Piezometer installation device and method

Abstract

A method for installing a sensor (40) underground comprising, in that order: providing a cone tip (1), a sensor holder (6) and a plurality of pushing rods (32); connecting the sensor holder (6) to the cone tip (1); pushing down the sensor holder (6) and the cone tip (1) to a predetermined depth with the assistance of the plurality of pushing rods (32); channeling a sensor (40) successively through each of the pushing rods (32); inserting the sensor (40) in the sensor holder (6); and pulling up the plurality of pushing rods (32), leaving the cone tip (1), the sensor holder (6) and the therein enclosed sensor (40) at the predetermined depth.

Description

[0001] PIEZOMETER INSTALLATION DEVICE AND METHOD TECHNICAL FIELD

[0002] The present invention relates to the technical field of soil analysis and in particular to a device and a method used to install a sensor into the ground, especially but not exclusively a piezometer.

[0003] BACKGROUND OF THE INVENTION

[0004] In the field of geotechnical and geoenvironmental site investigations, the characterization of soils and soil-like geomaterials holds significant importance.

[0005] The installation of piezometers in geotechnical engineering is pivotal for monitoring soil and tailings. These instruments provide real-time data on pore water pressures, crucial for assessing stability, groundwater flow, and detecting risks like liquefaction and seepage. In tailings management, piezometers are essential for early detection of potential breaches, ensuring containment integrity. Their use enhances decision-making in design, construction, and maintenance, thereby significantly improving safety and long-term performance of geotechnical structures.

[0006] A known method for installing a piezometer consists in drilling a hole and placing a piezometer therein. This method is slow and costly; the soil may be polluted by the use of drilling lubricant; and the drilled hole may need to be reinforced to prevent collapsing as the drill is being moved out of the hole.

[0007] Another known method, which eliminates soil contamination risks, consists in pushing down the piezometer in the ground in a manner inspired by a Cone Penetration Test (CPT) tooling. A piezometer with a conical tip is pushed down in a soil with the assistance of several hollow pushing rods. The cable linking the piezometer to a data acquisition device is passed through all the pushing rods beforehand. This is cumbersome and it exposes the piezometer and the cable to a risk of being damaged. In particular, the successive positioning of each pushing rod has to be made manually and cautiously.

[0008] There is therefore a need for an improved method for installing a sensor underground.

[0009] SUMMARY OF THE INVENTION

[0010] The present disclosure provides for such a need, thanks to a method for installing a sensor underground comprising, in that order: providing a cone tip, a sensor holder and a plurality of pushing rods; connecting the sensor holder to the cone tip; pushing down the sensor holder and the cone tip to a predetermined depth with the assistance of the plurality of pushing rods; channeling a sensor successively through each of the pushing rods; inserting the sensor in the sensor holder; and pulling up the plurality of pushing rods, leaving the cone tip, the sensor holder and the therein enclosed sensor at the predetermined depth.

[0011] Such a method enables installing a sensor underground without the prior need to insert a cable through all the pushing rods, which means that the method reduces the risk of damaging the sensor or its cable and is faster than the drilling method. This method also ensures an accurate placement of the sensor. Additionally, the method or at least the positioning and pushing of the pushing rods can be automated. Furthermore, this method can be performed with a variety of sensors and does not require the sensor to have a conical tip. Finally, should any event happen underground which prevents reaching the desired depth (stiff soil layers, rocks, etc.), the pushing rods may be pulled out and no (expensive) sensor is lost.

[0012] In some examples, inserting the sensor in the sensor holder comprises locking the sensor in the sensor holder by means of a one-way mechanism, the one-way mechanism enabling the sensor to be inserted into the sensor holder and preventing the sensor from exiting the sensor holder. This one-way mechanism ensures that the sensor remains in the sensor holder as the pushing rods are pulled out.

[0013] In some examples, the one-way mechanism comprises at least one elastic tab. The elastic tab may initially be positioned in a resting position. As the sensor is inserted into the pushing shoe, the elastic tab departs from the resting position, and once the sensor is fully inserted in the pushing shoe, the elastic tab recovers its resting position, preventing the sensor from exiting the pushing shoe. Alternatively or in combination, the tab may be hinged to the body of the sensor holder. A spring may be provided to apply a force to the tab in the direction of its resting position.

