| In this thesis, the danger brought from the ground base made by expansive soil to the construction is introduced. Main properties of expansive soil are analysed, the problems exist in constructing base with expansive soil are discussed and present resolvent. Laboratory experiments have been done on representative samples from Huan'an region of Ninghuai Expressway in this thesis. Physical and mechanical parameters such as natural moisture content, liquid limit, plastic limit, free swelling ratio are obtained. When lime is used as stabilized agent to improved the properties of expansive soil , compaction tests, dynamic load test, none pressure expansion tests, swelling force test, consolidation test, microcosmic test and non-confined compression tests of different periods have been made. The engineering properties of improved expansive soil are studied. The detailed contents as follows:(1) Expatiate of the main engineering properties of expansive soil and mechanism of expansive soil improved by lime.(2) Research the rules of change about optimum water content, maximum dry density, strength, none pressure expansion, swelling force and elasticity modulus of improved expansive soil adapted to different times of cycle loading.(3) Take the photos of samples of different plain soil and improved expansive soil by using the optical microstructure experiment system, get the relation between degree of compaction, period and area ratio of pore (grain) of soil mass, orientation degree, distribution, dimension. Show some rules of change of minuteness structure of improved expansive soil.(4) Research the rules of change about the compression modulus of plain soil and improved expansive soil on different conditions. Meanwhile calculate the settlement of roadbed, predict the later settlement.(5) Putting forward some advices aiming at the unsaved problems in road foundation of highway on the basis of theory combining with practice and reading lots of data about expansive soil in the world.
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