EP0185041B1 - Retainer works with structure of thin, double curvature elements - Google Patents

Abstract

The thin, double curvature elements are intended to the category of works with metal structure characterized in that the stability is provided by the collaboration between the mass to be retained and the structural elements. The fact that the structural elements are sollicited only by traction forces is original in this new type of works. The base element for the structure of the type of works proposed is a thin membrane which is ondulated (profiled) in the vertical plane and curved in the horizontal plane to form a spatial element which is self-stable during the construction. It is thus possible to make such an element from a corrugated metal sheet and bent with a "U" shape. Thus, a "THIN DOUBLE CURVATURE ELEMENT" (Fig. 2) (element DC) is obtained. An element is characterized by its curved central part (1) and by the two straight end parts (2). The tips of the straight ends may be provided with or without anchoring plates (3). The DC elements defined in Fig. 2, juxtaposed (Fig. 3) represent the structure of retainer works. The ballasting or filling by successive layers enables to perform the association between the DC elements and the earth. This is how the proposed retainer works is made.

Description

The retaining structures, better known under the name of RETAINING WALLS, belong to the category of the oldest constructions made by man.

From time immemorial, stone and wood have been used as materials to retain the sliding of earth masses or to carry out water retention.

Greco-Roman antiquity is a testimony to the magnificent achievements of the genre.

Nowadays, whether small retaining walls by the road, house basement walls or large dams, retaining structures are present everywhere and the sums invested in this area are more and more considerable.

In our modern era, the diversity of support structures and materials used is very great. Generally, retaining structures are carried out with one or more of the following materials: stone, wood, concrete, metal and of course earth.

For the sake of maximum rationalization, modern designs for the construction of retaining structures are increasingly using the resistance characteristics of the mass to be retained, namely the earth, with the aim of minimizing the structural elements.

This presentation shows a new concept for the construction of retaining structures, a concept which can in many cases replace conventional retaining walls at a lower cost.

To understand the principle, let's proceed by analogy.
Imagine the current of a river transporting debris or ice during the breakup. A cable floating across the stream, hooked by the ends on both banks will retain all debris or ice (fig. 1)

Following the horizontal thrust of debris or ice the cable will take a curve (1). The shape of this curve will depend on the length of the cable in relation to the distance between the fixing points. The cable will be stressed at a pure tensile force.

The ends (2) fixed to the anchor plates (3) will resist by the shearing of the earth mass. On the other hand, if the ends (2) were without an anchoring plate while having a sufficient length, they would provide stability by friction between the earth and the cable.

The cable described above and shown in Figure 1 can be considered as a flat retaining structure.

On the basis of this principle, let us develop the third dimension. By replacing the cable with a thin membrane of the corrugated iron type and the debris or ice with earth fill, a retaining or retaining structure is created.

Thus the type of structure proposed can be classified in the category of structures with metallic structure, which is characterized by the fact that stability is ensured by the collaboration between the mass to be retained and the structural elements.

A work of this category is described for example in patent US-A-3316721.

The invention aims to provide improvements to the prior art by simpler and more efficient arrangements. To this end, the invention relates to a work according to claim 1 appended; certain specific methods of implementation are the subject of the other claims. Other characteristics and the advantages which result therefrom will emerge more clearly in the light of the description which follows, given by way of example with reference to the figures of the appended drawings.

The basic element for the structure of the proposed type of structure is a thin corrugated (profiled) membrane in vertical plane and curved in horizontal plane, to form a freestanding spatial element during construction. Such an element can be produced from a corrugated sheet folded in the shape of a "U". Thus, we obtain a "DOUBLE CURVATURE THIN ELEMENT" * (fig.2).

A DC element (fig. 2) is characterized by its curved central part (1) and by the two straight ends (2). The ends of the straight ends can be provided with or without anchoring plates (3).

The DC elements defined in Figure 2 and juxtaposed according to Figure 3 represent the structure of the retaining structures. Backfilling in successive layers allows us to make the association between the DC elements and the Earth. This is how the type of retaining structure proposed is carried out (fig. 4).

TECHNOLOGY

The realization of the works is conditioned by the availability of two basic materials: earth (backfill) and DC elements.

