EP3728742B1

EP3728742B1 - Method for strengthening soils and operating vehicle usable in the method

Info

Publication number: EP3728742B1
Application number: EP18834045.9A
Authority: EP
Inventors: Renato Canteri
Original assignee: Nordwind Srl
Current assignee: Nordwind Srl
Priority date: 2017-12-18
Filing date: 2018-12-17
Publication date: 2023-06-07
Anticipated expiration: 2038-12-17
Also published as: WO2019123212A1; US20200308791A1; CA3085813A1; EP3728742A1

Description

This invention relates first to a method for strengthening soils, and second to an operating vehicle suitably developed so that it is usable in the strengthening method, such as generally known from US 4 023 325 A .
Specifically, this invention may be used for strengthening soils on which foundations or pavements already stand (both inside buildings, and outside such as yards, roads and motorways) and soils on which foundations or pavements must subsequently be built.
In the former case, the strengthening work becomes necessary when the soil yields after the foundation or pavement has already been built, whilst in the latter case the strengthening generally has a preventative function, to avoid subsequent yielding in the case of soils which are not compact and/or settled enough.
At present, strengthening techniques may be based on only injecting expanding resins or concrete into the soil, or on making resin or concrete piles, or driving piles and micro-piles to which the foundations or pavements are then anchored, or on mixed techniques.
Although, at least in some conditions of use, each of these techniques may give good results, there is still a great need in the sector for obtaining ever-increasing load-bearing capacities in the soil, and/or greater load-bearing capacities with less effort in terms of times and costs.
In this context the technical purpose which forms the basis of this invention is to provide a method for strengthening soils which overcomes the above-mentioned disadvantages.
Specifically, it is the technical purpose of this invention to provide a method for strengthening soils which allows a high load-bearing capacity of the soil to be obtained in a fast, simple way.
A further technical purpose of this invention is to make an operating vehicle with which to be able to perform several main steps of the method according to this invention.
The technical purpose specified and the aims indicated are substantially achieved by a method for strengthening soils and by an operating vehicle usable in the strengthening method, as described in the appended claims. Further features and the advantages of this invention are more apparent in the detailed description, with reference to the accompanying drawings which illustrate several preferred, non-limiting embodiments of a method for strengthening soils and of an operating vehicle usable in the strengthening method, in which:

Figure 1 is a schematic side view of an operating vehicle made in accordance with this invention which is about to begin a first step of the strengthening method;
Figure 2 shows the operating vehicle of Figure 1 during the making of a hole in the soil;
Figure 3 shows the operating vehicle of Figure 2 at the moment when it has completed making the hole in the soil;
Figure 4 shows the operating vehicle of Figure 3 after it has extracted from the soil a punch belonging to the vehicle with which it previously made the hole in the soil;
Figure 5 shows the hole in the soil of Figure 4 after it has been filled with a filling material according to a first embodiment of the strengthening method according to this invention;
Figure 6 shows the result of repeatedly performing the strengthening method at a plurality of adjacent zones of the soil to be strengthened;
Figure 7 shows the operating vehicle of Figure 4 while it performs a subsequent step of driving a micro-pile into the soil at the hole in the soil, according to a second embodiment of the method according to this invention; and
Figure 8 shows the hole in the soil of Figure 7 after completion of driving of the micro-pile, and after the hole has been filled with a filling material according to the second embodiment of the strengthening method according to this invention.

