The invention relates to the methods allowing to compact the soil, and devices for carrying out these methods. 
     It comprises the insertion into the soil at a predetermined depth (h) under which the compaction by the upper level of the soil becomes ineffective, of an underground compacting device. By advancing this device, the soil ( 104 ) can be compacted below this specified depth. 
     Thanks to this invention it is possible to compact thicker layers and to improve the railway tracks repairing systems.

CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Applicant claims priority under 35 U.S.C. 119 of French patent application no. 1001152 filed on 23 Mar. 2010. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to methods for compacting soils. It aims at increasing the density of the materials in depth, so as to improve the geotechnical characteristics of the considered layer. It concerns new construction works such as construction of foundation layers for road structures, airport structures, railway structures, etc., as well as the maintenance and repair works performed under a railway, without having to proceed to the removal of the rails and of the ties. 
         [0003]    It is known that compaction of soils or granular materials spread into a layer is usually carried out by means of compactors moving on the upper part of the layer. The compactors thus apply to the upper part of the layer an effort that will induce a pressure within the material and cause the irreversible deformations of compaction. The stresses induced within the material decrease as the depth increases and consequently the density obtained by compaction is not uniform throughout the thickness of the layer. Thus, the density distribution within the compacted material also decreases as the depth increases. 
         [0004]    It is known in the current state of the art to choose the compactors and to define their operating characteristics according to the soil and materials and to the layer thickness in order to obtain a satisfactory density of the layer bottom, provided that the layer thickness is not too important. 
         [0005]    Therefore, for silt or clay like soils treated with an hydraulic binder (in particular silts, more or less clayey fine sands), the maximum thickness of the compacted layer is in practice limited to 30 or 35 centimeters, because the use of the heaviest vibrating equipments would cause a surface lamination detrimental to the long term behavior/performance of the structure. 
         [0006]    The study and calculation methods for the structures in a treated soil take of course into account the current state of the technology. It is for instance well accepted that the required density of the layer bottom shall be of 96% of the standard Proctor density (reference used in road geotechnics). It is to be noted that if a density of layer bottom equal to 100% of the standard Proctor optimum could be guaranteed, the dimensioning of the layer, with the same lifetime, could be reduced by about 20%. 
         [0007]    It is also known that if the thickness of a foundation layer in a treated soil could be increased by 5 centimeters, with a density of the layer bottom equal to 100% of the Proctor optimum, its lifetime would be multiplied at least by 10. 
         [0008]    Moreover, the difficulties relating to the control of this basic parameter of the compactness of the achieved layer bottom, in particular its fatigue strength, lead to take into account high safety factors. 
         [0009]    It therefore appears that the capacity to compact the lower part of the layer and, more generally, to compact beyond the physical limits imposed by the compaction from the surface, would constitute an essential interest. It would then be possible to obtain higher compactnesses at the layer bottom and to make road layers which are thicker and in a reduced number. 
         [0010]    It is also known that compacting the soil beneath an existing structure is not possible. 
         [0011]    Thus, in the case of railways laid on a distribution layer made of ballast, maintenance works, without having to remove the tracks, enable the reconditioning or replacement of the ballast layer, but without the possibility to adjust and compact its base layer. 
         [0012]    The ballast is therefore applied on a distorted support with low bearing where the rainwater stagnates and accelerates deteriorations. After two or three interventions of this type, it is necessary to reconstruct or construct a foundation layer under the ballast layer. This work requires removal of the tracks and traffic disruption over a long period. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    To solve these problems, the invention provides a method and devices that allow to compact in thickness the soil below a covering or below an existing structure such as a railway. 
         [0014]    According to a first feature, in a first stage, a soil compacting device is inserted into the soil at a specified depth H, and in a second stage, said device is advanced while maintaining it at the specified depth, which allows to compact the soil continuously at a depth where the methods for compacting from above the soil become ineffective. 
         [0015]    According to another feature, a device for carrying out the invention comprises a wedge-shaped tooth whose leading edge is facing forward in order to separate the upper layers of the soil, this tooth being attached on a frame by means of an intermediate part serving as a common support for the tooth and for a blade which is also attached to the rear of the tooth and has a curved shape whose concavity is directed upward, whose front is at the bottom level of the separated soil and whose lowest portion is at the desired level of compaction for a single pass of the device. 
         [0016]    According to another feature, the blade is thick enough not to bend under the forces of compaction and its profile has a curved shape, corresponding to the desired average eccentricity. 
         [0017]    According to another feature, the blade acts itself as a spring or is attached to its front end by a transverse joint and is maintained in a compressed state by a spring. 
         [0018]    According to another feature, the device comprises a wedge-shaped tooth whose leading edge is directed forward in order to separate the upper layers of the soil and whose bottom portion is tilted downward to perform a first compaction at an intermediate level, said tooth being attached to a frame by means of an intermediate part which also supports, at the back of the tooth, a compacting roller for performing a second compaction to obtain the desired level, said roller being smooth or ridged, or supporting sheep's foot rollers. 
         [0019]    According to another feature, the device comprises a single wear blade tilted from front to rear to separate the upper layers of the soil, this blade being attached on a frame by means of an intermediate part serving as a common support for the blade and for a set of rollers attached to a second intermediate part which in turn is attached to the first part, these rollers being disposed substantially next to each other, parallel to the soil surface and perpendicular to the direction of motion of the device, the first of these rollers further being located slightly below the tip of the wear blade, and other rollers being slightly shifted along the depth direction so that the last is at the desired level for the depth of compaction h. 