The backfill is a local material that is found on site with all the grain sizes, from the mainstream, passing through the granular to the clay soil. Any material that can produce high friction on DC elements is suitable; that which has a high shear strength is also suitable as well as any material which makes it possible to avoid the possibility of development of pore pressures inside the structure. This precludes a priori the use of soils with a large percentage of clay or outright clays. The backfill must be free of organic matter and must meet certain electrochemical conditions with regard to corrosion of DC elements. Generally, the backfill should be chemically stable .
* In what follows, the DOUBLE CURVED THIN ELEMENT will be identified by the abbreviation: DC element (s).

As a basic principle, it can be said that the materials which satisfy the conditions for a road embankment may be suitable. When the backfill is different in the sense defined above, as well as for works of a certain size, laboratory tests are necessary.

The main structural element of the structure, the DC element (fig. 2 and 3) must be manufactured in the factory from materials which have a high tensile strength and other characteristics pre-established by the architectural conditions, environment, the destination of the work and of course the quality of the embankment.

DC elements can be with or without anchor plates. The choices of geometry and thickness of the DC elements result from the calculation of local stability and overall stability, so as to minimize the cost of the construction of the structure. The geometrical characteristics as well as the thickness of the DC elements can vary on the height of the structure.

The durability of the works depends essentially on the resistance of the structural elements to the phenomenon of corrosion. The rate of corrosion of DC elements is linked to the nature of the materials buried and the characteristics of the soil.

The choice of materials for the DC elements, or for their protection, must be made according to the pH of the pore water and the resistivity of the backfill material. A priori it can be considered that non-clay granular materials, as defined for roads, are compatible with all materials for DC elements. In some cases, to prevent corrosion, DC elements can be protected by the application of layers of paint based on bitumen, epoxy, etc ... provided that sufficient anchoring is ensured.

The main materials considered for the manufacture of DC elements are: galvanized steel or not, stainless steel, cor-ten steel, aluminum alloys, plastic materials, composite materials, steel or plastic mesh .

Depending on transport and mounting possibilities, the DC elements can be in a single unit or in several components, multi-plates assembled on site by bolting (fig. 5 and 6). The assembly can be made waterproof or not.

It can be concluded that the DC elements, used as the structure of the proposed structure, are characterized by their stress in pure traction, an anchorage developed through friction (shear) with the embankment, as well as good durability.

A DC element can be made of a single quality of material or of several provided that there is electrochemical compatibility between the components.

The DC elements can be the only structural elements of the structure where they can be associated with horizontal reinforcements made with metallic trellis, textile membranes, etc.

In some cases of heavy loads, the use DC elements, reinforced with armatures or cables, can be considered.

The anchor plates (3) can be metallic or precast concrete.

Works made with DC elements (fig. 4) lend themselves well to receiving on the facing a coating of precast concrete elements, bricks and especially shotcrete.

On the rocky slopes, in order to reduce the volume of excavation, the DC elements can be used in combination with bolted anchors in the rock mass.

The DC elements are freestanding during construction and deformable after completion of the structure, being able to follow the deformations of the foundation terrain.

Generally, the foundation surface should be horizontal. In specific cases, it can be tilted and even below the water level.

The embankment of a structure made with DC elements must be executed as a road embankment, in successive more or less thick layers. Compaction must be carried out with suitable machinery; however, it is not necessary for the good performance of the work. Compaction is used to limit settlement and deformation depending on the destination of the structure.

SIZING

For the realization of retaining works with DC elements, as for any work of its kind, it is a question of solving: the overall stability and the internal stability.

In the first case (compaction, punching of the foundation soil, sliding, overturning, etc.) we are faced with the classic problems of soil mechanics and we will have to refer to them.

In the second case, it is a question of ensuring the good behavior of the elements with double curvature and their good collaboration with the embankment.

The DC elements can be put out of use by breakage or tearing caused by too great a pulling force in the facing (1), or by the tearing of the part embedded in the solid mass (2).

