Geotechnical assessment of the Mejita tailing dam (Dom. Rep.) in karstic and seismic context

The tailing dam geotechnical assessment presented in this paper was carried out beyond the European SYSMIN program in Dominican Republic in 2003. The high seismic and hurricane occurrence risk of the area led to specific studies including: a seismic analysis of the area, an estimation of the liquefaction potential of tailings for dynamic analysis of the stability, an historical survey and the determination of maximum water flows induced by hurricane conditions. The seismicity of the site was studied to determine the magnitude of potential seismic activity and its effect on the existing embankment. A large laboratory and field testing program was defined for obtaining the typical geotechnical data needed for slope stability analysis. The testing program was including more than twenty geotechnical boreholes, soil and rocks classifications and mechanical testing (consolidation, shear and triaxial tests, hydraulic conductivity). The assessment was completed by a very large network of geotechnical monitoring devices installed into and around the dams (inclinometer tubes, vibrating wire piezometers and topographical targets). The stability analysis of the tailing dams focused on static and pseudo-static slope stability and the influence of karstic features within the foundation of the dam. The analyses presented in this paper include the actual static geometrical configuration, the seismic conditions including the liquefaction potential of the tailings, and karstic risk assessment. The results of the stability analysis lead to the necessity of considering in a near future a reinforcement of the dam.