FR2619585A1 - Process for making earth banks impervious by spraying with a mixture based on clay and cement - Google Patents

Abstract

The invention concerns a process for making all types of natural or artificial earth banks of any slope impervious above and under water. It comprises, in its preferred form, an application onto the bank of a mixture based on clay, cement and water in varying proportions in one or more successive coats using an installation which can be made self-propelled. This process for making earth banks impervious can be applied universally and is characterised by its simplicity, its flexibility, its ease of implementation, the easy availability of its components and its low cost.

Description

 The present invention relates to a method making it possible to seal slopes whatever they are. roughness, their slope (to the extreme, vertical or horizontal), their nature (natural slope, gravelly, sandy or clayey, or artificial: concrete, soil-cement, etc.) or the mode of implementation and use (eg embankment subsequently covered or not, or embankment under water).

There are very many methods for sealing a slope: either coating in place of a product only impermeable like various clays (bentonites or others) covered or not, or of a more or less self-hardening product, like concretes (with if necessary prior installation of a reinforcing mesh and / or nailing) or bituminous mastics them; either installation of a prefabricated layer (at the edge of the concrete slab), generally flexible or plastic sheets; the combination of several methods is obviously usable, with possible preparation of the embankment, eg by prior installation of a draining layer against under-pressures in the case where the embankment is subjected to sudden variations in hydraulic load,
All these methods are more or less adapted to each specific problem, none is universal; eg concrete has good mechanical strength, but is expensive to install and cracks; the flexible leaves tear and age badly; clays often have too little mechanical resistance.

The present invention provides a process, relatively universal, easy to implement (and therefore inexpensive) both in terms of the equipment required, in terms of raw materials, in terms of flexibility of use and improvement according to the degree tightness required and with regard to control and possible repair.

It is derived from a more complicated, developed, developed, described and applied method as a "device for sealing vertical or slightly inclined enclosures a (patent application N" 84 05193)
Its principle consists in simplifying and radically extending the use of so-called clay-cement grouts already used in public works p. ex. to make vertical, thin or thick walls inside the ground, implemented with excavating shovels or by injection through lances.

The grout has three main components, in varying proportions depending on the case of hope - water; - a clay or a silt ensuring its tightness, preferably, but
not exclusively, montmorillonite or bentonite (therefore thixotropic),
preferable for application and permeability, but not essential
thinkable (you can use any natural waterproof floor, even for example
loess reshuffle '); - And an element ensuring the mechanical support, preferably, for its
eventually, but not exclusively, a cement, if possible
wheat rich in slag for its inertia with respect to variations in y-
dratation; you can also use lime, for example,
care of adjuvants known as setting accelerator, anti-re admixture
line, coloring or weedkiller. I1 may indeed be useful to delete
existing plants or prevent them from growing back. The treatment
weedkiller can be applied before sealing or simultaneously,
eg by including it in the first layer.

The grout obtained has both a significant shear strength (approx. 0.1 to 10 MPa) and an elasticity comparable to that of natural soil, so that in the event of mechanical stress, the veil obtained has characteristics of deformation similar to that of the support, while becoming resistant to erosion
A main advantage of the method is indeed the possibility, thanks to the elasticity of the material and its cohesion which develops with the setting of the cement, of being able to be applied to any surface.

Thus, on a natural slope, one can treat, ie. both seal and mechanically stabilize, scree, topsoil, artificial fill or any other type of material for which conventional methods would require pre-treatment.

 The composition of the grout can also be adapted as a function of the desired shear strength and elasticity (in particular by simply varying the percentage of the components), eg by measuring the characteristics of the treated slope in the laboratory beforehand and giving grout the same characteristics or different characteristics if the case requires: generally it is preferable that the support and the waterproofing have comparable elastic moduli, but it may happen that the sealing a lower elasticity (eg to better adapt to subsequent deformations of the support), or higher to further improve the mechanical strength.

The method of implementation depends on the object to be sealed, the means available and the type of impermeability sought (eg degree of permeability, under-pressures, implementation under water, etc.) . Preferably, the apparatus consists (see plate l / lJ of a suitable motor vehicle (1) on which is mounted a mixer (2), possibly supplied from fixed or mobile silos, where the grout which is mixed pumped by a pump (3) (preferably piston or helical pump, but also more rudimentary means going up to the simple chute) whose delivery line is directed by the operator (4) on the area to be sealed, can the slope (5), under an adaptable pressure from zero to several MPa.

 Generally, the grout cracks by shrinkage after implementation in a few minutes to a few days depending on the components and conditions, which obviously affects sealing significantly. The proposed method allows, without any difficulty, to project a second layer on the first after the appearance of shrinkage cracks, the cracks in the second layer not being superimposed on those of the first layer, blocked by the second layer. If necessary, it is possible to introduce between two layers of grout, an intermediate layer of clay without cement intended to block the preferential paths of the water along the cracks and the punctual holes at their crossing, but the process also makes it possible to multiply the number of layers, eg to increase the total thickness, which can also be obtained by varying the quantitative ratios of cement to water and / or clay to cement, parameters on which one can also play according to the slope and roughness of the ground, or according to the desired degree of sealing.

