Technical Session 3.3A - Case Histories 3
Abstract
There are many existing tailings storage facilities, such as old tailings dams built with the upstream method or tailings dams founded on soft soils that show concerning displacements in instrumentation and control readings. These facilities are prone to failure, releasing their contents, and solutions to their instability problems must be addressed. One solution to the instability problems in these facilities is removal, which consists of progressively removing the facility. This solution is costly, and its viability depends on technical and economic analysis. This paper summarizes the efforts carried out on a tailings dam founded on saturated, contractive clays. Unacceptable displacements were monitored using the InSar system.
After a complementary geotechnical exploration campaign, it was concluded that the safety factors were lower than the minimum required by international standards. To achieve this, an adequate estimate of the peak and residual undrained shear strength was essential. Different estimation methods were applied, such as correlations of CPTu with the Nkt and sleeve friction, shear vane tests, and methods based on critical state soil mechanics using the state parameter. Likewise, the clay's susceptibility to seismic liquefaction was evaluated using cyclic triaxial tests, observing that the excess pore pressure ratio did not exceed 0.6, indicating that the material is not susceptible to liquefaction, but is susceptible to cyclic softening. Subsequently, foundation improvement alternatives were analyzed, but given a series of physical restrictions and the extension of the area to be improved, the alternative of stage-by-stage removal was selected. Finally, the results of the undrained shear strength evaluation were used to assess the stability of the deposit at each stage of removal until all tailings have been removed and it no longer poses a threat to the environment.
Authors
- Brahian Roman, Staff Consultant (Geotechnical Engineering) | SRK Peru
- Daniel Jauregui; Staff Consultant (Geotechnical Engineering) | SRK Peru
- Martín Villanueva, Senior Civil Engineer, Practice Leader | SRK Peru
Click here to see other SRK presentations at this event.
