Page 62 - Engineering Rock Mass Classification_ Tunnelling, Foundations and Landslides

g rock condition

eezing 0.3–0.4 Depends on Inverts essential. In
o 3%) primary stress excavation flexible
values, ph support preferred.
e squeezing 0.4–0.6 may exceed pv Circular section
to 5%) 6.0–1.4 with struts
-do- recommended
eezing 0.3–0.8
%) -do- -do-

rock -do-

lling Depends on type Inverts essential in
and content of excavation, arched
e swelling 0.8–1.4 swelling clays, roof essential
elling 1.4–2.0 ph may
exceed pv -do-
-do-
-do-

-do-

ng; Ht ¼ height of opening; ua ¼ radial tunnel closure; a ¼ B/2; thin shear zone ¼ up to