EP0185041A1

EP0185041A1 -

Info

Publication number: EP0185041A1
Application number: EP19850902574
Authority: EP
Original assignee: METULESCO ANDRE
Priority date: 1984-06-26
Filing date: 1985-06-06
Publication date: 1986-06-25
Anticipated expiration: 2005-06-06
Also published as: DE3585215D1; ATE71681T1; EP0185041B1; WO1986000354A1; AU4406585A; FR2566442A1; FR2566442B1

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

RETAINING STRUCTURES WITH DOUBLE CURVED THIN ELEMENT STRUCTURE

The retaining structures, better known as. WALLS name ^'OF RETAINING belong to the category of the oldest constructive tions 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 roadside, basement walls of houses or large dams, retaining structures are present everywhere and the sums invested in this field are becoming more and more considerable.

In our modern era, the variety of retaining structures and materials used is "very great. Generally, retaining structures are made with one or more of the following materials: stone, wood, concrete, metal and of course the 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, ie earth, with the aim of reducing structural elements as much as possible. .

This presentation shows a new concept for the construction of retaining structures, a concept which can replace conventional retaining walls in many cases more cheaply. To understand the principle, let's proceed by analogy.

Imagine the current of a river carrying debris or ice during the breakup. A cable floating across the stream, hooked by the ends on the two banks will retain all the debris or the; lace (fig.l)

^reϋlu * * x 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 relative 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 produced.

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

The fact that the structural elements are stressed only in tension is unprecedented in the new type of structure. proposes The basic element for the structure of the structure type is a thin corrugated (profiled) membrane in vertical plane and curved in horizontal plane, to form a self-supporting spatial element during construction. 'a corrugated sheet folded into a "U" shape. 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. The backfilling by successive layers allows us to realize 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 construction 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 resistance to shearing is also suitable as well as any material which makes it possible to avoid the possibility of a development of pore pressures inside the structure, This precludes a priori the use of soils with a large percentage of clay or even clay. The backfill must be free of organic matter and must meet certain electrochemical conditions vis-à-vis the 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 embankment is different in the sense defined above, as well as for works of a certain importance, 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 conditions architectural .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 the geometry and the thickness of the DC elements result from the calculation of the local stability and of the overall stability, so as to minimize the cost of the construction of the structure. The geometric characteristics as well as the thickness of the DC elements may 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 DC elements, or for their protection, must be made according to the pH of the pore water and the resistivity of the fill material. We can consider a priori that non-clay granular materials, as defined for roads, are compatible with all materials for DC elements. In some cases, to prevent the corrosion phenomenon, DC elements can be protected by the application of paint layers 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 the 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 produced from a single quality of material or from 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 armatures made with metal trellis, textile membranes, etc.

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

The anchor plates (3) can be metallic or precast concrete. Structures made with DC elements (fig. 4) lend themselves well to receiving on the facing a coating of precast concrete elements, bricks and above all shotcrete.

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

The DC elements are freestanding during construction and deformable after the completion of the structure being able to follow the deformations of the foundation terrain. Generally, the foundation surface must be horizontal ^" . In well-defined 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 structures with DC elements, as for any structure of its kind, it is a question of solving: overall stability and 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 (l), or by the tearing of the part embedded in the solid mass ( 2). Geometric characteristics

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 curved central part 1 of the element

DC defined by B, b and H, BUILT-IN PLAN the ends 2 of the element DC defined by L and H, REFERENCE PLAN the vertical plane, y o z 4

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

ACTIVE ZONE the part of the structure ^* which tends to dislocate depending on the sliding surface 7 _} PASSIVE ZONE OR the stable zone of the massif where the RESISTANT transmission of stresses to the earth is effected by friction or shearing 8 land

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

For the present account, the following hypotheses are taken into consideration: planar sliding surface (Coulomb), thrust of the earth applied on the reference plane, friction between the embankment and the elements DC equal to 1 angle of friction internal.

