Soil self-drilling process for installing a longitudinal electrically conductive element

Abstract

The invention relates to a method of self-drilling the ground (7) to install an electrically conductive longitudinal element (1, 2, 5), comprising the steps of: i. drilling the ground (7) using a drill or drilling rig equipped with a hollow self-drilling rod (5) made of an electrically conductive material, so as to insert said hollow self-drilling rod (5) into the ground; iv. electrically connecting an electrically conductive cable (1) to an upper end of the hollow self-drilling rod (5), said cable (1) being connected on one side to the hollow self-drilling rod (5) and being intended to be connected on the other side to an electrical system; v.electrically isolate the connection (2) between the upper end of the hollow self-drilling bar (5) and the electrically conductive cable (1), with respect to a surrounding electrolyte, the assembly formed of the hollow self-drilling bar (5), the electrically conductive cable (1) and the electrically insulated connection (2) constituting said longitudinal electrically conductive element. Figure 1.

Description

Title of the invention: Self-drilling method for installing a longitudinal electrically conductive element

[0001] The present invention relates to the field of cathodic protection and grounding. In particular, the invention relates to a method for installing and embedding an electrode in the ground, intended to be connected to an electrical system to provide this cathodic protection or grounding.

[0002] According to the invention, the term "electrode" means any conductive element through which electric current can enter or exit. Conventionally, electrodes are distinguished as "anodes," which are electrodes from which electric current exits, and "cathodes," which are electrodes into which electric current enters.

[0003] According to the invention, "anolyte" means any conductive element in which an electrode is capable of being immersed.

[0004] According to the invention, "soluble anode" means any anode which undergoes partial or total dissolution under the effect of oxidation.

[0005] Cathodic protection protects a metal against corrosion. To modify the potential of the metal to be cathodically protected, an anode is used. Anodes can be of two types: either anodes with a standard potential lower than that of the metal to be protected (sacrificial anode), or anodes coupled to a DC voltage generator that imposes a potential difference between the two metals (impressed current method). In the latter case, the anode belongs to a more general system called an anodic spillway.

[0006] Cathodic protection is used to protect metallic structures from corrosion, including steel, gas pipelines, oil pipelines, water or gas pipelines, tanks, metal piers, ships, oil platforms, and reinforced concrete structures. For buried structures, the anode intended to protect the structure against the effects of corrosion must be inserted into the ground.

[0007] In the field of cathodic protection, the management of unwanted currents such as alternating currents (for example, currents induced by high-voltage lines parallel to pipelines) or stray currents (for example, currents generated by train or tram traffic) are also included. In order to protect structures from the effects of corrosion caused by the circulation of these currents, special devices are electrically connected to grounding electrodes or anodic spillways.

[0008] Three technical solutions are currently known for inserting an electrode into the ground for cathodic protection or grounding purposes: - trench installation, which consists of placing the electrode at the bottom of the trench; - driving, which consists of inserting the electrode into the ground by mechanical penetration; and - drilling, which consists of digging a cylindrical hole in the ground with removal of material, then insertion of the electrode and filling the empty space by adding material.

[0009] However, the limitations of these three technical solutions are as follows: - for trench installation, the insufficient installation depth results in significant exposure to humidity variations, as well as a large footprint of the structure; - jacking is a difficult or even impossible installation technique in soils containing blocks of rock or materials that are too solid; - the implementation of the drilling technique is very costly because it requires significant technical resources and an intervention in several phases (drilling, removal of drill rods, insertion of electrodes and filling of the void space).

[0010] The present invention overcomes these shortcomings. Indeed, by using a hollow self-drilling rod made of an electrically conductive material to install an electrode in the ground for connection to an electrical system, the self-drilling process according to the invention makes it possible to: - to place directly in the ground, in a single operation of simultaneous digging and installation, the body of a longitudinal electrically conductive element (in this case consisting of the hollow self-drilling bar, which served at the same time as a drilling tool), which makes it possible to resolve the implementation costs and the problems related to drilling; - to resolve the problems associated with trench installation, due to the insertion of an electrode deep into the ground; and - to solve problems related to driving, due to the possibility of inserting the electrode into soils containing blocks of rock or very solid materials.

[0011] The placement of the longitudinal electrically conductive element vertically in the ground is further facilitated.

[0012] Thus, the invention relates to a method of self-drilling the ground to install a longitudinal electrically conductive element, said element being configured to form an electrode intended to be connected to an electrical system, the process includes the steps of: - i. to dig the ground using a drill or drilling mast equipped with a hollow self-drilling rod made of an electrically conductive material, so as to insert said hollow self-drilling rod into the ground; - iv. connect an electrically conductive cable to an upper end of the hollow self-drilling bar, said cable being connected on one side to the hollow self-drilling bar and intended to be connected on the other side to the electrical system; - v. electrically isolate the connection between the upper end of the hollow self-drilling bar and the electrically conductive cable, with respect to a surrounding electrolyte, the assembly formed of the hollow self-drilling bar, the electrically conductive cable and the electrically isolated connection constituting said longitudinal electrically conductive element.