[0014] In some examples, the method comprises, after connecting the sensor holder to the cone tip and before pushing down the sensor holder and the cone tip, encapsulating the sensor holder in a pushing shoe, wherein pushing down the sensor holder and the cone tip comprises pushing on the pushing shoe. This solution provides for more flexibility for the design of the sensor holder: there is no longer a need for the sensor holder to withstand the pushing force applied by the pushing rods. The method may further comprise pulling up the pushing shoe after pulling up the plurality of pushing rods.

[0015] In some examples, the sensor holder comprises two elongated pieces, and connecting the sensor holder to the cone tip comprises assembling the two elongated pieces together. The cone tip may comprise a disc-shaped protrusion, extending above a neck portion of the cone tip, and the two elongated pieces may comprise each a respective recess, wherein as the two elongated pieces are being assembled, the disc-shaped protrusion of the cone tip becomes locked in the respective recesses. This design facilitates the manufacture of the sensor holder and allows to reliably and easily connect the cone tip to the sensor holder without additional attaching elements or tools. Other locking mechanisms (not disc-shaped) can be provided to attach the cone tip to the sensor holder, e.g. screws, tight-fit arrangement, etc.

[0016] In some examples, the method further comprises inserting an attachment leg of a tab of a one-way mechanism in a housing of a first one of the two elongated pieces before assembling the two elongated pieces together.

[0017] In some examples, the sensor holder comprises a transversal aperture, and inserting the sensor in the sensor holder comprises placing the sensor such that the sensor protrudes in the transversal aperture. The transversal aperture may be a through-hole. This configuration allows for the sensor to be in fluid communication with the environment (soil, water, etc.), while being held steadily in the sensor holder.

[0018] In some examples, the sensor is a piezometer. In other embodiments, the sensor may be a thermal sensor, a strain gauge, an optical sensor, etc.

[0019] The invention further relates to a kit for performing the above-described method, the kit comprising: a cone tip, a sensor, a sensor holder and a plurality of pushing rods, wherein the sensor holder comprises a one-way mechanism enabling the sensor to be inserted into the sensor holder and preventing the sensor from exiting the sensor holder.

[0020] As noted above in relation to the method, in some examples, the one-way mechanism comprises at least one elastic tab. In some examples, the cone tip comprises a disc-shaped protrusion received in a recess of the sensor holder. In some examples, the sensor holder comprises two elongated pieces assembled together. In some examples, the sensor holder comprises a transversal aperture, and wherein the sensor protrudes in the transversal aperture. In some examples, the transversal aperture is a through-hole. In some examples, the sensor is a piezometer.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Further details and benefits of the present disclosure will become apparent in the appended figures in which:

[0023] FIGS. 1 to 9 show the successive steps of a method for installing a sensor underground. FIG. 10 shows a piece of a sensor holder.

[0024] FIG. 11 shows a flowchart of a method for installing a sensor underground.

[0025] DETAILED DESCRIPTION OF THE INVENTION FIGS. 1 to 9 illustrate the various combinations of elements progressively obtained when performing a method for installing a sensor.

[0026] FIG. 1 shows a cone tip 1. The cone tip 1 may be made of steel, for example stainless steel. The cone tip 1 comprises a conical surface 2 forming an angle of about 60°. The cone tip 1 further comprises a disc-shaped protrusion 4, opposite the conical surface 2. The disc-shaped protrusion 4 extends above a neck portion of the cone tip 1. The neck portion is a portion of smaller diameter than the disc-shaped protrusion 4. The cone tip 1 may have an external diameter comprised between 2 cm and 20 cm and may have an axial length (in the vertical direction of FIG. 1) comprised between 3 cm and 15 cm.

[0027] FIGS. 2 to 5 show that a sensor holder 6 can be connected to the cone tip 1. In the embodiments described here, the sensor holder 6 comprises two elongated pieces 6a, 6b but another design is possible, with a single piece or more than two pieces.

[0028] FIG. 2 shows a first elongated piece 6a positioned in contact with the cone tip 1. The first elongated piece 6a comprises a body 8a delimiting an inner cavity 10a. The inner cavity 10a extends in an elongated direction (vertical direction on FIG. 2) and extends over at least 70% of the total length of the first elongated piece 6a. The total length of the first elongated piece 6a may be comprised between 10cm and 100cm. The diameter of the first elongated piece 6a may be comprised between 20% and 80% of the diameter of the cone tip 1, i.e., between 4 mm to 16 cm.

