PULL-OUT BEHAVIOR OF THE INTERFACE BETWEEN GEOGRID AND COMPACTED EXPANSIVE SOIL

A large-scale shear test apparatus with the filling of 600mm×600mm×600mm size is employed to carry out a series of pull-out tests, to investigate the interface behavior between the geogrid and compacted expansive soil. In the tests, the high density polythene (HDPE) uniaxial geogrid and the weathered expansive marlite in Xinxiang, the Middle Route of South to North Water Transfer Project (SNWT) are adopted. The results show that under the great vertical load, the geogrid deformation is great, the pull-out force approaches the peak value when the rigid motion occur more, the interface friction distributes nonuniformly, and the uniform degree varies with the pull-out force. While under the lower vertical load, the rigid motion of geogrid takes a great proportion to the total displacement, and the interface friction distributes uniformly basically. When the interface friction distributes nonuniformly, the average friction may decrease even under a greater vertical load. The peak strength of the interface can be attained with the relative displacement no more than 1cm―2cm. The strength curve of the interface can be described as a linear function.