         [0020]    According to another feature, the device comprises an intermediate part provided with a known support, which includes a longitudinal hole for receiving soil decompacting tools, such as a chisel or a tooth, wherein a flat part is attached at the lower portion of said support, said flat part being on the lower end of said support, said flat part being provided, at its lower portion, with a first vertical fin with a hole at the front and, at its rear, with three holes spaced in the height direction, this assembly forming said intermediate part, and wherein the device also includes a compacting part provided with a blade having a curved shape whose concavity is directed upward, said blade reproducing the curve of settlement under the repeated effect of the passages of a compactor acting from the surface, said blade comprising a second vertical fin attached on the upper portion of the blade and being itself provided with a hole at the front and, at its rear, with three holes spaced in the height direction, these two fins being positioned against one another by aligning the two front holes and by pushing into these two holes fastening means which allow rotation of the second fin on the surface of the first fin, the rear holes on each of these fins being spaced so that when the second fin rotates on the first fin, only one hole of the rear holes thereof corresponds to only one rear hole of the first fin, which allows to obtain three positions of the fins relative to each other and thus three different eccentricities for said blade. 
         [0021]    According to another feature, a tractor vehicle is used to drive a rigid frame provided with means to maintain, at a specified and adjustable depth H under the soil level, a set of above-defined devices of the invention. 
         [0022]    According to another feature, said frame is subjected to a vibratory movement and the frame is decoupled from the tractor vehicle, regarding vibrations, by an elastic fastener. 
         [0023]    According to another feature, a rotor having at least one star provided with a set of spokes is used, a device according to the invention being attached to the end of at least one of these spokes, said rotor being rotated and being disposed under a protective hood, the whole assembly being driven in a translation movement which is horizontal and perpendicular to the axis of the rotor to compact a land strip with a width slightly smaller than the width of the hood. 
         [0024]    According to another feature, the direction of rotation of the rotor is the same as the direction of motion of the whole assembly. 
         [0025]    According to another feature, the rotor/hood assembly is attached on a carrier vehicle at the front, at the middle or at the rear of said vehicle. 
         [0026]    According to another feature, the invention is implemented in a stabilizer comprising a rotor provided with stars, at least one the stars being provided with one above-mentioned device, and said star having at least one thick tooth which wears at the same rate as said device. 
         [0027]    According to another feature, the invention is implemented by a device that includes at least one above-mentioned blade, said device being attached to the end of two arms rotatable on a horizontal axis perpendicular to the longitudinal axis of said device, the device comprising means to rotate the arms so as to keep the device under the level of the ballast of a railway track, and it also includes means for tensioning said compacting blade. 
         [0028]    According to another feature, the device comprises at least two other devices provided with a blade, these two blades being transversely distributed between ribs and between side faces, on one or more rows at the same depth or at different depths, to form a rigid frame, which allows to compact in a single pass a thick layer to form a base compacted at the desired density. 
         [0029]    According to another feature, said blades are spaced in the height direction to obtain a compacted layer whose height is greater than the height that can be achieved with a single pass. 
         [0030]    According to another feature, the compacting device comprises, before the actual compacting means, a small diameter shaft provided with easily exchangeable picks, to form a small milling tool allowing to separate the soil from the ballast before said compacting means in order to facilitate adjustment and compaction of said layer, the driving of the rotor being effected by a motor reducer located within upright posts forming a chamber. 
         [0031]    According to another feature, the device is intended for the treatment of soils under the ballast of railway tracks, and it comprises means for the initial earthwork of at least one trench to engage the engine of a milling tool, means to ensure the leveling of a binder, means for mixing said binder with said soil, and means for compacting this mixture into a thick layer, and these mixing means comprise a large diameter milling tool having a horizontal axis perpendicular to the direction of motion of a railcar and on which are fixed members such as teeth, which allows the mixing of the entire soil subjected to treatment with said hydraulic binder. 