Geometric characteristics

H

la hauteur de l'élément DC

B

la largeur de l'élément DC

L

la longueur du plan d'encastrement

b

la profondeur du parement

PAREMENT

la partie centrale courbe 1 de l'élément DC définie par B, b et H,

PLAN D'ENCASTREMENT

les extrémités 2 de l'élément DC définies par L et H,

PLAN DE REFERENCE

la plan vertical, y o z 4

PLAN DE GLISSEMENT

défini sur la figure 8 courbe 5 ou plan 6 selon le cas ou e est l'angle de frottement interne,

ZONE ACTIVE

la partie de l'ouvrage qui a la tendance à disloquer suivant la surface de glissement 7,

ZONE PASSIVE OU RESISTANTE

la zone stable du massif où se réalise la transmission des sollicitations à la terre par frottement ou cisaillement 8

Geometric characteristics of the DC element (fig. 7) as well as the essential elements for the sizing of the structure (fig. 8) are:

H

the height of the DC element

B

the width of the DC element

L

the length of the installation surface

b

the depth of the facing

FACING

the central curved part 1 of the DC element defined by B, b and H,

BUILT-IN PLAN

the ends 2 of the DC element defined by L and H,

REFERENCE PLAN

the vertical plane, yoz 4

SLIDING PLAN

defined in FIG. 8 curve 5 or plane 6 depending on the case where e is the internal friction angle,

ACTIVE ZONE

the part of the structure which tends to dislocate along the sliding surface 7,

PASSIVE OR RESISTANT ZONE

the stable area of the massif where the stresses are transmitted to the earth by friction or shear 8

Land push

Land pushing theories are widely discussed in the specialist literature to which reference should be made.

For the present presentation, the following hypotheses are taken into account: planar sliding surface (Coulomb), earth pressure applied to the reference plane, friction between the embankment and the DC elements equal to the internal friction angle.

The thrust of the land, vertical or horizontal is constant on a horizontal plane, but linearly variable with the depth (fig. 9).

Depending on the case, other calculation assumptions may be taken into account.

Unit constraints

la contrainte horizontale normale au plan de référence représentant la poussée des terres sur le parement ${\text{2 σ}}_{\text{x}}{\text{=K}}_{\text{x}}\text{YZ}$

la contrainte horizontale normale au plan d'encastrement peut être appelée contrainte d'étau ou de serrage ${\text{3 σ}}_{\text{y}}{\text{=K}}_{\text{y}}\text{YZ}$

ou ${\text{4 K}}_{\text{x}}{\text{=K}}_{\text{y}}\text{=K}$

sont les coefficients de poussée active et où γ est le poids spécifique du remblai, ce qui nous permet d'écrire ${\text{5) σ}}_{\text{x}}{\text{=σ}}_{\text{y}}{\text{=KYZ=p}}_{\text{z}}$

To determine the state of unit stresses inside the massif, we will take into account, in particular on the reference plane (the vertical plane yoz) any point M (oyz) determined by the intersection of the lines M 'M''and M1 M2 parallel to the axes (fig. 9). The lines M 'M''and M1 M2 can be considered at the same time as the intersection of a respectively vercal horizontal plane with the reference plane. Thus at point M the normal unit stresses are: the vertical stress, equal to the self-weight of the earth above the point considered $\text{1 σ₂ = YZ}$

the horizontal stress normal to the reference plane representing the thrust of the land on the facing ${\text{2 σ}}_{\text{x}}{\text{= K}}_{\text{x}}\text{YZ}$

the horizontal stress normal to the embedding plane can be called vice or clamping stress ${\text{3 σ}}_{\text{y}}{\text{= K}}_{\text{y}}\text{YZ}$

or ${\text{4K}}_{\text{x}}{\text{= K}}_{\text{y}}\text{= K}$

are the active thrust coefficients and where γ is the specific weight of the embankment, which allows us to write ${\text{5) σ}}_{\text{x}}{\text{= σ}}_{\text{y}}{\text{= KYZ = p}}_{\text{z}}$

In practice, for sizing, the horizontal thrust Pz is considered constant over the height ΔH, as shown in FIG. 10.

The stresses in the structure in DC elements will be determined as follows.

In a first step, we will take into consideration at depth Z the horizontal stresses perpendicular to the reference plane and over the width B of the DC element (fig.11). The horizontal stresses σ _x = p _z are applied along M 'M''and the elementary thickness dz will be equal to ΔH, as defined in Figures 9, 10 and 11.

The semi-circular facing adopted in FIG. 11 can be likened to a cylindrical shell where the reference plane merges with the diameter.

The thickness of the parliament of a DC element being small compared to the radius of curvature, the stresses can be obtained with sufficient precision by neglecting the bending of the wall, that is to say by supposing that the tensile stresses in the walls are uniformly distributed according to the thickness. The magnitude of the constraints can then be easily calculated from the LAPLACE relations in the membrane theory.

