EP0294430A1

EP0294430A1 - Method and device for laying on a surface a reinforced ground comprised of particulate elements and of a binder

Info

Publication number: EP0294430A1
Application number: EP88900378A
Authority: EP
Inventors: Hubert Perrier; Guy Morel; Edouard Gravouille
Original assignee: Laboratoire Central des Ponts et Chaussees
Current assignee: Laboratoire Central des Ponts et Chaussees
Priority date: 1986-12-15
Filing date: 1987-12-14
Publication date: 1988-12-14
Also published as: JPH01501958A; EP0274947A3; EP0274947B1; ATE66268T1; FR2608183B1; FR2608183A1; WO1988004709A1; EP0274947A2

Abstract

For laying a reinforced ground comprised of particulate elements and of a binder, the particulate material is taken from a surface layer of the ground (1) to be treated, the particulate material is projected, immediately after its taking, as a rain onto the ground to be treated, and the binder (11) is introduced in the rain of particulate material and the particulate material and the binder are deposited on the ground (1) to be treated. Substantially simultaneously, a spraying and rain projection of the material are carried out by taking the material by means of a blade-type (4) horizontal rotor (2) biting in the ground to be treated on the thickness (e) of said surface layer, the rotor having a general translation motion in a forward direction and rejecting by backwards projection the material taken from said layer.

Description

Method and device for placing on a surface a reinforced soil consisting of particulate elements and a binder

The invention relates to the installation of a particulate material reinforced with a chemical or mechanical binder. More particularly, the invention relates to the treatment of a layer of particulate soil in place with a view to its reinforcement with a binder.

Currently, in the technique of treatment in place on site, the mixing of the various constituents is generally carried out by kneading inside a chamber (or bell) of all the constituents. The powdery binders or solid additives are generally spread on the ground to be taken up by means of a powerful machine with the soil in place on the desired thickness. The liquid binders can be injected directly into the kneading chamber which ensures, in all cases, the homogenization of the mixture (cf. GB-A-1415 524).

This process, widely used in earthworks and the production of low traffic pavements, however has certain drawbacks:

. impossibility of treating soils with continuous threads, nets or tablecloths of large dimensions (mechanical binders), to obtain materials of the type known by documents GB-A-2 136 858 or EP-A-17 548.

. impossibility of carrying out, in a single pass, dosage layers with variable binder and adjusted according to the depth. Successive layers by adding untreated materials to one or more treated layers allow a variation in the dosage in the thickness direction, but then there is the problem of connection between the different layers.

The object of the invention is to remedy the aforementioned drawbacks by proposing a method, as well as a device specially designed for its implementation, making it possible to treat the floors in particular with mechanical binders and to measure the binders in a variable manner introduced.

The object is achieved in accordance with the invention in that the particulate material is removed from a surface layer of the soils to be treated, in that one immediately projects said material taken in rain falling on the soil to be treated, and in that one introduces the binder into the rain of particulate material.

Thus, the prior mixing of the two constituents is eliminated, and it is possible to adjust, as it is introduced into the rain of material (itself adjustable), the instantaneous quantity of binder introduced and deposited on the ground. The binder can be a liquid, pulverulent or mechanical binder.

The raining of the particulate material requires its prior spraying according to a grain size which depends on the nature of the soil and the intended use. It is particularly advantageous for the spraying and spraying in the form of rain to be carried out practically simultaneously by spraying means consisting of a horizontal rotor with blades biting into the soil to be treated over the thickness of said surface layer, animated by a general movement of translation towards the front (substantially perpendicular to the axis of the rotor) and reject by projection towards the rear the material taken from said layer. The binders are also dispersed, and projected into the rain of particulate material, by pneumatic, hydraulic or mechanical means. The introduction and projection means are adapted to water, sprinkle or deliver the product over the entire surface supplied with finely sprayed soil. Different shapes of blades can be provided on the rotor; but in general, blades constituted by substantially planar radial blades appear to be the most advantageous. In the case of treatment of loose soil, the system can be supplemented by claws. ”The rotor advantageously cooperates with adjustable elements for confining the jet of material by the rotor: a shield limits the range of the jet, a deflector the confines upwards, while a shoe serves as a springboard for projecting the material. In addition, a casing is provided above the rotor to avoid returning particles of material towards other organs of the device (in particular on the organs for distributing binders).

The blade rotor according to the invention can advantageously be integrated into existing soil stabilization machines in place, known under the name of sprayer-mixers, in which a tractor unit drives a rotating mixing rotor, in its part. lower engaged in the ground, in the direction of advance. Such machines are marketed, for example, by the companies BOMAG, RAY GO, PETTIBONE, HOES and BROS. The mixing rotor is generally equipped with numerous teeth.

In accordance with the invention, the mixing rotor is replaced by a rotor with blades, and preferably with blades, rotating in the opposite direction to the rotor of the known machine, so as to project the material backwards and upwards, so that it falls in rain on the ground. The blades are continuous across the width of the rotor so as to project the material uniformly.

