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lumrcn_v 15, '008 <br />/'crgc' !5 <br />Global instability was initially triggered by buckling of the floor in G-Dip Pit. Instability <br />would likely have occurred under these conditions, regardless of G-Dip Pit floor <br />buckling, when mining reached I,-Scam. <br />5.2 UNDERSTANDING OF MINE PLAN <br />5.2.1 7,-Dip Pit hfining flan <br />The mine plan for first portion of'/-Dip Pit is shown in Figure 31. Dip mining is planned <br />to progress eastward along strike. The mine plan for this area was modified after the landslide <br />event to include a barrier pillar between the old G-Test Pit area and the new Z-Dip Pit area. The <br />Z-Dip area hillside has old mining downdip in which mining opens the hillside on two sides, <br />similar to the pre-landslide conditions ofthe G-I'it area. The barrier pillar provides a 1 50-tt-wide <br />buttress between the Z-Dip cuts and the old G-Test Pit plus an additional buttress is provided by <br />the spoils that have been piled in the old G-Test Pit area. This barrier pillar is considered <br />conservative and takes into account ground disturbance extending uphill from G-"Kest Pit mining. <br />This disturbance is documented as surface cracking (Figure 32). <br />a <br />I I s v r? <br />- I <br />-j U1 %D P_ M <br />x <br />- n ?a rd z? nzi z u 1 ' ? Y <br />?. <br />too, <br />? •SITI l ? 1 \ ?j <br />l <br />Figure 31. Mine Plan for First Part of Z-Dip Pit <br />The stability of the 7.-Dip hillside was analyzed because a minor highwall failure had <br />occurred in G-Test Pit similar to the G-Strike Pit failures. The analysis' used the same rock <br />properties and groundwater conditions assumed in the landslide back-analysis study. Analysis <br />Associates, Inc.