At depth Z for an element of height ΔH the tensile force in the facing is: $$\text{6) Tz =}\frac{\text{1}}{\text{2}}\text{Pz B ΔH}$$

In a second step, the state of stresses on the embedding plane in the resistant zone, represented by point N in FIG. 11, will be analyzed.

Normally, the friction angle ρ 'between the embankment and the DC elements must be close to the value of the internal friction angle ρ: $\text{7) φ '≦ φ}$

Thus, to avoid sliding and to ensure embedding, it is possible either to design the surfaces concerned of the DC elements. Consequently, either provide anchor plates (fig. 2) so φ ≈ φ

Therefore, the sliding plane can be assimilated to the shearing plane (10) (fig. 12) $\text{8) f = tgφ '= gφ}$

pour les matériaux avec cohésion, terrain cohérent ${\text{10) τ=σ}}_{\text{y}}\text{tgφ+c}$

For the tangential stresses τ, the linear Coulomb law has been taken into account, thus: for materials without cohesion, dry powdery ground ${\text{9) τ = σ}}_{\text{y}}\text{tgφ}$

for cohesive materials, coherent terrain ${\text{10) τ = σ}}_{\text{y}}\text{tgφ + c}$

Note: the granular embankments have no cohesion or it is very weak and uncertain; on the other hand, cohesion can be created artificially.

ou éventuellement 12)

The embedding plan, being an extension of the facing must be able to transmit the stresses to the mass of the embankment by friction or by shearing. At each point of contact of the part embedded in the earth, it must be ensured that the friction (shearing) actually exists without sliding. He must satisfy the relationship 11)

or possibly 12)

By introducing the pull-out safety factor, the inequality 11) becomes: 13)

Returning to relation 6) and to FIG. 11, the tensile force of the facing Tz is transmitted to the embedding plane. To preserve the balance Tz must be canceled by the sum of the tangential constraints τ. To get there point N (fig. 11) will be isolated on an elementary surface of dimensions dl and ΔH, as shown in figure 13.

The condition of equilibrium of the elements allows us to express the value of the tangential stress as a function of Tz 14)

Taking into account the principle that the stresses on a horizontal plane at depth Z are constant (fig. 9) and relations 5) and 13) we can integrate equation 14) as follows: 15)

This allows us to obtain the installation length in the resistant or passive zone: 16)

Dimensions of the DC element.

où

σ_a =

la contrainte admissible du matériau de de l'élément DC

t_e =

l'épaisseur équivalente du parement

Facing: we previously determined the tensile force in the circular facing (fig. 11). Taking account of relation 6, we can write: ${\text{17) T}}_{\text{z}}{\text{= σ}}_{\text{at}}{\text{t}}_{\text{e}}\text{ΔH}$

or

σ _a =

the admissible stress of the material of the DC element

t _e =

the equivalent thickness of the facing

avec le coefficient µ>1To obtain the effective thickness, the undulation of the DC element must be taken into account (fig. 14). ${\text{18) t}}_{\text{e}}\text{= µt}$

with the coefficient µ> 1

A la base de l'ouvrage pour Z = H 20)

Thus the effective thickness t of the DC element will be obtained from equation 17) taking into account the relationships 5), 6), and 18). At depth Z 19)

At the base of the book for Z = H 20)

According to formulas 19) and 20) for a preset width, the theoretical thickness of resistance will vary from zero at the top of the structure to its maximum value at the base. In practice, it is not possible to have a variable thickness with respect to the height, a single thickness corresponding to equation 20 will be used for the entire height, or sometimes it may be economical to vary the thickness per section of sailor. .

Generally, for practical applications the height of the structure H is a basic data, on the other hand the width B of the DC elements is at the discretion of the designer. According to equation 20) it will be advantageous to choose B as small as possible. However B has an optimal limit determined by the length of the embedding plane. For its choice, it will be necessary to take into account the possibilities of production, transport and especially of implementation and realization of the work.

on peut écrire 22)

For $$\text{21) β =}\frac{\text{B}}{\text{H}}$$

we can write 22)

With various values of B we can draw charts for t as a function of H.

Installation plan.

As shown before, the installation plan is a logical extension of the facing. The force developed in the facing will be transmitted to the earth mass by the embedding plan. Mechanically, the embedding plane must be able, on the one hand, to take up all of the tensile force transmitted by the facing, and, on the other hand, to transmit stresses to the earth mass without disorder by friction or by shearing. .

