EP0463925B1 - Construction method adjacent to mountain side, of a semi-buried structure and thus realized structure - Google Patents

Abstract

The subject of the invention is a method for constructing a semi- buried structure for protecting a platform constructed on a mountain side, and also covers the structure thus constructed. <??>In accordance with the invention, the structure consists entirely of prefabricated concrete elements forming a sequence of adjacent sections, each consisting of three prefabricated elements, respectively an upper covering element (1) bearing, by means of longitudinal articulations (5, 5'), on two side elements comprising, respectively, a solid wall (2) on the upstream side and at least one pillar (3) on the downstream side, and each equipped with a widened sole plate (21, 31) enabling the element to be placed simply on the ground (4) and with an upper part in the form of a longitudinal girder (22, 32) on which are provided longitudinal parts (51, 52) for articulated bearing (5, 5') of the corresponding lateral edge of the covering element. <??>The invention applies especially to the protection of roadways or railways on a mountainous site. <IMAGE>

Description

The subject of the invention is a process for producing a semi-buried structure forming a roadway or railroad protection gallery produced on a mountainside and also covers the structures thus produced.

It is often necessary, in rough terrain, to realize the platform of a roadway or a railroad in ledge or at the foot of a strongly inclined terrain, sometimes even, a vertical cliff, for example, at the exit of a tunnel.

Such a structure is intended essentially to protect the roadway against landslides or avalanches. It must therefore be constituted, on the upstream side, by a solid wall which is connected to a cover making it possible to retain landslides or avalanches or else to make them pass over the roadway. On the other hand, on the downstream side, the cover generally rests on a wall pierced with orifices, often a series of pillars, so as to allow natural lighting of the roadway and not to unnecessarily lengthen the tunnel.

The roofing must be able to withstand very large shocks due, for example, to the fall of large blocks and we often prefer to give it the shape of a vault. In addition, it is preferably covered with an embankment which makes it possible to absorb shocks.

But such a structure must also be able to withstand significant lateral forces due to landslides and avalanches.

Such structures have been known for a long time.

US-A-3,282,056 describes, for example, such protection galleries but these are made entirely by means of metal panels made of corrugated sheet which must be held by tie rods. Such panels do not have the same resistance as a reinforced concrete wall but, above all, the risk of corrosion does not give the works thus produced sufficient durability. This is why, it is preferred, normally to use reinforced or prestressed concrete. For example, the magazine "Route et Circulation Routière" N ° 6 of June 2, 1967 shows a protective gallery made up of a vaulted concrete wall, embedded in the ground on the upstream side and resting on a series of pillars on the downstream side.

Swiss Patent No. 402,919 also shows such a gallery comprising a cover slab anchored in the rock wall on the upstream side and resting, on the downstream side, on a wall provided with movable panels making it possible to absorb the depression due to the passage of a avalanche.

Until now, such structures have been produced by the usual techniques of reinforced concrete, that is to say by molding in place, using formwork and hangers. These processes are relatively long and expensive.

However, in mountainous terrain, the season favorable to construction is very short. In addition, personnel and equipment are not fully protected against falling rocks or rockslides that may occur during construction.

The object of the invention is to solve these difficulties by means of a new method making it possible to construct such protection galleries very quickly and safely.

The invention therefore relates, in general, to the production of a semi-buried structure for the protection of a platform extending on the mountainside along a longitudinal axis and comprising a covering bearing on the upstream side, on a closed wall and on the downstream side on an open wall, for example a series of spaced apart pillars.

According to the invention, the protective structure is entirely made up of prefabricated concrete elements each covering a part of the cross section and forming a series of adjacent sections placed one after the other along the longitudinal axis, and constituted each of three prefabricated elements, respectively an upper cover element bearing, by means of longitudinal articulations, on two side elements comprising, respectively, a solid wall on the upstream side and at least one pillar on the downstream side, and provided each of a base in the form of an enlarged sole with a flat lower face allowing the element to be simply placed on the ground and of an upper part in the form of a sill on which are provided longitudinal articulated support parts of the edge corresponding side of the cover element.

