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1/av ?ooy trt, I ; <br />1 A A' <br />1 Shen Strain <br />Rate Contours <br />000005 <br />000010 <br />000015 <br />CA00_0 <br />D00025 <br />l 000030 <br />000035 <br />OCHX'-f 0 <br />Factor of Safety 1.91 <br />- 4- - Phreauc Surface <br />- ,Oc +0.00 41•ot 49.0'+` <br />4d) Spoil 2, Toe Area Model, Phreatic Surface at Base of Fill <br />Figure 4. FS Values for Fast-Section Model <br />1 <br />3.3 N1est-Section Model <br />' l he prcllllllllar\ IllodCI of \VCSt ',CCtlttll \\&, do\'clopcd ?Illlllal I\' to both the Mid scct1011 <br />.111d the fast section, and it included the K-Pit backtill and an elevated phreatic surtace pr(?Jected <br />1 trom field piezonletric levels. The toe buttress in this model was assigned properties of Spoil 1. <br />As observed in the case of'Mid-section models, the most likely failure surface developed within <br />the toe buttress and FS value against global slope failure within the toe buttress was tbund to be <br />' ?. 19 (Figure 5a). From the observation made during the simulation of Mid-section models. it <br />was understood that a toe buttress-only portion of this model will yield similar results. I Iellce, <br />this step was skipped and in the next step. the spoil-strength parameters were lowered while <br />' keeping, the phreatic surface the same. <br />Wall lover spoil-strength parameters (i.e., Spoil 2) assigned to the toe-buttress till, the <br />' 1 S Value against slope failure dropped to 1.119, significantly lover than the minimum value <br />required for long-term stability ofsuch a structure (Figure 511). It may be noted that this value <br />differs sli`,,fitly fi•om the FS value obtained during analysis of similar models for the Mid section <br />and Fast section, which may be attributed to differences in geometry and phreatic surface <br />clc\ ation. <br />In the next stage of analysis, the hvo most likely seepage conditions were simulated \\hile <br />keeping the spoil strength low (i.e., Spoil 2). For both the models with phreatic surface at the top <br />ofthe nnufstone floor laver and at the top ofoverburden layer, the FS values against slope failure <br />were tilund to be identical at 1.88 (Figure _5c and >d). ,Also, the failure surfaces in both cases <br />were very similar in nature. This FS value may also be regarded as adequate for loriu-terns <br />stability of the K-Pit buttress, in case such seepage conditions are established within the toe <br />buttress. <br />Agapito Associates, Inc.