Improved reinforcement by rockfill materials in small wooden check dams

Quoc Dung DANG, Yoshiharu ISHIKAWA and Taeko WAKAHARA

Shear deformation of small wooden check dams under the actions of earth pressure is an important factor in dam stability. In this research, experiments were conducted on dam models. Changes in shear behaviors and shear resistance forces from installing a wooden pile into rockfill materials (average diameter 69 mm) were investigated. Moreover, to check the applicability of Kitajima's equation and Itoh's equation for evaluating shear deformation, large scale direct shear tests (0.54m3) were carried out to examine the internal friction angle of rockfill materials. The results showed that the shear resistance force was remarkably increased when a wooden pile was installed with an attached protuberance at an angle of 30° against the shear plane of rockfill materials. The internal friction angle over a large range of stresses was44°. Thus, Kitajima's equation is not suitable for evaluating shear deformation in a wooden check dam. Itoh's equation gives an estimation of the deformation ratio γ=0.0755 that is 30% lower than the actual. On the basis of these results and testing, this economical reinforcement method, which has a strong reinforcement effect, is recommended.