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Technical Committee 208 /
Comité technique 208
Moisture content W = ( 5-29)% mean 15%
Specific gravity
0
= ( 26-27,2) kN/m
3
mean 26,5 kN/m
3
Bulk density
= ( 18,8-23) kN/m
3
mean 19,5 KN/m
3
Limits of plasticity ( liquid) LL= (18-50)% ( plastic)
PL = (13-28)% mean 34% and 25%
Void ratio e = 0,355-0,743 mean 0,62
Resistive parameters of soils by direct shear test :
C = 22-25 kPa mean 23 kPa
= 22
o
-24
o
mean23
o
Bearing capacity R = 150-300 Kpa mean 200kpa
Modulus of deformation E = ( 0,4-0,7).10
4
kPa mean
0,55.10
4
kPa etc.
4.3. Correlation between different soil parameters.
After elaboration of the results from laboratory tests and
in situ tests we have take the following correlations :
Correlation between bearing capacity of each layer “R”
and percentage of gravel.
Fig.2 Correlation between R and percentage of gravel
Correlation between bearing capacity “R” and
percentage of silty grains
Fig.3 Correlation between R and percentage of silty grains
Correlation between bearing capacity “R” and modulus
of deformation “E”( fig.4)
.
Fig.4 Correlation between R and E
Correlation between N
SPT
and void ratio “e”
Fig.5 Correlation N
SPT
-e
Correlation between N
SPT
and percentage of gravel
grains
Fig.6 Correlation N
SPT
and percentage of gravel grains
By the results of the test in direct shear apparatus we
have the following values :
In the upper layers ( 3-5 m depth), which are “UCS”
classification are silty-clay, maximum shear strength is
0,88, that to say the soils are with low sensibility.
The “pic” value and the “residual” value of the resistive
parameters of this layer are :
p
= 23
o
-24
o
res
= 20
o
; C
p
= 20-25KPa, C
res
= 10KPa
From static loading test, for the upper layer ( 3m depth)
they are suitable for the construction of the road because
they have R>150KPa and E> 40MPa.
5. THE CHOICE OF THE CUTTING’S TYPE
The choice we base in our calculations about the
stability of the cohesive slopes that have :
= 19-20 KN/m
3
,
= 23
o
-24
o,
C = 20-25 KPa. In
the zones where are visible slides we have determined
the depth of the sliding surface ( 4-5 )m and residual
resistive parameters of the soil
= 20
o
, C = 10 Kpa.
For the seismic zone with magnitude M = 5,5, depth of
epicentrum of the earthquake 25- 30 km, second
category of soils and a
max
= 0,2g, by [ 3 ] we have take
the coefficient K
s
= 0,07 for the calculation of the
supplement earth inertial force. The factor of safety
“FS”, in general, is FS = 1,5-1,8 but we have the cases
when FS,1,3. The types of cutting choice by us
satisfied three conditions:
Preservation of existing equilibrium of natural slopes
Unloading of the part of the slopes when they are in
limit state ( FS,1,3).
Harmonization of the cuttings with environment to
create beautiful landscape.
5.1Classification of the cuttings
For the road with length 29 km, where 80% passes in
cutting, by our study we have made some classification:
5.1.
1Classification by relief
