FR2547330A1 - Method for fitting active joints during the formation of a traffic way, panels for producing such joints, and equipment for the installation of the panels - Google Patents

Abstract

The present invention relates to traffic ways, such as roads, slabs, or the like, formed by at least one layer of mix made up of sands, gravel-sand mixtures, and of a hydraulic binder such as blast furnace slag, and which, under the effect of low temperatures, are subjected to contractions resulting in cracks. According to the invention, a multiplicity of depressions 16 are formed at the surface of the supporting ground 10, a layer of mix is spread so as to form a strip and, before compacting the said strip, parallel panels P, which are evenly spaced and comprise longitudinal undulations on either side of a central plane, are inserted transversely into this strip, the length and width of the said panels P being less respectively than the width and thickness of the said strip. Application : formation of roads, slabs, etc.

Description

 The subject of the present invention is a method for orienting the cracks which occur in the structures of road pavements, airstrips or other industrial pavements, the aforementioned cracks being in particular due to shrinkage; the invention also relates to materials making it possible to achieve the implementation of the method.

 It is specified now that by structure is meant all of the layers of material constituting a pavement or paving. Such structures generally include a shed layer, resting on the ground, called the foundation layer, possibly an intermediate layer, called the base layer, and a surface layer called the wear coating.

 The structures of road pavements are generally made with sand, or serious materials, treated with hydraulic binders, such as for example granulated slag from blast furnaces. If, among these mixtures with hydraulic setting, some have the advantage of having small or even zero setbacks, all are sensitive to significant temperature variations, which results in a thermal shrinkage causing the appearance of cracks particularly during cold periods.

 The withdrawal of a section of roadway gives rise to an overall cracking of the section considered, which is a function of temperature variations and the coefficient of expansion of the material. The withdrawal in question is independent of the support of the roadway in this case the ground. On the other hand, the number and the distribution of the cracks, depends mainly on the support and the friction forces which exist between the support and the structure. These friction forces depend on the friction coefficient of the structure on the ground, and on the value of the limit shear stress of the support.

 The cracks, generally transverse and relatively wide, end up appearing on the surface of the pavements causing their degradation, in line with the lips of the cracks and thereby significant maintenance costs regardless of the discomfort that the work of yours cause traffic.

 The object of the present invention is to remedy the drawbacks mentioned in the foregoing by an arrangement of the structure and of the support.

 To this end, the subject of the invention is a method for providing joints in a structure forming a traffic lane, in particular a road pavement, or any paving, having at least one layer produced with materials such as sand, or gravel. , mixed with a hydraulic binder, said layer being in the case of a roadway spread over the ground, forming a band, which is characterized in that, a large number of depressions are spared in the ground, at least one layer of materials, forming a strip, and in that, before compacting the strip thus formed, there are inserted into it, at regular and close intervals, and in a transverse direction, panels comprising on either side other from a median plane at least one longitudinal corrugation, the length and width of said panels being less than the width and thickness of said layer, after which the surface layer is put in place.

 The invention also relates to a machine for achieving the implementation of the method which is characterized in that it comprises, on a main chassis intended to be towed along the longitudinal axis of the strip formed, at least one apparatus suitable for inserting said panels into said strip before its compaction, such an apparatus comprising a table for storing the panels, pushing means capable of presenting these one by one, opposite a gripping and transfer device, located at right of a chute suitable for receiving said panel freed from the gripping and transfer device, and for channeling it inside burier means arranged for this purpose, said burier means being carried by a secondary chassis movable vertically between a high position for the reception of a panel, and a low position, for which they penetrate the strip, and are adapted to place the panel in the latter.

 According to a preferred embodiment of the invention, the main chassis of the machine carries two devices arranged on either side of a vertical plane of symmetry. Such a machine therefore comprises two devices capable of incorporating each, in the not yet compacted strip constituting the structure of the roadway, a panel as above; the burial means being, according to a preferred embodiment, spaced about 2 meters, it is understood that such a machine is capable of inserting into the strip a series of parallel corrugated panels spaced every 2 meters.

 According to another characteristic of the invention, the undulations that the panels in question comprise extend parallel to the length of these from one end to the other; they preferably have a determined number of undulations, for example three, regularly distributed over the width in the extension of which are provided flat areas extending over the entire length.

 With the method according to the invention, and the machine to achieve its implementation, the friction forces at the soil-structure interface are increased, due to the presence of depressions, while, in association with the arrangement above, the presence of the panels, gives the structure characteristics according to which it will tend to crack on shorter lengths than in the past, the width of the cracks being meanwhile therefore significantly reduced , even imperceptible.

