Sustainable Ground Improvement Technique for Geo-Disaster Mitigation - Sustainable Practices in Geoenvironmental Engineering - page 457

(a)

φ

τ f

σ ' 3 2θ σ ' 1

σ '

(b) φ

With cementation

Without cementation

τ f

Carbonate
cementation

c

σ ' 3 σ ' σ ' 1

FIGURE 12.12
(a) Failure criterion for sand without cementation. (b) Mohr's Coulomb failure criterion for cemented sand.

The cementation strength c —i.e., the strength contribution to the frictional strength by
the cementation bonds—can be expressed as follows:

q u 1

cos

φ

(12.16)

c = − tan

2 φ

where q u is the unconined compressive strength of cemented soil (sand).
Figure 12.13 shows a comparison between the actual triaxial compressive strength and
predicted strength in terms of p ′ and q using Equations 12.17 and 12.18, where p ′ and q are
deined as

σσ ′ + ′ + q σσ ′ + ′

v h u 1 3

p ′ = or = (12.17)

2 2

σ ′ +−′ q σ σσ ′ − ′

v u h 1 3

q = or = (12.18)

2 2

The p ′ -q relation obtained from the approach shown in Figure 12.12b shows that p ′ and
q agree well with the results obtained from triaxial compression tests, where p ′ and q are