Hereinafter the strengthening method according to this invention will be described, followed by a description of the operating vehicle provided for use in that method. However, it shall be understood that what is described below, relative to the method and to the vehicle respectively, shall also be applicable to the vehicle and to the method respectively, if technically compatible.
Similarly to other prior art strengthening methods, the method according to this invention also comprises two main steps, a step of making a hole 2 in the soil 1 and a step of filling the hole 2 with a filling material 3. The step of making the hole 2 in the soil 1 is performed in such a way that the hole 2 has a main line of extension which is at least mainly vertical, whilst the step of filling the hole 2 may be performed with a solidifiable material (such as concrete, resins or bituminous macadam).
According to a first innovative aspect of this invention, the step of making the hole 2 in the soil 1 comprises making a hole 2 with a cross-section, transversal to the main line of extension, that decreases from top to bottom; in other words, once completed, the hole 2 advantageously has a hopper or funnel shape.
Furthermore, according to a second innovative aspect of this invention, the hole 2 in the soil 1 is obtained by means of what may be considered actually punching the soil 1. In fact, advantageously, the step of making the hole 2 in the soil 1 comprises an inserting step, wherein a suitably shaped punch 4 is inserted in the soil 1. That punch 4 has a lower tip 5 insertable in the soil 1, a top portion 6 opposite to the lower tip 5, and an axis of extension that extends between the top portion 6 and the lower tip 5. The punch 4 also has a cross-section that increases along the axis of extension going away from the lower tip 5. Specifically, according to a first embodiment, the punch 4 has a cross-section which, going away from the lower tip 5, continuously increases along the axis of extension (the punch 4 may, for example, have the shape of a cone or inverted pyramid or, preferably, may be frustoconical or frustopyramidal). However, according to the preferred embodiment illustrated in the accompanying figures, the punch 4 has a plurality of stretches 7 with constant cross-section (for example, cylindrical or parallelepipeds) or increasing cross-section (for example, frustoconical or frustopyramidal) which are aligned along the axis of extension, where the cross-section of each stretch 7 is greater than the cross-sections of the stretches 7 closer to the lower tip 5 and is less than the cross-sections of the stretches 7 further from the lower tip 5. Advantageously, the difference in cross-section between two adjacent stretches 7 is in any case small.
The inserting step is also carried out by positioning the axis of extension of the punch 4 substantially parallel to the main line of extension of the hole 2 to be obtained (that is to say, vertical).
Thanks to the shape of the punch 4, the step of inserting the punch 4 in the soil 1 causes compression and compacting of the soil 1 surrounding the hole 2.
In the preferred embodiment the step of inserting the punch 4 in the soil 1 is performed without removing material from the soil 1. Despite that, it is also possible that the step of inserting the punch 4 in the soil 1 is preceded by a step of making a pilot hole in the soil 1 (where the pilot hole will be smaller than the hole 2 to be made) and that the step of inserting the punch 4 in the soil 1 is performed by inserting the punch 4 in the pilot hole in order to widen it.
Preferably, the step of inserting the punch 4 in the soil 1 is performed in such a way as to bring the lower tip 5 of the punch 4 to a depth of at least 2 m, advantageously, at least 3 m (although lesser or greater driving depths are in any case possible).
According to the preferred embodiment of this invention, the step of inserting the punch 4 in the soil 1 is performed by applying pressure, using a first actuating device 8 which is fixed to a first ballasted body 9. Specifically, in the accompanying figures, the first ballasted body 9, which acts as a reaction element for the force applied to the punch 4, is constituted of the rest of the operating vehicle 10 described below.
According to the simplest embodiment of this invention, illustrated in Figures 5 and 6, once insertion of the punch 4 in the soil 1 has been completed the punch 4 is extracted and the hole 2, which is thereby freed, is filled with the solidifiable filling material 3; then once the latter has solidified the compacting of the soil 1 may be considered completed. By repeating the same steps a plurality of times, with suitable spacing, it is also possible to strengthen soils of any extent.
