GB2158135A - Improvements relating to method for driving piles - Google Patents

Abstract

A method for driving a shell 10 into the ground together with a core 11 wherein the improvement includes penetrating the shell and the core alternately by using a combination of the hydraulic actuator 13 and the driving hammer 19, thereby reducing the energy required for driving the heavy shell against the high soil resistance. <IMAGE>

Description

SPECIFICATION Improvements relating to method for driving piles This invention relates to a method for driving a pile into the ground and particularly relates to an improvement of the method for driving a shell together with a core into the ground in which the shell and the core are alternately penetrated into the soil.

It is known in the art to drive a shell into the ground together with a core in the installations of cast-in-place piles wherein the driving blows are delivered on the core which is temporarily attached to the shell to bring it along therewith while penetrating into the soil and is withdrawn after the shell reaches a desired bearing strata.

The installation of a pile in a compact or hard soil usually requires a large driving energy to drive the pile against the high resistance of the soil. However, the shock induced by high impact would badly affect the surrounding soil condition and the adjacent piles, and in some cases, the heavily striking causes damages to the pile. In addition, the requirement of the large energy results in a high construction cost.

The damage of a pile is also resulted from the striking of the pile against an obstruction in the soil. To avoid the damages, it is necessary to withdraw the pile and destroy the obstruction by using an explosive which must be placed near the obstruction. This requires an increased labor work.

An object of the invention is to provide a method for driving a heavy pile into the hard soil without applying a large energy.

Another object of the invention is to provide a method for driving a heavy pile with minimum damage caused.

Further object of the invention is to provide a method of driving a pile against an obstruction without much labor work.

The foregoing and other objects can be achieved in accordance with the invention through the provision of a method of driving a shell together with a core wherein the improvement comprises (a) coupling a doubleacting hydraulic actuator to the shell and the core in such a manner that its cylinder is axially movably mounted to the top side of the shell in a coaxial relationship and its piston is connected to the core (b) delivering the driving blows on the top side of the cylinder and (c) operating the hydraulic actuator simultaneously with the delivery of the driving blows, whereby the cylinder and the piston are alternately moved against one another and the driving blows are transmitted to the shell and the core for penetrating the shell and the core alternately With alternately penetrating the shell and the core, the required driving force against the soil resistance can be reduced.

In accordance with the invention, a vibratory unit can be provided at the lower portion of the pile to facilitate the penetration against the obstruction.

The presently preferred exemplary embodiment will be described in detail with reference to the following drawings.

Figures 1 to 4 illustrate the different positions of the hydraulic actuator relative to the shell and the core during driving the shell and the core in accordance with a preferred embodiment of the invention; and Figure 5 illustrates the driving of a shell in accordance with another preferred embodiment of the invention.

Referring to the drawings, there is shown a shell 10 into which is inserted a core 11 having a conr-shaped tip passing through the open end of tne shell 1 0. At the top end of the shell 10 is provided a hydraulic cylinder 1 3 with a lower cover 1 3a, the wall of the cylinder 1 3 extending beyond the cover 1 3a and having an inwardly projecting member 1 3b at the end thereof.The core 11 is connected to the piston 11 a provided inside the cylinder 1 3. At the upper portion of the shell 10 is secured an annular guide member 1 4 which has a flange 1 4a adapted to be engaged with the inwardly projecting member 1 3b, thereby axially movably mounting the cylinder 1 3 to the upper portion of the shell 10. There are further provided ports 1 5 and 1 6 in the wall of the cylinder 1 3 respectively communicating with two variable volume chambers 1 7 and 18 divided by the piston 11 a. At the bottom side of the core 11 is provided a vibratory unit 20 and an expansion unit 21.The expansion unit 21 may be an inflatable article which can be expanded by introducing a fluid and contracted by removing the fluid.

In accordance with the invention, the shell 10 is driven into the ground together with the core 11 by operating a known pile hammer 19 which delivers the driving blows on the top side of the cylinder 13, the hydraulic actuator and the vibratory unit.

