Page 61 - Engineering Rock Mass Classification_ Tunnelling, Foundations and Landslides

VII Squeezing rock 1.1 to 2.1 VII Squeezing
at moderate depth (B þ Ht) VIIA
Mild sque
(ua/a up to

VIII Squeezing rock at 2.1 to 4.5 VIIB Moderate
IX great depth (B þ Ht) (ua/a ¼ 3
VIIC
Swelling rock Up to 80 m High sque
VIII (ua/a >5%
VIIIA
Swelling r

Mild swel

VIIIB Moderate
VIIIC High swe

pv ¼ vertical support pressure; ph ¼ horizontal support pressure; B ¼ width or span of openin
2 m thick.

Source: Singh et al., 1995.

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