Abstract:
The construction work erected in front of a pre-existing wall comprises a facing standing along a front face of the work, a fill occupying a gap between the facing and the pre-existing wall, and a retention system extending into the fill for keeping the facing in place relative to the pre-existing wall. The retention system comprises first stabilizing elements attached to the pre-existing wall and extending into a first region of the fill, and second stabilizing elements connected to the facing and extending into a second region of the fill. The first and second regions have a common part in which forces are transmitted between the first and second stabilizing elements by the fill material.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to the construction of civil engineering works using stabilized fill techniques.  
         [0002]     The works to which the invention relates may have a variety of uses such as, for example, for widening traffic lanes, for extending a constructible space, for preventing deterioration, erosion or collapse of stone or rock walls, or else for creating an attractive solid mass. In general, they comprise a fill placed vertically or approximately vertically against the solid mass or structure supporting the traffic lane or the constructible space, or the wall of which is deteriorating. The vertical wall to the front of the fill consists of a facing connected to the pre-existing structure.  
         [0003]     This pre-existing structure may have irregular geometrical characteristics.  
         [0004]     Thus, the construction of a fill, whose facing has to be straight with a linear shape, requires that the irregularities on the front side of the pre-existing structure be taken into account. This is because the width of the fill would have to vary both in the height direction and in the length direction.  
         [0005]     To avoid this difficulty, one solution consists in making the wall against which the fill will bear as plane as possible. Thus, the members connecting the facing to this wall will have roughly the same length. The residual imperfections in the wall are then remedied by pragmatic adjustments to the lengths by empirical time-consuming methods.  
         [0006]     Another solution consists in providing openings in the facing elements so as to pass thereinto the connection members anchored to the wall of the pre-existing structure. The connection members are then tensioned by means of rams and then anchored into the facing. This solution requires relatively substantial handling and a relatively long time, and accordingly increases the cost of constructing the fill.  
         [0007]     An object of the present invention is to propose another solution, which allows simple, rapid, and therefore inexpensive, construction of a fill having a facing of regular shape, typically a plane shape, to the front of a pre-existing wall whose shape may be irregular.  
       SUMMARY OF THE INVENTION  
       [0008]     The invention thus proposes a construction work erected in front of a pre-existing wall. The work comprises a facing erected along a front face of the work, a fill occupying a gap between the facing and the pre-existing wall, and a retention system extending into the fill for keeping the facing in place relative to the pre-existing wall. According to the invention, the retention system comprises first stabilizing elements attached to the pre-existing wall and extending into a first region of the fill, and second stabilizing elements connected to the facing and extending into a second region of the fill, said first and second regions having a common part in which forces are transmitted between the first and second stabilizing elements by the material of the fill.  
         [0009]     The friction between the stabilizing elements and the fill material ensures that forces are transmitted by the fill material in the common part between the first and second regions. Such a way of transmitting forces has already been proposed in the case of retaining walls (WO 2005/040506). In the application considered here to the construction of a new wall in front of a pre-existing wall, the profile of which may be irregular, this way of transmitting the forces ensures that the facing is held in place relative to the pre-existing wall.  
         [0010]     A major advantage is that the relative independence between the first and second stabilizing elements makes it possible for the first elements to be attached to the pre-existing wall without the particular concern for the relative alignment of the anchoring points relative to a vertical plane. The first elements will penetrate sufficiently into the fill in order to obtain sufficient thickness of the common part between the first and second regions without requiring a precise adjustment of their length. This results in great simplification in stabilizing the fill and in constructing the work.  
         [0011]     In preferred embodiments of the work according to the invention: 
        the facing comprises prefabricated elements in which the second stabilizing elements are partly embedded;     these prefabricated elements are preferably made of concrete, the second stabilizing elements being in the form of flexible synthetic reinforcements each having at least one part cast in the concrete of one of the prefabricated elements;     this cast part of the flexible synthetic reinforcement follows a loop in the prefabricated element so as to have two segments that project into the second region of the fill, the loop preferably being placed in the prefabricated element so that the two projecting segments of the flexible synthetic reinforcement emerge from the facing into the fill at vertically spaced positions;     the second stabilizing elements comprise geotextile layers extending into the second region of the fill. Preferably, the work then comprises geotextile sheets folded so as each to have a front part extending over the front face of the work and forming a portion of the facing, and two layers folded back from said front part and extending approximately horizontally into the fill in order to form two of the second stabilizing elements;     the second stabilizing elements comprise metal reinforcements attached to the facing and extending into the second region of the fill;     there is substantially no direct contact between the first stabilizing elements and the second stabilizing elements;     the first and/or second stabilizing elements are flexible synthetic strips; and     the first stabilizing elements in the form of flexible synthetic strips are placed along zigzag paths in the first region of the fill.        