• on réalise à l'avance, dans un chantier de préfabrication, trois séries d'éléments préfabriqués, respectivement des éléments de côté amont comprenant une paroi plane s'étendant entre une base élargie et une longrine supérieure, des éléments de côté aval comprenant au moins un pilier s'étendant entre une base élargie et une longrine supérieure, et des éléments supérieurs de couverture constitués chacun d'un voile rigide s'étendant entre deux bords latéraux parallèles, sur lesquelles sont ménagées des parties d'appui longitudinales susceptibles de coopérer avec des parties longitudinales conjuguées ménagées sur la face supérieure des longrines des éléments de côté de façon à former des appuis articulés,
• on réalise au moins une partie de plateforme aplanie au niveau voulu,
• on pose successivement sur ladite partie de plateforme, au moins un élément de côté amont, un élément de côté aval et un élément de voûte.

To construct, according to the invention, such a structure:

• three series of prefabricated elements are produced in advance, in a prefabrication site, respectively upstream side elements comprising a flat wall extending between an enlarged base and an upper sill, downstream side elements comprising at least a pillar extending between an enlarged base and an upper sill, and upper cover elements each consisting of a rigid veil extending between two parallel lateral edges, on which are provided longitudinal support parts capable of cooperating with longitudinal conjugate parts formed on the upper face of the sills of the side elements so as to form articulated supports,
• at least part of the platform is leveled to the desired level,
• at least one upstream side element, a downstream side element and an arch element are successively placed on said platform part.

The invention takes advantage of recent advances in prefabrication which make it possible to produce prefabricated elements of great strength and having large dimensions. In particular, the inventor had already proposed in patent EP 081,402, a technique for constructing underground structures such as nozzles or bridges by means of prefabricated elements placed on the bottom of a trench and then covered with a embankment.
This technique has been the subject of improvements and, for example, international application WO 86/02967, describes a process for producing a structure comprising two parallel passage sections each covered by an upper element in the form of a vault which rests, outwards on a side element and, inwards, on an intermediate foreshore bearing on the ground by a sole.

In this known method, side elements are also used which are provided at their base with a stabilization part allowing them to be simply placed on the ground while standing straight without scaffolding and supporting an upper element in the form of a curved arch which is tangentially connected to the side elements so that the applied loads are transmitted by arching effect on the side elements and up to a flat floor slab allowing the stresses to be distributed over a large area.

As a result, the prefabricated elements described in patent EP 081,402 were intended to transmit forces tangentially and not to withstand significant lateral stresses. This is why they could not be used without adaptation for the realization of semi-buried structures on the mountainside.

In particular, each covering element consists of a veil in the form of a cylindrical sector associated with at least one transverse stiffening rib formed on the underside of said veil and extending along a plane perpendicular to the axis, the assembly forming a rigid part substantially non-deformable, molded in a single piece of reinforced or prestressed concrete.

In this way, the vaulted shape of the cover is preserved, which makes it possible to better collect the load of the embankment and the shocks coming from the landslides, but the rigidity imparted by the rib makes it possible to maintain the spacing of the lateral edges and to transmit the loads to the side elements in essentially vertical directions by means of the articulated supports which are formed on horizontal faces opposite the upper element and the support beams.

Such an articulated gantry structure better withstands the lateral forces which are occasionally exerted in the event of landslides or avalanches.

However, the side edges of the cover element are subjected to significant vertical forces and must therefore be able to be reinforced accordingly.

For this purpose, each cover element can be provided, along its two parallel longitudinal edges, respectively of two reinforcement beams bearing on the upper sills of the side elements and the articulated longitudinal supports consist of conjugated parts provided, respectively recessed and protruding, on the horizontal faces opposite the side members of the covering element and the sills of the side elements.

It is also advantageous for the upstream side element to consist of a curved wall tangentially connecting to the cylindrical web of the cover element. In this case, the curved wall is provided, at its upper end and on the extrados side, with an enlarged part with triangular section comprising a horizontal face on which the corresponding part of the articulated support is formed.

Since the cover element is simply placed on the upper sills, side elements, its width is not necessarily limited to the spacing of said sills and it can advantageously be extended, at least on the downstream side, by a part extending in door-to-door false from the corresponding lateral support edge and comprising a cylindrical wall section associated with at least one stiffening rib extending between the upper surfaces of the upper element and of said extension, perpendicular to the axis and on both sides 'other of said lateral support edge.

