GB2116614A - Method and apparatus for driving hollow piles into the ground - Google Patents

Abstract

A hollow pile (1) is driven into the ground by using a hollow drive shaft (2) having a short auger (3) fast to a leading end portion thereof. Excavated earth and sand are lifted up round the upper portion of the auger where compressed air is blown through nozzle orifices (6) formed in the hollow drive shaft thereby lifting the excavated material through the hollow pile and discharging it from the top of the pile. As excavated material is discharged from the hollow pile, the pile is sunk or driven into the ground. <IMAGE>

Description

SPECIFICATION Method and apparatus for driving hollow piles into the ground This invention relates to a method and apparatus for driving a pile into the ground.

It has been proposed to drive a pile into the earth or ground simply by striking it by means of a hammer or, in the case of a hollow pile, by removing the plug of soil from the centre of the pile using an auger. The first method has the advantage of low cost, but the disadvantage of being accompanied by increased vibration and noise. The second method enables the vibration and noise to be reduced, but is disadvantageous in that it is slow.

Stated in more detail, the second pile driving method discussed above comprises placing an auger inside a hollow pile and rotating the auger so as to excavate the earth in the leading end of the pile and remove the excavated earth therefrom thereby enabling the pile to be driven into the earth. Therefore, it is necessary to remove and lift the excavated soil the full height of the hollow pile by means of the auger, which must therefore have a iength approximately equal to that of the pile to be driven. Accordingly, the longer the pile to be driven into the earth, the longer the auger to be used, the greater the distance along which the excavated earth and sand are carried, and the larger the auger torque. As a result, the auger cannot be rotated at high speed and so the speed of removing excavated earth and sand is low.

Consequently the pile driving speed will become low thereby increasing the work execution cost.

In order to increase the rate of removal of excavated earth and sand, the speed of rotation of the auger has previously been increased by provision of a high horse power electric motor.

Because of the high torque of such a motor, there is however always a risk that the structure supporting the motor may be upset.

The invention provides a method of driving a hollow pile into the ground, wherein a cutter and a relatively short auger at the lower end of the pile are rotatably driven by a hollow shaft extending downwardly through the pile and having in the vicinity of the auger a nozzle or nozzles through which compressed air is blown to lift excavated earth and sand up through the pile and discharge it from the upper end thereof.

The invention also provides an apparatus for driving a hollow pile into the ground, comprising a crane vehicle for supporting the hollow pile vertically above ground level and for lowering the pile into the ground, a hollow drive shaft for extending downwardly through a pile so supported, drive means supported by the crane vehicle for imparting a rotary drive to the drive shaft at the upper end thereof, a cutter and relatively short auger fast to the lower end of the drive shaft, at least one nozzle orifice extending through the wall of the drive shaft in the vicinity of the auger, and means for supplying compressed air to the hollow interior of the drive shaft, to cause the air to issue through the nozzle orifice or orifices.

Drawings Figure 1 is a schematic elevation view partly in cross section explanatory of the pile driving principle of the present invention; Figures 2A to 2G show schematically how a series of hollow piles can be driven into the ground according to the present invention; Figures 3A to 3D show schematically but in a different way from Figures 2A to 2G how excavated earth and sand are discharged from the hollow pile; Figure 4 is a schematic side elevational view, partly in cross section, of a pile driving apparatus mounted on a crane vehicle according to the present invention; Figure 5 is a cross sectional view taken along the line V-V of Figure 4; Figure 6 is a total construction view partly in cross section of a pile driving apparatus according to the present invention;; Figure 7 is a cross sectional view of a coupling section between a hollow rod and a hollow drive shaft; Figure 8 is a cross sectional view taken along line VIll-Vill of Figure 7; Figure 9 is similar to Figure 6 but showing another embodiment of the present invention; Figure 10 is a fragmentary perspective view of a hollow rod having a free auger mounted thereon through a rib; Figure 11 is a fragmentary perspective view of a hollow rod showing a section in which a stopper is mounted to a rib; and Figures 1 2A to 1 2D show schematically how excavated earth and sand are discharged from the hollow pile when the pile driving apparatus shown in Figure 9 is employed.

