The invention relates to a method for inserting a foundation element such as a foundation pile into the ground .

A number of methods are known in practice for insertin a foundation pile. A soil-displacement method makes use of driving a solid pile, wherein this pile is struck into the ground using a ram. The soil around the pile is displaced here so that this soil is compacted. A problem in this method is the resulting noise nuisance as well as the vibration nuisance occurring in the surrounding area, wherein damage may even be caused to nearby buildings. In order to obviate these problems to some extent, diverse types of foundation pile have been developed with different pile tips and other dimensions. An alternative method relates to a soil-removing/soil-displacing insertion of foundation piles using drilling. So-called screw piles are generally used here. A problem occurring in this method is formed by the heat produced as a result of the friction, particularly in the pile tip. A frequent occurrence here is that it is necessary to wait some time before it is possibl to continue with insertion of the foundation pile in order to allow the foundation pile to cool. In order to reduce this waiting time use is also made of a forced cooling system. Caking of concrete may occur due to for instance a drilling tube becoming warmer. A further problem is formed by the relatively high required power used in this method. In the case of soil removal, the soil has to be discharged. This entails additional cost and requires additional work on site .

An object of the present invention is to obviate or to reduce the above stated problems.

This object is achieved using the method for inserting a foundation element into the ground as according to the present invention, the method comprising the steps of:

- placing a foundation element at a desired position;

- introducing the foundation element in continuously or periodically rotating manner; and

- introducing the foundation element simultaneously and/or alternately therewith in continuously or periodically vibrating manner.

According to the method, a foundation element is positioned at the position where it has to be introduced into the ground. Such a foundation element comprises for instance a foundation pile with a bearing or pulling function, or a retaining wall with an earth or water- retaining function, or a tube which, having been placed at depth, is filled with concrete and optional reinforcement and subsequently withdrawn. The element is then introduced into the ground with a first arranging force in the ground in rotating manner, which in the context of the invention is also understood to mean in screwing, oscillating

(alternately to the right and left) and drilling manner. The soil is displaced here. During insertion use is also made of a second arranging force in the ground by making use of vibrating insertion of the pile or other element. Both forces and movements can be applied continuously and/or periodically. Both these forces and movements can also be applied in combination and/or alternately.

In the case that a foundation element such as said tube must be taken out of the ground after the foundation has been arranged, use is preferably also made of the combination of rotation and vibration. It has been found here that the shaft friction is reduced significantly so that removal from the ground is simplified. Among other effects, this reduces the time reguired for the operations.

It has been found that by combining a rotating and a vibrating movement as according to the above stated method the total power required is lower and less heat is produced, particularly at the tip of the foundation element, than compared to conventional methods. The power required to introduce a pile or other element into the ground is in this way reduced relative to for instance a solely rotation method. Owing to the reduced heat production compared to a solely rotation method, the waiting time necessary for cooling is reduced or can even be wholly dispensed with, whereby the capacity which can be achieved with a device performing the method is greatly increased. This greatly increases the efficiency of the method according to the present invention. In addition, it has been found that the problem of caking of concrete and the premature failure of a drilling tube is prevented with the method according to the invention .

Through the combination of vibration and rotation the total quantity of vibrations produced in the ground is greatly limited and/or can be controlled compared to conventional pile-driving. Alternatively or additionally, the type of vibration is also modified. This relates for instance to the frequency and/or amplitude of the

vibrations. This has the result, among others, that damage caused to nearby buildings can be avoided or is in any case reduced.

According to the invention it is possible to perform a combined rotating-vibrating movement substantially simultaneously. It is however also possible according to the invention to utilize these two forces in periodic

alternation, for instance depending on the specific

situation on site. This specific situation relates for instance to the presence of buildings in the immediate vicinity of the foundation pile or other foundation element to be inserted. This also depends on the type of ground and other factors. In the case of a clay layer it is thus for instance possible to place more emphasis on rotation, and in the case of a sand layer more emphasis can be placed on vibration. An additional axial force can optionally be applied to the foundation element during insertion.

A further additional advantage of the method according to the present invention is the increased flexibility which is obtained. With conventional methods a specific method must be selected inter alia as a function of the ground, for instance clay or sand. The method according to the present invention can be widely utilized in different types of ground, for instance by adjusting the ratio of vibration and rotation thereto. This enables efficient utilization of the means available, thereby considerably increasing the effectiveness in practice.