The same mode of implementation also allows its control with the naked eye to progress (low-skilled workforce) as well as if necessary its recovery in more or less long term by wrustinesw after visual inspection.

 The method makes it possible, among other things, to undergo certain deformations without damage thanks to the multi-layers and to the deformation module similar to that of the ground, as well as to cover the waterproof veil, after start of setting, eg with all-comers.

 I1 also allows, as for the invention mentioned above concerning vertical or slightly inclined enclosures, to fix the grout on a felt previously extended on the surface to be treated or else to cover it with a felt before or after setting the grout, p . ex. when subsequent earthworks may tear the veil.

The fixing element can be a felt or any other type of veil or lattice, prefabricated or not, perforated or not. Prior to treatment preferably, but also simultaneously or later, it is possible to fill cavities or macrocracks, by injecting eg grout used for sealing, or using any other material.

The mode of implementation finally allows inter alia the following variants: - extension without discontinuity of another type of veil, eg a
vertical veil inside the ground; - combination with other sealing processes, in particular
used simultaneously, or preferably later, with clay,
eg powdered bentonite for thickening the treated layer, as
soften its surface or further reduce permeability by driving
ment in existing microcracks or likely to form.

The bentonite can then be used, for example by spreading for
dreux or liguide, or by entrainment by the filling liquid or
by sprinkling on the surface of this liquid; - smoothing of the surface obtained, before complete setting of the grout, the ru
gosities of the veil before smoothing, depending on those of the support, deter
undermining the thickness of the veil to be used; - preparation of the slope before treatment, eg by setting up a
One of the practical advantages of the process is nevertheless to per
implement it on heterogeneous unprepared soils,
contrary to known methods which require costly preparation; - placement underwater: when the embankment is underwater, eg for
excavations of land deeper than the water table, the
grout can be set up either by systematic projection under
water, at a distance from the embankment to be chosen according to the case, either
by spreading on the surface of the water, in one or more phases,
prepared grout or its constituents, liquid or solid (at the
limit, powder without liquid). To ensure optimal placement
(e.g. uniform), a gauge can be used. Finally, for water
chemically charged (e.g. sea water), the components can be modified
killing as a result, as with all techniques of using
cements In the event of impoundment of the slope (eg reservoir or dam)
possibility of waiting for complete setting and cracking of the material,
but also to put in water if necessary with protection, temporary not drunk,
against erosion due to impoundment, as milking takes place
is lying.

- for areas inaccessible by land, the process can be
used eg by dispersing a helicopter, in powder or in
grout.

 The invention can be used wherever it is necessary to seal natural or artificial ground, either as a first treatment or as a resumption, eg coating of canals, or else re-sealing of cracked canals, eg.

ex. concrete; insulation of 2 aquifers, to avoid contamination of the water table by accidental pollution or by a landfill installed in an excavation (disused quarry, etc.); sealed enclosures intended to receive water (buffer basins) or another liquid (eg hydrocarbons, residual water), reservoirs and dams, especially in areas difficult to earth.

It makes it possible to extend to all soils, in particular to very permeable soils, such as karsts, hill retaining techniques practiced in naturally impermeable soils such as granite arenas, the high natural impermeable thickness of arenas being compensated by the very permeability slight haze obtained by the process over a small thickness.

 The process is particularly suitable for use in developing countries by its economy and flexibility, by its simple implementation, directly controllable and easy to improve, but above all by the fact that, in its basic formulation, it requires only raw materials almost available in all countries and implemented with simple equipment.

 The invention extends to all types of application in some way taking up the particular description above.

Claims (10)

REVENUEICA1IOS  1) Procodd d'S'anchEificatzon of slope, nntirr.l or artificicls (5), of entirely variable slope, out of water or under water, characterized by the projection of a grout based on fine materials, and binders hydraulic, grout manufactured (2) on site, and projected (4) on the slope as and when manufactured.  2) Method according to claim 1, characterized by the successive superposition of several projected layers.  3) Method according to claim 2, characterized in that a layer is projected only after the appearance of shrinkage cracks in the previous layers.  4) Procedd according to claims 2 or 3, characterized in that at least one of the layers consists of fine materials, brought in liquid or pulverulent phase, without hydraulic binder.  5) Method according to any one of the preceding claims, characterized in that at least part of the projection takes place on a prefabricated support covering the slope.  6) Method according to any one of the preceding claims, characterized in that the sealing performed is in connection with another veil, in the ground.  7) Method according to any one of the preceding claims, characterized in that the sealing performed is covered by any thickness of material.  8) Method according to any one of the preceding claims, characterized in that, the embankment to be sealed being underwater, the final grout or its constituents are spread at any level relative to the surface of the water .  e  9) Method according to any one of the preceding claims, characterized by the fact that at least one of the layers of the grout receives a specific adjuvant such as a weedkiller, a dye, a setting accelerator, an anti-shrinkage.  10) Method according to any one of the preceding claims, characterized in that the grout or its constituents are put in place using a gauge.