Preferably, the space between the natural terrain and the side element placed towards the ridge is filled with a relatively flexible backfill material and the assembly is covered with topsoil up to the opposite lateral edge of the element. superior.

• la figure 1 est une vue générale, en coupe transversale, d'une structure réalisée selon l'invention;
• la figure 2 est une vue en coupe selon II-II de la figure 1;
• la figure 3 est une vue en coupe selon III-III de la figure 1;
• la figure 4 est une vue schématique, en coupe transversale, d'une chaussée réalisée à flanc de montagne sur une plateforme aplanie et tassée 4.

However, the invention will be better understood from the following description of a particular embodiment given by way of example and shown in the accompanying drawings.

• Figure 1 is a general view, in cross section, of a structure produced according to the invention;
• Figure 2 is a sectional view along II-II of Figure 1;
• Figure 3 is a sectional view along III-III of Figure 1;
• FIG. 4 is a diagrammatic view, in cross section, of a roadway formed on a mountainside on a leveled and packed platform 4.

The structure shown in Figure 1 comprises an upper element 1 placed on two side elements, respectively upstream 2 and downstream 3 resting on the ground each by means of a sole 21, 31. All the elements are made of reinforced concrete or prestressed.

No anchoring in the ground and no foundation work is necessary, the two side elements 2 and 3 being simply placed on the platform 4 by means of their soles 21, 31, which are provided to allow them to stand straight without scaffolding.

The upper cover element 1 consists of a concrete veil in the form of a cylinder of revolution sector centered on a longitudinal axis 10 and provided, on its lower surface 11a, with two transverse ribs 12 which extend along perpendicular planes to the longitudinal axis 10. In addition, along its two lateral edges 13, 13 ′ parallel to the axis 10, the upper element 1 is provided with two reinforcement beams 51, 52 bearing respectively on beams 22 , 32 formed on the upper ends of the side elements 2 and 3, by means of articulated longitudinal support members 5 (5 ′).

In the embodiment shown, in the figures, each upstream side element 2 consists of a solid wall curved inwards and extending, in a substantially vertical direction, from the base 21.

The curvature of the curved wall 2, at least at its upper end, is equal to that of the cylindrical web 1 so that the elements are joined tangentially.

However, to allow the recovery by the side element 2 of the vertical forces applied to the supports 5, the upper end of the element 2 is widened on the upper surface side by a part 22 having a horizontal upper face 23 and in which can be placed the reinforcement necessary to absorb the forces applied, the upper end 22 thus forming a reinforcement sill with a substantially triangular section.

Normally, the sill 22 will be molded in one piece with the side element 2. It could, however, be made up of an added beam, placed and sealed on the upper end of element 2.

Each support member 5 consists of two conjugate parts 53, 54, formed respectively, projecting and recessed, on the opposite faces of the side members 51, 52, and the sills 22, 32, or vice versa.

For example, the lower face of each spar 51, 52 of the covering element is provided with a rib 53 with a convex rounded profile engaging in a groove 54 formed on the upper face 23 of the sill 22 (32) of side element 2 (3).

Seals 55 (55 ′), for example made of neoprene, can advantageously be placed between the two parts 53, 54, bearing one on the other.

The upper element 1, stiffened for the ribs 12 and the side members 51, 52, constitutes a rigid assembly, substantially non-deformable, molded in one piece. Consequently, even when loaded with an embankment, the upper element 1 transmits to the side elements 2 and 3 only vertical forces passing through the median planes P, P ′ of the support members 5, 5 ′ .

The entire structure thus forms an articulated gantry resting on the flanges 21, 31 which can be calculated to occasionally resist horizontal forces resulting from landslides or from the passage of avalanches, vertical forces being predominant.

Thus, the internal part 21a of the sole 21 of the side element 2 can extend sufficiently inwards from the support plane P to ensure the stability of the element 2. In addition, the external part 21b of the sole 21 can advantageously be extended considerably outwards so as to contribute to the stability of the element 2 by spade effect when it is loaded with an embankment.