 As it is in particular a structure intended to constitute a lane for road traffic, the width of the strip of material spread to constitute the structure is close to 3.50 m, and, in such a case, the corrugated panels in question are provided with a length of about 2m and with a width slightly less than the thickness of the structure; said panels are embedded in the structure by being placed transversely to the strip, on either side of the longitudinal axis thereof, they are mutually parallel, being spaced apart by a distance of approximately 2 meters.

 The depressions formed in the surface of the ground increase both the frictional forces, and the characteristics peculiar to the panels, the cracks caused by the withdrawal of the structure and which, until now, appear randomly are not eliminated, but they are oriented.

 The panels being relatively close to each other in a length of structural section, it follows that the shrinkage of the structure is collected, no longer by one or more "large" cracks due in particular to a lower local frictional force between the ground and the structure, but by a plurality of oriented and predetermined cracks. In addition, the artificial increase in friction between the structure and the ground, favors the organization of the cracking into small imperceptible cracks so that the problem hitherto posed concerning cracks due to shrinkage is resolved.

 The presence of the panels at close intervals, thus creates in a length of structure a series of slabs, with between them a "joint" whose longitudinal edge close to the upper face of the strip of material requires, -when there is shrinkage - the strip to be yielded at this location, so that the cracks are not only oriented, but also predetermined. In addition, the undulations provided in the panels have the essential roll of creating an interlocking of the lips of the crack, thus allowing the quasi-integral transmission of the vertical loads, caused by the vehicles, in line with the "joint" thus formed without risk of 'rapid attrition of the lips of the crack.

Other characteristics and advantages of the invention will also emerge from the description which follows, given by way of example with reference to the appended drawings in which
Figure 1 shows in longitudinal section a structural section of a roadway having a crack;
Figure 2 is a view similar to Figure 1 showing a pavement structure equipped according to the invention
Figure 3 is a perspective view of an embodiment of a panel
Figure 4 shows in longitudinal elevation a machine for incorporating panels in the thickness of the structure
Figure 5 is a plan view corresponding to Figure 4
Figures 6 to 9 show different phases of incorporating a panel into a pavement structure.

 Referring to Figure 1, reference 10 indicates the ground, ll a pavement structure whose thickness E is predetermined, and 12 a wear coating. The structure 11 being produced in a strip and with materials such as sand, or gravels, treated with hydraulic binder, for example from granulated slag from blast furnaces, it is in known manner sensitive to atmospheric conditions, which leads to the creation of cracks 13 in cold weather due to shrinkage of materials. However, these cracks are created randomly, generally in a direction transverse to the strip, at intervals which depend largely on the friction force between the ground and the structure, and for a part of the stress available in the latter. .The cracks thus created are not only random in their course, but relatively distant from each other, so that the withdrawal gives rise to a restricted number of cracks with risks of rapid attrition of the lips (14,15) of the cracks , leading to an accelerated deterioration of the roadway due to the effects of vertical loads due to traffic, and also of water infiltration.

The method of the invention aims to reduce the width of the cracks to practically make them imperceptible, while sparing
a) before the implementation of the materials constituting the structure of the depressions in the support soil in order to increase the friction forces
b) by introducing into the strip of material, during its production and before its compaction, a plurality of panels forming close "joints" parallel to each other, which are oriented transversely to the strip so that in the event of removal of this one, the cracks appear following the "joints".

 In other words, the shrinkage value being distributed over the length of the strip by a plurality of "small" oriented cracks, these are practically imperceptible, and have no harmful repercussions on the strip.

 In FIG. 2, a structure is seen forming a tread similar to that of FIG. 1, but in which, according to the invention, a series of "joints" indicated overall by J, have been incorporated while being oriented transversely by relative to the axis of the strip, on either side thereof; so that the strip 11 is compartmentalized in tiles llA, llB ... llN; in this figure we also see that the soil 10 is fitted with a multiplicity of depressions 16 of depth S which contribute to increasing the frictional forces, and to shift the shear plane in the layer of the supporting soil, in an area where the characteristics of the latter, cohesion c and friction angle, and consequently the limit shear t = C + ff (e + p) tg Q, are the highest.

 Figure 3 illustrates in perspective an embodiment of a panel intended to be incorporated into the structure to form a joint J, such a panel P having a rectangular shape, and being made of any suitable material, preferably plastic.