In other words, what is obtained at the end of the method described above is one or more wedge-shaped elements (which may or may not be in a single block - Figure 6), inserted in the soil 1 and which keep the soil 1 surrounding them compressed and compacted.
In contrast, according to a more complex embodiment (to be used, for example, where higher load-bearing capacities are necessary), once insertion of the punch 4 in the soil 1 has been completed, the punch 4 is extracted and before the step of filling the hole 2, a driving step is carried out, during which a foundation micro-pile 11 is driven into the soil 1 at the hole 2, and, preferably, at the bottom of it (Figure 7). In other words, the micro-pile 11 is driven into the soil 1 which surrounds the hole 2, starting from the hole 2 itself. Advantageously, the micro-pile 11 is driven into the soil 1 with its longitudinal axis substantially coinciding with the main line of extension of the hole 2.
In the known way, the micro-pile 11 may be constituted of multiple short modules (for example, 1 m long), connectable to one another end-on until they cover the entire driving depth, which may be more or less deep.
In the preferred embodiment the step of driving the micro-pile 11 is performed by applying pressure, using a second actuating device 12 which is fixed to a second ballasted body 13. In the accompanying figures in which the second actuating device 12 is also mounted on the operating vehicle 10, the second ballasted body 13 is constituted of the operating vehicle 10 itself. Depending on the chosen embodiments, during the driving step the micro-pile 11 may always be kept with same angular orientation, or it may be made to rotate about its own longitudinal axis thereby achieving pressing - rotating driving of the micro-pile 11 into the soil 1.
Driving of the micro-pile 11 into the soil 1 is completed when the desired depth has been reached and, preferably, when the upper portion 14 of the micro-pile 11 is positioned inside the hole 2 (advantageously the top of the pile is substantially aligned with the treadable surface of the soil 1).
At that point, the step of filling the hole 2 may take place, embedding the upper portion 14 of the micro-pile 11 positioned inside the hole 2; however, in this case it will be necessary to use a material able to adhere to the micro-pile 11, preferably able to adhere to the micro-pile 11 in such a way as to constitute with it substantially a single body; advantageously, this comprises the use of concrete.
In order to improve the adhesion between the micro-pile 11 and the filling material 3 the upper portion 14 of the micro-pile 11 may have surface working which increases its roughness (at macroscopic or microscopic level) and adhesion capacity, plus projecting elements are connected to it which will then be set in the filling material 3. For example, the surface of the micro-pile 11 may have a plurality of axially spaced annular grooves.
Figure 8 shows the end result achieved once the material has solidified. In this case too, the method may be repeated a plurality of times, with appropriate spacing, to strengthen soils of any extent.
As already indicated in the above description, according to this invention an operating vehicle 10 usable in the strengthening method has also been provided, whose use is particularly advantageous in the case in which driving micro-piles using pressure is also involved.
The vehicle comprises a chassis 15 on which a movement system for moving the vehicle on the soil 1 is mounted. The movement system may be either of the passive type (e.g.: simple wheels or tracks 16 for making the operating vehicle 10 a carriage to be towed), or of the active type (which, in addition to wheels or tracks 16 also has an engine 17 connected to them). Mounted on the operating vehicle 10 are at least one driving apparatus 18 for driving a micro-pile into the soil 1 and at least one punching device 19 for punching the soil 1 in order to make a hole 2 in the soil 1. Optionally, there may also be a second driving apparatus for driving a second micro-pile into the soil 1, preferably activatable alternating with the first driving apparatus 18.