         [0032]    According to another feature, this device includes probes, means for processing signals from these probes, and means for adjusting the depth of the compacting tool based on the results of this signal processing. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0033]    Other features and advantages of the invention will become apparent from the following description given by way of example with reference to the attached Figures which represent: 
           [0034]      FIG. 1  is a perspective view of an embodiment of a tool according to the invention, limited to a tooth of a relatively small width; 
           [0035]      FIG. 2  is a side view of an alternative embodiment, comprising a large roller instead of a blade; 
           [0036]      FIG. 3  is a side view of an alternative embodiment, comprising a row of small diameter rollers; 
           [0037]      FIG. 4  is a sectional view of the embodiment of  FIG. 3 ; 
           [0038]      FIG. 5  is a side view of a set of known members; 
           [0039]      FIG. 6  is a side view of another embodiment, using members of  FIG. 5 ; 
           [0040]      FIG. 7  is a side view of a tractor towing a first application of a device according to the invention; 
           [0041]      FIG. 8  is a side view of a rotor equipped with members according to  FIGS. 5 and 6  to form a second application of a device according to the invention; 
           [0042]      FIGS. 9-11  are side views of three carrier vehicles equipped with a rotor such as that of  FIG. 8 ; 
           [0043]      FIG. 12  is a side view of a workshop railcar to carry out a third application of the invention; 
           [0044]      FIG. 13  is a top view of a rigid frame provided with means to carry out a first embodiment of this third application; 
           [0045]      FIGS. 14 and 15  are side views of a repair railcar equipped with said rigid frame, in position of transport and travel, respectively; 
           [0046]      FIG. 16  is a partial and sectional view of  FIG. 15 ; 
           [0047]      FIG. 17  is a schematic view of a device allowing to move the frame transversely with respect to the railcar; and 
           [0048]      FIGS. 18 and 19  are side and top views of a repair railcar to carry out a second embodiment of the third application of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0049]    The principle of soil compaction according to the invention is that, in a first stage, a soil compacting device is inserted in the soil at a specified depth H, the device being carried by a construction machine. This device includes at least one wedge-shaped tool, which has a convex surface, tilted downward from front to back, with a convexity directed toward the soil depth in a working position of the tool, that is in a position where it is driven into the soil, parallel to the soil, between a leading edge and a heel located below the surface generated by the leading edge upon displacement of the tool parallel to the soil. In a second stage, this device is advanced while keeping it at the specified depth under the surface, which allows to deform the soil on a height h equal to the difference in height between the front and the rear of the wedge. This difference, which is the offset between the trajectories followed by the leading edge and the heel respectively, is also called the eccentricity of the tool. 
         [0050]    The convex underside of the tool works by compression, and thus the soil can be compacted to a depth greater than the depth where the methods of compaction from above the soil become ineffective. 
         [0051]    Compaction is obtained by the imprint of the tool into the soil, caused by the movement of the tool carried by an equipment. The depth of the imprint is equal to the eccentricity of the tool, that is to say the height difference between the leading edge and the heel of the base plate. It determines the amount of materials brought into the soil just below. This height h must be related to the intake that the soil can accept without causing disruption in view of its condition. The thickness of the compacted layer corresponds to the level difference between the upper (compacted) part and the lower part which reaches the prescribed compactness level of the layer bottom. 
         [0052]    The energy used for the compaction by this method is not constant. It varies significantly, depending on the efforts required to overcome the reaction of the soil which undergoes the deformation imposed by the tool. It may be small in the case of very bulked soil with a tool with a low eccentricity. On the contrary, in case of a too large eccentricity, the energy may be too large with respect to what the soil can accept without causing failure. 
         [0053]    Therefore, the effectiveness of the compacting device depends on the choice of the eccentricity of the tool and of the operating procedure. 
         [0054]    To allow some variation in order to allow a certain range,  FIG. 6 , which will be described in detail below, shows a device with a constant profile. 
         [0055]    It results from this that within the scope of the invention, many forms of tools may be used, in particular tools where the eccentricity h is constant, others where the eccentricity can vary by setting, or still many others where the eccentricity may vary by rotating the base plate made of a flexible blade or a rigid base plate articulated with a compression spring, or also combined tools with rollers to reduce the friction forces. 
         [0056]    As part of the invention, we will also describe the applications based on compacting teeth mounted on a frame with a single movement of translation, as well as teeth mounted on the stars of a rotor. 
         [0057]    Still as part of the invention, we will also describe the applications of the invention, given the possibilities for compaction, under railways for shaping the support of the ballast layer, which also allows to treat “in situ” the soil located below the ballast of the railway track, as well as for doing foundation layers. 
         [0058]    The tool shown in  FIG. 1  is, for clarity of presentation, a unique tool with a relatively small width of a device according to invention. If this tool can be used alone to treat the soil on a small width, several tools will be used to treat the soil on the necessary width, corresponding for example to a running path of a road. This set of teeth will be fixed on a frame, or a rotor, not shown in the Figure, with the teeth arranged either in staggered rows on several rows of the same frame, or on the stars (or branches) of a rotor, with at least one compacting device on each star that is replacing a mixing tooth. 
         [0059]    This tool is formed, in this example, by a wedge-shaped tooth  101  whose leading edge is directed forward, and which is attached to an intermediate part  103 , itself welded to a vertical post  102  of the frame or at the end of the branch of a rotor star. The plate of the part  103  serves as a common base for all types of compacting tools. The tooth  101  is on top of the intermediate part  103 , on which it is attached by a key  108  which allows to replace it easily and inexpensively when worn. The frame  102  allows to push the tooth  101  under the surface of the soil at a depth such that the upper layer of the soil thus removed can be treated from the surface by conventional means, unless it is decided to compact a second layer, above the first layer, at a shallower depth, when forming very thick layers. 
         [0060]    This upper layer, of height H, not shown in the Figure, is therefore separated from the virtual surface  104  which separates the two layers, and slides on the upper surface of the tooth  101 , separates into two parts around the frame  102  and finally falls at the rear of the device on the virtual surface  105  which corresponds to the virtual surface  104  which has gone down to a depth h under the effect of the compacting treatment. The underside of the tooth  101  is slightly tilted upward from front to rear to remove this face from the surface  104  to avoid undesired effects, due for example to the rubbing of this face on the surface  104 . 