 In the example shown, the panel P has a width 1 slightly less than the thickness El (FIG. 2) of the strip in which it is to be incorporated; as for its length L, it is a function of the width of said strip while being limited to 2.00 m.

 The panel P in question comprises a surface having a number of undulations - at least two distributed over the width 1- these undulations extending over the entire length L of the panel. In the example shown, the panel has corrugations O to 04, generally sinusoidal, extending on either side of the general median plane of the panel; in the extension of the undulations, the panel has lips with a flat surface 25, 26.

 One of the lips in this case the lip 25 has a width 27 greater than the width 28 of the other lip 26.

 In practice, and by way of example, in the case where the strip 11 has a thickness El of 15 to 20 cm, and a width of 3.50 m, the total width 1 of the panels to be incorporated in a strip of this type will be substantially 12cl9 while the length L will be 2m.

 As can be seen in particular in FIG. 2, the panels P are incorporated into the strip perpendicular to the surface thereof, the edge of the lip 26 being in the immediate vicinity of the ground 10, while the lip 25 is set back from the surface of the strip of materials constituting the structure, in order to prevent said panels from being subjected to excessive stresses when compacting the strip and adjusting the surface using a grader .

 The presence of "J joints" gives the strip privileged areas of ruptures oriented during removal; but the panels P forming these "joints" also have the role of creating a meshing of the lips of the crack due to the undulations which they comprise, and also of ensuring the quasi-integral transmission of the vertical loads. As a result, the risks of rapid attrition of the lips of the crack are eliminated.

The present invention also relates to a machine for placing panels in the strip of uncompacted materials.
P as above, to form a "J joint".

 Reference is made to FIGS. 4 to 9 showing an embodiment of the machine in question.

 According to the illustrated embodiment, the machine comprises a main towed chassis 30, with a front axle 31, and a rear axle 32, the wheels of which are adjustable in height using suitable means not described here, because known in self; this main chassis carries two devices 50, 51, suitable for inserting the panels P into the strip of materials constituting the structure before the compaction thereof, the devices in question being arranged on either side of a vertical plane of symmetry.

 In what follows, given that the two apparatuses 50, 51 are of identical construction, only one of them will be described, in this case the apparatus 50, the same references being used for the other switchgear with index A to designate similar elements.

The longitudinal axis of the main hunt is indicated by X-X in Figure 3.

 The apparatus 50 comprises, on the upper face of the chassis, a table for storing the panels P which is formed by a series of parallel beams 52 on which the panels P rest, and are capable of being brought in by means of a device d advancement step by step 53, in the vicinity of a gripping and transfer device indicated as a whole by 54, this latter device itself being located in line with the chute 55, overhanging burial means 56.

The step-by-step advance device 53 comprises (see also FIG. 5) a drive motor 57, capable of driving an endless chain transmission 58; meshing with pinions 59,60, on the upper strand of which is fixed a push bar 61 transverse to the longitudinal axis XX; this bar is guided laterally by sockets 62, 63, slidably mounted on guides 64, 65. The push bar 61 can therefore be moved in the direction of the gripping device 54 (arrow F), then in the opposite direction (arrow F1) to return to its starting position when the stock of panels
P resting on the storage table is exhausted.

 Note that the push bar 61 has an inclined push face 66 (Figure 4) adapted to give an inclination to the stock of panels P so that they do not tilt in particular during their advancement. The storage table is limited towards the gripping device 54 by a perforated vertical stop 68 to allow the passage of the gripping means which will be described below. In the example shown, the gripping device 54 comprises at least two spaced cylinders 70, 71 which are supported by a cross member 72 pivotally mounted at 73 on a console 74 secured to the casings, said cross member being itself coupled at 75 to a another cylinder 76, also pivoting at 77 on a fitting 78 secured to the chassis.

 The aforementioned cylinders 70, 71, are, in the standby position, as shown in FIGS. 4 and 9, inclined so that their respective longitudinal axes are substantially perpendicular to the plane of the panels P, and, the end of the piston rods that they comprise are provided with a suction cup 80 suitable for the profile of said panels P, said suction cups being connected to a source of vacuum not shown.

 The storage table is arranged to form at its end part -situated on the gripping device side- the vertical chute 55 constituted in the present case by two fixed parallel walls (FIGS. 6 to 9 in particular), one being formed by a extension of the abutment wall 68, and the other, by a wall 85 forming the end of the panel storage table. The aforementioned walls extend transversely so that the upper opening of the chute 55 opens at the storage table, while the lower opening is designed to open in the immediate vicinity of the burial device 56 when the latter is in the waiting position as shown in Figures 4 to 8, such a device being adapted to ensure the reception of a panel P, to ensure its transfer, and to ensure its incorporation into the structure.

