Expansive soil reinforced with geogrids to construct embankment

or to strengthen and protect the excavated expansive soils and rock slope is successfully applied; and this techonology has significant values both in the prevention of geological disaster and project construction. So a filling soils with dimensions of 600 mm×600 mm×600 mm laminated shear test apparatus is employed to carry out a series of pull-out tests

with HDPE uniaxial geogrid

and the weathered expansive marlite in Xinxiang

the middle route of the South-to-North Water Transfer Project. The factors of test conditions effecting the pull-out behaviors of the interface

such as distance between geogrid and the test box wall

the pull-out velocity

and the upper load are studied. Results show that the peak value of pull-out force

the strength and tangent rigidity of the interface are not evidently effected by the distance between geogrid and wall of the test box under the undrained conditions. The pull-out force increases rapidly with the increase of pull-out velocity

and the peak value of pull-out force and the interface strength is greater. The geogrid deformation and the relative displacement between geogrid and soils differ with the difference of the upper load and pull-out forces. The heterogeneous degree of friction of the interface distribution along the embeded length of geogrid differs with the different upper load; and this can lead to the abnormal behavior that the average friction of the interface is bigger even when the upper load is smaller.