[0029] At an end of the first elongated piece 6a opposite the cone tip 1, the inner cavity 10a ends with a funnel entrance 12a, which aims at facilitating the penetration of the sensor into the sensor holder. The body 8a further comprises two housings 13a and two recesses 14a for receiving a oneway mechanism (described below).

[0030] The first elongated piece 6a may also comprise connectors 16a which may be protrusions or recesses designed to engage a complementary shape (recesses or protrusions) in the second elongated piece 6b. The connectors 16a extend from a planar surface. The first elongated piece 6a may be connected to the cone tip 1 such that the planar surface contains an axis of symmetry of the cone tip 1. The first elongated piece 6a may further comprise a first transversal aperture portion 18a, aimed at forming, with a second transversal aperture portion of the second elongated piece 6b, a transversal aperture (18 on FIG. 9).

[0031] The first elongated piece 6a may further comprise a first cone tip recess 20a forming, with a second cone tip recess of the second elongated piece 6b, a housing for the disc-shaped protrusion 4 of the cone tip 1. The first cone tip recess 20a may have the shape of half a cylinder.

[0032] FIG. 3 shows a one-way mechanism 22 comprising an elastic tab 24 having an attachment leg 26 engaged in a housing 13a of the first elongated piece 6a. The elastic tab 24 has a resting position (as shown on FIG.3) where it protrudes in the inner cavity 10a. As will be explained below, when a sensor is inserted through the inner cavity 10a (from above), the elastic tab 24 moves radially outwardly into the recess 14a. Once the entire sensor has moved down past the elastic tab 24, the elastic tab 24 flexes back in the resting position.

[0033] FIG. 4 shows that the one-way mechanism 22 may comprise a second elastic tab 24 opposite the first elastic tab 24 of FIG. 3. A higher or a lower number of tabs can be foreseen.

[0034] Alternatively, the tab 24 may be hinged to the sensor holder 6.

[0035] FIG. 5 shows the sensor holder 6, once assembled and attached to the cone tip 1. The sensor holder 6 comprises the two elongated pieces 6a, 6b and the enclosed one-way mechanism 22.

[0036] The elongate pieces 6a, 6b and / or the tabs 24 may be made by additive manufacturing. Alternatively, these elements may be made of metal (forged and machined for example).

[0037] The second elongated piece 6b is only partially visible here. Its design substantially mirrors the design of the first elongated piece 6a. As the second elongated piece 6b is brought in contact with the first elongated piece 6a, the protrusions / recesses 16a of the two pieces 6a, 6b engage each other; the disc-shaped protrusion 4 (FIG. 1) is locked in a recess (20a on FIG. 10); and the tabs 24 are locked in their housing 13 a, while remaining free to flex in or out of the inner cavity 10a.

[0038] FIG. 6 shows that the sensor holder 6 can be enclosed in a pushing shoe 26. The pushing shoe 26 is a generally tubular element which has an inner cavity 28 receiving the sensor holder 6. The pushing shoe 26 can be positioned to abut on the cone tip 1. The pushing shoe 26 has a connecting portion 30 which enables pushing rods of a CPT tooling to push on the pushing shoe 26, with the intention of pushing the cone tip 1, the sensor holder 6 and the pushing shoe 26 down in the ground. In an alternative embodiment, the sensor holder 6 is sufficiently strong for withstanding the pushing force, the pushing shoe being therefore optional. FIG. 7 shows the assembly of FIG. 6 which is already pushed underground. A pushing rod 32 has been fixed to the pushing shoe 26 to push the assembly further down. The pushing rod 32 comprises a first end 34 connected to the connecting portion 30 of the pushing shoe 26. The pushing rod 32 comprises a second end 36 opposite the first end 34, the second end 36 being adapted to connect to a further pushing rod (not shown). Pushing rods are thus installed and connected to one another successively until a sufficient number of pushing rods has been used for the sensor holder 6 and the cone tip 1 to reach a predetermined depth.