Description of the Preferred Embodiments The present invention will now be described in detail below by way of example only with reference to the accompanying drawings.

Figure 1 is a schematic explanatory view of an apparatus for carrying out a pile driving method according to the present invention. Placed inside a hollow pile 1 such as hollow concrete pipe or steel pipe is a hollow shaft or rod 2 having an auger 3 formed as an integral part thereof at its leading end. The other end of the hollow shaft 2 is connected through a transmission with a motor 5 mounted on a body such as a crane vehicle 4. The hollow shaft 2 has a first nozzle orifice 6 formed therein so as to communicate with the hollow inside 2a of the shaft 2 at a position slightly above the auger 3 and a second nozzle orifice 7 formed so as to communicate with the hollow inside 2a at a leading end thereof below the auger 3.In use pressurized fluid such as compressed air or compressed air mixed with viscous fluid or water is supplied through an inlet 8 into the hollow inside 2a of the shaft 2, and blows out through the nozzle orifices 6 and 7.

One embodiment of the pile driving method according to the present invention will now be described below with reference to Figures 2A to 2G.

(1) After inserting the hollow shaft 2 provided with the auger 3 into a hollow pile 1, the pile is set on the earth surface and the shaft 2 is caused to rotate by means of a motor 5 so that the earth and sand may be drawn by the auger 3 into the inside of the pile 1 to a position above the auger (refer to Figure 2A).

(2) The drawn in earth and sand are carried up through and discharged from the pile 1 by the action of the compressed air spouting from the first nozzle 6 and the second nozzle 7 (refer to Figures 2B and 2C).

(3) Upon completion of driving of the pile 1, another hollow shaft 2' is inserted in the pile 1 (refer to Figure 2D).

(4) Another pile 1' is suspended and held above the driven pile 1 and the other hollow shaft 2' is puiled up to the inside of the pile 1' (refer to Figure 2E).

(5) Then, the lower end of another hollow shaft 2' is connected with the upper end of the hollow shaft 2 provided with the auger 3 (refer to Figure 2F).

(6) The other pile 1' is then connected with the driven pile 1 (refer to Figure 2G).

(7) The other pile 1' is then connected with the motor 5.

(8) The operations described in items (2) and (3) are then repeated.

By carrying out the above-mentioned steps, a series of piles may be driven successively into the earth.

As mentioned above, because the excavated earth and sand may be conveyed upwards along the whole distance inside the pile 1 not only by means of the auger 3 but also by the action of the compressed air, the earth and sand discharge speed can be increased and the pile driving speed or the work execution speed can be increased thereby enabling the work execution cost to be reduced remarkably. Also, even if the rate of revolution of the auger 3 is increased, the turning torque can be kept low so that even for a high speed of rotation of the auger there is no need to increase the capacity of the motor 5 and there is no fear of upsetting the body 4 due to excessive torque.

Further, if and when water or a viscous fluid is mixed with the compressed air, even gravels or pebbles can be readily removed at a high speed.

Further, as an alternative method for removing the excavated earth and sand, as shown in Figures 3A to 3D, the auger 3 may periodically be raised (Figure 3B), rotated forwardly and then moved downwards while compressed air is being blown through the second nozzle orifice 7 at the leading end of the hollow shaft so that the excavated earth and sand is more readily moved upwardly above the auger (Figure 3C), and then the earth and sand remaining inside the pile 1 may be removed upwardly under pressure by blowing the compressed air through the first and second nozzle orifices 6 and 7 (Figure 3D).

In the method of Figures 2A to 2G, either the first nozzle orifice 6 or the second nozzle orifice 7 may be omitted, in the method of Figures 3A to 3D, the first nozzle orifice 6 may be omitted.

