Abstract: As one of the basic issues, the evolutions of humidity field must be studied to avoid roadbed water damage. To study changes and distributions of the subgrade humidity field affected by compaction methods, 4 kinds of scale-down laboratory subgrade physical models with different compaction methods were tested. Through analyzing tow-dimensional infiltration rainfall test results，the influences of different compaction methods on the extended distances in roadbed humidity disturbed zone, humidity distributions in front disturbed zone, humidity gradients and humidity values of embankment were summarized. Their mechanisms were explained and relevant engineering suggestions were proposed. The results show that extended distances in roadbed humidity disturbed zone decrease linearly with the increase of compaction degree. The whole humidity disturbed zone can be divided into front and back zones. The front zone humidity shows a quick linear decrease distribution and humidity gradient increases linearly with the increase of roadbed compaction degree. Embankment humidity is affected significantly by the compaction degree of its upper roadbed. The combined effect reveals that embankment humidity decreases linearly with the increase of roadbed compaction degree. It should place a strict control on the upper subgrade impaction to avoid deeper subgrade damages due to water in engineering construction.

Key words: compaction method, subgrade, humidity field, evolution rule, similar simulation test