         [0061]    The compaction, object of the invention, is achieved in the example of implementation described herein, by a blade  106  having a curved shape reproducing the curve of settlement under the repeated effect of the passes of a compactor operating from the surface, whose concavity is directed upward. This blade may be thin and flexible or thick and rigid. The profile of this blade is designed such that its front portion is located substantially at the rear of the tooth  101  so that, during the forward movement of the device, the bottom surface of the blade  106  gradually comes tangent to the surface  104 , which is no more virtual here since it has been removed by the tooth, and then gradually presses on this surface to compact the soil so that the surface  104  comes into contact with the surface  105 . The height h corresponding to the difference between the surfaces  104  and  105 , is determined so that the lower layers below this surface  106  are compacted to the desired level. 
         [0062]    However, if a single pass does not allow to achieve the desired degree of compaction, the equipment will be passed again the number of times that is necessary, taking into account what may be accepted by the soil before failure. To avoid a premature wear of the blade  106 , for example, it may be covered on its frictional face by wear blades  107  arranged against each other perpendicular to the direction of motion of the device. These wear blades will be attached by any known means, such as welding points. 
         [0063]    The desired eccentricity is obtained by the profile of the blade. 
         [0064]    In a first case, where the blade is flexible, a permanent state of compression may be maintained using rods  109 , in order to limit the bending of the blade and thereby its eccentricity. These rods will be maintained for example by means of eyelets  110  attached perpendicularly to the inside face of this blade  106 , substantially at the lowest level of the blade, and allowing them to slide to the other end by passing through oblong holes  111  located at the upper portion of the blade  106 . Thus the eccentricity of the blade varies freely between two values, depending on the soil reaction. The eccentricity is maximum when the head of the rods is abutting against the outer face of the upper portion of the blade, and is minimal, or even equal to zero, when the bended blade is fully contained within the surface  104 . This allows to compact with the maximum energy that the soil can accept before failure. The selection of the suitable tool is made in advance, based on laboratory shear tests. 
         [0065]    In a second case, where the blade is rigid, a curved shape will be given to the blade, corresponding to the desired average eccentricity, and it will possibly be fixed up with means similar to the members  109  to  111 , but firmly blocked. It can also be attached to its front end with a transverse joint and held with a compression spring, not shown in the Figure. 
         [0066]    In the embodiment of  FIG. 2 , there is a wedge  201 , similar to the wedge  101 , attached to a vertical post or to a rotor branch  202  by means of an intermediate part  203  which serves as a base for all the tools. The upper layer, again not shown in the Figure, is separated by the wedge  201  from the virtual surface  204  and is subjected to the same treatment as in the previous example. However, in this case, the wedge  201  is tilted downward so that its lower face  211  comes to press the surface  204  to achieve a first compaction that generates a real surface  214 . Part  206 , attached by bolts  220  to the plate of the base  203 , is formed at the front by a short length base plate  215  and at the rear by a large cylinder which can be smooth or toothed, or be provided with sheep's foot rollers  210 . This cylinder is tangent to the extension of the profile of the base plate. The cylinder rotates freely about an axis  216  retained by the sides of the part  206 . In contact with the soil, the cylinder rolls and compacts the soil with minimal resistance. The level of the real surface  214  is lowered to the desired level  205 . As in the first embodiment, the surface  205  is covered at the rear of these second compacting means by the cuttings from the stripping of the upper layer by the wedge  201 , which cuttings are treated as above. 
         [0067]    In a third embodiment, shown in  FIGS. 3 and 4 , the stripping member is reduced to a simple wear plate  301  particularly resistant, for example in tungsten carbide, attached to an intermediate part  303  by welding or possibly by removable means. This intermediate part acts, as above, as a common support to the blade  301  and to the members described below. The upper layer of the soil, not shown, is treated as in the two previous embodiments. The compaction of the virtual surface  304 , allowing to bring this surface  304  back at the desired level of the surface  305  by a compacting of a height h, is obtained in this embodiment by a set of small rollers  309  of small diameter. These rollers are arranged substantially next to each other, parallel to the surface of the soil and perpendicular to the direction of motion of the device. They are attached to another intermediate part  313  which has in this embodiment, downwardly, substantially a U shape with two vertical wings on the sides and defining the two side faces of the device. Their vertical position is defined such that the highest roller is slightly lower than the leading tip of the blade  301 , the second roller being slightly lower than the first, and so on. In this way, the last roller will be at the level of the surface  305  and will terminate the desired compaction of the lower layer of the soil. 
         [0068]      FIG. 5  shows known members which can be used in a fourth embodiment. 
         [0069]    These members include an intermediate part  503  which can be mounted on any support, such as for example a branch of a star  522 , through a transverse hole  502  and a bolt not shown. It also includes a longitudinal hole, not visible in the Figure, to receive soil milling tools, such as a pick  511  or a tooth  501 / 531 , which are maintained by a key  504 . It is to be noted that the pick  511  and the tooth  531  are particularly reinforced as compared to the standard tooth  501 . 
         [0070]    A fourth embodiment, shown according to a first example in  FIG. 6 , comprises an intermediate part as described above, completed by a flat part  513  attached, for example by welding, on the lower end of the part  503  to obtain an intermediate part within the meaning of the invention. 
         [0071]    This intermediate part is fixed by its hole  502  to a vertical post  522  of a frame, or to the end of a branch of a star. It is provided for example with a pick  511  or a tooth  531  of the same type as the above-mentioned tooth  501 , but particularly reinforced as compared to the teeth used in the prior art. This intermediate part has a vertical central portion  514  comprising a first U-shaped profile turned downward, or two sides of relatively small width. This profile has a hole  515  at the front for engagement of a pin and, on its rear, three holes  516  spaced in the height direction. 