A more detailed embodiment of an apparatus for carrying out the method of the invention is shown in Figures 4 to 8.

Figure 4 is an overali side elevational view of a pile driving apparatus comprising a crane vehicle 4 which is comprised of an undercarriage 10 and a revolving upper body 11. Attached to the revolving upper body 11 is a leader 12. The leader 12 has a guide 13 on which a pile driving unit 14 is mounted so as to be slidable freely vertically therealong. The pile driving unit 14 may be moved up and down by means of a wire 15 wound round a winch (not shown).

The pile driving apparatus is constructed as shown in Figure 6.

Stating in detail, a gear case 1 7 for a driving unit 1 6 is vertically slidably mounted on and along the guide 1 3. A hollow drive shaft 1 8 extends through the gear case 1 7 and is provided with a gear 1 9 which engages with a gear 20. The gear 20 is in turn connected with a motor 5 installed in the gear case 1 7 through a transmission 5'.

In the gear case 17, there is suspended a base plate 23 provided with a weight 22 through cylinders 21. The base plate 23 is vertically slidably fitted to the guide 13. A cap 25 is mounted to the lower part of the base plate 23 through an annular member 24. The lower part of the drive shaft 1 8 passes through a hole 26 of the cap 25 and is connected through a coupling 27 with the hollow shaft 2 suspending therefrom. The upper end of the drive shaft 1 8 is connected through a swivel joint 28 with a first hose 29.

The aforementioned annular member 24 is formed with an earth and sand discharge port 30 adapted to be opened and shut by means of a cover 31. The annular member 24 has a cover 32 fitted inside which is adapted to connect the hole 26 to the earth and sand discharge port 30. The cover 32 has a hole 34 formed therein and which is connected with a second hose 33.

A pile 1 is detachably mounted on the cap 25.

The gear case 17, the weight 22 and the cap 25 may be moved vertically by wires or cables 15" 152 and 153, respectively.

Reference numeral 40 denotes a pressurized fluid supply means which comprises a first tank 41 filled with water, a second tank 42 filled with a viscous fluid and a third tank 43 filled with cement milk. The fluids contained in the tanks 41,42 and 43 are fed by means of first, second and third pumps 44, 45 and 46 through first, second and third valves 47, 48 and 49 into a mixer 50 into which the compressed air from a pneumatic pump 51 is supplied through a fourth valve 52 and is fed into the aforementioned first host 29.

The compressed air from the pneumatic pump 51 is also supplied through a fifth valve 53 into a plug forming material supply unit 54 so that the plug forming material may be supplied into the second hose 33.

The above-mentioned coupling 27 comprises, as shown in Figures 7 and 8, a small diameter portion 2a formed in the upper part of the hollow shaft 2, a recess 1 8a which is formed in the lower part of the drive shaft 1 8 and in which the small diameter portion 2a is fitted, and pins 60 adapted to be inserted in the fitting portions thereof. The hollow shaft 2 and the drive shaft 18 may be readily connected and disconnected by inserting and removing the pins 60.

Mounted on the lowermost leading end of the hollow shaft 2 is an expandable cutter 61 which assumes a retracted condition when it is being inserted in the pile 1 but assumes an outwardly expanded condition by the resistance of the earth to be excavated when excavation of soil is made.

The operation of the pile driving apparatus will now be described below.

By driving the motor 5, the drive shaft 18 is rotated thereby rotating the hollow shaft 2 and the auger 3 fitted thereto.

The downward force of the weight 22 is exerted through the base plate 23, the annular member 24 and the cap 25 onto the pile 1 per se thereby to give the pile 1 a thrusting force. If the thrusting force is insufficient, it can be increased by pushing the cap 25 down by means of cable 1 53. At that time, the cylinders 21 are extended.

Further, by moving the weight 22 up and down by means of the cable 152 so as to strike it against the base plate 23, an impact force can be exerted on the pile 1.

