In this paper

a large number of one-dimensional tests

including constant water content compression and soaking under constant stress

are conducted. The microstructure evolution and deformation mechanism of the compacted loess under loading and wetting conditions are investigated with mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) analysis. Experimental results show that

as the saturation of compacted loess increases at a constant moisture content

it will develop into a saturated consolidation process under further compression. At the microscopic level

the compression of the unsaturated compacted loess results from the collapse reduction of its macrospores

while the distribution of microspores is unaffected in compression. During increasing wetting under the constant vertical stress

the wetting deformation of compacted loess shows a trend of increasing and then decreasing with the increase of vertical stress

and the maximum wetting strain occurs near the compaction stress. Under wetting conditions

the bonds between particles and aggregations are weakened

and the particles and agglomerates collapse and slip

resulting in the reduction of macrospores and the increase of microspores. Also

the soil structure tends to be more uniform and stable after wetting. The creep of compacted loess is caused by the further slippage of particles under constant load and further compression of macrospores. In addition

the settlement law of compacted loess fill is summarized from the construction and post-construction period according to testing results.