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

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

To determine the state of the unitary stresses inside the massif, we will take into consideration, in par- particular on the reference plane (the vertical plane yoz) any point M (oyz) determined by the intersection of the lines M 'M ¹ ' and Ml M2 parallel to the axes (fig. 9). The lines M 'M''and Ml M2 can be considered at the same time as the intersection of a horizontal plane respectively vertical 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 1 6 _. = 7Z the horizontal stress normal to the reference plane representing the thrust of the earth on the facing 2 G. = K_YZ the horizontal stress normal to the embedding plane can be called vise or tightening stress 3 6 ^" _y = K _y 7Z or 4 are the coefficients of active thrust and where 0 is the specific weight of the embankment, which allows us to write 5) 6. = 6 ^" _y = K7Z = p _z

In practice, for dimensioning, 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 perpen¬ dicular to the reference plane and over the width B of the element DC (fig.11). The horizontal stresses U " ⁼ 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 Figure 11 can be assimilated to a cylindrical shell where the reference plane merges with the diameter. The thickness of the facing 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 assuming that the tensile stresses in the walls are uniformly distributed along 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: 6) Tz = 1_ Pz B ΔH

2 S

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

Normally, the friction angle - *** _, between the embankment and 5 the DC elements must be close to the value of the internet friction angle. f'- f

Thus, to avoid slipping and to ensure embedding, it is possible either to design the surfaces concerned of the DC elements. Consequently, either provide anchor plates 10 (fig. 2) so%

Therefore, the sliding plane can be assimilated to the shearing plane (10) (fig. 12) 8) f = "g _ * '= tg €

For the tangential constraints δ, the linear law of Coulomb was taken into consideration, thus::. i5 for materials without cohesion, powdery ground for materials with cohesion, coherent terrain ιo) T. = 6Vtgf + c

Note: ^ the ^• embankments. "In granular have no cohesion

20 sion or it is very weak and uncertain; on the other hand, cohesion can be created artificially.

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

tension of the Tz facing is transmitted to the embedding plane. To preserve the balance Tz must be canceled by the sum of the tangential constraints o. To achieve this point N 35 (fig- 11) will be isolated on an elementary surface of dimensions l & - ΔhT ^' j as shown in figure 13 •

The equilibrium condition of the element allows us to express the value of the tangential stress as a function of Tz 14) I = -1-.J_I * ΔH dl Taking into account the principle that the stresses on a horizontal plane at — depth Z are constant (fig. 9) and relations 5) 'equation 14) as follows: > 5 This allows us to obtain the installation length in the resistant or passive zone: 16) ι _ ~. _{α τ}

Dimensions of the DC element. fp _z ΔH

Facing: we previously determined the tensile force in the circular facing (fig. 11). Holding com-

10 pte of relation 6, we can write: 17) where (_ ~ _ = the admissible stress of the material of the element DC

'= the equivalent thickness of the facing

To obtain the effective thickness it will be necessary to take into account

IS of the ripple of the DC element (fig. 14) - 18) t _{ï =} πt with the coefficient Jl> 1

Thus the effective thickness ^" t- of the element DC will be obtained from equation 17) taking into account the relationships

5), 6), and 18). In the depth

20 At the base of the book for Z

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, we cannot have a variable thickness compared to the height,

25 A single thickness corresponding to equation 20 will be used for the entire height, or sometimes it may be economical to vary the thickness by length of height.

Generally, for practical applications the height αe of the structure H is a basic data, on the other hand the width b of the

30 elements DC is at the discretion of the designer, according to equation 20) it will be advantageous to choose B as small as possible. Ce¬ pendant 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

35 in work and realization of the work.

For 21) β c can write 22)

With various alues 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 effort developed in the facing will be transmitted to the earth mass by the embedding plan. Mechanically, the embedding plan must be able, on the one hand, to take up all of the tractive effort transmitted by the facing and, on the other hand, to transmit the stresses to the earth mass without disorder. friction or shearing. e embedding plan must ensure by its length, the stability of the entire structure: tearing, pouring, 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 of figure 15-

The extent of the active area a will be determined geometrically: '23) α = (Hz) t "g (τ - y) ^a is a function of z and varies from zero at the base to its maximum value at the top

The embedding length L in the passive or resistive zone was established before with the formula lo) to which it is necessary to refer. If in equation 10 we replace the value of the strong Tz by its value given by t> the length L at the base of the structure becomes the maximum length La of the embedding plane to resist the tearing as follows:

The safety factor t for lifting Tj ₀ 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 backfill with a high internal friction angle or to use reinforcing plies in the backfill. b) Condition of non-overturning. In the case of conventional retaining walls made of reinforced concrete or not, it is absolutely necessary to check the reversal of the wall under the influence of the moment due to the pushing force of the embankments or of 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 installation surface is insufficient.