The cap 25 supports the upper end of the pile 1 and serves to set the centre position of the hollow shaft 2 to be driven.

Further the extension and contraction of the cylinders 21 permits the length of attachment between the drive unit 1 6 and cap 25 to be varied as desired so that the relative positions of the connecting members can be controlled.

Still further, the compressed air discharged by the pneumatic pump 51 will flow through the fourth valve 52, the mixer 50, the first hose 29 and the swivel joint 28 into the inside of the hollow drive shaft 18 and will blow through the first and second nozzle orifices 6 and 7 or either one of them.

Further, by selectively opening and closing the first, second and third valves 47, 48 and 49, any of water, viscous fluid and cement milk can be supplied into the mixer 50 and mixed with the compressed air. Therefore, the various proportions and combinations of the mixed fluids may be spouted through one or both of the first and second nozzle orifices 6 and 7.

Moreover, by opening a sixth valve 55, the compressed air may be supplied under pressure into the earth discharge port 30 so that any earth and sand deposited on the earth discharge port 30 may be removed and the port cleaned.

Further, since a plug forming material can be supplied by the plug forming material supply unit 54, in case the excavated earth and sand is gravel through which the compressed air can blow readily, a plug forming material such as a viscous fluid or cement milk may be supplied from above on the gravel thereby forming a plug thereof and facilitating its removal.

Referring to Figure 9, there is shown another embodiment of the present invention. In this embodiment, the hollow shaft 2 has a rib 70 secured to one side thereof. As shown in Figure 10 a free auger 71 has a key slot 72 engaging the rib 70 to key the free auger 71 to the shaft 2 to be axially slidable thereon. The lower end of the rib 70 extends to a position slightly above the auger 3 and the first nozzle orifices 6 and, as shown in Figure 11, a stopper 73 is provided to prevent the free auger 71 from dropping further.

Reference numerai 40' denotes a pressurized fluid supply means which comprises a cement milk supply unit 74, a first compressor 75, a second compressor 76 and a water supply unit 77 which are connected through first, second, third and fourth valves 78, 79, 80 and 81, respectively, with first and second hoses 29 and 33. The other configuration of this embodiment is the same as that of the aforementioned embodiment. In this embodiment, in the case of excavating the ground consisting mainly of clays, the rib 70 fitted to the hollow shaft 2 serves to break down the earth and sand deposited on the inner surface of the pile 1 thereby preventing occurrence of blockage of the pile. Consequently, it becomes possible to move the earth and sand inside the pile 1 smoothly so that they can be discharged outside the pile at a very high speed.

Either a single rib 70 may be provided on one side of the hollow shaft 2 as shown, or ribs 70 may be provided on both sides thereof.

The action or function of the free auger 72 is illustrated in Figures 1 2A to 12D. The earth and sand excavated by the action of the cutter 61 will be carried upwards by means of the auger 3 and will form a loose lump around it. The free auger 71 will drop on the earth and sand lumped around the auger 3 and rotate together with the hollow shaft 2 and move down through them until it strikes against the stopper 73 (Figure 12A).

As a result, both the free auger 71 and the earth and sand sent to the free auger 71 will cause blockage of the pile 1 thereby forming an earth and sand plug. By blowing compressed air through the nozzle orifices 6 and 7 continuously or intermittently, the pressure in the region between the free auger 71 and the auger 3 will increase and push upwards the free auger 71 and its entrained plug of earth and sand (refer to Figure 1 2B). When the free auger 71 has been pushed up within the annular member 25, the earth and sand will be discharged from the soil discharge port 30.

At that time, since the compressed air is blown through the hole 34, the excavated earth and sand can be readily discharged (refer to Figure 12C).

When the excavated earth and sand are discharged, the pressure in the area between the free auger 71 and the auger 3 will be reduced and consequently the free auger 71 will descend until it strikes against the stopper as mentioned above (refer to Figure 12D).

