Soil Collapse due to Water Infiltration - Environmental Geomechanics - page 161

Gibbs and Bara [GIB 62] proposed a criterion based on the values of the dry-unit
mass ρ d and of the water content w of the soil. They considered that any soil having
a dry-unit mass low enough to achieve water content equal or higher than the liquid
limit upon saturation would be collapsible. Figure 6.14 shows the graphic
representation of this criterion together with the points corresponding to the samples
tested here. It shows that the 1.2 m and 4.9 m samples are considered as non-
collapsible, whereas the 2.2 m and 3.5 m samples are considered collapsible. Since
the 2.2 m sample is located further from the separation line than the 3.5m sample, it
is more collapsible.

Other less well-known criteria, presented and used in [HUE 89] are now
considered. As Gibbs and Bara's criterion, these criteria are based mainly on
characteristics of density and plasticity. The relevant geotechnical parameters for all
criteria are those presented in Table 6.1 and completed by those of Table 6.3
regarding the values of void ratio. Table 6.3 also gives the values of the relevant
parameters of each criterion.

δ (%)
Stephanoff &
Kremakov

Depth
(m)

K e
Denisov

w p -w Nat >0
Priklonskij

K L
Feda

δ (%)
measured

e 0 e(w L )

1.2 0.780 0.815 1.04 2.1 0.85 3.37 00.23 0.23

2.2 0.937 0.760 0.81 3.9 2.03 5.00 2.41

3.5 0.822 0.705 0.86 3.4 1.70 3.48 0.72

4.9 0.762 0.814 1.07 -2.7 0.88 1.66 0.28

Table 6.3. Results of various collapse criteria

Denisov's criterion [DEN 51] (in [HUE 89]) is based on a parameter K e obtained
when comparing the void ratio corresponding to the liquid limit e(w L ) to the natural
void ratio e Nat , as follows: K e =e(w L )/e Nat . A soil is collapsible if K e <0.75.
Observation of Table 6.3 shows that none of the samples are collapsible according
to this criterion.

According to Priklonskij (in [HUE 89]), a soil is collapsible if its natural water
content is greater than its plastic limit, giving w P − w Nat <0. Data in Table 6.3 show
that it is only the case in the 4.9 m sample.

Feda ([FED 66] in [HUE 89]) proposes a criterion based on a parameter function
of the natural water content, of the degree of saturation, plastic limit and plasticity
index K L = [( w Nat /S rNat )− w P ]/ I P . According to Feda, a loess is collapsible if K L > 0.85
and S rNat >0.6. Table 6.3 shows that all samples are collapsible according to this
criterion.