         [0072]    The compacting part  518  includes a blade  519  of a curved shape whose concavity is directed upward, this blade reproducing the curve of settlement under the repeated effect of the passages of a compactor acting from the surface, and of two vertical posts or walls  520  forming a second facing U-shaped profile directed upward, fitting in the part  514  from the outside or inside or astride. It also comprises a hole  515  at the front and at its rear three holes  521  spaced in the height direction. 
         [0073]    To attach this compacting part on the intermediate part, the part  520  is fitted in the part  514 , by aligning the holes  515 . Then, the parts are maintained together using a bolt or a pin going through both holes and moderately tightened in order to rotate freely and without friction the part  520  relative to the part  514 . The holes  516  and  521  on each of the parts are spaced so that when the part  518  is rotated, only one of the holes  521  is facing only one of the holes  516  of the other part  520 , as shown at  521 . This provides three positions of the parts relative to one another. In this way three possibilities for adjusting the height of the blade  519  relative to the part  513  and the wedge  501  are obtained. These three settings correspond to three heights of compaction and three values of h. 
         [0074]    A first application, shown in  FIG. 7 , is to mount, for example on a crawler tractor  712 , a device  711  according to the invention. This device is preferably attached to the rear of the tractor for stability issues of the whole assembly. This attachment is done by using two longitudinal arms  713  and  714  and a vertical part  715  forming a deformable parallelogram which will allow, using a cylinder  716  attached between the rear of the tractor and the arm  714 , to set the depth of the device into the soil. 
         [0075]    The whole assembly is shown in  FIG. 7  during a second pass of the device. The first pass allowed to compact the soil in depth to obtain a first layer  701  compacted on a height h. For the second pass, the device is lifted, using the cylinder  716 , of the height H 2  to compact a second layer  702  resting on the first layer  701 . This layer  702  will be compacted on a height h. The difference H 2 −h is equal to the difference between the leading edge of the tooth and the lower portion of the two tools  717  and  718  described below. 
         [0076]    The device consists of two rows of tools  717  and  718  according to the invention, such as those described above. They are preferably arranged in staggered rows and supported by supports  719  and  720 . These supports are themselves attached to a rigid frame  721 , which is itself attached directly to the vertical part  715 . The attachment of the supports  719  and  720  to the frame  721  is adjustable step by step, using holes  723 , to complement the action of the cylinder  716 . 
         [0077]    Alternatively, a vibratory movement represented by the arrow  723  and obtained through a known mechanism not shown can be communicated to the tools/supports/frame assembly. Only in this case, elastic means  722  of the type “silentbloc” (vibration damping rubber) are useful to prevent the transmission of vibrations to the tractor. This reduces to some extent the tensile force and increases the efficiency of compaction in some soils. 
         [0078]    In another alternative, the supports  719  and  720 , as well as the compacting teeth  717  and  718 , can be hollow so as to allow the passage of pressurized powder binders and their dispersion above the compacted layer. A rough dispersion of the binder with this upper soil is done using a small rotor with a diameter substantially equal to H 2 , not shown in the Figure. This improves the mechanical properties of the upper layer before it is compacted with the same means. 
         [0079]    A second application, shown in  FIG. 8 , is to mount tools according to the invention on the branches of a rotor  801  equipped with stars  802 . In this example, only one star is shown, and it has four arms. Two of these diametrically opposite arms support known members  804  and  814  such as those shown in  FIG. 5 , and the two other diametrically opposite arms support members  803  according to the invention, such as those shown in  FIG. 6 . The wear of the tooth  804  and the good behavior of the tooth  814  are to be noted, the latter being reinforced according to the invention. Therefore, the worn tooth  804  has to be replaced by a reinforced tooth of the type of the tooth  814 . 
         [0080]    This application relates in particular to the device known as a “stabilizer”. It then requires the replacement on each star of at least one tooth (preferably two) by a compacting tool according to the invention, to allow the compaction of a band. It also requires changing the other teeth by teeth doing the same work, but reinforced according to the invention, for example by thickening or by a tungsten carbide pellet, to have the same wear as those of the compacting tools. 
         [0081]    This allows to compact the support soil and to mix the layer at the same time. In this second application, it is useful to arrange the rotor inside a resistant and thick protective hood, which both provides protection against projections and forms a chamber for the mixing. The rotor/hood assembly is attached to a carrier machine, either at the front or at the middle or at the back thereof, as shown respectively in  FIGS. 9 to 10 . In these embodiments, the carrier machines are equipped with large diameter tires. 
         [0082]    In the example of  FIG. 9 , where the hood  920  and the rotor  921  are attached at the front of a construction machine  922 , the means for driving the rotor in rotation are known and not shown, in this embodiment as well as in all other Figures, for an easier reading of the Figures. 
         [0083]    This second application allows to compact the treated layer from bottom to top by successive passes of the compacting machine. 