It is further noted that in the present application a foundation element is understood to mean inter alia a pile, and in particular a foundation pile on which buildings can for instance be placed. It is also possible according to the invention to place for instance inclined piles, anchors or earth or water-retaining walls. It is also possible to arrange a drilling tube instead of a foundation pile with the method according to the present invention. A central passage is preferably also provided for the concrete pump. Such a passage can also be used for grout and the like. Lubrication with grout is hereby a possibility. It is also possible to provide the element with reinforcement.

In an advantageous preferred embodiment vibrating insertion and rotating insertion are applied simultaneously over a substantial part of an insertion depth of the foundation element.

Simultaneous application avoids unnecessary vibrations in the surrounding area. Heat production can also be prevented. Surprisingly, the total power required can be reduced in most practical situations through the combined effect of rotation and vibration, whereby a foundation element can be introduced into the ground more effectively.

A controller preferably adjusts the mutual ratio of vibrating insertion and rotating insertion during insertion of a foundation element into the ground. This adjustment is further preferably performed wholly automatically by the controller. The controller preferably makes use here of a vibration sensor in the vicinity of the device and detectors on the device in order to determine for instance forces exerted and displacements realized and/or power consumed. An almost autonomous system is hereby obtained with which it is possible to respond automatically to for instance hard underground layers. This for instance limits damage and thereby also standstill of the device.

In an advantageous preferred embodiment according to the present invention the insertion of the element is performed by rotation alone over the first 2-20 metres, preferably 5-15 metres and most preferably about 10 metres as seen from the ground surface.

By placing the emphasis on rotating insertion of the foundation element over the first metres from the ground surface the vibrations produced in the ground over this distance are reduced and/or controlled. It has been found that buildings in the immediate vicinity of the foundation element to be arranged are subject to nuisance and damage particularly from vibrations produced in the ground over this first distance. By using the method according to the invention, which enables a combination of rotation and vibration, and placing the emphasis here on rotation over the first metres, preferably the first 10 metres, the stated drawbacks are greatly reduced.

In an advantageous preferred embodiment according to the present invention the insertion of the foundation element is performed by rotation alone over the final 0.5-10 metres, preferably 1-5 metres and most preferably about 2 metres .

Using the method solely with rotation over said final distance, preferably about 2 metres, and almost wholly dispensing with vibration over this distance, achieves that the ground under the tip of the foundation element is not disturbed after placing. The cohesion and stability of this ground, on which the foundation element directly rests and with which the bearing strength is in large part obtained, are hereby maintained. It has been found here that a distance of about 2 metres suffices in most applications.

In an advantageous preferred embodiment according to the present invention the method comprises of controlling the insertion of the foundation element on the basis of stroke length and/or rotation speed and/or vibration frequency using a controller.

Providing a controller achieves that the process of inserting an element can be adapted to the specific

conditions as already noted above. A controller can be used here which is suitable for controlling a number of specific settings and/or parameters during the drilling process and/or vibrating process. It has been found here that it is advantageous during rotation to vary the rotation speed or speed of revolution. It has been found advantageous in the vibrating process to vary the stroke length of the vibration and/or the vibration frequency. It has emerged in practice that a stroke length of about 20 mm at about 2300

revolutions per minute is advantageous, wherein the

controller varies these values subject to the above

mentioned specific conditions. The frequency and stroke length are preferably also varied during startup, for instance using an eccentric adjustment. Using said

variations the impact force realized can be adjusted and preferably controlled.

In a further advantageous preferred embodiment

according to the present invention the vibrating insertion is performed at a load above 5 ton per metre, preferably above 15 ton/m and most preferably above 20 ton/m.

By applying the vibrating insertion particularly when greater loads occur during insertion of the foundation pile it has been found that the capacity of the installation used to perform the method according to the invention is greatly increased. This can be partially explained in that at the higher loads more friction occurs during the rotating insertion, whereby more heat is produced, resulting in waiting times and greater power being required. An effective method for inserting an element into the ground is hereby realized.

In a further advantageous preferred embodiment

according to the present invention the tip of the foundation element is provided with a pitch.

Providing a pitch, which means that a pitch is provided over at least a part of the pile and in particular the tip, achieves that the drilling process can be performed more efficiently. It has been found here that the combination of providing a kind of screw thread with a certain pitch and applying vibration is particularly advantageous. This considerably increases flexibility.

The invention further relates to a device for inserting a foundation element into the ground, the device comprising:

- a hoisting frame for holding the element and/or tube, wherein the frame is provided with a rotating part and a vibrating part;

- a first drive operatively connected to the frame for driving the rotating part; and

- a second drive operatively connected to the frame for driving the vibrating part.

