NL2020551B1 - Method of forming a column in a ground - Google Patents

Abstract

The present invention relates to a method of forming a column in a ground, comprising the steps of: 5 - inserting a casing at least partially into the ground; - filling an interior of the casing at least partially With a curable material; and - retracting the casing out of the ground While resonating said casing at a natural frequency thereof.

Description

© 2020551 © B1 PATENT (2?) Application number: 2020551 © Application submitted: 8 March 2018 © Int. Cl .:

E02D 5/38 (2018.01) E02D 5/66 (2018.01) E02D 7/18 (2018.01) E02D 7/22 (2018.01)

Application registered:

September 2019 © Patent holder (s):

Van der Straaten Aannemingsmaatschappij B.V. in Hansweert.

(43) Application published:

47) Patent granted:

September 2019 © Inventor (s):

Leonard Pieter Franklin Pkaarte Yerseke.

© Patent issued:

September 2019 © Authorized representative:

ir. P.J. Hylarides et al. In The Hague.

54) Method of forming a column in a ground

5 ^ The present invention relates to a method of forming a column in a ground, including the steps of:

- inserting a casing at least partially into the ground;

- filling an interior of the casing at least partially with a curable material; and

- retracting the casing out of the ground while resonating said casing at a natural frequency.

B1 2020551

This patent has been granted regardless of the attached result of the research into the state of the art and written opinion. The patent corresponds to the documents originally submitted.

Method of forming a column in a ground

The present invention relates to a method of forming a column in a ground.

Columns in a ground are often required to provide a support for a building or other structure. Especially when the ground is relatively soft, such columns are indispensable to prevent sagging or the supported building or structure over time.

Known methods of providing supporting columns comprises driving piles into the ground with heavy piling rigs that drive a pile into the ground using a heavy hammer. Besides causing loud noise, piling using a conventional hammer causes heavy vibrations in the ground and surroundings, and may cause cause damage to nearby constructions. For example, cracks may be formed in walls or nearby buildings. Such prior art methods are energy demanding and not very sustainable.

Alternatives that are less obtrusive, include drilling a column into the ground with a special drill, and filling the drilled hole with a curable material while retracting said drill.

An object of the present invention is to provide a method of forming a column in a ground, that is improved relative to the prior art and that is least one of the above stated problems is obviated.

Said object is achieved with the method of forming a column in a ground according to the present invention, including the steps of:

- inserting a casing at least partially into the ground;

- filling an interior of the casing at least partially with a curable material; and

- retracting the casing out of the ground while resonating said casing at a natural frequency.

Resonating the casing while retracting it out of the ground causes the curable material to smoothly flow out the casing. Moreover, the resonating facilitates compacting or the curable material. Because the casing is retracted out of the ground, it may be re-used multiple times, contributing to a sustainable nature or the method according to the invention.

Although the specific control is not specifically described in this application, it is briefly mentioned that the natural frequency of a casing is dependent on many factors, such as the depth of the casing is extended into and out of the ground, characteristics of the ground (layers ) outside the casing and the curable material inside the casing, as well as the ground water level and the wall thickness of the casing. As the casing is retracted and the length of said casing in the ground decreases while the length of the casing extending out of the ground increases, the natural frequency changes. Thus, the step of retracting the casing out of the ground while resonating said casing at a natural frequency including adjusting the natural frequency in correspondence to the current situation.

In the following description preferred out of the present invention are further elucidated with reference to the drawing, in which:

Figure 1 is a schematic overview of a crane with column forming equipment;

Figures 2 and 3 are perspective views of a drill head from above and below;

Figure 4 shows successive steps of forming a column in a ground with a method according to the invention.

The crane 1 in Figure 1 is standing on a ground 2 and is holding an upright 3 along which a drive 4 is moveable in downward and upward directions. The drive 4 engages a casing 5 at an upper end 6 thereof. The casing 5 is closed with a closure 8 at a lower end 7 thereof. This closure 8 may be embodied as a drill head 9.

The drill head 9 preferably comprises a receiving chamber 10 that is enclosed between an inner wall 11 and an outer wall 12 (Figures 2 and 3). The casing 5, which comprises a tubular cross sectional shape in the preferred embodiment shown, is dimensioned in correspondence with the receiving chamber 10.

A seal 13, preferably in the form of at least one o-ring 14, is preferably arranged between the lower end 7 or the casing 5 and the closure 8, ie the drill head 9. This seal 13 may prevent ground water from entering an interior 15 of the casing 5, where it may negatively influence the curable material 16 that is arranged in the interior 15 during the method of forming a column 17 in the ground 2. For example, the curing process may be delayed or the final strength that is obtained after curing may be reduced when (too much) water enters the interior 15 of the casing 5.