Assuming the formation of arches in a horizontal plane, between the embedding planes, the mass of the massif will be mobilized to prevent the phenomenon of overturning.

With a pre-established overturning safety factor ^] r, the length of the embedding plane Lr to ensure stability at overturning will be: 2ό) Lr = L c) Condition of non-slip. The philosophy to follow is the same as for the reversal.

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

With a sliding safety coefficient T) g preset the length of the embedding plane Lg to ensure sliding stability will be: ^" 27) i -HiKHctα-6 <L Safety '

To ensure internal stability must check firstly that the maximum tensile stresses are compatible with the tensile strength of the DC components, and secondly that _a recessed surface in the passive region or _resistant} is sufficient to allow a 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 tension 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 backfilling materials (the certainty of a minimum coefficient of friction, the type of structure (permanent or temporary), the risk (the extent of the damage in the event of destruction), the risk of corrosion.

The safety coefficients for overall stability will be determined from the: type of structure (permanent or temporary), risk (the extent of damage in the event of destruction). Generally, they cannot be lower than 1.5 for stability to overturning and sliding and 2- for the punching of the foundation.

Analysis of a reservoir. A retaining structure produced using jux¬ tapped DC elements, varying in height from 0 to 30 meters and of any length, has been analyzed in detail and shown in the charts in Figure 18 to Figure 23. The elements DC 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 provided 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 | m3j 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" in fig. 18, 19, 0 The length of the embedding plane "L" is generally determined by the condition of not being torn off.

In the various calculations, the concept of specific thickness "e" was introduced, which represents the thickness of the entire DC element in relation to the length of the rectilinear front of the structure, thus: eo the thickness net without excess thickness for corrosion, and 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.

The abacuses of ^' fig 21,22,23 represent the variation of "eo" and "e2" as a function of the height for various ratios between "B" and "H" and various coefficients of the thrust of the ter¬ res. We can see that the most economical value for "e2" corresponds to a ratio of "B" on "H" equal to or less than 05 13

Remarks: a) the thickness of the DC elements is determined for the maximum sol¬ licitation either at the base of the structure and is kept constant over the entire height. For works of one

At some importance, it can be cost effective to vary the thickness. b) extra thickness as protection against corrosion must be taken into account. It is 0.5 nun or 1 mm for each side depending on the aggressiveness of the

10 environment and expected life expectancy of the structure. c) for minor works, the installation plan is carried out by the juxtaposition of the various DC elements and no bolting is required.

On the other hand, for other works, the multipla DC elements are connected to 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 thrust coefficient

20 active backfill is taken as 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. 25 The facing of structures taking into account ^the coating possibilities, may take the form and the 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 unlimited 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.

By the capacity of deformation of the DC elements, the structures 35 can easily follow the movements of the foundation ground. The realization of temporary works becomes very interesting, by the speed of execution, by the ease of demolition and recovery _. total of DC elements. The type of structure proposed is very flexible for landscaping terraced accommodation for housing or 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 build impermeable structures, such as dikes or reservoirs.

With the type of structure proposed, the construction of flood protection dikes can ^" s ^" prove to be an extremely important application taking speed into account. 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 increasing c.ooaéiîdérably the stocks. Some 20 ^{applications:} ^• Terracing

It is a question of terracing on the steep slopes. These arrangements allow urban development, recreation, agriculture, communication routes, etc ... ^'25 (Fig.17) "" The lands are held with a' .to-fcructure performed with DC elements made of galvanized sheet steel or ^• another, juxtaposed or in multi-plates. The facing is cons¬ titué semi-circular elements, elliptical, etc .. with or without fitting convex. 30 It should be noted that the standard elements have their two parallel embedding planes. However, as the DC elements have low rigidity, they can be deformed so as to make the two embedding planes divergent or convergent. This characteristic allows changes of 35 direction of siding as desired. Channels of communication

The communication routes involve earthworks. awe-inspiring relief which brings about the need for various elements retaining elements. These can be created 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 of decorative elements of pre-fabricated concrete.

Roads on very steep slopes can be laid with a minimum of excavation. The embedding plans can be supplemented by anchoring in the rock mass - 10. Excavation in non-rocky terrain is minimized because we just do a few. grooves for installation plans.