The device provides the same advantages and effects as described for the method. The device is particularly

suitable for application of the method. In a currently preferred embodiment the drives make use of a so-called hydraulic aggregate provided with two or more motors. An additional advantage of embodying the device according to the invention in this manner is that the fuel consumption is surprisingly lower. It has been found here that applying two or more relatively small motors for the purpose of combining rotation and vibration results in a lower fuel consumption than applying a single motor with which both processes are controlled. In addition, the CO ₂ emission is hereby reduced. The separate drives are preferably integrated. As already described, it is possible here to control the different drives with one motor which drives the vibration and the rotation periodically or in combination. Use is however preferably made of said two separate motors. The drive is preferably also embodied such that a rotation can be

performed to the left and to the right, for instance through an angle of about 60 degrees. In a currently preferred embodiment an upward or downward bias is also made possible in order to facilitate insertion of the foundation element into the ground. It has been found that in a number of situations the foundation element can be introduced into the ground in more effective manner. In a possible embodiment this is achieved by providing steel cables from the

rotating/vibrating head to a drive, whereby force can be applied to a cable such that the desired bias can thereby be realized. This bias can be directed upward or downward as desired.

In a currently preferred embodiment use is preferably made, for the purpose of the settings, of a controller which is provided in the device according to the invention. The controller preferably makes use of detectors discussed in respect of the method. Such a controller preferably sets the above stated parameters of the process, viz. the rotation speed or speed of revolution for the rotation and for the vibration the stroke length of the vibration and the frequency thereof. The controller is preferably utilized to control the moment during the vibration. The data are optionally stored in a data logger for purposes of analysis and/or as evidence.

In a favourable embodiment said controller makes use of a detector placed in the vicinity of the hoisting frame during use of the device according to the invention. By making use of this detector it is possible to detect vibrations in the immediate vicinity of the hoisting frame and to set said parameters on the basis of these measured values using the controller. The controller preferably controls both the first and the second drive. It is however also possible to have the controller control only one individual drive.

The device preferably makes use of a drill tip with coupling means such that the drill tip is operatively connected to the foundation element in a first rotation direction and is uncoupled in a second rotation direction. An effective operation is hereby realized.

Further advantages, features and details of the invention are elucidated on the basis of preferred

embodiments thereof, wherein reference is made to the accompanying drawings, in which:

- figure 1 shows a view of a device for performing the method according to the invention;

- figures 2-4 show alternative embodiments of devices according to the invention; and

- figure 5 shows a view of a tube which can be used in the embodiments according to the invention.

A device 2 (figure 1) is suitable for inserting a foundation element such as foundation pile 4 into ground 6. In the shown embodiment device 2 is a mobile installation which can be displaced in suitable manner to the position where foundation pile 4 has to be provided. Foundation pile 4 is provided with a shaft 8, wherein a pile tip 10 is provided on the underside in position of use. In the shown embodiment pile tip 10 is provided over the bottom length with a pitch 12. Foundation pile 4 is held in a

substantially vertical position in device 2 using hoisting frame 14. Alternatively, pile 4 or other foundation elements can also be held in a shoring position. Use is made here of support arm 16 which forms the connection between hoisting frame 14 and the mobile vehicle of device 2. Drive unit 18 is provided for the purpose of inserting foundation pile 4 into ground 6. Drive unit 18 is provided with a first drive 20 for realizing the rotating movement of pile 4 and a second drive 22 for realizing the vibrating movement of pile 4. In the shown embodiment drive unit 18 also has a

controller 24 for setting a number of specific parameters for the vibration and/or rotation. Further provided in the shown embodiment are two cables 26, 28 running between unit 18 and the mobile vehicle of device 2. If desired, cables 26, 28 provide for an additional force directed respectively upward or downward.

During the rotating movement a movement of pile 4 is realized in the direction of arrow A. During vibration a movement of pile 4 is realized in the direction of arrow B. In the shown embodiment it is possible to place hoisting frame 14 at an angle to the vertical using support arm 16 by realizing a movement in the direction of arrow C. It is hereby possible to place hoisting frame 14 at an angle to the vertical relative to ground 6 and to introduce a foundation pile 4 at an angle into this ground 6.

When a foundation pile 4 has to be arranged in ground 6 use is generally made in practice of a soil-drilling test to determine the soil conditions. Partly on the basis of these soil conditions and for instance the presence of nearby buildings it is possible to establish what are the necessary dimensions and number of foundation piles 4. It is also possible to determine what is the required or most suitable method for inserting foundation piles 4 into ground 6.