[0039] The predetermined depth may be up to 20 meters, or up to 50 meters, or up to 100 meters or up to 200 meters. Each pushing rod 32 may have a length comprised between 30 cm and 1 meter.

[0040] The pushing rods 32 are hollow and comprise an inner conduit 38, extending through the entire length of the pushing rod.

[0041] The pushing rods may have an external diameter comprised between 2cm and 20cm and may have a length comprised between 30cm and 150cm.

[0042] As shown on FIG. 7, a sensor 40 can be passed through all the pushing rods 32 until reaching the inner cavity 10a of the sensor holder 6. The sensor 40 is inserted down and channeled successively through the conduits 38 of each of the pushing rods 32. Then, the sensor 40 passes the one-way mechanism 22 and seats permanently in the sensor holder 6.

[0043] A cable 42 connects the sensor 40 to a data acquisition device (computer device or similar), that is positioned on the ground.

[0044] FIG. 8 shows the final position of the sensor 40 in the sensor holder 6. Notably, FIG. 8 shows that the sensor 40 (or at least a lower end thereof) protrudes in the transversal aperture 18.

[0045] The following step of the method consists in pulling out the pushing rods 32 and the pushing shoe 26, leaving the transversal aperture 18 in fluid communication with the environment and enabling the sensor 40 to provide appropriate measurements.

[0046] As shown on FIG. 8, the one-way mechanism 22 makes it possible for the sensor 40 to remain seated in the sensor holder 6 as the pushing rods 32 and the pushing shoe 26 are being pulled out: applying a tension on the cable 42 does not result in the sensor 40 leaving the sensor holder 6.

[0047] FIG. 9 shows a final configuration, where the pushing shoe has been removed. The cone tip 1, the sensor holder 6 and the sensor 40 remain down in the ground. One can see an example of how the sensor 40 can protrude in the transversal aperture 18, so as to be in fluid communication with the environment to be measured.

[0048] FIG. 10 shows in greater detail the first elongated piece 6a without the cone tip 1. The design of the second elongated piece 6b substantially mirrors the design of the first elongated piece 6a, apart from the complementary forms 16a which allow interlocking the two pieces 6a, 6b. We refer to FIG. 2 for the detailed description of this piece 6a.

[0049] A kit can be provided with the various pieces presented above, i.e., a cone tip, a sensor holder, a sensor and a number of pushing rods. Some of these elements (e.g. pushing rods, pushing shoe, sensor) may be off-the-shelf elements whereas others (sensor holder, cone tip) are specifically designed for the above-mentioned method of installation.

[0050] FIG. 11 shows a flow chart of the method 1100 for installing a sensor. The method comprises: providing 1110 a cone tip 1, a sensor holder 6 and a plurality of pushing rods 32, as depicted above.

[0051] The method further comprises connecting 1120, 1130, 1140 the sensor holder 6 to the cone tip 1. This connection can be made as shown on FIGS. 2 to 5, i.e. by connecting 1120 a first elongated piece 6a to the cone tip 1, inserting 1130 the one-way mechanism 22 (e.g. the elastic tabs 24 in the recesses 13a), and assembling 1140 a second elongated piece 6b to the first elongated piece 6a.

[0052] Optionally, the method can comprise encapsulating 1150 the sensor holder 6 in a pushing shoe.

[0053] Then, the assembly comprising the cone tip 1, the sensor holder 6 and potentially the pushing shoe 26 is pushed down (step 1160) by a series of pushing rods 32 successively positioned and pushed down (for example with a hydraulic piston). The step of pushing down 1160 is carried out until the sensor holder and the cone tip reach a desired predetermined depth.

[0054] Once the predetermined depth has been reached, a sensor 40 is channeled 1170 through the conduit 38 of the pushing rods 32.

[0055] The sensor 40 reaches the sensor holder 6 and is inserted 1180 into the inner cavity 10a of the sensor holder 6. The sensor 40 is locked in the sensor holder 6 by the one-way mechanism 22.

[0056] Once the sensor 40 is firmly received in the sensor holder 6, the pushing rods 32 and the optional pushing shoe 26 are pulled out (step 1190 and 1200). The cone tip 1, the sensor holder 6 and the sensor 40 remain at the predetermined depth. The sensor 40 can then provide data to the surface, e.g. pressure at the predetermined depth. The method can be repeated, with a same set of pushing rods (and pushing shoe) at different locations with a series of sensors, sensor holders and cone tips.