The curable material may be concrete, the concrete is preferably or a quality suitable for underwater applications.

The method of forming a column 17 in the ground according to the present invention is now further explained using Figures 4a-4h, showing the steps of:

- inserting the casing 5 at least partially into the ground 2 (Figures 4c and 4d);

- filling the interior 15 of the casing 5 at least partially with the curable material 16 (Figure 4f); and

- refracting the casing 5 out of the ground 2 while resonating said casing 5 at a natural frequency (Figure 4g). The drive 4 thus functions as a resonator, capable of resonating said casing 5 at a natural frequency (Figure 4g). The resonator preferably adapts the natural frequency when the natural frequency changes due to the casing 5 being moved out of the ground 2.

The method preferably comprises the step of closing the casing 5 at the lower end 7 considered with a closure 8 prior to the step of filling the interior 15 of the casing 5 at least partially with the curable material 16. If the casing 5 is closed at a lower end 7 thereof, two advantages are obtained. On the one hand, the casing 5 will not be filled with ground 2 that has been removed (eg via drilling or suction) prior to the step of filing the interior 15 of the casing 5 at least partially with the curable material 16. On the other hand, the step of filling the interior 15 of the casing 5 at least partially with the curable material 16 may, in a not shown alternative method, just be executed prior to the step of inserting said casing 5 at least partially into the ground .

In the preferred embodiment shown, the closure 8 is a drill head 9, and the casing 5 and drill head 9 form an assembly 18, and the step of inserting the casing at least partially into the ground comprises the step of drilling the assembly 18 or the casing 5 and the drill head 9 into the ground (Figure 4c). Alternatively, the casing 5 may be inserted at least partially into the ground by only resonating said casing 5 at a natural frequency.

Due to the resonating or casing 5, the lengthens and shortens at a high frequency or e.g. 140 Hz. The total elongation of the casing 5 may be in the order of 4-6 mm, ie 2-3 mm at each of the ends 6, 7, considering there is no elongation midway the length of the casing 5. If the lower end 7 moves at a frequency or eg 140 Hz and an amplitude of 2-3 mm, local accelerations in the order or 200 G are realistic. The resonating causes the casing 5 to lower into the ground 2.

The step of drilling the assembly 18 of the casing 5 and the drill head 9 into the ground 2 preferably comprises rotating and simultaneously resonating said assembly 18 at a natural frequency or said assembly 18. As described above, the resonating of the casing 5 may cause a total elongation of the casing 5 in the order or 4-6 mm at 140 Hz. This is about 2-3 mm at each end, considering there is no elongation halfway along the length of the casing 5. Hence, the shear resistance between the casing 5 and the surrounding ground 2 is highest halfway along the length of the casing 5, but gradually decreases in magnitude towards the ends. Respect, a relative light rotator suffices to overcome the shear resistance that is already reduced as a result of the resonating action. The drive 4 may function both as a resonator and a rotator at once. Alternatively, a (not shown) further drive may be applied, at least one of the drive 4 or the further drive is a resonator, and at least one of the other of the drive 4 or the further drive is a rotator. If the assembly 18 or the casing 5 and the drill head 9 is inserted into the ground 2 by rotating and simultaneously resonating at a natural frequency or said assembly 18, the wear of the casing 5 will be reduced to a minimum. As a result, the casing 5 may be re-used multiple times, resulting in a sustainable method or forming the column 17 in the ground 2.

It is mentioned here that the method as described in the previous paragraph is described at least resonating said assembly 18 at a natural frequency or said assembly 18 when the assembly 18 of the casing 5 and the drill head 9 is inserted into the ground 2, and at least resonating the casing 5 at a natural frequency of the casing 5 when the casing 5 is retracted out of the ground. Thus, when the casing 5 is inserted into the ground 2, the natural frequency of the assembly 18 is leading. However, when the casing 5 is retracted from the ground 2, the natural frequency of only the casing 5, also being influenced by the curable material 16 arranged therein, is leading.

Preferably, the casing 5 is also rotated during inserting into the ground 2 and during retraction out of the ground 2. The step of retracting the casing 5 out of the ground 2 while resonating said casing 5 at the natural frequency, thus preferably also comprises simultaneously rotating said casing 5. The resonating of the casing 5 while retracting it out of the ground 2 causes the curable material 16 to smoothly flow out of the casing 5. Moreover, the resonating facilitates compacting of the curable material 16. If the casing 5 is simultaneously rotated and resonated, the casing can be removed in a controlled way.

