Method and system for producing a prefabricated, compressive concrete pile, coated with a transition sheath

Abstract

METHOD AND SYSTEM FOR PRODUCING A PREFABRICATED AND COMPRESSIVE CONCRETE PILE COATED WITH A TRANSITION SHEATH Method for producing a pile using a drilling tube (30) and a prefabricated pile element (50) previously fitted into said tube, comprising: a step (A) of lifting and positioning the drilling tube (30); a step (B) of drilling soil layers unsuitable for a pile base, by rotating the drilling tube (30) with lateral displacement of the excavated materials against the wall of the borehole; said method further comprising: a step (C) of continuing the descent of the drilling tube (30) into more resistant layers by a driving action of the prefabricated pile element (50) concomitant with the rotation of said tube; a step (D) of filling an upper portion of the drill pipe (30) with fresh concrete (55) up to a finished level of the pile; and a step (E) of withdrawing the drill pipe (30). Figure for abstract: figure 3

Description

Title of the invention: Method and system for producing a prefabricated, compressive concrete pile, coated with a transition sheath Technical field

[0001] The present invention belongs to the general field of the production of deep or special foundations, in particular those ensuring in the best conditions the foundation of civil engineering works on very heterogeneous ground with surface layers of too low bearing capacity. It relates more particularly to a method of producing a prefabricated and compressive concrete pile, coated with a transition sheath, and a system for implementing said method. State of the art

[0002] In areas where the surface layers of the soil are not suitable for receiving traditional foundations, due to their inability to support the imposed loads, the use of deep foundations, in particular piles, becomes necessary.

[0003] Piles are long, thin columns, made from materials such as concrete, steel or wood, designed to transfer the load from the superstructure to a deeper, more stable layer of soil.

[0004] Load transfer in piles can be achieved in two main ways: via the support of the pile tip and by lateral friction along its shaft. These two methods can be used separately or in combination, depending on the characteristics of the soil.

[0005] Bearing point piles rest on a deep resistant soil layer. The load is transmitted mainly by the tip of the pile, which reaches a soil layer having sufficient mechanical strength to support the load. Friction piles, on the other hand, transfer the load through lateral friction between the pile shaft and the soil layers it passes through. These piles are particularly useful in lower quality soils, as they use a larger contact surface for load transfer. However, their effectiveness may be reduced in the event of soil liquefaction, as can occur during earthquakes.

[0007] When a surface layer of ground has low bearing capacity, it requires the descent of a special foundation by piles to a depth allowing sufficient anchoring to be found in layers of bearing soil.

[0008] In this case, the low-bearing layers are generally made up of embankments, soft clays, altered or even cavernous limestone rocks.

[0009] Currently, the most widely used method is to drill using a hex bit a hole that is filled by injecting fresh concrete when the drill bit rises.

[0010] This results in significant lateral pressures in the aforementioned surface layers, causing excessive consumption of concrete and even risks of rupture of the pile shafts.

[0011] Indeed, despite much progress made in controlling these concrete pressures, the fact remains that fresh concrete column heights of the order of twenty meters, for example, induce lateral thrusts against the borehole walls which, when they are made of poor ground, prove to be greater than the limit of the finishing of this ground, thus creating excess consumption of fresh concrete, with negative friction forces and risks of necking of the pile shafts.

[0012] In summary, the construction of civil works on land with layers of too low bearing capacity poses a major challenge in foundation engineering. Traditional foundation methods do not always succeed in reaching the necessary bearing soil layers, resulting in a risk to the stability and safety of the structures. Summary of the invention

[0013] The present invention aims to overcome all or part of the disadvantages of the prior art set out above by proposing an innovative solution which consists of drilling by rotation of a metal tube enveloping a prefabricated concrete pile element after crossing the ground unsuitable for a foundation of a civil engineering structure. The anchoring of the pile in the layers of supporting ground is carried out still by rotation of the drilling tube but also by jointly adding a driving applied to the drilling tube containing the prefabricated element to increase the perforation capacity of the assembly consisting of the drilling tube and the prefabricated concrete element.

[0014] The main advantages of this method include a significant reduction in construction time and greater accuracy in pile placement. In addition, the adaptability of this method allows its use in various construction scenarios, making it particularly useful for projects with complex terrain constraints.

