The aim of this exercise is to illustrate two fundamental techniques in defining in-situ stresses for a rock mass respectively the K0-procedure and the field stress to represent an initial stress situation defined as:

where,

• K_0,H is the coefficient of earth pressure at rest (in major horizontal direction)
• K_0,h is the coefficient of earth pressure at rest (in minor horizontal direction)

for the analysis of a circular tunnel excavation at a depth of 500 m in a uniform rock mass characterized by γ = 25 kN.m-3, K_0,H = 1.2 and K_0,h = 0.8. In this example, two PLAXIS models will be built up for the analysis of the tunnel excavation process followed by the activation of a 20 cm thickness shotcrete lining each model using a different initial stress definition technique.