(Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources，Yangze River Scientific Research Institute，Wuhan，Hubei 430010，China)
Abstract：To reveal the strength and deformation characteristics of sandy gravel material covering the dam foundation in Suwalong hydropower station affected by the intermediate principal stress ratio and the stress level，a series of large-scale true triaxial tests were performed，combined with a special friction-reduction technique. The stress，strength and dilation were then analyzed under the framework of generalized deviatoric stress and mean effective stress. The internal friction angle was found to increase with the rising of intermediate principal stress ratio，but decrease with the stress level. Among three classical strength criteria，Lade-Duncan criterion shows the best fitting to the tested results，despite of the underestimation at higher level of b values. With the increasing of b value，the slope of the stress path reduces. Meanwhile，the peak strength increases with the decreasing of the stress ratio q/p (q is deviatoric stress，p is mean effective stress)，indicating that the mobilized strength reduces at unit mean effective stress. The angle of dilation decreases with the increasing of stress level and intermediate principal stress.
2017, Vol. 36 