[0015] To this end, the present invention relates to a method for producing a concrete pile, for a deep foundation of a civil structure, by means of a drilling tube and a prefabricated pile element, said method comprising: • a step of lifting and positioning the drilling tube; and • a stage of drilling layers of soil unsuitable for a pile base, for example rotation of the drill pipe with lateral displacement of the excavated materials against the wall of the borehole.

[0016] This method is remarkable in that the prefabricated pile element is pre- securely fitted into the drilling tube before the step of lifting and positioning said tube, and in that it further comprises: • a step of continuing the descent of the drilling tube into more resistant layers by a beating action of the head of the drilling tube, concomitant with the rotation of said tube; • a step of filling an upper part of the drill tube, located above the prefabricated pile element, with fresh concrete up to a finished level of the pile; and • a step of removing the drilling tube.

[0017] The precast concrete pile element has a length determined by the soil study so that when its driving is complete, it remains below the finished level of the pile to avoid cutting back the pile and this low level is made up for by adding fresh concrete to the drilling tube.

[0018] According to a particular embodiment, the prefabricated pile element is fitted into the drilling tube by means of a winch-pulley system.

[0019] According to a particular embodiment, the rotation and the beating of the drilling tube are carried out by means of a rotation table and a ram respectively.

[0020] It should be noted that beating is different from the percussion movements that can be found in particular in so-called roto-percussion systems.

[0021] Advantageously, the method according to the invention further comprises a step of injecting, via a conduit passing longitudinally through the drilling tube, a grout composed of a mixture of cement and thixotropic product to improve the penetration of the excavated materials and compress by pushing against the wall of the drilling hole, a transition sheath forming around the drilling tube.

[0022] The present invention also relates to a system for producing a concrete pile, for a deep foundation of a civil structure, comprising a mast, a carrier machine, a drilling tube and a prefabricated pile element, for implementing a method as presented.

[0023] The fundamental concepts of the invention having just been set out above in their most elementary form, other details and characteristics will emerge more clearly on reading the description which follows and with reference to the appended drawings, giving by way of non-limiting example an embodiment of a method and a system for producing a prefabricated and compressive concrete pile, in accordance with the principles of the invention. Presentation of the drawings

[0024] The figures are given purely for illustrative purposes for a better understanding of the invention without limiting its scope. The various elements may be represented schematically and are not necessarily to scale. Throughout the figures, identical or equivalent elements bear the same numerical reference.

[0025] It is thus illustrated in:

[0026] [Fig-1]: a longitudinal sectional view of a system for implementing the method according to one embodiment of the invention;

[0027] [Fig.2]: a cross-sectional view of the system of [Fig.l];

[0028] [Fig.3]: the main stages of the method of producing the pile according to the invention;

[0029] [Fig.4]: the introduction of the prefabricated pile element into the drilling tube at means of winches and return pulleys;

[0030] [Fig.5a]: a longitudinal sectional view of the drilling tube;

[0031] [Fig.5b]: an elevation view of the drill pipe of [Fig.5a];

[0032] [Fig.6a]: a cross-section, along plane A - A of [Fig.5a];

[0033] [Fig.6b]: a cross-section, according to plane B - B of [Fig.5b];

[0034] [Fig.7]: a sectional view of the driving of the pile according to the invention;

[0035] [Fig.8]: a sectional view showing the execution of the pile in a ground with a cavity;

[0036] [Fig.9]: a cross-section of the current section of the finished pile embedded in a transition sheath;

[0037] [Fig. 10]: a tracked platform for implementing the method according to a mode of carrying out the invention. Detailed description of embodiments

[0038] It should be noted that certain technical elements well known to those skilled in the art are recalled here to avoid any insufficiency or ambiguity in the understanding of the present invention.

[0039] More particularly, it is recalled here that for the design of pile foundations, a detailed analysis of the soil is crucial. This includes the evaluation of the bearing capacity of the different soil layers, the depth at which the stable layers are found, and potential conditions such as erosion or liquefaction. The length, diameter, type and number of piles to be used depend on these analyses as well as the load to be supported and the specific conditions of the construction site, according to practices well known in the art.

[0040] In the embodiment described below, reference is made to a method for producing a prefabricated concrete pile and its implementation system, intended mainly for the foundation of civil works. This non-limiting example is given for a better understanding of the invention and does not exclude similar implementation alternatives.

[0041] Figures 1 and 2 represent a system 100 for implementing a method for producing a prefabricated pile according to the invention.