 According to the example of embodiment shown, the burial device 56 is carried by a secondary flush 92 in the form of a frame comprising two longitudinal sides 93, 94, (FIG. 5), at the swan neck ends 95, these sides being parallel to the longitudinal members 96 of the main casing, and joined by means of spacer 97; the secondary chassis in question 92 is carried by the main chassis by means of jacks 98 (four vertical jacks in the example shown) arranged towards the four vertices of the secondary chassis 92, which is therefore movable between a high position and a low position , under the impulse of said jacks 98.

 The swan necks 95 carry two parallel cylinders 100, lol, mounted oscillating on axes 102, 103, and whose rods are coupled to complementary jaws 104, 105, themselves pivotally mounted by axes 106, 107, on said swan necks . The jaws are naturally made of a resistant material, for example steel, and they have an outer surface adapted to facilitate penetration into the thickness of the structure. To this end, they have bevelled ends 108, 109, extended by flanks 110, 111, slightly diverging upwards.

 The jaws 104, 105 extend over practically the entire width of the secondary chassis, and internally they provide a housing 112 for the reception of a panel P. The main casing also carries equipment suitable for the cyclic operation of the organs described in the above, said equipment comprising a generator 115, a compressor 116, and a control desk 117.

 The burial devices 56, 56A are spaced longitudinally of about 2 meters, so that the machine simultaneously buries two panels P separated by a corresponding distance.

 In order to produce a section of structure according to the invention, a multiplicity of depressions 16 is formed in the surface of the ground under the pavement, during the final phase of the compaction thereof; for this purpose, the rim of the compacting machine (not shown) is provided with bosses of semi-elipsordal shape, judiciously distributed, for example. The compactor thus equipped achieves, during the last phase of compaction passing over the ground , depressions of depth p, as shown in Figure 2, the shear plane is no longer with such an arrangement, at the soil-structure interface but at depth P, in the soil itself.

The friction forces are then increased by the fact that:
- the normal stress on the soil is no longer n = e (= specific weight of the soil - e = slab thickness) but n = Y (e + p);
- the limit shear of the soil t is increased, at the depth P; the soil is no longer subjected to desiccation or to an excess of water before the structure is put in place, its compactness is higher than at the soil-pavement interface, its characteristics are therefore high
- the friction forces will therefore be greater,
F1 = ft + (e + p) tg = f pC1 + (e + p) tg with respect to the tensile forces available in the slab, and this will therefore tend to crack on shorter lengths, the width of each of the cracks thus being practically imperceptible.

 The soil thus prepared, at least one layer of materials 11A of thickness El is spread, and before compacting this layer, the "J joints" are put in place.

 The installation of the "J joints" with the machine described above is carried out in the following manner, a panel P being in the standby position opposite the gripping means 54, the jacks 70, 71, (FIG. 6) are pressurized so that the pneumatic suction cups 80 (connected to a source of vacuum) are pressed against the panels to which they join; the cylinders 70 71, are then returned to their initial starting position and pivoted by pivoting (arrow F2) around the axis 73 under the action of the cylinder 76. The panel P (FIG. 7) is then presented at the right of the upper orifice of the chute 55. The vacuuming of the pneumatic suction cups 80 is stopped, which has the effect of releasing the panel P which falls into the chute 55 by gravity and is housed in the housing 112 formed by the jaws 110, 111, in the close position.

 The pressure being brought into the jacks 98, the latter drive the secondary chassis 92 downwards and cause the jaws 110, 111 to penetrate into the strip of material spread; at the end of stroke of the jacks 98, the end of the jaws 110, 111 is at ground level 10 and these are then opened (FIG. 9) by pressurizing the jacks 100, 101. The panel P, released then by gravity, and rests on the ground. The secondary flush 92 is then returned to its starting position by the jacks 97, and the jaws closed using the jacks 100, 101.

 The pusher 59 is controlled to advance by one notch and brought another panel P IN the waiting position for a new cycle after advancing the machine by a predetermined distance.

 Given that the burial devices 56, 56A are spaced apart in the case considered by 2 meters, the advance of the machine will be four meters to provide "J joints" in the layer of materials every 2 meters.

