Peak states - The Mechanics of Soils and Foundations - page 146

and Eq. (10.2) becomes

σ p
σ c

tan

tan

φ p

τ p
σ c =

φ c − φ p tan + (10.6)

φ c do not depend on the voids
ratio, or water content, which is contained in the critical stress

In Eqs. (10.2) and (10.6) the parameters c p , φ p and

σ c through Eq. (9.8),
so they are material parameters but they are only material parameters if the Mohr-
Coulomb equation is a good representation for the peak strength of soil.

10.3 Mohr-Coulomb line for peak strength in
triaxial tests
In triaxial tests the peak states depend on the specific volume in the same way as for
shear tests. Figure 10.6(a) shows the peak state line for the particular specific volume v
in Fig. 10.6(b). In the region AB this is given by

q p = H p p p G pv + (10.7)

where H p is the gradient and G pv is the intercept on the q axis. The broken line OT at
a gradient d q /d p = σ r = 3 represents the condition 0. Since uncemented soils cannot

Figure 10.6 Peak states in triaxial tests.