Note also that when the elements 2 are curved, the sill 22 makes it possible to push the application plane P of the support forces outwards.

The cover 1 can simply cover the space between the side elements 2 and 3. The side members 51 and 52 are then identical. However, in the preferred embodiment shown in the figures, the upper element 1 is provided on one side with a cover extension 6 consisting of a curved veil 61 extending in cantilever from the spar 52. The veil 61 may have the shape of a cylindrical sector of the same radius as the veil 11 so that the apertures of the two arches form a symmetrical assembly with respect to the support beam 52.

Furthermore, one or more transverse ribs 63, perpendicular to the longitudinal axis 10, are arranged upwards, between the upper surfaces 11b and 61b, so as to connect the two arches 11 and 61 together. The upper element 1 constitutes thus a rigid assembly which is molded in a single piece of reinforced or prestressed concrete and which comprises the arch 11 and its extension 6, the ribs 12 and 63 and the longitudinal members 51 and 52. The dimensional characteristics of the cylindrical walls and their ribs, as well as the reinforcements are determined so as to form an assembly which is both rigid and light capable of supporting its own weight and the weight of a bank of limited thickness without deformation.

The longitudinal support member 5 ′ of the spar 52 of the upper element on the side element 3 is also symmetrical with respect to the vertical plane P ′, the groove 54 ′ being formed on the upper face 33 of the spar 32 which therefore does not need to be widened like the side member 22 of the side element 2.

The structure which has just been described is particularly suitable for the realization of a road in cornice, as shown in Figure 4.

The prefabricated elements 1, 2, 3 can advantageously be produced in a prefabrication plant possibly distant from the construction site. Indeed, one can limit their dimensions, in the longitudinal direction, to the width of a road trailer to allow their transport. The roadway, which can have two parallel tracks A and B, is placed on a platform 40 made on the mountainside.

For the construction of the gallery, after having made the platform 4, possibly over a reduced length to reduce the risk of landslides, first a number of upstream elements 2 are laid by aligning them, then the downstream elements 3 and finally the cover elements 1.

The side of the platform 4 facing the ridge can be dug in cuttings and if the nature of the soil allows, the upstream face 41 can be substantially vertical so as to limit the footprint and the volume of cuttings. Indeed, the personnel benefit, from the installation of the upstream elements 2, of a certain protection against landslides which become blocked between the mountain 41 and the element 2. This protection is further improved by the curved shape of the wall 2 When the structure has been built over a certain length, the pavement can be built under cover.

For a two-lane carriageway, the downstream element 3 is placed substantially in the middle of the platform 4. However, since the foundations are removed and the load is well distributed by the sole 31, the side element 3 could be placed, in the case of a narrow track, very close to the downstream edge of the platform 4.

The pavement 46 is produced in a conventional manner, the internal parts of the soles 21 and 31 being able to constitute an embedding and support, possibly sidewalks.

Of course, the invention is not limited to the single embodiment which has just been described and which could be the subject of variants. For example, the side element 2 placed towards the crest is advantageously curved to better resist the thrust of the ground and to protect a sidewalk, but it could also consist of a flat wall extending vertically from the sole 21 .

The dimensions and the reinforcement of the different elements are determined to withstand the forces and in particular to give the upper element 1 the desired rigidity without excessively increasing the weight. In particular, as shown in the figures, the underside 14 of the rib 12 can be curved to lighten the assembly and release a larger clearance gauge. However, in certain applications, for example residential or industrial buildings, the lower face 14 could be horizontal so as to facilitate the installation of a ceiling, the ribs 12 then being able to be thinner.

One could also arrange in the ribs 12 orifices 15 allowing the passage of sheaths, pipes and various circuits.

Furthermore, the structure according to the invention could be the subject of other applications, for example for the production of protective walls between noise, in an urban site, in this case, the creation of an embankment and a slope in topsoil above the structure would remain interesting for its noise damping effect and from an aesthetic point of view.

A structure of the same type could also be used for the realization of semi-buried buildings, for example on the hillside in tourist sites, such buildings, possibly covered with gardens, integrating well into the landscape and being well protected against possible landslides or avalanches in winter.