 After the installation of the panels P, the structure is compacted in the usual way, and a wear coating is put in place.

 Of course, the invention is not limited to the embodiment chosen and shown, which may on the contrary be subject to modifications, without thereby departing from the scope of the present invention. Thus the thickness E1 of the structure chosen by way of example, is formed by a single layer of materials, but it is understood that the joints J could also be incorporated in a structure formed from several layers of materials.

Claims (14)

 1. A method for providing joints in particular in a road pavement, or else a paving, having at least one layer made with materials such as sand, or gravels, mixed with a hydraulic binder, said layer being spread on the ground, forming a strip constituting a structure, characterized in that a multiplicity of depressions (16) is left in the ground, at least one layer of material is spread, forming a strip, and in that, reinforcing the compaction of said strip (11 ), there are inserted into the latter, at regular and close intervals, and in a transverse direction, panels (P) comprising on either side of a median plane, at least one longitudinal undulation (o to 04), the length (L) and the width (1) of said panels being respectively less than the size and the thickness (e) of said strip.  2. Method according to claim 1, characterized in that the aforementioned panels (P) are inserted, perpendicular to the strip (11).  3. Method according to any one of the preceding claims, characterized in that the depressions (16) are formed in the ground, during the compaction thereof using a compactor arranged for this purpose.  4. Panel to achieve the implementation of the method according to any one of the preceding claims, characterized in that it comprises several undulations (oà 04 which, for an observer looking at the panel along its width are sinusoidal, lesditEs undulations s extending on either side of a median plane of the panel.  5. Panel according to claim 3, characterized in that over the width (1), it comprises on one side of the median plane three convex undulations (0,02,04) and successive and, on the other side, two undulations concave (01, 03), the said undulations extending over its entire length (L) of the panel (P).  6. Panel according to any one of claims 4 and 5, characterized in that it comprises, in its median plane and in the extension of the undulations (O to 04), flat lips (25,26), one lips (25) being wider than the other (26), and said lips extending over the entire length of the panel.  7. Machine for achieving the implementation of the method according to any one of the preceding claims, characterized in that it comprises, on a main chassis intended to be towed along the longitudinal axis of the strip at least one clean apparatus inserting said panels (P) into said non-compacted strip, such an apparatus (50, 51) comprising a table for storing panels (P), pushing means (53) capable of presenting them one by one, opposite of a gripping and transfer device (54) located in line with a chute (55), capable of receiving said panel freed from the gripping and transfer device, and of channeling it inside burial means (56 ) arranged for this purpose, said burial means (56) being carried by a secondary frame (92) movable vertically between a high position for the reception of a panel (P) and a low position for which they penetrate into the strip of material , and are suitable for setting the purlin to (P) in the latter.  8. Machine according to claim 6, characterized in that the main chassis carries two devices (50, 51) arranged on either side of a vertical plane of symmetry.  9. Machine according to any one of claims 6 and 7, characterized in that the storage table is horizontal and it is arranged to receive a series of panels (P) oriented transversely relative to the axis of the strip (11 ), said panels (P) being driven step by step towards the gripping and transfer device (54) using a push bar (61) parallel to the panels (P).  10. Machine according to claim 9, characterized in that the push bar (61) has a front face (66) obliquely diverging upwards, to place the series of panels (P) on standby with a corresponding inclination.  11. Machine according to claim 7, characterized in that the gripping and transfer device (54) comprises at least one, but advantageously two jacks (70,71) spaced in the direction of the length (L) of the panels (P ); said jacks being fitted with suction cups (80) connected to a vacuum source, and adapted to occupy, by means of an oscillating assembly, a gripping position for which they are oriented so that the suction cups (80) that they comprise, are brought perpendicular to the plane of a panel waiting to grasp it, and a transfer position for which said jacks (70,71) are delayed so as to bring the lower edge of the said panel (P) to the vicinity immediately above the upper edge of the chute (55) into which it falls by gravity, by cutting off the source of vacuum in the suction cups (80).  12. Machine according to claim 7, characterized in that the chute (55) extends in a vertical plane relative to the storage table.  13. Machine according to any one of the preceding claims, characterized in that each of the burial means (56, 56A) consists of two articulated jaws (104, 105) associated with means capable of controlling them in opening-closing, said jaws forming in the closed state a housing (112) for a panel (l.  14. Jaw according to claim 13, characterized in that the jaws have beveled ends (108,109) and, in the extension of said bevels, oblique faces (110,111) diverging upwards.