Deformability of rock mass significantly influences its behaviour and
is, therefore, an important consideration for the design of undergroun
d openings. The modulus of deformation of rock mass is, however, norma
lly obtained from expensive and time-consuming uniaxial jacking tests,
whose results often have a large scatter. An empirical correlation ha
s, therefore, been proposed for a quick and inexpensive preliminary es
timation of the modulus of deformation of rock mass on the basis of fi
eld instrumentation carried out in tunnels in India.