[0042] The system 100 comprises a multipurpose mast 10 fixed on a carrier machine 12, said mast being able to pivot around a vertical axis and to occupy different positions: a working position PI and positions P2 and P3 for presenting work tools by carriages 21 and 22, as shown in [Fig.2].

[0043] The rotation of the mast 10 is done by means of IL jacks

[0044] The carriages 21 and 22 respectively carry a rotation table 211 and a threshing system not shown, and can slide independently of each other.

[0045] [Fig. 1] represents the drilling phase by driving a drilling tube 30 in which a prefabricated pile element 50 is housed.

[0046] The drilling tube 30 has at its lower end a point 31 equipped with disintegration fingers 311 for perforating the ground.

[0047] The handling of the trolleys 21 and 22 is ensured by winches 13 or by handling chains.

[0048] Furthermore, the adaptation of the mast 10 to the ground is ensured by a jack 14 which rests on a base 15.

[0049] The system 100 thus described makes it possible to implement a method for producing a prefabricated and compressive pile according to an embodiment of the invention.

[0050] [Fig.3] represents the main steps of this process, including: • a step A of lifting and positioning the drilling tube 30; • a stage B of drilling layers of soil unsuitable for a pile base, by rotation of the drill pipe 30 with lateral discharge of the excavated materials against the wall of the drill hole; • a step C of continuing the descent of the drilling tube 30 into more resistant layers by a driving action of the prefabricated pile element 50 concomitant with the rotation of said tube; • a step D of filling the upper part of the drilling tube 30, located above the prefabricated pile element 50, with fresh concrete 55 up to the finished level of the pile; and • a step E of removing the drilling tube.

[0051] The driving during step C is not done directly on the prefabricated pile element 50, but on the head of the drilling tube 30. For this purpose, the driving ram 60 slides partly in the drilling tube to be guided and has a peripheral shoulder 61 which drives the edge of the head of the drilling tube. This edge is mechanically reinforced to resist the effects of matting.

[0052] The withdrawal of the drilling tube 30 can be done by means of a jack acting on a lifting beam equipped with a set of return pulleys which act on handling chains.

[0053] [Fig.4] shows a means of fitting the prefabricated pile element 50 into the drilling tube 30 by means of the winch 13 fixed on said drilling tube and pulling on the pile element 50 using a cable passing through a return pulley.

[0054] [Fig.5a] shows the drilling tube 30 with all the elements arranged for drive the stake into the ground.

[0055] According to the illustrated embodiment, the drilling tube 30 is equipped on the external face of its wall with square metal profiles 32, oriented according to opposing inclinations as shown in [Fig.5b], and metal profiles 33 arranged longitudinally.

[0056] The drill pipe 30 and the prefabricated pile element 50 are connected together by a steel bar 35.

[0057] At the top portion of the prefabricated pile element 50, the drill pipe 30 may be reinforced with a steel collar. This has the effect of widening the drill pipe 30 from this reinforcement and enabling it to withstand the shock effects of piling (masting).

[0058] Although less effective, the drilling tube can nevertheless be capped with an automatic mixer.

[0059] In the sectional views of Figures 6a and 6b, the prefabricated pile element 50 appears beveled, this shape allowing its insertion as close as possible into the drilling tube 30.

[0060] More particularly, figures 5b and 6b represent the metal profile 33 arranged longitudinally to allow the grasping of the rotation table 211 represented in [Fig.l].

[0061] [Fig.7] represents the execution of a pile made according to the method of the present invention with, on the left of the figure, the crossing of the drilling tube 30 of a loose ground TM thanks to its drive by the rotation table 211 on which it is coupled. This crossing causes the excavated materials 210 to be pushed back against the walls of the borehole.

[0062] From the entry of the drilling tube 30 into the layer of hard load-bearing ground TD, the anchoring of the pile is achieved by using two functions simultaneously: on the one hand, the rotation generated by the rotation table 211 and on the other hand, a driving system applied to the head of the drilling tube 30.

[0063] This driving is obtained by animating a vertical back and forth movement of a dry ram 60. In order to improve the bearing capacity of the ground, a grout 150 composed of a mixture of cement and thixotropic product is injected through the lower end of the conduit 40, the function of which is to improve the penetration of the excavated materials and to compress by pushing back against the wall of the surrounding soil, a sheath 250 surrounding the drilling tube 30.