Claims (11)

1. A semi-buried covered structure for protecting a subgrade extending on a mountainside along a longitudinal axis and having a closed side on the uphill side and an open side on the downhill side, said structure being constructed from concrete and comprising a covering bearing, on the uphill side, on a solid wall and, on the downhill side, on a series of spaced pillars, characterized in that it consists entirely of precast concrete elements, each covering a portion of the cross-section and forming a succession of adjacent sections placed one after the other along the longitudinal axis, and each consisting of three precast elements, respectively an upper covering element (1) bearing, via longitudinal articulations, on two side elements comprising, respectively, a solid wall (2) on the uphill side and at least one pillar (3) on the downhill side, and each equipped with a base (21, 31) in the form of a widened footing with a plane lower face enabling the element simply to be placed on the ground (4), and with an upper portion in the form of a stringer (22, 32) on which are formed longitudinal portions for the articulated bearing of the corresponding lateral edge of the covering element.
2. The covered structure according to claim 1, characterized in that each covering element (1) consists of a shell in the shape of a cylindrical sector associated with at least one transverse stiffening rib formed on the intrados of said shell and extending in a plane perpendicular to the axis, the whole forming a substantially undeformable rigid piece cast in a single piece.
3. The covered structure according to one of claims 1 and 2, characterized in that each covering element (1) is equipped, along two parallel longitudinal edges, respectively with two longitudinal beams bearing on the upper stringers of the side elements and the dimensions and the reinforcement of which are determined as a function of the bearing forces.
4. The covered structure according to any one of claims 1 to 3, characterized in that the articulated longitudinal bearings consist of matching portions formed, respectively recessed and projecting, on the opposite faces of the longitudinal edges of the covering element and of the upper stringers of the side elements.
5. The covered structure according to claim 2, characterized in that each uphill side element consists of an inwardly curved wall joined tangentially to the cylindrical shell of the covering element and equipped, at its upper end and on the side of the extrados, with a widened portion of triangular cross-section comprising a horizontal face on which is formed the corresponding portion of the articulated bearing.
6. The covered structure according to any one of the preceding claims, characterized in that the upper element (1) is equipped, on at least one side, with a covering extension (6) extending in cantilevered fashion from the corresponding lateral bearing edge (13') and comprising a section of a cylindrical shell (61) associated with at least one stiffening rib (63) extending between the extrados (11b, 61b) of the upper element and of said extension, perpendicularly to the axis (10) and on either side of said lateral bearing edge (13').
7. The covered structure according to any one of the preceding claims, characterized in that the dimensions of the precast elements, in the direction parallel to the longitudinal axis of the subgrade, are limited to the vehicle clearance on a highway or on a railroad track in order to enable the transportation of the elements from the precasting factory to the building site.
8. The covered structure according to any one of the preceding claims, characterized in that the space (43) between the side element (2) placed nearest the top of the incline and the natural terrain (41) is filled with a backfill material (43), and the whole is covered with topsoil (44) as far as the opposite lateral edge of the upper element (1).
9. A process for the construction of a semi-buried covered structure for the protection of a subgrade extending on a mountainside along a longitudinal axis, said structure being constructed from concrete and comprising a covering bearing, on the uphill side, on a closed wall and, on the downhill side, on a series of spaced pillars, characterized in that :

   - three series of precast elements are made in advance in a precasting factory, respectively uphill side elements comprising a solid wall extending between a widened base and an upper stringer, downhill side elements comprising at least one pillar extending between a widened base and an upper stringer, and upper covering elements, each consisting of a rigid shell extending between two parallel lateral edges, on which upper elements are formed longitudinal bearing portions capable of interacting with matching longitudinal portions formed on the upper face of the stringers of the side elements in order to form articulated bearings,

   - at least a portion of the flattened subgrade is formed at the desired level,

   - at least one uphill side element, one downhill side element and one vault element are placed successively on said subgrade portion.
10. Application of a covered structure according to one of claims 1 to 8 to the construction of a structure for protection against landslides or avalanches.
11. Application of a covered structure according to one of claims 1 to 8 to the construction of a semi-buried building.

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