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<br />~, <br />San Luis Mine - Phaso II, Rsae 1 Deai®r Report <br />' 4.5.2.3 Dynamic Displacements <br />Dynamic stability of the embankment in its raised configuration has been evaluated in terms of the <br />amount of deformation or displacement which could occur under various levels of seismic loading. <br />The analyses incorporated peak ground accelerations of 0.2, 0.4 and 0.6 g arising as a result of a <br />magnitude 7.5 earthquake. It should be noted that a M=6.8-7.0 seismic event producing an <br />acceleration of 0.6g - 0.7g at the site has been defined as the maximum credible earthquake (MCE) <br />for the site (Permit section D.1). <br />' Displacement calculations which were computed using the Makdisi and Seed method incorporated <br />the use of [he displacement envelope for a magnitude 7.5 earthquake within graphs which are <br />presented for calculating displacements. Thus, the displacement calculations using the Makdisi and <br />Seed method have incorporated an earthquake with a slightly longer duration than the MCE for the <br />' site and the resulting displacements should be conservative. Displacement calculations computed <br />using the Corps of Engineers (COE} method utilized the upper bound envelope curve, presented in <br />' graphical form, for all earthquake records processed including numerous records of events with <br />M> 7.0, and should also produce conservative results. <br />' As shown in the calculations included as Appendu D, displacements calculated utilizing the two <br />methods are in excellent agreement. The upper bound displacement for M=1.5 computed using the <br />' Makdisi and Seed method is nearly identical to the displacement calculated by the COE method <br />depending on the particle velocity which is used to estimate displacement frortt the normalized <br />displacement chart. <br />' For a peak ground acceleration of 0.2g, no displacement is indicated to occur and there would be <br />1 no detrimental impact to the structure. For a peak ground acceleration of 0.4g arising from a <br />M=7+ earthquake, the displacement along the critical (lowest yield acceleration), downstream <br />slope, sliding block failure surface (surface No.2 on Figure 4.2) is estimated to the approximately <br />' S inches. The displacement along the upstream face failure surfaces depicted on Figure 4.1 is <br />estimated to be approximately 4 inches for both surfaces. The dam structure should be able to <br />' tolerate deformation of this magnitude without any detrimental impacts. <br />For a peak ground acceleration of 0.6g arising from a M=7+ earthquake, the displacement along <br />' the critical downstream face potential failure surface is estimated to be approximately 2.2 ft. Under <br />the same loading conditions, the displacement along the downstream face rotational failure surface <br />depicted on Figure 4,2 is estimated to be on the order of 0.5 ft. For the upstream face of the <br />1 <br />July l3, 1993 1f SRK Project No. 14719 <br /> <br />