         [0084]    This is the case in  FIG. 9 , wherein the hood  920  and the rotor  921  form a dedicated tool for this application. In this embodiment, the rotor rotates in the direction of motion. This allows the soil  923  in the layer bottom to come in abutment against an already compacted soil  924 . If the rotor rotates in the opposite direction, the compacted soil would be again pushed forward toward an uncompacted soil, to come in abutment against an already compacted soil  924 . By doing so, it is possible to obtain a higher rate of compactness with a reduced risk of cracking. If the rotor was to rotate in the opposite direction, the compacted soil would be again pushed forward toward an uncompacted soil, which would limit the rate of compaction and result in a risk of cracking. 
         [0085]    The hood equipped with its rotor can be attached either at the front as shown in  FIG. 9 , similarly to a “vibrating ball” compactor, or at the center as in  FIG. 10 , similarly to a stabilizer, or at the rear of a powerful tractor, as in  FIG. 11 . It can be noted that in  FIG. 9 , the hood was provided with a screen  926  in materials such as sheet metal, to avoid projection of debris and especially of dust. 
         [0086]    The advantage of having a specific hood/rotor equipment mounted for example at the rear of an agricultural tractor, or of a carrier machine designed for this purpose, is to reduce operating and construction costs by keeping only the specifications required for the compaction. 
         [0087]    In this case, the rotor may be attached relative to the hood with protective housings at the front and at the rear thereof, such as the members  926 . These housings may be lowered by rotation, for example. The rotor diameter can then be smaller. Moreover, this equipment may have all the functions to automate the production. 
         [0088]    Moreover, it is possible to add to the equipment a water tank and a spray bar located in the hood, to supply to the materials to be compacted further water inside the hood itself, if necessary. 
         [0089]    A third application, relatively more complex, consists in applying the method according to the invention to the reconstruction of railway tracks, as shown in  FIG. 12 . 
         [0090]    It is to be reminded that the ballast acts as a spring and damper to communicate to the soil the forces due to the passage of trains and prevents the ties from going gradually deeper into the soil. 
         [0091]    However, as trains pass, the ballast pebbles fragment by attrition, resulting in a settlement of the ballast and therefore a degradation of its performances. 
         [0092]    To repair this, a special train is used, comprising railcars provided with a chassis  1501  and bogies  1502 , which allow to raise the railway track, to screen the ballast, to strengthen it with new good-sized pebbles and to proceed to the setting of the railway track. 
         [0093]    The invention contemplates using the above-described method, without having to remove the track, to enable to carry out works such as setting and compaction of the structure under the ballast, the building of a foundation layer by treatment in situ, or the building of a foundation layer with addition of materials, sand-gravel aggregate, cement-bound graded aggregate, etc., after completing the earthwork required for the casing. These works are then conducted “in situ” under the ballast, without having to remove the rails and before the operations of treatment of the ballast and setting of the railway tracks. 
         [0094]    For this, a device that allows to implement the method according to the invention is used. This device could for example be one of those described above, or any other device corresponding to the definition of the invention. In the case illustrated in  FIG. 12 , which represents a repair railcar comprising a frame  1501  and bogies  1502 , this railcar is equipped with such an device  1520  of the invention. It has a blade  1528  whose cutting edge is directed toward the direction of motion of the railcar, that is to say toward the left in the Figure. This blade is inclined downward from front to rear in order to compact the soil according to the invention. The blade is as thin as possible in order to minimize the settlement of the ballast against the ties and its uplift between these ties. The upper portion of the blade is horizontal or slightly tilted to limit the friction forces when in contact with the ballast. 
         [0095]    The blade is attached, in a manner described below, at the lower ends of two arms  1521 . These two arms are extended upward and connected at their upper ends by a transverse cylinder, not shown. The lower portions of these two arms, to which the blade  1528  of the invention is attached, are formed by two narrow and tapered thin solid blades able to make their trace into the ballast on each side of the track beyond the ties. 
         [0096]    Where appropriate, it could be useful to attach at the front of the railcar two ladder ditcher known, not shown in this Figure but shown in  FIG. 18 . They allow to make two side trenches at the boundary of the ballast to allow the passage of the lower ends of the arms in order to position them in the soil at the height corresponding to the layer to be treated. These trenches also allow, if necessary, to improve drainage of the railway track. 
         [0097]    The transverse cylinder pulls on the upper ends of the two arms  1521 , so that when the blade  1528  is active, it exerts a tension for tensioning the blade so as to reduce the compressive stresses and “ultimately” to reduce its thickness. 
         [0098]    In the Figure, only the cylinder on the left side relative to the motion may be seen, because it hides the one on the right side. This is also true for all the mechanism for attaching and adjusting the position of the compacting device. 
         [0099]    These arms are rotatively attached to the ends of a shaft  1523 . A longitudinal cylinder  1522  allows to perform this rotation. 
         [0100]    This shaft is itself attached to the frame  1501  by means of wishbones  1524  which maintain the shaft above the rails, parallel to the axis of the wheels and substantially at the same height as the latter relative to the level of the railway tracks. This shaft  1523  extends on both sides of the railcar to maintain the arms  1521  at the level where the width of the ballast stops. The compacting device  1520  can thus be kept under the ballast at the interface between the ballast and the soil. 
         [0101]    The maintenance at the desired depth is done by acting on a cylinder, for example using a servomechanism. 
         [0102]    The arms  1521 , cylinders  1522  and compacting device  1520  assembly is sized such that this device is positioned at the correct angle so that the blade  1528  actually has its compacting effect of the soil under the ballast, for average sizes of the thickness of the ballast/ties/track assembly. 
