Environmental Engineering Reference
In-Depth Information
embedded in it (scoria). as from the gradual dete-
rioration of this matrix “micro-cutting” could be
produced to the edges embedded in the ground
mass thus causing it to fall when finally a sufficient
volume of the matrix has disappeared.
a rocky material exposed to the atmosphere
deteriorates more on the surface than on the inside.
This deterioration could be accompanied by the for-
mation of hard surface crusts with low porosity.
Basically a compaction treatment must improve
the mechanical resistance of the material, especially
to traction, whilst improving its structure making
water ingress more difficult and the circulation of
saline or acidic solutions.
These products adhere to the walls thus reduc-
ing the empty space and creating connection points
between these walls. in short, their objective is to act
as a mineral cement, non-existent originally or lost
due to alteration. The improvement in the mechan-
ical properties of the rock depends, in this case, on
the abundance of links or anchoring points which
are established between the precipitated compound
and the components of the stone material.
as a consequence of the compaction treatment
there should be an increase in the resistance to
alteration processes which conduct volume changes
in the porous network of the material and which
imply mechanical stress which affects the structure
of the material (crystallisation of salts, etc.).
The compaction treatment considered had,
as such, the objective of acting on the rock sufr-
face by increasing the cohesion of its matrix and
increasing its resistance to weathering.
With the objective of complying with all the
requirements a treatment is considered based on
ethyl silicate as the active ingredient diluted in sol-
vent in varying concentrations depending on the
penetration desired.
With these kinds of products the thickness is
between 5 and 10 centimeters which means that the
ethyl silicate must be applied in variable concentra-
tions in successive phases using a smaller or greater
concentration. This enables restoring the material
matrix by making it more resistant and less prone
to weathering.
The selection of the product application method
was carried out on site in such a way as to obtain as
much penetration as possible in the material. This
is a fundamental characteristic which conditions
the effectiveness of the product. This penetration
capacity is influenced, not only by the character-
istics of the compaction agent, but by the product
application mode, the type of solvent, the contact
time, relative humidity and the pressure and tem-
perature at which it is carried out.
a limit in the use of this type of treatment is the
existence of salts on the rock surface which occurs
in the case of the auditorium in some parts close to
direction of movement of the unstable block which
in general will be considerably vertical).
The maximum length commercially available for
these types of rods is 2 meters which covers the range
of lengths planned for use for this treatment.
5.2.2
Solution type 2-B: Chemical welding
of smaller blocks
These are the cases where it was not possible to make
holes in the blocks due to their small size (third-level
problem), i.e. blocks of approx. 20 ⋅ 20 cm maxi-
mum. This would be equivalent to weights between
1 and 1.6 kn, with an increase factor of 1.6. it was
considered joining the blocks by using so-called
“chemical welding”, which is basically the creation
of bridges between different blocks using low vis-
cosity epoxy resin weld beads applied manually.
This creates one larger block with which it could,
at least theoretically, be possible to treat using
micro-seaming. as occurred with treatment 2-a
there is already a first previous action level since
the generalised injections type 1a have already been
performed. This action is therefore complementary
in those cases in which there is no safety in the fin-
ish of the first action level.
5.3
Superficial solutions: Solutions type 3
This is the treatment which solves more minor prob-
lems i.e. this includes gravel-type sizes (between 2
and 50 mm). logically it was considered that this
could affect any point of the Jameos auditorium
due to the very small dimensions of the particles
to be supported.
To find a solution to this problem it was planned
to apply a compaction treatment to the surface of
the rock where this phenomenon was expected
to appear. a rock behaviour model was studied
which assumed a material formed by a sandy and
silty matrix containing inclusions of larger edges
