Laboratory Tests - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 443

Figure 14.23 Test apparatus for swelling tests with stepwise irrigation (Gattermann 1998)

The test apparatus illustrated in Fig. 14.23 allows us to estimate the swelling parameter
σ q0 of intact rock as a function of dimensionless water content defi ned in Section

8.3. For this purpose, in each step of irrigation corresponding to a certain value of

ω

ω ,

the related maximum axial stress ) is determined. If isotropic elastic behavior and

swelling behavior are assumed, the stress state in the specimen during the test can be
considered as hydrostatic. Using the generalized Hooke's law and the three-dimensional
formulation of the swelling law, the assumption of zero volumetric strain (

σ z0 ( ω

ε V = 0) yields

(Kiehl 1991a):

(14.51)

The swelling parameter σ q0 ( ω ) then can be calculated by solving (14.51) for σ q0 ( ω )

(14.52)

provided that the elastic constants E IR and ν IR and the swelling parameter K q are known.