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

The parapets made with DC elements are securi¬ tary given their great flexibility while being quite heavy. Λ

Islands - offshore platforms 20 On a body of water, artificial islands or peninsulas can be made 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 produced using DC elements. In order to minimize the work, the debris is to 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 of ma-. 35 ni ^ re waterproof. When the facings are provided with connectors, these can be the same as the first ones. The facing thus produced has a more aesthetic appearance of continuity. The "embedding-connection plan" nodes can. be_assembled either in the factory or on a site. Once these knots are in place, the central part of the facing can be fixed.

The bottom of the tanks consists of a waterproof layer supplemented if necessary by a synthetic membrane. 5 A trellis fixed on the various joining elements allows the production of a sprayed concrete covering. The latter can be smooth or covered with any other finish. tion such as ceramic.

The range of ponds can be of a wide variety and 10 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 one can consider that they are buried. Therefore, this type of tank offers a very large operating safety, completely eliminating the safety bowl and the drawbacks which. 25 .. 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. 30 To prevent corrosion and preserve hygienic conditions (for edible products) the vertical structure ^{• "} :: Le -fond ^{" as} well as ^' qvêvl' intrados d. the ^" roof must be compatible with the stored liquid and the vapors which dega¬ gent.

35 DC tank 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 made of: prestressed precast 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 the carrying out of repair work (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 substantially reduced. 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. The backfilling is very simple and quick to perform compared to an area structure. An overflow opening can be produced without problems for stabilization. of the whole structure.

Spillways or spillways can be made for minor hydro developments serving as storage 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 works 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 tra- poured from desert regions.

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

Claims

1) Retaining wall type structure characterized with regard to the structural element consisting of a thin membrane or lattice) corrugated or profiled in a vertical and curved plane

5 in horizontal plane in the shape of a "U", the curved part is sol¬ licite in traction and represents the facade or the facing (1) of the structure, the straight parts of the "U". Represent the embedding plans (2) transmitting the traction of the facing in the mass to be retained (8) where they react by friction or friction-shearing depending on whether or not the free ends of (2) are provided, plates of anchor (3) thus obtaining a thin structure with double curvature

2) A structure according to claim 1 in which the "U" elements are arranged side by side and subsequently, the backfilling of the ground

15 by successive layers inside the "U" allow to realize the association between the structural elements and the mass to retain the earth, ore or any floating material.

3) Work according to claims 1 and 2 characterized

^' in that. the facings (1) are curves (circles, ellip-

20 se; spiral, etc.) in tension, in position. concave in relation to the facade and apart from their continuity with the casing planes, they can be connected together with elements of the same type in the convex position, thus obtaining a facade, a facing with a continuous appearance sinusoidal.

25 4) A structure according to the preceding claims taken as a whole, characterized in that the elements with double curvature in the shape of a "U" are elements in one piece and their installation is carried out by juxtaposition, by against the large "U" shaped elements.

30 will be manufactured and transported in several compounds, ultra-plates, and assembled on site, in the latter case the embedding plane (2) will be produced from a single sheet of suitable thickness.

5) Works according to the preceding claims taken

^'35 together, characterized in that the' shaped elements with double curvature "U" are formed of one or a combination of the following materials: metals, plastics, synthetic textiles, glass fibers, composite materials, wire mesh or plastics, reinforced or pre-stressed concrete, with adequate protection against corrosion depending on the case. 5 6) A structure according to the preceding claims taken as a whole, characterized by the fact that the thin elements with double curvature or their compounds - the multi-plates - are assembled by mechanical means, such as welding, bolting, riveting or simply by overlap, in the latter 0 case, the transmission of stresses takes place by friction.

7) A structure according to the preceding claims taken as a whole, characterized in that the elements with double curvature are associated with the bolted anchors, the 5 piles or the sheet piles.

8) A structure according to claims 1 and 2, caracté¬ ized in that the thin membrane structure is rem-

^• - placed with a metallic or plastic mesh of the same shape as the thin elements with double curvature. 9) A structure according to the preceding claims taken as a whole, characterized in that the structure in thin elements with double curvature is implemented with the inclined facing or terraces .; ^' on urie surface- of horizontal foundations ^' or inclined. 10) A structure according to the preceding claims taken as a whole, for the realization of terraces, communication routes, islands, peninsulas, .. platforms off. shore, basins, reservoirs, tanks, various hydro-installations, quay and port arrangements, material parks, etc. is characterized by the fact that for the masses to be retained, thin structures with double curvature are used, associations with or without other recognized construction techniques.