This paper presents a possible approach for the assessment of the cond
itions of rock around a railway tunnel (Ankara, Turkey), through a sec
tion of moderate-quality andesite rock and gives the preliminary desig
n considerations for support requirements. For this purpose, different
types of rock behaviour and conditions of rock have been investigated
by employing analytical, numerical and empirical methods in conjuncti
on with data obtained from site investigation and a laboratory testing
program. The results of the analytical investigations have shown that
no plastic zone and indicator of rock conditions (such as popping, ro
ck bursts or slabbing) around the opening are expected for intact rock
conditions. However, when a jointed rock mass is considered, the anal
yses performed using rock mass properties indicated that the developme
nt of a plastic zone is possible. These results have also been confirm
ed by two-dimensional finite-element analyses. It is noted that the ma
ximum principal stresses develop at the sidewalls. Numerical analyses
also suggested that negligible displacements will take place around th
e opening. Particular reference was made to the Geomechanics or Rock M
ass Rating (RMR) System for the assessment of rock mass conditions and
the selection of a support system. The andesite rock mass investigate
d (RMR values between 41 and 52 with an average of 47) falls within th
e moderate rock mass category. On the basis of this classification, ro
ck bolting and shotcreting are suggested as support systems.