Foundation pile 4 is then preferably supplied and, using hoisting frame 14, placed in a substantially vertical position on ground 6. During the first metres over which foundation pile 4 is inserted into ground 6 particular use is preferably made of rotation using first drive 20. Once foundation pile 4 has been inserted into ground 6 over this first distance, use is made of a combination of rotation and vibration in order to thereby insert foundation pile in efficient manner into ground 6. When foundation pile 4 has almost arrived at the desired, most optimal depth

established from the soil-drilling test, use is preferably made once again of rotation only over the final distance of for instance about 2 metres. The combination of rotation and vibration is used in the intermediate distance. It is possible here to make use of a combination of the two movements simultaneously or to perform these two movements alternately. Depending on the ground layers encountered in ground 6, it is also possible here to adjust the mutual ratios of the rotation and the vibration to these layers. A further aspect which is a factor in this choice is for instance the presence of buildings in the immediate vicinity of the foundation pile 4 to be inserted. After insertion of foundation pile 4 further foundation piles 4 can be provided until sufficient foundation has been arranged for placing for instance a building thereon, or for otherwise producing sufficient bearing strength, tensile strength and/or retaining action.

A so-called top-drive system 30 (figure 2) is embodied with a vibrator block 32 for vibration B and a drill table 34 for rotation A. System 30 inserts tube or pile 36 into ground 38. Tip 40 is screwed and/or vibrated here into ground 38. Drill table 34 is connected via a so-called spline-shaft coupling 42 to tube 36. Vibrations B hereby have no effect on drill table 34. Vibrator block 32 is connected via fixed connection 44 to tube 36. Bearing 46 is provided here so that rotation A has no effect on vibrator block 32.

An alternative so-called drive-through system 48

(figures 3A and B) has drill table 50 for rotation A, vibrator block 52 for vibration B for inserting tube 54 into ground 56 using tip 58. Coupling 60 is formed by two gear rings 62, 64 which, making use of wedge 66, reduce the inner diameter of gear rings 62, 64 using a preferably hydraulic control. This clamping is therefore applied or released in each case depending on the desired movement, vibration B or rotation A, of tube 54. Clamping 60 can be performed at any desired position on tube 54. The advantage hereof is that the stability of system 48 is hereby greatly improved since drill table 52 can also be provided in the vicinity of ground surface 56.

System 68,82 (figures 4A and B) makes use of a vibrator block 70, 86 which engages on an inner tube 74 (figure 4A) or outer tube 90 (figure 4B) , and a drill table 72, 84 which engages on outer tube 76 (figure 4A) or inner tube 88

(figure 4B) . Tubes 74,76,88,90 are inserted into ground 78,92 using tip 80,94. System 68,82 is used to insert piles with a diameter of about 200-1200 mm, preferably about 350- 609 mm, into ground 78,92. Inner tube 74,88 is here as large as possible so that the reinforcing cage which is placed in inner tube 74,88 is preferably also as large as possible. The strongest possible construction is hereby obtained, which is specially advantageous when a so-called casing must be introduced into ground 78,92.

In the shown embodiment use is preferably made of a lost-point technigue, wherein pile 96 is operatively

connected to tip 98 (figure 5) . In the shown embodiment tip 98 is rotatably connected here to pile 96 via recesses 100 in pile 96 and protrusions 102 on tip 98. Tip 98 follows the rotation A of pile 96. In axial direction tip 98 follows downward vibration B only. Since tip 98 is not connected in axial direction to pile 96, tip 98 does not move upward in axial direction with pile 96. In the shown embodiment protrusions 102 and recesses 100 are such that in a first rotation direction A tip 98 is co-displaced in the rotation. A downward movement deeper into the ground is of course also followed. A rotation in opposite direction ensures in the shown embodiment that tip 98 is uncoupled from pile 96 so that pile 96 can be removed from the ground without tip 98.

Systems 2,30,48,68,82 preferably make use of a combined vibration B and rotation A when inserting a pile or tube into the ground as described above. The mutual ratio is preferably set by controller 104 (figure 1) . In the shown embodiment controller 104 receives information regarding vibrations produced in the vicinity of sensor during the process. A sensor 108 is preferably also provided for measuring the force exerted in axial direction. Together with preferably displacement sensor 110, controller 104 hereby controls the individually adjustable vibrations B and rotations A.

Experiments with system 30 have shown that inserting a pile into the ground can take place in a more effective manner. Compared to conventional systems the pile is inserted into the ground in a shorter time, with less heat production and with a an overall lower required power. Less nuisance is also caused to the environment. During the experiments it was found that owing to vibration B the operating pressure in the drill table is smaller for rotation A.

Experiments have also demonstrated that it is possible to insert piles in all the most relevant substrata with one system by making use of the option of relative adjustment of vibration B and rotation A.

The invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.