Table 4 YAI of the middle point of rock pillar under different SPC.

From: Stability evaluation of rock pillar between twin tunnels using the YAI

SPC

YAI

Left–right tunnels

Up-down tunnels

I

II

III

IV

0.2

0.574

0.392

0.950

0.859

0.4

0.590

0.395

0.873

0.699

0.6

0.606

0.399

0.785

0.577

0.8

0.622

0.402

0.706

0.482

1.0

0.639

0.405

0.639

0.405

  1. I refer to “after excavation of the left tunnel”; II refers to “excavation about the left and right tunnels”; III refers to “after excavation of the up tunnel”; IV refers to “after excavation of the up and down tunnels”.
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