Study On Wetting Deformation And Liquefaction Potential Of Filters For Earth And Rockfill Dams

The earth and rockfill dam, which shows good performance, strong adaptability and excellent seismic resistance, is widely constructed in the engineering practice. A series of high dams, especially high earth and rockfill dams that the maximum height is as much as 300m, are designed and planned in the southwest district at present. However, engineering experiences show that serious wetting-induced collapse in the upstream shell of earth and rockfill dams and longitudinal cracks around the dam crest and slope, are always observed during the reservoir filling after construction. Problems associated with the wetting-induced collapse in compacted fills during the first reservoir filling include damage to structures, cracking and slope failure within fills, as well as failure of dams. Moreover, the southwest district of China is located in a seismically active area with high frequency and intensity of earthquake. Filters of fine particles are essential to the permeable stability of soil core dams. The filter shouldn’t be compacted too dense in order to relieve the arc effect of the core, and can’t be too loose in order to be functional. Therefore, the effect of liquefaction probability of the filter on the core is also important to the safety operation of high earth and rockfill dams under earthquake.A plenty of research work of wetting deformation test and numerical analysis have been carried out by researcher around the world. But the considering factors varied by different wetting model and the Duncan-Chang hyperbolic model is widely adopted in numerical analysis. However, the stress path during reservoir filling is very complicated, but the Duncan-Chang model can’t reflect the deformation characteristics of dam filling material under the complex stress path. Meanwhile, very few studies on liquefaction potential of filters is conducted in literature, which mainly analyzed using the total stress method that can’t evaluate liquefaction potential rationally.Under the support of the national science fund project(51279025,51379028), the national natural science fund integration project(91215301) and the new century excellent talents support plan (NCET-12-0083), the main research works in this thesis are listed as follow:(1) A series of reproducible large scale triaxial compression and wetting deformation tests for the conglomerate that is widely used as gravel filling material in Xinjiang district of China are conducted, and the main wetting deformation factors are analyzed. A wetting model that based on single line method and reflect wetting volumetric dilatancy is proposed, and the applicability of the model is validated.(2) The generalized plastic model and proposed wetting model are adopted and numerical analysis of wetting-induced deformation of an asphalt concrete core dam is performed. The effect of wetting on stress and deformation distribution of the dam is analyzed and compared with the measured results in engineering practice. The results show that the proposed wetting model combined with the generalized plastic model can well reflect the wetting effect of dam filling material.(3) A series of triaxial tests for the main rockfill, filter are conducted, and the corresponding generalized plastic model parameters are calibrated. The generalized plastic model and effective stress method are adopted and numerical analysis of liquefaction potential of filters under earthquake is performed. The pore pressure and pore pressure ratio distributions of the filters are analyzed, and the dangerous liquefaction area is also discussed.