• a) Condition de non arrachement. L'état des contraintes entre la masse en terre et le plan d'encastrement a été montré auparavant. Pour déterminer la longueur totale de résistance à l' arrachement La il faudra suivre le cheminement de la figure 15.
  L'étendue de la zone active a sera déterminée géométriquement : 23)
  
  a est fonction de z et varie de zéro à la base à sa valeur maximale au sommet 24)
  
  
  La longueur d'encastrement L dans la zone passive ou résistante a été établie auparavant avec la formule 10) à laquelle il faut se reférer. Si dans l'équation 10 on remplace la valeur de l'effort Tz par sa valeur donnée par 0 la longueur L a la base de l'ouvrage devient la longueur maximale La du plan d'encastrement pour résister à l'arrachement ainsi : 25)
  
  
  Le coefficient de securité à l'arrachement η_a peut être différent sur la hauteur de l'ouvrage si cela est justifié.
  Pour réduire la longueur du plan d'encastrement il faudra choisir les matériaux du remblai avec un angle de frottement interne élevé ou employer des nappes d'armature dans le remblai.
• b) Condition de non renversement. Dans le cas des murs de souténement classiques en béton armé ou non, il est absolument nécessaire de vérifier le renversement du mur sous l'influence du moment dû à la force de poussée des remolais ou de l'eau.
  Si le renversement pour les murs en béton est un phénoméne très important, dans les ouvrages avec éléments DC, ce type de de rupture est très improbable.
  Le phénoméne de renversement pour les ouvrages avec les éléments DC peut se produire par le déversement de la partie supérieure de l'ouvrage lorsque la longueur du plan d'encastrement est insuffisante.
  En supposant la formation de voûtes en plan horizontal, entre les plans d'encastrement, la masse du massif sera mobilisée pour empêcher le phénoméne de renversement.
  Avec un coefficient de sécurité au renversement η_r préétabli, la longueur du plan d'encastrement Lr pour assurer la stabilité au renversement sera : 26)
  
• c) Condition de non glissement. La philosophie à suivre est la même que pour le renversement.

The installation plan must ensure by its length, the stability of the entire structure: tearing, overturning, sliding.

• a) Condition of non-wrenching. The state of the constraints between the earth mass and the embedding plan has been shown before. To determine the total tear resistance length La, you will have to follow the path in figure 15.
  The extent of the active area a will be determined geometrically: 23)
  
  a is a function of z and varies from zero at the base to its maximum value at the top 24)
  
  
  The installation length L in the passive or resistant zone was previously established with formula 10) to which we must refer. If in equation 10 we replace the value of the force Tz by its value given by 0 the length L at the base of the structure becomes the maximum length La of the embedding plane to resist tearing as follows: 25 )
  
  
  The pull-out safety coefficient η _a may be different over the height of the structure if this is justified.
  To reduce the length of the embedding plane, it will be necessary to choose the materials for the embankment with a high internal friction angle or to use reinforcing plies in the embankment.
• b) Condition of non-overturning. In the case of conventional retaining walls in reinforced or unreinforced concrete, it is absolutely necessary to check the overturning of the wall under the influence of the moment due to the thrust force of the remolais or the water.
  If overturning for concrete walls is a very important phenomenon, in works with DC elements, this type of breaking is very unlikely.
  The overturning phenomenon for structures with DC elements can occur by the overflow of the upper part of the structure when the length of the embedding plane is insufficient.
  Assuming the formation of arches in horizontal plane, between the embedding planes, the mass of the massif will be mobilized to prevent the phenomenon of overturning.
  With a pre-established overturn safety factor η _r , the length of the mounting surface Lr to ensure overturn stability will be: 26)
  
• c) Non-slip condition. The philosophy to follow is the same as for overturning.

Assuming the formation of arches in horizontal plane, between the embedding planes the length of these must be sufficient to prevent sliding on the base.

With a pre-established sliding safety coefficient η _g , the length of the embedding plane Lg to ensure sliding stability will be: 27)

security

To ensure internal stability, it must be checked, on the one hand that the maximum tensile stresses are compatible with the tensile strength of the DC elements and on the other hand that the surface embedded in the passive or resistant zone, is sufficient to allow the balance between the friction or shear forces and the corresponding maximum pulls, and this in a safe manner.