         [0103]    Apart from this average position, the adjustment by pivoting around the axis  1512  causes a variation in the positioning angle of the blade  1528 . To compensate for this variation, which plays a large part on the settlement effect, in this embodiment, for example, two small cylinders  1526  and  1527  are used for modifying slightly the orientation of the lower portion of the arm  1521  and therefore the orientation of the device  1520 . 
         [0104]    If necessary, a servomechanism may be used to maintain at the proper height and with a good inclination the compacting device  1520  by acting on the cylinders  1522  and  1526 / 1527 . 
         [0105]    The forces exerting on the compacting device  1520  tend to lift it, as well as the rest of the railcar, in a rather important way. It is thus necessary to dispose on the chassis of the railcar weights  1529 , whose number and weight will be determined experimentally. 
         [0106]    It is clear that the assembly thus represented is in the operating position. To start the work, it will be necessary to carry out earthwork to position the compacting device  1520 . 
         [0107]    For this, the blade  1528  is detached from the posts  1521 . The assembly is done during the approaching motion of the railcar by the engagement of lugs of the posts  1521 , not shown here, in recesses integral with the blade. Locks not shown block the whole assembly. This assembly and disassembly operation has to be done again from time to time to change the blade  1528 , when the degree of wear of the blade will be too important and between each daily interruption of the site. The blade then remains in place. 
         [0108]    According to another embodiment of the invention, useful for example to compact a thicker layer, a rigid frame  1610  can be used, such as the one shown in  FIG. 13 , and attached on a railcar shown in  FIGS. 14 and 15 .  FIG. 16  shows in turn a partial and enlarged view of  FIG. 15 , limited to the active portion of the frame  1610 . Finally,  FIG. 17  schematically shows a device for moving the frame transversely relatively to the railcar. 
         [0109]    In  FIG. 14 , the frame  1610  is in a raised position, for example to move the railcar between two working positions. 
         [0110]    In  FIG. 15 , this frame is lowered in the working position in order to compact the thickness of the soil  1607  situated below the ballast layer  1606 . 
         [0111]    The displacement of the frame between these two positions is done by sliding along four vertical posts attached to the railcar so as to correspond to the four corners of the frame. The frame is blocked on the posts by known means, for example by means of bolts. 
         [0112]    To allow a transverse movement of the frame, in this example, each post is attached to two cylindrical rods  1631  placed respectively above and below the chassis  1501 . These rods can slide in hollow cylinders  1632  attached, for example by welding, on the top and bottom of the chassis. Thus, the frame can be offset to the right or to the left, according to the needs on site. Moreover, frames of varying widths can be used, depending on the material available, for example. 
         [0113]    This frame includes, for example, two side plates  1611  which are attached together at their lower portion by two blades  1619  of the invention. Stiffeners  1614 , and more precisely two stiffeners in the Figure, allow to stiffen the assembly to form a rigid frame which supports, without deforming, the forces that will be applied thereto during compaction. 
         [0114]    In another embodiment, the blades are shorter and their length is equal to the distance between a side plate  1611  and the stiffener  1614  closest to it. The centre-to-centre distances between each of these side plates and the nearest stiffener are the same as the centre-to-centre distance between the stiffeners, so that these blades can be arranged in staggered rows. 
         [0115]    In this embodiment, on the side plates, on the outside and at a little distance therefrom, two other plates  1621  have been attached, which exhibit at the front a low blade profile in order to push laterally the ballast and to reduce the tensile forces. 
         [0116]    In the case illustrated in  FIGS. 13 to 16 , this frame supports two blades  1619  whose cutting edge is directed in the direction of motion of the railcar, that is to say toward the left in the Figures. These blades are tilted downward from front to rear in order to compact the soil in accordance with the invention. The number of blades is fixed here to process in only one pass the entire layer. 
         [0117]    The blades can also be arranged recessed in the height direction and backwards, like the steps of a staircase, at different depths, so as to compact in only one pass a thicker layer. The inclination of the blades is different. It corresponds to the thickness and density of the compacted layer to obtain the same density. 
         [0118]    The attachment height and the number of the various blades are set relative to the thickness of the layer  1607  and to the height of the fraction of this layer that can be compacted by each of the blades. 
         [0119]    The invention further contemplates, in order to promote the penetration of the blades  1619 , to put forward of said blades a mini rotor or a small milling tool  1616 . 
         [0120]    This milling tool is formed, in this embodiment, by a small diameter shaft  1656  supporting a set of tools  1666 , such as picks for example, regularly attached on this shaft. Each pick is arranged in a cylindrical or slightly tapered housing where it is held by a ring. Each housing is extended by a small diameter cylindrical hole opening diametrically on the opposite side of the housing. These holes allow to expel the picks when worn. 
         [0121]    The shaft is attached to the side plates and to the ribs  1614  by means of bearings. It is rotated relatively fast as compared to the advance of the railcar by known means such as hydraulic motor reducers  1617 , attached in this example within chambers formed by the space between the plates  1611  and  1621 , which protects it against friction with earth or with the ballast of the furrows and against the projections of any kind due to the soil treatment. 
         [0122]    The advantage of this arrangement lies in the fact that the milling tool disintegrates the interface ballast/soil to separate them in more easily, in order to treat the ballast in one hand and to compact the soil on the other hand. 