Claims

866M 9CLAIMSWhat is claimed is:

1. A method (1100) for installing a sensor (40) underground comprising, in that order:providing (1110) a cone tip (1), a sensor holder (6) and a plurality of pushing rods (32);connecting (1120, 1130, 1140) the sensor holder (6) to the cone tip (1); pushing down (1160) the sensor holder (6) and the cone tip (1) to a predetermined depth with the assistance of the plurality of pushing rods (32);channeling (1170) a sensor (40) successively through each of the pushing rods (32);inserting (1180) the sensor (40) in the sensor holder (6); andpulling up (1190) the plurality of pushing rods (32), leaving the cone tip (1), the sensor holder (6) and the therein enclosed sensor (40) at the predetermined depth.

2. The method of claim 1, wherein inserting (1180) the sensor (40) in the sensor holder (6) comprises locking the sensor (40) in the sensor holder (6) by means of a one-way mechanism (22), the one-way mechanism (22) enabling the sensor (40) to be inserted into the sensor holder (6) and preventing the sensor (40) from exiting the sensor holder (6).

3. The method of claim 2, wherein the one-way mechanism (22) comprises at least one elastic tab (24).

4. The method of any of claims 1-3, further comprising, after connecting (1120, 1130, 1140) the sensor holder (6) to the cone tip (1) and before pushing down (1160) the sensor holder (6) and the cone tip (1), encapsulating (1150) the sensor holder (6) in a pushing shoe (26), wherein pushing down (1160) the sensor holder (6) and the cone tip (1) comprises pushing on the pushing shoe (26).

5. The method of claim 4, further comprising pulling up (1200) the pushing shoe (26) after866M 10pulling up the plurality of pushing rods (32).

6. The method of any of claims 1-5, wherein the sensor holder (6) comprises two elongated pieces (6a, 6b), and connecting (1120, 1130, 1140) the sensor holder (6) to the cone tip (1) comprises assembling (1140) the two elongated pieces (6a, 6b) together.

7. The method of claim 6, wherein the cone tip (1) comprises a disc-shaped protrusion (4) extending above a neck portion of the cone tip (1), and the two elongated pieces (6a, 6b) comprise each a respective recess (20a), wherein as the two elongated pieces (6a, 6b) are being assembled, the disc-shaped protrusion (4) of the cone tip (1) becomes locked in the respective recesses (20a).

8. The method of claim 6 or 7, further comprising inserting (1130) an attachment leg (26) of a tab (24) of a one-way mechanism (22) in a housing (13a) of a first one (6a) of the two elongated pieces (6a, 6b) before assembling (1140) the two elongated pieces (6a, 6b) together.

9. The method of any of claims 1-8, wherein the sensor holder (6) comprises a transversal aperture (18), and wherein inserting the sensor (40) in the sensor holder (6) comprises placing the sensor (40) such that the sensor (40) protrudes in the transversal aperture (18).

10. The method of claim 9, wherein the transversal aperture (18) is a through-hole.

11. The method of any of claims 1-10, wherein the sensor (40) is a piezometer.

12. A kit for performing a method according to any of claims 1 to 11, the kit comprising:a cone tip (1), a sensor, a sensor holder (6) and a plurality of pushing rods (32), wherein the sensor holder (6) comprises a one-way mechanism (22) enabling the sensor (40) to be inserted into the sensor holder (6) and preventing the sensor (40) from exiting the sensor holder (6).866M 1113. The kit of claim 12, wherein the one-way mechanism (22) comprises at least one elastic tab (24).

14. The kit of claim 12 or 13, wherein the cone tip (1) comprises a disc-shaped protrusion (4) received in a recess (20a) of the sensor holder (6).

15. The kit of any of claims 12-14, wherein the sensor holder (6) comprises two elongated pieces (6a, 6b) assembled together.

16. The kit of any of claims 12-15, wherein the sensor holder (6) comprises a transversal aperture (18), and wherein the sensor (40) protrudes in the transversal aperture (18).

17. The kit of any of claims 12-16, wherein the transversal aperture (18) is a through-hole.

18. The kit of any of claims 12-17, wherein the sensor (40) is a piezometer.

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