By repeating the aforementioned operations, the earth and sand excavated by the cutter 61 may be discharged efficiently by the action of both the compressed air and the free auger 71. Further, in the arrangement of Figures 9 to 12, the amount of compressed air supplied into the hollow shaft 2 can be increased or decreased by opening and shutting off the second and third valves 79 and 80 of the pressurized fluid supply means 40'.

Therefore, the amount of the compressed air to be supplied into the pile can be adjusted depending on the nature or property of the earth and sand to be excavated, and also it can be increased or decreased intermittently by opening and closing the third valve 80 intermittently thereby enabling an impact force to be imparted to the earth being removed.

Claims (12)

1. A method of driving a hollow pile into the ground, wherein a cutter and a relatively short auger at the lower end of the pile are rotatably driven by a hollow shaft extending downwardly through the pile and having in the vicinity of the auger a nozzle or nozzles through which compressed air is blown to lift excavated earth and sand up through the pile and discharge it from the upper end thereof.

2. A method according to claim 1, wherein the nozzle or nozzles are provided through the wall of the hollow shaft at a position immediately above the auger.

3. A method according to claim 2 wherein a further nozzle or nozzles are provided through the wall of the hollow shaft at a position immediately below the auger between the auger and the cutter.

4. A method according to any preceding claim, wherein the blowing of the compressed air through the nozzle or nozzles is intermittent.

5. A method according to any preceding claim, wherein the compressed air is used to blow water or a viscous fluid through the nozzle or nozzles, the better to entrain particulate matter in the excavated material and to raise it to the upper end of the pile for discharge therefrom.

6. An apparatus for driving a hollow pile into the ground, comprising a crane vehicle for supporting the hollow pile vertically above ground level and for lowering the pile into the ground, a hollow drive shaft for extending downwardly through a pile so supported, drive means supported by the crane vehicle for imparting a rotary drive to the drive shaft at the upper end thereof, a cutter and relatively short auger fast to the lower end of the drive shaft, at least one nozzle orifice extending through the wall of the drive shaft in the vicinity of the auger, and means for supplying compressed air to the hollow interior of the drive shaft, to cause the air to issue through the nozzle orifice or orifices.

7. An apparatus according to claim 6, wherein the nozzle orifice or orifices are provided through the wall of the drive shaft at a position immediately above the auger.

8. An apparatus according to claim 6, wherein the nozzle orifices are provided through the wall of the drive shaft at positions both immediately above the auger and immediately below the auger between the auger and the cutter.

9. An apparatus according to any of claims 6 to 8, wherein a radially projecting longitudinal rib is formed on the drive shaft for scraping off excavated material adhering to the inside of the hollow pile in use.

10. An apparatus according to any of claims 6 to 9, wherein an auxiliary auger is provided, keyed to the drive shaft but axially movable thereon.

11. An apparatus according to any of claims 6 to 10, having a top plate for location over the upper end of the pile in use and a weight mounted on the top plate, the weight being reciprocable vertically relative to the top plate for imparting shock loads to the top plate and to the pile being driven.

12. An apparatus according to any of claims 6 to 11, wherein the means for supporting the hollow pile includes a cylindrical member having a discharge opening for discharging the material excavated and means are provided for supplying compressed air into the cylindrical member to help discharge the material excavated from the discharge opening.

1 3. An apparatus according to any of claims 6 to 12, further comprising means for entraining water or a viscous liquid in the compressed air that is blown through the one or more nozzle orifices.

1 4. A method of driving a hollow pile into the ground, substantially as described herein with reference to Figures 1 to 3D of the drawings.

1 5. An apparatus for driving a hollow pile into the ground, substantially as described herein with reference to Figures 4 to 8 of the drawings.

1 6. An apparatus for driving a hollow pile into the ground, substantially as described herein with reference to Figures 9 to 1 2D of the drawings.