Advantageously, on the vehicle there are also ballasts 20 to make it heavy enough to allow it to act as a reaction element for the forces applied to the punch 4 and to the micro-piles. The overall weight of the operating vehicle 10 with the ballasts 20 must have a centre of gravity such as to guarantee the correct reaction force to the punching device 19 and to the driving apparatus 18, also taking into account the lever arms which may form in use. In the preferred embodiment the driving apparatus 18 (or the driving apparatuses if there is more than one) is positioned at a central portion of the operating vehicle 10, whilst the punching device 19 is mounted cantilever-style at the front or rear side of the vehicle. However, other layouts are also possible.
In more detail, the punching device 19 comprises a first member 21, a second member 22 and a first actuating device 8 which is mounted between the first member 21 and the second member 22 for moving the second member 22 relative to the first member 21.
The first member 21 is constrained to the chassis 15 and is constituted of a rigid arm in the accompanying figures. In contrast, the second member 22 is movable relative to the first member 21 between a first position and a second position along a punching line, and has the shape of a punch 4. The second member 22 also has an axis of extension which extends between a lower tip 5, insertable in the soil 1, and a top portion 6. According to this invention, the second member 22 has a cross-section which increases along the axis of extension (from the lower tip 5 towards the top portion 6).
The movement of the second member 22 relative to the first member 21 is of the reciprocating type and comprises an outward stroke and a return stroke. The outward stroke goes from the first position (Figure 1) towards the second position (Figure 3), and during it the first actuating device 8 pushes the second member 22 towards the soil 1, whilst the return stroke goes from the second position towards the first position and during it the second member 22 is moved away from the soil 1. During the outward stroke the first actuating device 8 applies a force on the second member 22 along the driving line; thanks to its shape with (upwardly) increasing cross-section, the second member 22 is configured to apply to the soil 1, according to a line of action which is radial relative to the line of insertion, a portion of the force which it receives from the first actuating device 8.
In turn, each driving apparatus 18 comprises a third member 23 which is constrained to the chassis 15, a fourth member 25 which is movable relative to the third member 23 between a first position and a second position along the driving line, and a second actuating device 12 for moving the fourth member 25 relative to the third member 23.
The movement of the fourth member 25 also comprises an outward stroke and a return stroke. On the outward stroke the fourth member 25 goes towards the second position and the second actuating device 12 pushes the fourth member 25 towards the soil 1, whilst during the return stroke the fourth member 25 goes towards the first position, and is moved away from the soil 1. During the outward stroke, the second actuating device 12 applies a force on the fourth member 25 along the driving line, a force which the fourth member 25 is configured to transmit practically entirely to the micro-pile to be driven in.
As can easily be inferred from the structural description above, in use the operating vehicle 10 can always be used to make the hole 2 in the soil 1. If micro-pile 11 driving is also required, the operating vehicle 10 can simply be moved until the second actuating device 12 is at the hole 2.
This invention brings important advantages.
Specifically, the fact that it makes the hole in the soil using a punch which has a cross-section increasing upwards allows the hole to be made at extremely low cost, and local compacting of the soil surrounding the hole, thereby significantly increasing the load-bearing capacity of the soil.
By combining hole making and filling with micro-pile driving at the same hole, it makes it possible to either further increase the load-bearing capacity of the soil or to obtain load-bearing capacities similar to those obtainable with only micro-piles, but using significantly shorter piles.
Last but not least, the operating vehicle according to this invention makes the strengthening method applicable in almost any work context.
Finally, it should be noticed that this invention is relatively easy to produce and that even the cost linked to implementing the invention is not very high.