The safety coefficients for the DC elements working in traction as well as for their embedding will be established according to: the nature of the materials for the DC elements (more or less brittle materials), the nature of the backfill materials (the certainty of a minimum coefficient of friction, type of structure (permanent or temporary), risk (extent of damage in the event of destruction), risk of corrosion.

The safety coefficients for overall stability will be determined on the basis of: type of structure (permanent or temporary), risk (the extent of damage in the event of destruction).

Generally, they cannot be less than 1.5 for stability to overturning and sliding and 2 for punching the foundation.

Analysis of a reservoir.

A retaining structure produced using juxtaposed DC elements, varying in height from 0 to 30 meters and of any length, was analyzed in detail and shown in the charts in Figure 18 to Figure 23.

The DC elements consist of corrugated or profiled sheets covered with corrosion protection (by galvanization or any other proven means).

For the larger dimensions, they are in several plates assembled by bolting.

In the present example, the facing will consist of semi-circular DC elements, made of mild steel with an admissible resistance of approximately 150 MPa.

The backfill is planned in granular equivalent to those approved for roads. For the present example, the following values have been adopted: the specific weight of the embankment of 18 kN | m3, the active thrust coefficient of 0.25, 0.33 or 0.45 as appropriate.

The effective thickness "t" of the DC element is determined by the resistance conditions, being directly proportional to the width "B" and the height "H" of the DC element. We can follow the variation of the thickness "t" on fig.18,19,20

The length of the embedding plane "L" is generally determined by the condition of not being torn off.

In the various calculations was introduced the concept of specific thickness "e" which represents the thickness of the whole of the DC element compared to the length of the rectilinear front of the work, thus: e0 the net thickness without additional thickness for corrosion, e1 the net thickness plus an additional thickness of 0.5 mm for each face, e2 the net thickness plus an additional thickness of 1.0 mm for each face.

• a) l'épaisseur des éléments DC est déterminée pour la sollicitation maximale soit à la base de l'ouvrage et est maintenue constante sur toute la hauteur. Pour les ouvrages d'une certaine importance, il peut s'avérer rentable de faire varier l'épaisseur.
• b) une surépaisseur comme protection vis-à-vis-de la corrosion doit être prise en considération. Elle est de 0,5 mm ou de 1 mm pour chaque face en fonction de l'agressivité du milieu et de l'espérance de vie attendue de l'ouvrage.
• c) pour les ouvrages de peu d'importance, le plan d'encastrement est réalisé par la juxtaposition des divers élémentsDC et aucun boulonnage n'est requis. Par contre, pour les autres ouvrages les éléments DC multiplaques se raccordent sur une seule feuille d'encasrement d'épaisseur appropriée.
• d) dans les divers cas considérés, le remblai est supposé horizontal à la partie supérieure et la fondation de l'ouvrage est considérée horizontale et stable. Le coefficient de poussée active du remblai est pris égal à 0,33 mais les valeurs extrêmes de 0,25 et 0,45 ont également été considérées.

The abacuses of figs. 21,22,23 represent the variation of "e0" and "e2" according to the height for various ratios between "B" and "H" and various coefficients of the push of the grounds. We can see that the most economical value for "e2" corresponds to a ratio of "B" to "H" equal to or less than 05 Notes:

• a) the thickness of the DC elements is determined for the maximum stress either at the base of the structure and is kept constant over the entire height. For works of a certain size, it can be profitable to vary the thickness.
• b) allowance for corrosion protection must be taken into account. It is 0.5 mm or 1 mm for each side depending on the aggressiveness of the environment and the expected life expectancy of the structure.
• c) for minor works, the installation plan is made by juxtaposing the various DC elements and no bolting is required. On the other hand, for other works, the multi-plate DC elements are connected on a single encasing sheet of appropriate thickness.
• d) in the various cases considered, the embankment is assumed to be horizontal at the top and the foundation of the structure is considered to be horizontal and stable. The coefficient of active thrust of the embankment is taken equal to 0.33 but the extreme values of 0.25 and 0.45 have also been considered.

AREAS OF USE

The types of structures proposed according to their nature are retaining or retaining structures.

The facing of works taking into account the possibilities of coating, can take the desired shape and color. In height, the facing can be vertical, inclined or on the terrace.

