Method and system for constructing a prefabricated, compressive concrete pile encased in a transition sleeve

Abstract

METHOD AND SYSTEM FOR CONSTRUCTING A PREFABRICATED, COMPRESSIVE CONCRETE PILE ENCLOSED IN A TRANSITION SLEEVE Method for constructing a pile using a drill pipe (30) and a prefabricated pile element (50) previously fitted into said pipe, comprising: a step (A) of lifting and positioning the drill pipe (30); a step (B) of drilling through soil layers unsuitable for a pile foundation, by rotating the drill pipe (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 drill pipe (30) into more resistant layers by driving the prefabricated pile element (50) concomitantly with the rotation of said pipe; a step (D) of filling the upper portion of the drill pipe (30) with fresh concrete (55) up to a finished pile level; and a step (E) of withdrawing the drill pipe (30). Figure for the abstract: Figure 3

Description

Title of the invention: Method and system for constructing a prefabricated, compressive concrete pile encased in a transition sleeve. Technical field

[0001] The present invention belongs to the general field of the construction of deep or special foundations, particularly those ensuring optimal support for civil engineering structures on highly heterogeneous soils with surface layers of insufficient bearing capacity. More specifically, it relates to a method for constructing a prefabricated, compressive concrete pile encased in a transition sleeve, 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 occur 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 soil characteristics.

[0005] Bearing-point piles rest on a deep, resistant soil layer. The load is transmitted mainly through the tip of the pile, which reaches a soil layer with sufficient mechanical strength to support the load.

[0006] Friction piles, on the other hand, transfer the load through lateral friction between the pile shaft and the soil layers it penetrates. These piles are particularly useful in lower-quality soils because they utilize a larger contact area for load transfer. However, their effectiveness can be reduced in the event of soil liquefaction, such as can occur during earthquakes.

[0007] When a surface layer of ground has a low bearing capacity, it requires the descent of special foundations by piles to a depth that allows sufficient anchorage to be found in load-bearing soil layers.

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

[0009] Currently, the most used method consists of drilling a hole with a helical drill bit which is filled by injecting fresh concrete when the drill bit is pulled up.

[0010] This results in significant lateral pressures in the aforementioned surface layers, causing overconsumption of concrete, or even risks of rupture of the pile shaft.

[0011] Indeed, despite numerous advances made in controlling these concrete pressures, it remains the case that fresh concrete column heights of the order of twenty meters, for example, induce lateral thrusts against the borehole walls which, when made up of poor soils, prove to be greater than the limit of the finishing of these soils, thus creating overconsumption of fresh concrete, with negative friction forces and risks of necking of the pile shafts.

[0012] In summary, the construction of civil works on ground with layers of insufficient bearing capacity poses a major challenge in foundation engineering. Traditional foundation methods do not always succeed in reaching the necessary load-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 drawbacks of the prior art described above by proposing an innovative solution consisting of drilling by rotation of a metal tube encasing a prefabricated concrete pile element after it has passed through soils unsuitable for the foundation of a civil engineering structure. The anchoring of the pile in the bearing soil layers is achieved not only by rotating the drilling tube but also by simultaneously applying a driving force to the drilling tube containing the prefabricated element to increase the drilling 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 precision in pile placement. Furthermore, the adaptability of this method allows its use in various construction scenarios, making it particularly useful for projects with complex site constraints.

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

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

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

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

[0019] According to a particular embodiment, the rotation and driving of the drill pipe are carried out by means of a rotation table and a ram respectively.

[0020] It should be noted that the hammering 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 an injection step, through a conduit longitudinally traversing the drill pipe, of a grout composed of a mixture of cement and thixotropic product to improve the penetration of the excavated materials and compress by displacement against the wall of the borehole, a transition sleeve forming around the drill pipe.

[0022] The present invention also relates to a system for producing a concrete pile, for a deep foundation of a civil work, comprising a mast, a carrying machine, a drilling tube and a prefabricated pile element, for the implementation of a process as presented.

[0023] The fundamental concepts of the invention having been set out above in their most elementary form, other details and characteristics will become clearer from the reading of the following description and with regard to the attached drawings, giving by way of non-limiting example an embodiment of a method and a system for making a prefabricated and compressive concrete pile, in accordance with the principles of the invention. Presentation of the drawings

[0024] The figures are given for illustrative purposes only to aid in understanding 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 are identified by the same numerical reference.

[0025] It is thus illustrated in:

[0026] [Fig-1]: a longitudinal cross-sectional view of a process implementation system according to one embodiment of the invention;

[0027] [Fig.2]: a cross-sectional view of the system of the [Fig.1];

[0028] [Fig.3]: the main steps of the pile-making process according to the invention;

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

[0030] [Fig.5a]: a longitudinal cross-sectional view of the drill pipe;

[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, along plane B - B of [Fig.5b];

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

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

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

[0037] [Fig. 10]: a tracked platform for implementing the process according to an embodiment of the invention. Detailed description of implementation methods

[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] In particular, it is recalled here that for the design of pile foundations, a detailed soil analysis is crucial. This includes evaluating the bearing capacity of the different soil layers, the depth at which 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 well-established practices in the art.

[0040] The embodiment described below refers to a method for manufacturing a prefabricated concrete pile and its implementation system, intended primarily for the foundation of civil structures. This non-limiting example is given for a better understanding of the invention and does not exclude similar alternative embodiments.