 
         [0020]     Another aspect of the invention relates to a method of constructing a work in front of a pre-existing wall, comprising the steps of: 
        erecting a facing along a front face of the work, delimiting a volume to be filled;     positioning a retention system in a gap between the facing and the wall for holding the facing in position relative to the wall;     providing fill material into said gap; and     compacting the fill material.        
 
         [0025]     According to the invention, the retention system comprises first stabilizing elements attached to the wall and extending into a first region of the fill, and second stabilizing elements connected to the facing and extending into a second region of the fill, said first and second regions having a common part so that, after fill material has been introduced and compacted, forces are transmitted between the first and second stabilizing elements by the fill material located in said common part.  
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0026]      FIG. 1  is a schematic view in lateral section of one example of a construction work according to the invention.  
         [0027]      FIG. 2  is a schematic top view of the construction work shown in  FIG. 1 .  
         [0028]      FIG. 3  is a schematic view in lateral section of an alternative embodiment of a construction work according to the invention.  
         [0029]      FIG. 4  is a schematic top view of the construction work shown in  FIG. 3 .  
         [0030]      FIGS. 5 and 6  are partial perspective views of other embodiments of a construction work according to the invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]     FIGS.  1  to  5  illustrate the non-limiting application of the invention to the construction of a straight vertical wall to the front of a solid terrain mass  1  on which a road  2  has been constructed. The mass  1  has an irregular profile on its front side.  
         [0032]     The front side of the construction work has a facing  3 , for example made of juxtaposed prefabricated elements  4  of reinforced concrete. A compacted fill  5  fills the gap between the facing  3  and the wall formed by the front side of the mass  1 .  
         [0033]      FIGS. 1 and 2  show stabilizing elements  6 ,  7  buried in the fill  5  in order to hold the facing  3  in position relative to the mass  1 .  
         [0034]     In the example shown, the stabilizing elements  6 ,  7  are linear elements, such as reinforcements made of rolled steel or geotextile strips. The elements  6  are anchored to the face on the front side of the mass  1  by means of conventional anchoring members  8 , such as for example expansion bolts, masonry anchors or nails. The elements  7  are fastened to the rear of the facing  3 , which is for example provided with metal rings for accommodating them.  
         [0035]     In the example shown in  FIGS. 1 and 2 , the stabilizing elements  6 ,  7  are placed approximately in horizontal planes and perpendicular to the facing  3 . The elements  6  attached to the mass  1  stabilize the fill  5  in a region Z 1  that extends over more than half the width of the filled gap. Likewise, the elements  7  attached to the facing  3  stabilize the fill  5  in a region Z 2  that extends over more than half the width of the filled gap. These two regions Z 1 , Z 2  thus overlap in a common part Z′, the thickness of which is intended to be sufficient for the friction between the elements  6 ,  7  and the cohesion of the fill material  5  to ensure that the facing  3  is held in position relative to the mass  1 . In this common part Z′, the material of the fill  5  is very strong because it is stabilized by the elements  6  and  7 . It is thus capable of withstanding gravitational forces and forces due to the application of possible loads on the top of it.  
         [0036]     Depending on the dimensions of the work, on the materials employed and on the spacing between the stabilizing elements  6 ,  7  (which spacing may be reduced as required), structure calculation allows the minimum thickness to be respected for the common part Z′ to be determined. The irregularities in the mass  1  may cause this thickness of the zone Z′ to vary locally, but it is easy to ensure that it is never below the predetermined minimum thickness.  
         [0037]     In order for the frictional forces to be properly controlled, it is preferable to ensure that there is no direct contact between the first and second stabilizing elements  6 ,  7 .  
         [0038]      FIGS. 3 and 4  illustrate an alternative embodiment in which the stabilizing elements  16 ,  17  are flexible synthetic reinforcements in the form of strips. As an example, these reinforcements are synthetic stabilizing strips based on polyester fibers, such as those sold under the brand name “Freyssissol”.  
         [0039]     In the example shown in  FIGS. 3 and 4 , the strip reinforcements  16  attached to the solid wall are placed along zigzag paths in horizontal planes in the region Z 1  of the fill  5 . The anchoring members  8  are used for fastening rings or hooks  9  into the mass  1 , the strip that will form the reinforcement  16  passing into said rings or hooks. The front side of the strip is advanced towards the facing so as to ensure the sufficient thickness of the force-transmitting zone Z′.  