As shown in Fig. 1, the fluid is supplied into the chamber 17, when the piston 11 a is at the upper portion of the cylinder 1 3. At this moment, the inwardly projecting member 1 3b is engaged with the annular guide member 1 4. The fluid pressure only actuates the piston to move downward since the cylinder 1 3 is prevented against the upward movement by the annular guide member 14 fixed to the shell 11 which is held against movement in the soil by the friction. When the piston 11 a is at the lower portion of the cylinder 13, the expansion unit 21 is expanded to increase the friction between the core 11 and the soil so as to hold the core against movement, as shown in Fig. 2.Then the fluid is supplied into the chamber 1 8 through the port 1 6 and the fluid in the chamber 1 7 is withdrawn.

Since the piston 11 a is held against the movement, the cylinder 1 3 moves downward and the annular projecting member 1 3b disengages from the flange 1 4a. The downward movement of the cylinder 1 3 stops when the cover 1 3a abuts against the top of the shell 10. The successive supply of the fluid into the chamber 18 forces the shell 10 which is in abutment with the cover 1 3a into the ground.

When the shell 10 is driven into the ground to a certain depth, the position of the piston 1 a is again at the upper portion of the cylinder 13, as shown in Fig. 4. At this moment, the expansion unit 21 is contracted again and the fluid is supplied into the chamber 1 7 again as shown in Fig. 1.

The driving hammer 1 9 is operated simultaneously with the operation of the hydraulic actuator. The driving blows are delivered on the top side of the cylinder 1 3 at regular intervals and the hydraulic actuator transmits the driving force to the shell and the core alternatively. The driving blows that are delivered on the top side of the cylinder 1 3 are transmitted to the shell 10 when the lower cover 1 3a is in abutment with the the top side of the shell 10 and is transmitted to the core 11 any time else. It can be appreciated that the hydraulic actuator not only transmit the driving force to the shell and the core but also develops the depth penetrated.

The vibratory unit 20 facilitates the penetrating of the core 11 and even assists the core to penetrate through the obstruction. It is operated when the core 11 is moved downward.

When the shell 10 is properly located in the soil, the core and the hydraulic actuator can be removed from the shell and reused for other piles.

The method according to the invention has an advantage that the shell and core can be penetrated into the ground against the soil resistance more easily than the conventional method. It can be appreciated that the shell is penetrated only against the resistance of the surrounding soil and the core is penetrated only against the resistance of the soil around the tip of the core and thus the driving force required for alternatively penetrating the shell and the core is less than that required for penetrating the shell and the core at the same time. In addition, the method can minimize damages caused to the pile and shock induced upon impact. This method can be effectively applied to the installation of a large pile in the compact or hard soil which needs a large driving energy.

As shown in Fig. 5, if a large pile is installed in the soil which is not very hard, the large diameter shell P1 can be driven into the soil together with an assembly which includes a core P3 and one or more concentric pipes P2 sleeved onto the core P3 with the smaller one extending beyond the larger one at the lower side of the shell P1. The core P3 has a cone-shaped tip extending beyond the small pipe P3. By this assembly, the large diameter shell P1 can be provided with a gradually converging penetration end for ease of penetrating into the ground and the obstruction. In this case, the shell P1, pipe P2 and the core P3 are driven into the ground at the same time. The core assembly are withdrawn when the shell is located.

With the invention thus explained, it is apparent that obvious modifications and variations can be made without departing from the scope of the invention. It is therefore intended that the invention be limited only as indicated in the appended claims.

Claims (6)

1. In the installation of a pile, a method for driving a shell into the ground together with a core by a driving hammer wherein the improvement comprises driving the shell and the core alternately into the ground.

2. In the installation of a pile, a method for driving a shell into the ground together with a core (a) coupling a double-acting hydraulic actuator to the shell and the core in such a manner that its cylinder is axially movably mounted to the top side of the shell in a coaxial relationship and its piston is connected to the core (b) delivering the driving blows on the top side of the cylinder and (c) operating the hydraulic actuator simultaneously with the delivery of the driving blows, whereby the cylinder and the piston are alternately moved against one another and the driving blows are transmitted to the shell and the core for penetrating the shell and the core alternately.

3. A method as claimed in Claim 2, further comprisng providing a vibratory unit at the lower end of the core to facilitate the penetration.

4. A method as claimed in Claim 1, further comprising providing a volume variable member at the bottom side of the core.

5. In the installation of a pile, a method for driving a large shell into the ground comprising: driving the large shell together with a core assembly which includes a core and one or more concentric pipes sleeved onto the core with the smaller one extending beyond the end of the larger.

6. A method of driving a shell into the ground substantially as described herein with reference to the accompanying drawings.