[0013] Advantageously, the process further comprises a step iii, consisting of injecting an anolyte through the hollow self-drilling rod. Such an anolyte, also called a "regulating mixture," improves the conductivity and distribution of the electric field around the electrode. Indeed, the anolyte ensures better conductive contact between the ground and the self-drilling rod and, consequently, allows for better regulation over the entire metallic structure to be protected by the electrode, as well as improved current conduction. When the electrode is a grounding electrode, the presence of such an anolyte increases the current flow and diffusion, and therefore improves grounding.

[0014] According to a first embodiment of the invention, the electrically conductive material of the hollow self-drilling bar is an insoluble material, said electrode forming a grounding electrode. The insoluble material used as the electrically conductive material for the hollow self-drilling bar is, for example, galvanized steel, copper, or stainless steel, without this being limiting within the scope of the present invention.

[0015] According to a second embodiment of the invention, the method further comprises a step ii. consisting of inserting at least one anode connected to a second electrically conductive cable through the hollow self-drilling bar; the second electrically conductive cable being intended to be connected to the electrical system; the assembly formed by the hollow self-drilling bar, each electrically conductive cable, the electrically insulated connection, and said at least one anode forming an anodic spillway. This second embodiment of the invention relates in particular to the field of cathodic protection. Each anode may be a soluble anode or no, of the Ti / MMO type, ferrosilicon, graphite, steel, without this being limiting within the scope of the present invention.

[0016] Advantageously, the hollow self-drilling rod is pre-equipped with an electrically insulating coating on the outer wall of the upper portion of the hollow self-drilling rod, or the method further comprises a step of inserting an electrically insulating sleeve into the borehole, around the upper portion of the hollow self-drilling rod. This prevents electrical contamination of third-party structures located in the electrical environment of the created anodic or grounding spillways. The electrically insulating coating is, for example, in the form of a layer of paint or an insulating strip. The electrically insulating sleeve is, for example, made of a thermoplastic material, typically a thermoplastic polymer such as polyvinyl chloride (PVC).

[0017] According to one embodiment, the connection between the electrically conductive cable and the upper end of the hollow self-drilling bar is made by welding, bolting, or by insertion / snap-fitting (typically via a tapered key). This last option proves to be particularly reliable, easy to implement, and durable.

[0018] The invention also relates to the use of a hollow self-drilling bar made of an electrically conductive material to place in the ground, by means of a soil self-drilling process according to the invention, a longitudinal electrically conductive element forming an electrode intended to be connected to an electrical system.

[0019] Such a hollow self-drilling bar, initially intended for the consolidation of soils or buildings, finds here a completely new use by connecting it electrically to an electrical system on the surface (via the electrically conductive cable), transforming the self-drilling bar / cable assembly into a conductive electrode.

[0020] The present invention will be better understood upon reading the following non-limiting example of embodiment and examining the accompanying single drawing in which:

[0021] [Fig.1] is a schematic cross-sectional view of an electrically conductive longitudinal element installed by a soil self-drilling process according to an embodiment of the invention.

[0022] On [Fig.1], the relative proportions of the different constituent elements have not been respected and do not correspond to reality, for the sake of clarity.

[0023] The invention relates to a method for self-drilling the soil 7 to install a longitudinal electrically conductive element 1, 2, 5. The element 1, 2, 5, once installed in the soil 7, is configured to form an electrode intended to be connected to an electrical system (such an electrical system not being shown in [Fig. 1] for clarity). Depending on the end use case of the electrode 1, 2, 5 (the two (The main use cases are described later.) The electrical system is, for example, a surface-mounted direct current generator (in the case of a "cathodic protection" application), or a surface-mounted AC or stray current filtering system (in the case of a "grounding" application). The process is called "self-drilling" because the same element 5 serves both as a drilling tool and as the body of the electrode 1, 2, 5, which remains permanently in the ground 7, as will be described later.

[0024] The method comprises a first step of drilling through the soil 7 using a drill rig or drilling mast (not shown) equipped with a hollow self-drilling rod 5, so as to insert this rod 5 into the soil 7. The hollow self-drilling rod 5 extends along a principal longitudinal direction (corresponding to the vertical direction, or sometimes oblique in certain specific cases, when the rod 5 is inserted into the soil 7), and is made of an electrically conductive material, such as, for example, galvanized steel, copper, stainless steel, or any other conductive metal or metal alloy. The hollow self-drilling rod 5 is typically provided with a drilling cutter 6 at its lower end. The hollow self-drilling rod 5 is, for example, made up of several rod sections connected to each other by joining sleeves 3.Each section of the bar, for example, has a length of approximately 1.5 m, although this is not a limitation within the scope of the present invention. Cascading such sections of the bar to form the hollow self-drilling bar 5 allows depths of several tens of meters to be reached, depending on the soil type 7 and the general drilling technique used.

[0025] According to a first embodiment of the invention (corresponding to the use case of "cathodic protection"), the method comprises a subsequent step consisting of inserting at least one anode connected to an electrically conductive cable through the hollow self-drilling bar 5 (neither the anode nor the electrically conductive cable connected to the anode is shown in [Fig. 1] for reasons of clarity). The electrically conductive cable is intended to be connected to the electrical system. Each anode may be soluble or insoluble. In the case of soluble anodes, each anode is gradually "consumed" in place of a metallic component (not shown) to be protected. Each anode is then, for example, made of a material chosen from the group consisting of: ferrosilicon, steel, graphite, without this being limiting within the scope of the present invention.