[0064] To the right of [Fig.7], is shown the drilling tube 30 anchored in the supporting ground TD filled with fresh concrete 55 in the upper part up to the finished level of the pile.

[0065] [Fig.8] concerns the fairly common case of the presence of dissolution pockets in limestone geological formations that have undergone erosion due to aquatic circulation. The implementation of the prefabricated pile element 55 over the entire height of the cavity C makes it possible to bridge it without having to have a usual lost sheath to contain the fresh concrete during the construction of the pile.

[0066] [Fig.9] represents the current prefabricated pile element 50, coated in its cemented sheath 250. This sheath is obtained by injecting a thixotropic grout mixed with cement and mixed with the materials resulting from the crushing of the attack fingers 311 and the pushing back of the drilling tube 30 against the wall of the surrounding soil.

[0067] It must be understood that, of course, injected pile systems exist, but the innovation of this invention consists of recovering and improving the friction characteristics of materials in place to create a transition sheath between the wall of the prefabricated concrete pile and the surrounding soil.

[0068] [Fig. 10] represents a solution which makes it possible to implement the significant means necessary to produce piles with a diameter greater than 0.500m by taking for example a pile with a diameter of 0.610m at the head, the prefabricated concrete element 55 of which is a square with a beveled side of 0.570m, with a length of 15m for example. The drilling tube 30 has a diameter of 0.610m with a length of 19m for example. This gives the following loads: • for the prefabricated element 55: 10T; • for drilling pipe 30: 2T.

[0069] A total of 12T, and if we add the rotation table 211 which can be estimated at around 4T, we obtain a total thrust on the drilling head 31 of around 16T.

[0070] This results in a definite advantage in facilitating the execution of the pile but in return this solution requires the use of a carrier weighing around 50T to ensure its stability, and this equipment is very expensive to use.

[0071] Consequently, the present invention also provides the use of a tracked platform 500 holding on one side a firmly fixed rotation table 510. This rotation table 510 ensures a free passage 511 and two drive slides 515 of the drilling tube which are fixed longitudinally on its internal face.

[0072] The platform receives a 520 hydraulic group for supplying the various work stations.

[0073] The extraction of the drilling tube 30 is obtained by a jack 531 acting on a lifting beam 532 equipped with two pairs of two return pulleys 535 acting on handling chains (not shown).

[0074] The method and its implementation system not only make it possible to reach significant depths to find a suitable anchorage but also offers greater flexibility and adaptability to varied terrain conditions. The method is distinguished by its efficiency, speed of implementation, and its ability to minimize impacts on the immediate environment of the construction site.

Claims

Claims

1. Method for producing a concrete pile, for a deep foundation of a civil structure, by means of a drilling tube (30) and a prefabricated pile element (50), said method comprising: • a step (A) of lifting and positioning the drilling tube (30); • a step (B) of drilling layers of soil unsuitable for a pile base, by rotating the drilling tube (30) with lateral displacement of the excavated materials against the wall of the borehole; and characterized in that the prefabricated pile element (50) is previously fitted into the drilling tube (30) before step (A) of lifting and positioning said tube, and in that it further comprises: • a step (C) of continuing the descent of the drilling tube (30) into more resistant layers by a driving action of the head of the drilling tube (30), concomitant with the rotation of said tube;• a step (D) of filling an upper part of the drilling tube (30), located above the prefabricated pile element (50), with fresh concrete (55) up to a finished level of the pile; and • a step (E) of withdrawing the drilling tube (30).;

2. A method according to claim 1, wherein the prefabricated pile element (50) is fitted into the drill pipe (30) by means of a winch-pulley system (13).

3. A method according to claim 1 or 2, wherein the rotation and driving of the drill pipe (30) are carried out by means of a rotation table (211) and a ram (60) respectively.

4. Method according to any one of the preceding claims, further comprising a step of injecting, through a conduit (40) passing longitudinally through the drilling tube (30), a grout (150) composed of a mixture of cement and thixotropic product to improve the penetration of the excavated materials and compress by re- pressing against the wall of the borehole, a transition sleeve (250) forming around the drill pipe (30).

5. System (100) for producing a concrete pile, for a deep foundation of a civil structure, comprising a mast (10), a carrier machine (12), a drilling tube (30) and a prefabricated pile element (50), for implementing a method according to any one of the preceding claims.

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