296
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
cemented clays are used as a backfill for quay walls and bridge
abutments. This session deals with various kinds of treated soils
including lime treated soil, cement mixed soft clay, clay with
diatom microfossils, cement mixed gravelly soil, asphalt
aggregate, and lightweight cemented clay.
In paper 1831, Hibouche et al. studied the small strain
behaviours of lime treated soil using small strain triaxial tests
equipped with two types of sensors to measure local strains:
strain gauges and Hall effect sensors. Both measurements were
compared. The elastic moduli derived from cycles in strains less
than 10
-4
were compared with those deduced from the elastic
wave speed. Relations between the modulus, the strain level,
and the hardening were established.
Compared to other methods of improving the soft ground, deep
cement mixing and mass stabilization with binders are rapid
techniques of ground improvement. In paper 2174, the
interaction of binders with the soft clay and improvement in
strength were studied based on water/cement ratio, water
content of clay, and curing time. The used binders include
cement, lime, fly ash, slag and Sodium Silicate. The unconfined
strength increased with decreasing water/cement ratio
irrespective of initial water content of clay and the addition of
Sodium Silicate to cement enhance the strength significantly.
There are several sites in the world where diatom microfossils
have been detected in the soil deposits. Those soil deposits have
singular physical and mechanical properties that do not follow
the well-established empirical relations. In paper 2239, a series
of oedometer tests was performed on artificially prepared
mixtures of diatom microfossils and kaolin and it was observed
that the presence of diatom microfossils substantially alters the
index properties as well as compressibility.
The cement-mixed gravelly soil (CMG) is widely used in
geotechnical engineering and it is needed to develop the design
and construction procedures. In paper 2287, a series of drained
triaxial compression tests were performed on laboratory
prepared specimens and rotary core samples from the field. To
better correlate the strength and deformation characteristics of
CMG, two independent parameters are postulated; the soil
skeleton porosity, n
s
(representing the structure of the skeleton
of gravelly soil particles only), and the cement void ratio, C
r
(representing the fraction of the void of the soil skeleton
occupied by cement). An empirical equation to predict the
compressive strength is proposed using soil skeleton porosity,
which controls initial compressive strength, and the cement void
ratio which controls the increasing manner of q
max
with curing
time. The effects of grading characteristics on the strength were
not significant but the effects of specimen volume were
significant.
The soil cement technique has been used in pavement base
layers, slope protection for earth dams, as a base layer for
shallow foundations, and to prevent sand liquefaction. In paper
2579, the elastic moduli of soil-cement mixtures in terms of
shear and constrained moduli at small strain were measured
with time based on wave propagation by Consoli et al.
Significant increase in stiffness was observed compared to the
uncemented sands as curing process continues. The unique
relationships linking modulus values with porosity/cement ratio
and curing time was developed.
The behaviour of asphalt under slow rates of loading and of the
role of the aggregate skeleton is important when pavement is
subject to subsidence. In paper 2851, Airey and Prathapa
performed a series of conventional drained and undrained
triaxial tests on two types of asphalt, stone mastic asphalt(SMA)
and dense asphaltic concrete(DAC). Tests without asphalt
binder have also been conducted. The behaviour of asphalt was
observed sensitive to the details of the aggregate grading. For
DAC, the behaviour was controlled by the aggregate particles
but little affected by bitumen, whereas the bitumen has a
significant effect on stress-strain-strength behaviour for SMA.
Lightweight cemented clays have wide applications as a backfill
to reduce the earth pressure, as a fill on soft soil to reduce
overburden pressure, and as a method of reducing pressure on
the tunnel lining. In paper 3040, Horpibulsuk et al. found that
the void/cement ratio, V/C, is the prime parameter governing
the strength and compression characteristics. The yield stress in
K
o
-consolidation and compressive strength increase as V/C
decreases and a relationship between strength, void/cement ratio
for a particular water content and curing time was proposed.
4. TESTING METHOD
This section describes six papers that review the testing
methods for soil properties. The measured soil properties
include compaction, particle size distribution, tensile strength of
soil, permeability, dispersive soil, and dry density of soil. The
importance to understand proper mechanism, reliability of test
results, source of errors and the need to develop optimum
procedure without ambiguity are discussed in this session.
In paper 2210, Perez et al. studied gyratory compactor which is
developed to simulate the field compaction mechanism
produced by the sheep foot roller. The controlled variables were
gyration angle, vertical pressure, and number of gyrations. The
optimum water content was reduced and dry density was
increased as the vertical pressure increases, but the compaction
curves are similar regardless of gyration angle and rate. It was
suggested that using heavy equipment rather than many passes
is more effective to increase the dry density.
The particle size distribution of coarse-grained soils is
traditionally determined by sieve tests. In paper 2248, Ohm and
Hryciw discussed two image-based systems, the Sedimaging
(for 2.0 mm to 0.075 mm particles) and the Translucent
Segregation Table (TST) (for 75 mm to 2 mm particles). These
tests do not require that particles be physically detached from
one another unlike previous image-based methods. Testing
setup of TST is shown in Fig. 6. Sedimaging uses mathematical
wavelets to determine particle sizes and requires a camera
magnification that provides at least 3 pixels per particle
(PPD=3). The TST uses watershed analysis to digitally detach
particles and requires PPD=9. The minimum PPDs must be
achieved while capturing entire specimens in the camera’s field
of view. Extension of the systems to silt sized particles is
explored.
Fig 6. Translucent Segregation Table (TST) from Ohm & Hryciw et al.,
paper 2248.
The tensile strength of soil is an important parameter in the
design of geo-systems, where tensile cracks contribute to the
progressive erosion or landslides in excavation, slopes, dams,