The angular speed is variable in order to control the jet of material. It can be for example from 0 to 450 revolutions / min, which, taking into account the diameter of the rotor in an exemplary embodiment, corresponds to tangential blade speeds of the order of 0 to 13 m / s. The diameter of the rotor is approximately three times the thickness of the redeposited soil layer (this thickness being for example 15 cm). The forward speed is variable, for example between 1.5 and 10 m / min.

Although the process and the device of the invention are adapted to conventional binders (a sauce is then sprayed: emulsion, hydraulic binder, organo-mineral binder, chemical binder, resin, etc.), they are very advantageously associated with the projection of 'continuous linear elements according to the teaching of document FR-A-2 572 449 which will be assumed to be known here. The injection ramp of the continuous linear elements (wires) is driven by a transverse movement (in the axis of the ramp) and an angular oscillation (along the axis of the ramp) at frequencies close to the hertz, these movements having for object a homogeneous distribution of linear elements in interlocking patterns on the forming surface of the treated layer.

The continuous linear elements are unwound from coils supported by a creel driven in translation with the entire device.

It is possible to project, instead of continuous threads, a tablecloth, a net or a grid, conditioned in rolls per element of great length, or in containers by elementary surfaces.

2 2 shutters of a few cm or m. The projection ramps for chemical or mechanical binders are arranged either inside and in extension of the shoe, or at the intersection of the shield and the deflector, or even outside the zone delimited by the base layer. , the rotor, the deflector and the shield. The binder can advantageously be prepared before its projection, for example: lime or cement milk, beam or textile roll in a coating bath.

A vibration compacting device can be associated with the device of the invention. It is necessary to insist on an original characteristic of the invention: the fact that the material removed falls in rain on the soil to be treated. By this is meant that the material falls freely and without hindrance of any kind on the ground, so that the binder can be introduced within this rain and reach the ground itself without being hindered in its path, and therefore find on the ground in a fully controlled form. The entire re-deposited layer is thus controlled, whether it is the form of the deposit, its dosage, its homogeneity or its desired heterogeneity (it is possible to choose to deposit a binder only over a given thickness of the redeposited soil layer). This free fall in rain implies a transport, a displacement of the soil to be treated, to project said soil away from the sampling and projection organs: this is obtained by a sufficient speed of the rotor and an appropriate adjustment of the adjustable elements for confining the jet. As can be seen, such a characteristic totally distinguishes the invention from other methods such as that described in document FR-A-948 968. In this, a soil sampling rotor is provided which cooperates with a rotor stop to disaggregate the sampled material; this pulverized material then receives a liquid binder; but instead of falling back to rain on the ground, the material passes between the pallets of two pulverizing rotors intended to shear, crush and further disaggregate the material in order to ensure the coating of the particles with the conditioned binder, before their redeposit. Such a process is incompatible with the aims of the invention: it only makes it possible to ensure a homogeneous distribution of a liquid binder in a particu¬ lar material, but no control of this distribution; heterogeneity is not allowed. In addition, such a process is manifestly incompatible with the distribution of a mechanical binder such as a continuous wire, which could not pass freely between the rotor-sprayers.

Other characteristics and advantages of the invention will emerge from the following description of a particular embodiment. Reference will be made to the appended drawings in which:

. Figure 1 is a block diagram illustrating a method according to the invention.

. Figure 2 is a schematic side view of a device according to the invention.

. Figures 3 and 4 illustrate the ballistics of sand projected at three different speeds, for rotors whose blades are respectively spoon blades and flat blades.

FIG. 1 shows a layer of soil 1 (sand, for example), a thickness of which will be milled by the rotor 2 of axis 3, equipped with blades 4. The rotor 2 is driven in rotation about its axis 3 in the direction of arrow w, and the assembly is driven in translation in the direction of arrow V, which corresponds to the opposite direction of the peripheral speed of the rotor at the bottom so that the rotor digs the layer 1 and rejects the material taken backwards, forming the jet 5.

The chassis supporting the rotor 2 also supports a deflector 6, a shield 7 and a shoe 8. It also supports an arm 9 on which the projection means 10 of the binder, for example wire 11 coming from a coil 12, are arranged.

The deflector 6 and the shoe 8 are intended to better channel the sand discharged upwards and backwards by the ro¬ tor 2, while the shield 7 limits the range of said jet. It is advantageous that these elements are adjustable, to take into account the quality of the projected sand and the desired layer profiles.

The blades 4 advantageously have the shape of flat blades shown in FIGS. 1 and 4. Experiments have made it possible to compare these flat blades with "spoon" blades, as shown in FIG. 3. The trajectory of the sand has been compared. at three rotor speeds, respectively w = 100,200 and 400 rpm, corresponding to tangential blade speeds of 3 to 12 m / s.