The geometry of the facing and the range of colors are practically limitless and can meet the most demanding architectural and environmental standards.

Structures with a DC element structure can be erected as watertight or not, temporary or permanent retaining structures.

Due to the deformation capacity of the DC elements, the structures can easily follow the movements of the foundation ground. The realization of the provisional works becomes very interesting, by the speed of the execution, by the ease of demolition and the total recovery of the DC elements.

The type of structure offered is very flexible for landscaping terraces for housing or for agriculture.

Retaining structures with structure in DC 5 elements can receive very large overloads and lend themselves to the construction of retaining walls for communication routes, bridge abutments, etc.

The possibility of making the DC elements waterproof makes it easier to create impermeable structures, such as dikes or reservoirs.

With the type of structure proposed, the construction of flood protection dikes can prove to be an extremely important application taking into account the speed of execution. The low dikes can be executed with a general embankment.

In the industrial field, the mass to be retained may not be earth, but many mineral, industrial or vegetable products, with the aim of considerably increasing storage.

Some applications: Layout of terraces

This is the landscaping on the uneven slopes. These developments allow urban development of leisure, for agriculture, communication routes, etc ... (fig. 17). The earth is retained using a structure made with DC elements made of galvanized or other sheet steel, juxtaposed or in multi-plates. The facing consists of semi-circular, elliptical, etc. elements with or without a convex connection.

It should be noted that the standard elements have their two parallel installation planes. However, as the DC elements have a low rigidity, they can be deformed so as to make the two embedding planes divergent or convergent. This characteristic allows the direction of the facing to be changed as desired.

Means of communication

The communication routes lead to grandiose earthworks which bring about the need for various elements of support. The latter can be formed using DC element structures. This can range from the retaining wall to the abutment of engineering structures.

In urban or tourist areas the facing can receive a sprayed concrete coating or a veneer in decorative elements of pre-cast concrete.

Roads on very steep slopes can be made with a minimum of excavation. The embedding plans can be completed using anchoring in the rock mass. Excavation in non-rocky terrain is minimized because we are content to make some grooves for the embedding plans.

In areas with maximum safety, DC elements with double facing have deformable cells which can absorb the shock of vehicles in the event of an accident.

Parapets made with DC elements are safe given their great flexibility while being quite heavy.

Islands - offshore platforms

On a body of water, you can make artificial islands or peninsulas for recreation, ice control, industry, etc. The execution can be carried out dry or under the water level.

An off-shore platform is an artificial island made in shallow water for explorations. A combination of short metal piles and DC elements can be realized. Backfilling can be done by dredging.

Basins - reservoirs

A tank dug in the ground can be made using DC elements. In order to minimize the work, the excavated material must be deposited around the excavation; thus, the reservoir created is partly raised above the natural terrain

DC elements whose facings are semi-circular, elliptical or other, their assemblies are made in a sealed manner. When the facings are provided with fittings, these can be the same as the first elsewhere. The facing thus produced has a more aesthetic appearance of continuity. The "embedding-connection plan" nodes can be pre-assembled either in the factory or on a building site. Once these knots are in place, the central part of the facing can be fixed.

The bottom of the tanks consists of an impermeable layer supplemented if necessary by a synthetic membrane. A trellis fixed on the various assembly elements allows the production of a sprayed concrete covering. The latter can be smooth or covered with any other finish such as ceramic.

The range of pools can be of a wide variety and can be used for municipal, industrial or agricultural purposes.

Tanks

A DC structure with its elements assembled in a sealed manner, arranged in a closed outline of circular, rectangular or polygonal shape in such a way as to store a liquid volume, allows us to produce large capacity tanks. The whole being provided with an adequate roof.

The DC structures by their design allow us to realize buried tank tanks. Even when they are partially on the surface, the mass of the earth around the reservoir is large enough that we can consider that they are buried. Therefore, this type of tank offers very high operating safety, completely eliminating the safety bowl and the drawbacks which arise.

The tanks made with DC structures can be erected on a deformable foundation ground. These deformations do not affect the vertical part, the bottom and the flexible walls must be compatible with rigid roofs.

To prevent corrosion and preserve hygienic conditions (for edible products) the vertical structure, the bottom as well as the underside of the roof must be compatible with the stored liquid and the vapors which are released.

DC tanks can be used to store: petroleum products and their derivatives, chemicals, drinking water and miscellaneous.

