380
M. Hattab et al.
quote for instance structures such as engineering barriers, consisting of clayey barrier
system that seals wastes; the latter might be with different dangerousness level. The
barrier is used to ensure the isolation and the confinement of wastes (Albrecht and
Benson 2001). It thus appears obvious that any variation in the initial expected performances of this kind of structure, especially of the compressibility and of the permeability, risks a loss of sealing and leaks of dangerous substances into the environment.
Hence, the clayey barriers behavior has to be precisely followed and mastered. In
common geotechnical engineering practice, desiccation cracks are widely reported in
clayey soils, see for instance Longwell (1928), Willden and Mabey (1961), Mitchell
(1986), Morris et al. (1992), Kong (1994).
Because of ecological and environmental concerns, eco-geo-materials such as
raw earth building materials, having a minimum embodied energy, are currently
receiving special attention (Gallipoli et al. 2017). Treated with a low percentage
of binders, the raw earth becomes a suitable eco-material in the raw earth ecostructures. One of the used techniques concerns, for instance, the casted raw earth
for structural and non-structural walls. The technique in fact is not new, it has been
developed all over the centuries in the past to build small structures. Today the
material finds a real keen interest and is more and more used in the eco-construction
sector. Casted raw earth requires the material to be prepared at water contents reaching
the liquid limit of the used clayey earth. Consequently, many problems related to the
preparation method can appear such as shrinkage desiccation resulting in an increased
risk of cracking. To correct the imperfections of this type of eco-materials, aiming to
generalize their use, it is necessary to understand the mechanisms of shrinkage and
of the initiation and propagation of desiccation cracking. All these issues involve the
shrinkage-swelling phenomenon, defined as the volume changes of the soils under the
action of capillary stress. However, the essential mechanisms of desiccation cracking
are not well understood in clayey materials, and consequently, predictive tools are
inadequately developed. It should be pointed out here that works on other materials
such as concrete, for instance, can provide large lighting on how to model such
complex material during drying. Modeling based on the high ability of the material
to dissipate excess energy could be an interesting approach to consider and to adapt
to clayey soils under high suctions (Giorgio and Scerrato 2017; Giorgio et al. 2019).
One of the hypotheses put forward in the literature to explain the initiation of
cracks in soft mud clays (the material being initially close to saturation and under
drying) is related to a blockage of the shrinkage process. This rather local mechanism, related to different parameters of structural origin and/or geometrical boundary
conditions, gives rise to a concentration of stresses which, when they reach the failure
limit of the clay, lead to crack initiation.
Experimental investigations showed that the locally developed stresses are often
of tensile type (Corte and Higashi 1960; Lachenbruch 1961; Lloret et al. 1998; Péron
2008; Péron et al. 2009; Wei 2014; Eid et al. 2015), and that cracking propagates
in mode I. Assuming anisotropic shrinkage in a specimen of small thickness and
rectangular surface as suggested in Wei et al. (2016), the works of Wei (2014), Ighil
Ameur (2016) and more recently Cheng et al. (2020) highlighted the effect of stress
concentration development. Experimentally, the process can be indirectly observed
M. Hattab et al.
quote for instance structures such as engineering barriers, consisting of clayey barrier
system that seals wastes; the latter might be with different dangerousness level. The
barrier is used to ensure the isolation and the confinement of wastes (Albrecht and
Benson 2001). It thus appears obvious that any variation in the initial expected performances of this kind of structure, especially of the compressibility and of the permeability, risks a loss of sealing and leaks of dangerous substances into the environment.
Hence, the clayey barriers behavior has to be precisely followed and mastered. In
common geotechnical engineering practice, desiccation cracks are widely reported in
clayey soils, see for instance Longwell (1928), Willden and Mabey (1961), Mitchell
(1986), Morris et al. (1992), Kong (1994).
Because of ecological and environmental concerns, eco-geo-materials such as
raw earth building materials, having a minimum embodied energy, are currently
receiving special attention (Gallipoli et al. 2017). Treated with a low percentage
of binders, the raw earth becomes a suitable eco-material in the raw earth ecostructures. One of the used techniques concerns, for instance, the casted raw earth
for structural and non-structural walls. The technique in fact is not new, it has been
developed all over the centuries in the past to build small structures. Today the
material finds a real keen interest and is more and more used in the eco-construction
sector. Casted raw earth requires the material to be prepared at water contents reaching
the liquid limit of the used clayey earth. Consequently, many problems related to the
preparation method can appear such as shrinkage desiccation resulting in an increased
risk of cracking. To correct the imperfections of this type of eco-materials, aiming to
generalize their use, it is necessary to understand the mechanisms of shrinkage and
of the initiation and propagation of desiccation cracking. All these issues involve the
shrinkage-swelling phenomenon, defined as the volume changes of the soils under the
action of capillary stress. However, the essential mechanisms of desiccation cracking
are not well understood in clayey materials, and consequently, predictive tools are
inadequately developed. It should be pointed out here that works on other materials
such as concrete, for instance, can provide large lighting on how to model such
complex material during drying. Modeling based on the high ability of the material
to dissipate excess energy could be an interesting approach to consider and to adapt
to clayey soils under high suctions (Giorgio and Scerrato 2017; Giorgio et al. 2019).
One of the hypotheses put forward in the literature to explain the initiation of
cracks in soft mud clays (the material being initially close to saturation and under
drying) is related to a blockage of the shrinkage process. This rather local mechanism, related to different parameters of structural origin and/or geometrical boundary
conditions, gives rise to a concentration of stresses which, when they reach the failure
limit of the clay, lead to crack initiation.
Experimental investigations showed that the locally developed stresses are often
of tensile type (Corte and Higashi 1960; Lachenbruch 1961; Lloret et al. 1998; Péron
2008; Péron et al. 2009; Wei 2014; Eid et al. 2015), and that cracking propagates
in mode I. Assuming anisotropic shrinkage in a specimen of small thickness and
rectangular surface as suggested in Wei et al. (2016), the works of Wei (2014), Ighil
Ameur (2016) and more recently Cheng et al. (2020) highlighted the effect of stress
concentration development. Experimentally, the process can be indirectly observed