[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 includes 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 working tools by trolleys 21 and 22, as shown in [Fig.2].

[0043] The rotation of the mast 10 is done by means of jacks 11.

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

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

[0046] The drill tube 30 has at its lower end a tip 31 equipped with disintegrating fingers 311 for drilling the soil.

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

[0048] In addition, the adaptation of the mast 10 on 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 making a prefabricated and compressive pile according to an embodiment of the invention.

[0050] Figure 3 illustrates the main steps of this process, including: • a step A of lifting and positioning the drilling tube 30; • a step B of drilling through soil layers unsuitable for pile foundation, by rotation of the drill pipe 30 with lateral discharge of the excavated materials against the wall of the borehole; • a step C of continuing the descent of the drill pipe 30 into more resistant layers by a driving action of the prefabricated pile element 50 concomitant with the rotation of said pipe; • a step D of filling the upper part of the borehole 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 drill pipe.

[0051] The driving during step C is not performed directly on the prefabricated pile element 50, but on the head of the drill pipe 30. For this purpose, the driving hammer 60 slides partially within the drill pipe for guidance and has a peripheral shoulder 61 that strikes the edge of the drill pipe head. This edge is mechanically reinforced to resist the effects of driving.

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

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

[0054] Fig. 5a shows the drill pipe 30 with all the elements arranged to drive the pile into the ground.

[0055] According to the illustrated embodiment, the drill pipe 30 is equipped on the outer face of its wall with square metal profiles 32, oriented at 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 of the prefabricated pile element 50, the drill pipe 30 can be reinforced by a steel collar. This has the effect of widening the drill pipe 30 from this reinforcement and enabling it to withstand the impact effects of driving (piling).

[0058] Although less efficient, the drill tube can nevertheless be fitted with an automatic beater.

[0059] In the cross-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 borehole tube 30.

[0060] More particularly, figures 5b and 6b represent the metal profile 33 arranged longitudinally to allow the grasping of the rotating table 211 shown in [Fig.1].

[0061] Figure 7 shows the construction of a pile according to the method of the present invention, with, on the left of the figure, the drilling tube 30 passing through a loose soil TM thanks to its drive by the rotating table 211 to which it is coupled. This passage causes the excavated material 210 to be forced against the walls of the borehole.

[0062] From the entry of the drill tube 30 into the hard bearing ground layer TD, the pile anchoring 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 drill tube 30.

[0063] This driving is achieved 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 a 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 pressure against the wall of the surrounding soil, a 250 sheath surrounding the 30 drilling tube.

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

[0065] Figure 8 relates to the fairly common case of the presence of dissolution pockets in limestone geological formations that have undergone erosion due to water circulation. The installation of the prefabricated pile element 55 over the entire height of cavity C allows it to be bridged without the need for a conventional lost casing to contain the fresh concrete during pile construction.

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

[0067] It must be understood that, while there are injected pile systems, the innovation of this invention consists in 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] Figure 10 represents a solution that makes it possible to implement the significant resources necessary for constructing piles with a diameter greater than 0.500 m, taking, for example, a pile with a diameter of 0.610 m at the head, the prefabricated concrete element 55 of which is a beveled square with sides of 0.570 m and a length of 15 m, for example. The borehole 30 has a diameter of 0.610 m and a length of 19 m, for example. This results in the following loads: • for prefabricated element 55: 10T; • for the drill pipe 30: 2T.

[0069] That makes a total of 12T, and if we add the rotary table 211 which can be estimated to be around 4T, we obtain a total thrust on the drill head 31 of around 16T.

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

[0071] Consequently, the present invention also provides for the use of a tracked platform 500 holding on one side a securely fixed rotating table 510. This rotating table 510 provides a free passage 511 and two drive guides 515 for the drill pipe which are fixed longitudinally on its inner face.

[0072] The platform receives a 520 hydraulic unit for supplying the various workstations.

[0073] The extraction of the drill pipe 30 is obtained by a cylinder 531 acting on a spreader bar 532 equipped with two pairs of two return pulleys 535 acting on handling chains (not shown).

[0074] The process and its implementation system not only allow for reaching significant depths to find suitable anchorage but also offer greater flexibility and better adaptability to varying ground conditions. The method is distinguished by its efficiency, speed of implementation, and ability to minimize impacts on the immediate environment of the construction site.

Claims

Demands

1. Method for constructing a concrete pile, for a deep foundation of a civil structure, by means of a drill pipe (30) and a prefabricated pile element (50), said method comprising: • a step (A) of lifting and positioning the drill pipe (30); • a step (B) of drilling soil layers unsuitable for a pile foundation, by rotating the drill pipe (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 drill tube (30) before the step (A) of lifting and positioning said tube, and in that it further comprises: • a step (C) of continuing the descent of the drill tube (30) into more resistant layers by a driving action of the head of the drill tube (30), concomitant with the rotation of said tube;• a step (D) of filling an upper part of the drill 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 drill tube (30).

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

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

4. A method according to any one of the preceding claims, further comprising an injection step, through a conduit (40) longitudinally traversing the drill pipe (30), of a grout (150) composed of a mixture of cement and thixotropic product to improve the penetration of excavated materials and compress by pressure against the wall of the borehole, a transition sleeve (250) forming around the drill pipe (30).

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