The roof of DC tank tanks will be of conventional type rigid or flexible, exposed, floating or covered with soil. It will be supported or anchored on a reinforced concrete belt made at the top of the DC structure (the wall).

For large capacity tanks, a central support tower for the roof is recommended. Intermediate support can be envisaged.

The structure of the roof can be in: precast prestressed concrete, metal boxes, domes, structure on cables, inflatable structure, floating structure.

Hydro installations

The structures in DC elements by the fact that watertight screens can be made lend themselves favorably to carrying out repair works (refurbishment), raising, enlargement of dikes and dams. The design of new retaining structures (dikes, dams, spillways) is possible and can be very economical.

It can be seen that the volume of materials can be reduced substantially. If there is a lot of traffic on the crowning, large traffic lanes can be made without a significant increase in the fill. On a permeable foundation, the sample screen can be extended in depth using a mud trench. The structures in DC elements do not fear settlements. Backfilling is very simple and quick to perform compared to a zoned structure. An overflow structure can be built without problems for the stability of the entire structure.

Spillways or spillways can be made for smaller hydro installations serving as accumulation for irrigation purposes or the establishment of micro hydroelectric plants.

The possibility of widening conventional structures (dikes and dams) at the location of other structures allows significant savings on the volume of embankment and on the volume of embankment support structures on the central side or spillway. The realization of channels with waterproof DC elements for the lateral parts, married with a waterproof membrane for the bottom can be extremely interesting for certain applications, in particular for the crossing desert regions.

Miscellaneous: a multitude of other works can be carried out with DC structures in agriculture, environmental work (soil erosion, floods, bank protection), housing and leisure constructions, development of quays and ports, etc.

Claims (11)

1. Work of the wall type for retaining a substantially solid mass, comprising at least one structural element constituted by a thin membrane curved in the horizontal plane into a "U" shape having a curved part (1) and two straight parts (2), the curved part of the "U", subjected to tensile stress, forming by its outer surface the facing of the work, and the straight parts of the "U" forming embedding parts transmitting by frictional reaction the tension of the facing into the mass to be retained, characterised in that the said curved (1) and straight (2) parts of the membrane are corrugated in the vertical cross-section, thus forming a structural element with double curvature.
2. Work according to Claim 1, characterised in that it comprises anchoring plates (3) arranged at the end of the straight parts (2) of the structural element so as to form embedding parts transmitting by frictional-shearing reaction the tension of the facing into the mass to be retained.
3. Work according to Claim 1 or 2, characterised in that it comprises a plurality of "U"-shaped structural elements arranged side by side, a filling by successive layers being carried out inside the "U"s in order to produce an association of the said elements with the mass to be retained.
4. Work according to one of the preceding claims, characterised in that it comprises connecting elements of the same type as the said structural elements and arranged in a convex position so as to form a facing having a continuously sinusoidal shape.
5. Work according to one of the preceding claims, characterised in that it comprises a plurality of structural elements juxtaposed at right angles to their respective straight parts (2), each structural element being formed from a membrane in a single piece.
6. Work according to one of Claims 1 to 4, comprising an installation of structural elements of large dimensions, characterised in that it comprises a plurality of juxtaposed structural elements, the said elements being constituted by on-site assembly of several components, the embedding part (2) being made from a single sheet of appropriate thickness.
7. Work according to one of the preceding claims, characterised in that the "U"-shaped structural elements with double curvature are constituted by one or more of the following materials: metal, plastic, synthetic textile, fibre glass, composite material, metal or plastic mesh, reinforced or prestressed concrete, with adequate protection against corrosion.
8. Work according to one of Claims 2 to 7, characterised in that the structural elements are assembled together by mechanical means (welding, bolting, rivetting) or are simply juxtaposed, in which case the transmission of the stresses is achieved solely by friction.
9. Work according to one of the preceding claims, characterised in that it comprises bolted anchorages, piles, or sheet piling, associated with the said structural elements.
10. Work according to one of the preceding claims, characterised in that the said structural elements are installed with their facing inclined or terraced on a horizontal or inclined foundation surface.
11. Use of the work according to one of the preceding claims for the construction of terracing, highways, islands, peninsulas, offshore platforms, artificial lakes, reservoirs, hydraulic installations, wharfs, ports, storage facilities for materials, in association with other methods of construction or otherwise.

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