Claims

A method for strengthening soils comprising:
a step of making in the soil (1) a hole (2) that has a main line of extension which is at least mainly vertical; and

a step of filling the hole (2) with a solidifiable material;

wherein the step of making the hole (2) in the soil (1) comprises making a hole (2) with a cross-section transversal to the main line of extension, that decreases from top to bottom, and wherein the step of making the hole (2) in the soil (1) comprises an inserting step wherein a punch (4) is inserted in the soil (1) by applying a pressure to the punch, the punch comprising a lower tip (5) insertable in the soil (1), a top portion (6) opposite to the lower tip (5), an axis of extension that extends between the top portion (6) and the lower tip (5) and a cross-section that increases along the axis of extension going away from the lower tip (5), wherein the inserting step is performed by positioning the axis of extension of the punch (4) substantially parallel to the main line of extension of the hole (2) to be obtained, and wherein the step of inserting the punch (4) in the soil (1) also causes compression and compacting of the soil (1) surrounding the hole (2);

characterised in that it also comprises, after the step of making a hole (2) in the soil (1) and before the step of filling the hole (2), a driving step wherein a micro-pile (11) is driven into the soil (1) at the hole (2).
The method according to claim 1, characterised in that the step of inserting the punch (4) in the soil (1) is performed without removing material from the soil (1).
The method according to claim 1, characterised in that the step of inserting the punch (4) in the soil (1) is preceded by a step of making a pilot hole in the soil (1) which is smaller than the hole (2) to be made and in that the step of inserting the punch (4) in the soil (1) is performed by inserting the punch (4) in the pilot hole in order to widen it.
The method according to any of the preceding claims, characterised in that the step of inserting the punch (4) in the soil (1) is performed by applying pressure, using a first actuating device (8) that is fixed to a first ballasted body (9).
The method according to any of the preceding claims, characterised in that the step of inserting the punch (4) in the soil (1) is performed using a punch (4) with a cross-section that, going away from the lower tip (5), continuously increases along the axis of extension or a punch (4) having a plurality of stretches (7) with constant cross-section that are aligned along the axis of extension where the cross-section of each stretch (7) is greater than cross-sections of the stretches (7) closer to the lower tip (5) and is less than cross-sections of the stretches (7) further from the lower tip (5).
The method according to any of the preceding claims, characterised in that the micro-pile (11) is driven into the soil (1) with its longitudinal axis substantially coinciding with the main line of extension of the hole (2).
The method according to any of the preceding claims, characterised in that the step of filling the hole (2) is performed by embedding an upper portion (14) of the micro-pile (11) positioned inside the hole (2) and using a solidifiable material.
The method according to any of the preceding claims, characterised in that the step of driving the micro-pile (11) is performed by applying pressure, using a second actuating device (12) that is fixed to a second ballasted body (13).
The method according to claim 8, characterised in that during the driving step the micro-pile (11) is also made to rotate about its own longitudinal axis thereby achieving pressing - rotating driving of the micro-pile (11) into the soil (1).
The method according to any of the preceding claims, characterised in that the step of inserting the punch (4) in the soil (1) is performed in such a way as to bring the lower tip (5) of the punch (4) to a depth of at least 2 m.
An operating vehicle usable in the method according to any of the preceding claims, comprising:
a chassis (15);

a movement system for moving the vehicle on a soil (1);

at least one driving apparatus (18) for driving a micro-pile into the soil (1); and

at least one punching device (19) for punching the soil (1) in order to make a hole (2) in the soil (1);
wherein:
the punching device (19) in turn comprises a first member (21), and second member (22) and a first actuating device (8);

the first member (21) is constrained to the chassis (15);

the second member (22) is movable relative to the first member (21) between a first position and a second position along a punching line;

the second member (22) has the shape of a punch (4) with an axis of extension that extends between a lower tip (5), insertable in the soil (1), and a top portion (6);

the second member (22) has a cross-section that increases along the axis of extension, going away from the lower tip (5);

the first actuating device (8) is mounted between the first member (21) and the second member (22) for moving the second member (22) relative to the first member (21);

the movement of the second member (22) comprising an outward stroke towards the second position, during which the first actuating device (8) pushes the second member (22) towards the soil (1), applying a force on the second member (22) along the driving line, the second member (22) being designed to apply a portion of said force to the soil (1) according to a radial line of action;

the movement of the second member (22) also comprising a return stroke towards the first position, during which the second member (22) is moved away from the soil (1),
and wherein:
each driving apparatus (18) comprises a third member (23) that is constrained to the chassis (15), the vehicle being characterised by a fourth member (25) that is movable relative to the third member (23) between a first position and a second position along a driving line and a second actuating device (12) for moving the fourth member (25) relative to the third member (23);

the movement of the fourth member (25) comprising an outward stroke towards the second position, during which the second actuating device (12) pushes the fourth member (25) towards the soil (1), applying a force on the fourth member (25) along the driving line, the fourth member (25) being designed to transmit said force to the micro-pile to be driven in;

the movement of the fourth member (25) also comprising a return stroke towards the first position, during which the fourth member (25) is moved away from the soil (1).
The operating vehicle according to claim 11, also comprising a second driving apparatus for driving a second micro-pile into the soil (1).