[0026] Preferably, the process includes a subsequent step of injecting an anolyte 4 through the hollow self-drilling rod 5. The anolyte 4 is injected, for example, into the rod 5 by means of the drill rig or drilling mast, or even manually. In certain types of soil 7, the injection of the anolyte 4 takes place not only within the hollow self-drilling rod 5, but also extends up around it to fill the void around it. of the bar 5, if applicable. In other soil types 7 (for example, sandy soils), there is no void around the hollow self-drilling bar 5 because the soil immediately returns to its original position after drilling. In this case, the anolyte 4 remains in the bar 5.

[0027] The method includes a subsequent step of electrically connecting an electrically conductive cable 1 to an upper end of the hollow self-drilling bar 5, at a connection 2. The cable 1 is preferably externally sheathed along its entire length. The connection 2 between the electrically conductive cable 1 and the upper end of the hollow self-drilling bar 5 is made, for example, by welding, bolting, or by inserting / socketching into the upper opening of the bar 5 (typically via a tapered key).

[0028] The method includes a subsequent step of electrically isolating the connection 2 between the upper end of the hollow self-drilling rod 5 and the electrically conductive cable 1 from a surrounding electrolyte. The assembly formed by the hollow self-drilling rod 5, the electrically conductive cable 1, and the electrically insulated connection 2 constitutes the longitudinal electrically conductive element. According to the first embodiment of the invention described above, the assembly formed by the hollow self-drilling rod 5, each electrically conductive cable, the electrically insulated connection 2, and the anode(s) forms an anodic spillway intended to protect a metallic structure from corrosion.According to a second embodiment of the invention, the assembly formed by the hollow self-drilling bar 5, the electrically conductive cable 1, and the electrically insulated connection 2 forms a grounding electrode for a metallic structure (the latter not being shown). According to this second embodiment, the electrically conductive material of the hollow self-drilling bar 5 is then an insoluble material.

[0029] Preferably, the method includes a final step of inserting an electrically insulating sleeve (not shown in [Fig. 1]) into the drill hole, around an upper portion of the hollow self-drilling rod 5. The electrically insulating sleeve is, for example, made of a thermoplastic material, typically a thermoplastic polymer such as poly(vinyl chloride) (PVC). Alternatively, the method does not include this final step, but the hollow self-drilling rod 5 is directly pre-equipped with an electrically insulating coating on the outer wall of an upper portion of the rod 5 (such a coating is not shown in [Fig. 1]). The electrically insulating coating is, for example, in the form of a layer of paint or an insulating strip.

[0030] At the end of the process, the electrically conductive cable or cables 1 are connected to the electrical system, in order to make the whole thing operational.

Claims

Demands

1. A method for self-drilling the ground (7) to install an electrically conductive longitudinal element (1, 2, 5), said element (1, 2, 5) being configured to form an electrode for connection to an electrical system, the method comprising the steps of: - i. drilling the ground (7) using a drill rig or drilling mast equipped with a hollow self-drilling rod (5) made of an electrically conductive material, so as to insert said hollow self-drilling rod (5) into the ground (7); - iv. electrically connecting an electrically conductive cable (1) to an upper end of the hollow self-drilling rod (5), said cable (1) being connected on one side to the hollow self-drilling rod (5) and being intended to be connected on the other side to the electrical system; - v.electrically isolate the connection (2) between the upper end of the hollow self-drilling bar (5) and the electrically conductive cable (1), with respect to a surrounding electrolyte, the assembly formed of the hollow self-drilling bar (5), the electrically conductive cable (1) and the electrically insulated connection (2) constituting said electrically conductive longitudinal element.

2. Method according to claim 1, further comprising a step iii. consisting of injecting a regulating mixture (4) through the hollow self-drilling bar (5).

3. A method according to claim 1 or 2, wherein the electrically conductive material of the hollow self-drilling bar (5) is an insoluble material, said electrode forming a grounding electrode.

4. A method according to claim 1 or 2, further comprising a step ii. of inserting at least one anode connected to a second electrically conductive cable through the hollow self-drilling bar (5); the second electrically conductive cable being intended to be connected to the electrical system; the assembly formed of the hollow self-drilling bar (5), each electrically conductive cable, the electrically insulated connection (2) and said at least one anode forming an anodic spillway.

5. A method according to any one of the preceding claims, wherein the hollow self-drilling bar (5) is pre-equipped with an electrically insulating coating disposed at the outer wall of an upper part of the hollow self-drilling bar, or wherein the method further comprises a step of inserting an electrically insulating sleeve into the borehole, around an upper part of the hollow self-drilling bar (5).

6. Use of a hollow self-drilling bar (5) made of an electrically conductive material to place in the ground, by means of a soil self-drilling process according to any one of the preceding claims, an electrically conductive longitudinal element (1, 2, 5) forming an electrode intended to be connected to an electrical system.

Images