Table 8 Thresholds for variability classification and associated scoring system.

From: Machine learning approach for prediction of TBM performance and risk of jamming in Himalayan geology using a cross-project tunnelling database

Variability Threshold

Variability Classifications

Torque/Thrust

PRnet

Variable Class

Score

value > P95

value < P5

Highly variable (HV)

3

P75 < value ≤ P95

P5 ≤ value < P25

Moderately variable (MV)

2

mean < value ≤ P75

P25 ≤ value < mean

Slightly variable (SV)

1

all others

all others

Normal

0

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