         [0040]     On the facing  3  side, the reinforcements  17  are partly cast in the concrete of the prefabricated elements, thereby ensuring that they are attached to the facing. The cast part of the flexible synthetic reinforcement  17  follows a loop in the prefabricated element  4 , and thus has two segments projecting into the region Z 2  with the fill  5 . These two projecting segments of a reinforcement  17  emerge from the facing  3  at vertically offset positions. One of the reinforcements  16  attached to the solid wall penetrates into the gap separating the two projecting segments of any one reinforcement  17 . Another of the reinforcements  16  attached to the solid wall is inserted between the upper segment of a reinforcement  17  embedded in a facing element  4  and the lower segment of the reinforcement  17  embedded in the facing element  4  located just beneath.  
         [0041]     It will be appreciated that, within the context of the present invention, the possible arrangements of the reinforcing strips in the gap separating the pre-existing wall  1  from the facing  3  are very numerous. Likewise, all kinds of facings may be used—prefabricated elements in the form of slabs, blocks, etc., wire mesh, window-box, etc. Moreover, it is perfectly conceivable to construct the facing  3  by casting it in situ from special cements or concrete, taking care to connect the stabilizing elements  7 ,  17  thereto.  
         [0042]     The three-dimensional configurations adopted by the stabilizing elements within the fill  5  may also be highly varied: the patterns may be in a form other than a zigzag or a comb; elements  6 ,  16  and  7 ,  17  may lie in the same horizontal plane (preferably avoiding mutual contacts); in the common part Z′, the ratio of the density of elements  6 ,  16  and that of the elements  7 ,  17  may vary; etc.  
         [0043]     To construct a work according to the invention, the procedure may for example be as follows: 
        a) the anchoring members  8  are installed on the front face of the mass to be covered;     b) some of the facing elements  4  are put into position so that the fill material can be introduced to a certain height. The mounting and positioning of the facing elements may be facilitated in a known manner by assembling members placed therebetween;     c) a layer of stabilizing elements  6 ,  16  is installed on the fill already present. The elements  6  are attached to the anchoring points  8  in the embodiment according to  FIGS. 1 and 2 . In the embodiment according to  FIGS. 3 and 4 , the reinforcement strip  16  is laid in a zigzag, making it pass into the rings  9 , and slight tension is exerted at the line where the strip turns back towards the front, for example by means of a bar placed along this line and around which the strip is folded at each point of inflection;     d) fill material is introduced over the top of the layer of stabilizing elements  6 ,  16  that has just been installed, up to the next level of stabilizing elements  7 ,  17  on the rear side of the facing elements  4 . This fill material is compacted progressively as it is being introduced;     e) the stabilizing elements  7 ,  17  located at said level are put into place on the fill, tension being exerted thereon;     f) fill material is introduced on top of this level and progressively compacted until the specified level for introducing stabilizing elements  6 ,  16  has been reached; and     g) steps b) to f) are repeated until the top level of the fill is reached.        
 
         [0051]     Another embodiment of the invention is illustrated in  FIG. 5 . The facing elements and the stabilizing elements that are connected thereto, such as those described above, are replaced by geotextile. The geotextile is placed on the ground or on a layer of fill material, and is then folded back on itself towards the solid wall so as to cover and retain a new layer of fill material and to extend into a region Z 1  of the fill. The stabilizing elements anchored in the mass pass through the layer of fill material and extend over a region Z 2 . The regions Z 1  and Z 2  share a common region Z′, thus allowing the forces between the stabilizing elements anchored into the solid wall and the geotextile layers  27  to be transmitted by the fill material located in this common region.  
         [0052]     Each geotextile sheet  30  folded back on itself thus has a front part  24  extending over the front face of the work and forming one portion of the facing  23 . The two folded-back layers  27  extend horizontally from this front part  24  into the second region Z 2  of the fill in order to form two stabilizing elements for holding the facing in place.  
         [0053]     In the advantageous embodiment illustrated in  FIG. 6 , the facing  33  is formed from a welded wire mesh, and the stabilizing elements  37  consist of metal reinforcements in the form of rolled steel strips. Alternatively, these reinforcements  37  could be replaced with welded mesh strips. The fill may not be homogeneous between the pre-existing wall  31  and the facing  33 . For example, it may comprise stones on the front face, retained by the mesh and giving the finished work an attractive appearance, and sand or other filling material between the pre-existing wall and the layer of stones. Alternatively, the sand may extend right up to the wire mesh facing  37 , being held in place by a geotextile placed on the rear side thereof.  
         [0054]      FIG. 6  also shows that the pre-existing wall  31 , onto which the work backs, need not consist of a terrain mass, but also of an artificial structure, for example made of masonry or concrete.