         [0123]    Having several blades for compacting allows to strengthen the structure of the compacting tool, which is subjected to significant deformation forces, imparting it a greater rigidity. It also allows compacting in only one pass a greater thickness. By doing so, the support platform is of a better quality and yields are increased. 
         [0124]    The ballast  1606  is processed by known means, not shown, which sort the pebbles which became too small and which replace them by pebbles of normal size, causing the thickening of the ballast layer  1627  on the back of the soil treating members. Of course, it can be noted from  FIGS. 15 and 16 , that the upper surface of the thus compacted soil  1607  is lower than the upper surface of the soil  1627 , which corresponds to the increase in thickness of this ballast layer, due to treatment thereof. 
         [0125]    One can also note the two veins  1627  of the compacted soil, which extend below the thus treated ballast  1626 . 
         [0126]    A second embodiment of the previous application, shown in a side view in  FIG. 18  and in a top view in  FIG. 19 , allows to carry out the treatment of the soil in situ. 
         [0127]    For this, a railcar very similar to that of  FIGS. 14 and 15  is used, and for clarity of the Figures, only the members which are not the same between the two groups of Figures have been listed. 
         [0128]    The railcar is therefore provided with a frame  610  which includes devices (here three blades)  619  according to the invention, for simultaneously compacting and processing a layer  507  of the soil beneath the ballast  606 , which is processed at the same time by one of the above-described methods, to give a renovated/rebuilt ballast layer  521 . 
         [0129]    The soil is initially separated from the ballast by a thin and resistant blade  615  placed at the front of the frame. 
         [0130]    This thus exposed soil is triturated and bulked on the desired thickness by a large rotor or a milling tool  616 . The latter is formed, as is known, by a shaft with members such as picks, chisels, etc. 
         [0131]    During this operation, products for improving its physical characteristics, such as a hydraulic binder, are poured on the soil, by known means not shown. The nature and volume of these products are determined in advance by a soil analysis. 
         [0132]    The thus spread products are thoroughly mixed with the soil by the action of the milling tool. 
         [0133]    The resulting mixture can then be compacted by the devices  619  to obtain a soil  527  with the improved characteristics through both treatment and compaction. 
         [0134]    The milling tool  615  is driven by motors  617  which extend on each side of the frame. To let them pass, the invention proposes to provide on each side of the railcar a trench of sufficient size. To do this, slicers  601  of known type are used. 
         [0135]    The device according to the invention also enables an automatic control, or feedback control, between the machine parameters and the rate of compactness to be obtained, to provide assistance in the conducting as well as the monitoring and the continuous control of the compacting. 
         [0136]    It is to be reminded here that the device according the invention is used to compact a thin layer. This thickness is related with the strain imposed by the profile of the base plate, at the rate of compactness required with a single pass of the equipment. 
         [0137]    Under these circumstances, the frictional forces of the base plate in contact with the soil and the pressure exerted by the equipment must be identical all the time. To find these values, depending on the application, carefully chosen parameters, correlated with the exerted frictional forces and pressure, are measured during a test pad, using sensors or probes, for example. Then, during the compacting, it is sufficient to continuously adjust the depth of the compacting tool to match the values of the parameters measured during the compacting, with the reference values defined during the test. The continuous adjustment of the depth can be automated. If the parameters are too low, the thickness of the layer must be reduced. 
         [0138]    Otherwise, if the measured parameters are superior to the reference values, to meet the conditions of compacting, the thickness of the layer must be increased. 
         [0139]    Proceeding in the same manner, layer by layer, gradually ascending from the base plate of the tool, the required total thickness is obtained, with a rate of compactness that is uniform, substantially constant and independent of the depth. 
         [0140]    According to another embodiment of the invention, a continuous and controlled compaction may be obtained by adding to the device a guiding and x,y,z positioning system, with recording. 
         [0141]    In the case of the invention, each passage allows to achieve the desired rate of compactness on a layer with reduced thickness, provided that the thickness of the layer is continuously adjusted, since the tool is carried. This can be done by simply making the necessary adjustments based on the response of the soil/equipment assembly. Compacting a thicker layer will require several passages in the same conditions, each time after having raised the tool by the thickness of the previously compacted layer. Ultimately, this allows to obtain a compacted layer of the desired thickness, with a regular and high rate of compactness throughout its entire thickness. 
         [0142]    In the case of a compaction with conventional means, the compactor multiplies the number of passages, as long as the measured rigidity of the platform will be sufficient. This procedure does not however mean that one can be sure to obtain the desired rate of compactness at the layer bottom, the gradient of compactness being decreasing. 
         [0143]    The proposed automatic control method consists in using the information from the sensors to measure the tensile forces and the mass forces in the case of compaction by displacement, and moreover in using sensors for measuring vibrations or accelerations in the case of compaction by displacement and rotation of the tools, for correlating these measures with the compactness curves obtained in another way, to determine the optimum operating conditions. 
         [0144]    Under these circumstances, it is possible to vary by automatic control the depth of the tool so that the “response” always corresponds to the reference determined on the basis of a test pad. 
         [0145]    With the advantageous association of a positioning and tool depth measuring device, with recording, the material receives the information necessary for performing a new pass, and this until the layer corresponding to the thickness projected with the prescribed rate of compactness on any height is obtained. 
       SEQUENCE LISTING 
       [0146]    Not Applicable