The step of filling the interior 15 of the casing 5 at least partially with the curable material 16 (Figure 4f) comprises the step of at least partially pumping said curable material 16 therein. Although pouring said curable material 16 is also possible, pumping is preferred to obtain an optimal fill.

The method preferably comprises the further step of arranging a reinforcement 19 in the curable material 16 (Figures 4d and 4th). Preferably, the reinforcement 19 is arranged in said interior 15 or said casing 5 before the step of filling said interior 5 (Figure 4f) at least partially with said curable material 16. In this order, the reinforcement 19 can be securely placed inside the interior space 15. In order to obtain an optimal filling of the interior space 15 with reinforcement 19, it may be advisable to apply a curable material 16 that easily passes the reinforcement 19, If concrete is used, a relatively small grain size may be chosen.

The method comprises the steps of disengaging the casing 5 from the closure 8 in the step of retracting the casing 5 out of the ground 2 (Figure 4g), and leaving the closure 8 in the ground 2 below the column of curable material 16 (Figures 4g and 4h). If the closure 8 is a drill head 9, it comprises the step of disengaging the casing 5 from the drill head 9 in the step of retracting the casing 5 out of the ground 2, and leaving the drill head 9 in the ground 2 below the column 17.

In step 4f, the interior 15 or the casing 5 is preferably filled above the ground level (Figure 4f), e.g., till about 2 meters above ground level. The resonating of the casing 5 while retracting it out of the ground 2 causes the curable material 16 to smoothly flow out of the casing 5. The curable material 16 then fills the void left by the wall of the retracting casing 5. Negative, the level of the curable material 16 lowers from above ground level (Figure 4f) to about at ground level (Figure 4h), indicated with ΔΕ in Figure 4.

Dependent on the dimensions of the casing 5, the method may include the additional step of introducing further curable material 16 into the interior 15 of the casing during the step of retracting the casing 5 out of the ground. For example, if a casing 5 has a length of 19 m and a diameter of 0.355 m, the casing 5 may extend at least about 2 meters above ground level in the step shown in Figure 4, and the interior 15 is preferably completely filled with curable material in the step shown in Figure 4f. In order to provide a column 17 that has an upper end near ground level (as shown in Figure 4h), it may be required to introduce a further height of 8-10 m or 5 curable material 16 into the interior 15 in the step shown in Figure 4g.

The above described embodiment is intended only to illustrate the invention and not to limit in any way the scope of the invention. Applied claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of claims and are in no way limiting the scope of claims. The scope of the invention is defined solely by the following claims.

Claims (15)

Conclusions A method for forming a column in a soil, comprising the steps of: - applying a formwork at least partially in the ground; - at least partially filling an interior of the formwork with a curable material; and - withdrawing the formwork from the ground and simultaneously resonating the formwork at its own frequency. Method according to claim 1, wherein the step of at least partially placing the formwork in the ground comprises the step of resonating the formwork at its natural frequency. Method according to claim 1 or 2, comprising the step of closing the formwork at a lower end thereof, prior to the step of at least partially filling the interior of the formwork with the curable material. A method according to claim 3, wherein the closure is a drill bit, and the casing and the drill bit form an assembly, and wherein the step of at least partially placing the formwork in the ground, the step of drilling into the ground comprises the assembly of the formwork and the drill bit. The method of claim 4, wherein the step of drilling the casing and drill chuck assembly into the ground comprises rotating and simultaneously resonating the assembly at a natural frequency of the assembly. A method according to any of the preceding claims, wherein the step of withdrawing the formwork from the ground and simultaneously resonating the formwork at its natural frequency comprises simultaneous rotation of the formwork. A method according to any of claims 3-6, comprising the step of applying a seal between the formwork and the closure. The method of claim 7, wherein the seal comprises at least one o-ring. A method according to any of the preceding claims, wherein the step of at least partially filling the interior of the formwork with the curable material comprises the step of pumping the curable material at least partially therein. Method according to any of the preceding claims, further comprising the step of introducing further curable material into the interior of the formwork during the step of withdrawing the formwork from the ground. A method according to any of the preceding claims, wherein the curable material is concrete. The method of claim 11, wherein the concrete is of a quality suitable for use under water. A method according to any of the preceding claims, further comprising the step of the applicator in the curable material! of a reinforcement. A method according to claim 13, wherein the reinforcement, prior to the step of at least partially filling the interior of the formwork with the curable material, is arranged in the interior of the formwork. The method of any one of claims 3-14, comprising the steps of: - releasing the formwork from the closure during the step of withdrawing the formwork from the ground; and - leaving the seal in the ground under the column of curable material. 1/3

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