluation; but also can be taken as the reference foundation treatment floor depth in large thickness collapsible loess area when the foundation is treated. Average compacting factors and coefficient of collapsibility of different pile spacing between 1.1 m and 1.4 m are in accord with the requirement of “Code”. The settlement of (lime) soil compaction pile in 15.0 m area is small; but its remnant collapse doesn’t satisfy with the “Code”. The research results also support the conclusion that loess below depths of 22.5-25.0 m collapses difficultly. The test results might be useful to similar projects in the area of dead-weight collapse loess with heavy section and to revise “Code for building construction in collapsible loess regions”.