The spoon blades (fig. 3) favor, at low speed of rotation (100 and 200 rpm) shots of sand in a bell, a phenomenon which is accentuated with the increase in the speed of translation V (and therefore with l 'increase in the projected flow) taking into account the greater weight of each packet of sand projected with little different kinetic energy. There is a tendency for segregation for high rotational speeds (400 rpm), which is also accentuated by a higher translational speed.

On the contrary, blades with radial blades favor more tense shots (fig. 4). There is a segregation linked to the high rotational speeds.

As well for one model of blades as for the other, we are witnessing, at slow speeds (100 and 200 rpm), the formation of a sand wall. Immediately after the rotor preventing any treatment.

It is to prevent the formation of this sand wall that the shoe 8 has been provided, to act as a springboard for the material. The deflector 6 cooperates with the shoe 8 to channel the path initial material.

The same experiments were repeated as before, with the shoe 8 and the deflector 6. It was found that at low speeds of rotation, the "spoon" blades clog the shoe, preventing any projection of sand towards the rear and creating a deposit upstream of the rotor. On the other hand, for paddle blades, a deposit of sand is created, constituting a natural springboard which does not prevent projection backwards: this natural slope provides an indication of the optimal inclination to be given to the hoof.

The blades can be mounted on elastic means so as to partially retract in the event that a too large stone is caught between the rotor 2 and the shoe 8.

The sand 5 projected backwards and mixed with the binder from the means 10 falls back onto the ground 1 according to a profile 13 thickening from front to back until forming the complete layer 14.

The exact shape of the profile 13 is influenced by the positioning of the adjustable means 6, 7, 8: for example, a steeper inclination of the shield 7 results in a more brutal thickening of the profile 13 directly above said shield.

FIG. 2 represents a practical embodiment of the device according to the invention.

The rotor 2 is attached to the rear of a tractor 20, by means of a lifting frame 21. The rotor 2 is housed between two lateral cheeks 22 to which the connecting pieces 23 carrying the articulation axis 24 of shoe 8, the inclination of which is adjustable by means of fixing bars 25 at several positions.

The lifting frame 21 also supports bars 26, horizontal in the lowered working position, on which are fixed in adjustable manner in translation the deflector support 27 and the shield support 28 7. The deflector 6 and the shield 7 are suspended to their respective supports 27,28 by adjustable joints 29,30. The wire ejection means 10 are advantageously type which is described, in the document FR-A-2572449, and are supported by the bars 26 of the lifting frame 21. The ejected wires come from reels arranged on a creel 31 supported by the towing vehicle 20: taking into account the high quantity of necessary wire, it is possible to provide for installing on the vehicle 20 several dunces: for example two side dunnings 32 at the front and two lateral canters 31 at the rear.

Claims

1. A method of placing a reinforced soil consisting of particulate elements and a binder, of the type according to which the particulate material is removed from a surface layer of the soil to be treated, the binder (11) is introduced into the within the particulate material, and the particulate material and the binder are deposited on the ground (1) to be treated, characterized in that the particulate material is projected, immediately after sampling, in rain falling on the ground to be treated, and in that the binder (11) is introduced into the rain of particulate material.

2. Method according to claim 1, characterized in that a substantially simultaneous spraying and spraying of the material by removing it by means of a horizontal rotor (2) with blades (4) biting into the ground to be treated over the thickness (e) of said surface layer, animated by a general movement of translation towards the front and reject by projection towards the rear the material taken from said layer.

3. Device for placing a reinforced soil consisting of particulate elements and a binder, of the type comprising:

. means (10) for introducing the binder (11) into the particulate material,

. means for redepositing the particulate material and the binder on the soil to be treated, characterized in that it comprises means (2) for projecting the particulate material, immediately after sampling, in rain falling on the soil (1) to be treated, and in that the means (10) for introducing the binder are arranged to introduce it into the rain of particulate material.

4. Device according to claim 3, characterized in that the means for removing and spraying the material with rain consist of a rotor (2) with horizontal blades (4) arranged to bite into the soil to be treated over the thickness of said surface layer, advancement means (20) being provided to drive the rotor (2) in a general translational movement, and means of rotation being provided for driving the rotor (2) in rotation in a direction allowing it to reject in rain towards the rear the material taken from the front.

5. Device according to claim 4, characterized in that the blades (4) are substantially planar radial vanes.

6. Device according to any one of claims 4 or 5, characterized in that the rotor (2) cooperates with an adjustable shield (8) limiting the scope of the projection of material by the rotor (2).

7. Device according to any one of claims 4 to 6, characterized in that the rotor (2) cooperates with an adjustable deflector (7) confining upward the projection of material by the rotor (2).

8. Device according to any one of claims 4 to 7, characterized in that the rotor (2) cooperates with an adjustable shoe (8) serving as a springboard for the projection of material by the rotor (2).

9. Device according to any one of claims 4 to 8, characterized in that the binder is a mechanical binder (11).

10. Device according to claim 9, characterized in that the mechanical binder (11) consists of at least one continuous linear element of great length.