GB2157751A

GB2157751A - Driven piling system

Info

Publication number: GB2157751A
Application number: GB08508296A
Authority: GB
Inventors: Paul Kiss
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-03-30
Filing date: 1985-03-29
Publication date: 1985-10-30
Also published as: GB8508296D0; GB8408345D0

Abstract

The driven piling system facilitates the driving of a relatively inexpensive permanent casing. The casings 4,8, follow the annular hole created by a circular washer 10, which in turn is driven by a driving assembly 101. Energy is delivered to the driving assembly via pneumatic hammer 1 and the process is continued until no further penetration into the group is possible. Removal of the driving assembly allows soil testing through the central aperture in washer 10. A base is then formed at the end of the pile by withdrawing the driving assembly, introducing and driving a cement/sand mixture through the base of the pile 15, with the driving assembly. Concrete is then poured into the casing, and steel reinforcement may also be installed. <IMAGE>

Description

SPECIFICATION Driven piling system This invention relates to an improved driven piling assembly and to a piling process using that assembly.

Piles are long sections of material, usually timber, steel or concrete, which are driven into or constructed within the ground to provide stable foundations for various types of construction. There are currently many methods of constructing piles and they generally fall into two main categories. Driven piles involve the driving or hammering of sections into the ground, while bored piles involve boring holes into the ground and then filling the holes with concrete and/or steel.

Methods using driven piles have the advantage of relative speed, the production of no spoil, and greater ease of use in unstable ground since an empty hole into which soil may fall back is never present. On the other hand, the driven pile must be constructed of robust and therefore expensive material since the pile must be able to transmit the driving force throughout its length. Bored piles, through normally cheaper, lack the mentioned advantages of driven piles. The bored piles method does however have the important advantage of allowing the nature of the soil being driven through to be sampled and obstructions to be detected and avoided.

It has now surprisingly been found that an assembly and method of the present invention allows the advantages of the driven pile to be enjoyed while allowing the pile to be formed of less robust, relative inexpensive material.

The present invention also allows the opportunity of sampling the supporting soils to the pile as in the bored piling system whilst avoiding the disadvantages of that system.

According to the present invention we provide a driven piling assembly comprising a hollow pile casing open at its lower end, a transverse annular member aligned across the lower end of the pile casing and a driving head adapted to pass within the casing, wherein the driving head comprises a portion adapted to pass through, close, and engage the annular member during driving and in which a dolly connected to the driving head via driving rod(s) is arranged to bear on the upper end of the casing with sufficient pressure to maintain contact between the lower end of the casing and the annular member during driving where the annular member is separable from the casing. The annular member may form an integral part of the piling casing, but preferably the annular member is separate, e.g. in the form of a separate metal washer.

Preferably in assemblies of the invention the annular member extends outwardly of the circumference of the pile casing to form a peripheral shoulder.

The pile may be formed of plastics or of thin metal (as hereinafter defined). It is preferred that the pile is formed of a corrosive resistant plastics or another non-corrosive material. The annular member is preferably provided with a central aperture dimensioned to allow access for soil-sampling and assessment of the pile load carrying capacity.

Apart from the mentioned advantages of the ability to use inexpensive "non-performance" plastics and other materials and the ability to carry out sampling, the present invention may allow the construction of a pile with all of the driving energy being transmitted to the driving head/and supporting soil, thereby maximising the efficiency of the system. A further important advantage of all of the driving energy being transmitted to the driving head/and supporting soil by the assembly of this invention is that surface vibration is thereby minimised.

The present invention further provides a method of forming a pile comprising positioning a piling assembly of the invention in the desired position, driving the assembly into the ground to the desired depth, removing the driving head, introducing a sand/cement mixture or concrete mixture into the pile casing, re-introducing the driving head and driving the sand/cement mixture or concrete mixture downwards to partially exit from the bottom of the pile, again withdrawing the driving head and finally introducing the desired reinforcement into the pile.

In a preferred method a soil sample is taken through the aperture in the annular member prior to the introduction of the said sand/cement mixture or concrete mixture.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a vertical sectional view of the driving and pile case assembly.

Figure 2 is a vertical sectional view of soil being sampled within the pile case.

Figure 3 is a vertical sectional view of the formation of the pile base.

Figure 4 is a vertical sectional view of the complete pile section.

With reference to Fig. 1, the piling process is started by placing a steel washer 10, on the ground surface. A first driving rod 7 is coupled to the driving head 9. A first pile casing 8, is then positioned with its outer periphery aligned with the periphery of the washer 1 0.

Preferably the diameter of the casing is slightly smaller than the diameter of the washer so that a small shoulder 1 0a is present. A dolly 2, is put into position at the top of the first driving rod 7 with its outwardly extending shoulder 2a resting on the upper end of the pile casing 8. A pneumatic hammer 1, is placed on the dolly 2 and used to drive the assembly into the ground. The driving head 9 has a pointed ground-penetrating portion 9a which, serves to break any obstructions while the washer 10, forms an annular hole which allows the casing 8, to follow with a relatively light pressure from the dolly 2.

When the dolly has reached ground level, the pneumatic hammer 1 and dolly 2 are withdrawn. A second driving rod 3 is next placed onto rod 7 and is located with transverse pin 5 and a second casing 4 is then attached telescopically over the first casing 8 at its lower extended-diameter shouldered region 6.

Sacrificial mild steel striking inserts 11 between dolly 2 and the first driving rod 7, between driving rods 3 and 7 and between any subsequent driving rods are used to absorb shock from the system thereby minimising deterioration of the main components. The process is repeated adding successive driving rods, inserts and casings until no further penetration into the ground is possible; this is known as "refusal". Traditional dynamic formulae allow the calculation of the load carrying capacity of the pile, given the energy rating of the pneumatic hammer.

After refusal has been reached, the driving rods are withdrawn. Fig. 2 illustrates how sampling of the soil supporting the pile may be facilitated. A sample tube 14, is passed into the soil through the aperture of the washer by using a system of connecting sampling rods 1 2. A sample may then be retracted and taken for analysis to check the load carrying capacity of the pile.

Fig. 3 illustrates the next stage of the piling process. A sand and cement mixture 15, is introduced into the pile casing. A bulb 1 5a of the sand and cement mixture extending from within the lower end of the casing 8 into a region beneath the casing is formed by reintroducing the driving assembly 10 comprising driving head 9, driving rod 3 and the intervening components and re-driving with the pneumatic hammer.

Fig. 4 illustrates the final constructional stage. Concrete 17, is poured into the pile casing and where necessary a steel reinforcement 18, is introduced.

In this specification terms such as "lower" refer to the orientation of the piling assembly when it is positioned for use. The casing may be formed of "thin" metal, that is to say metal of a lesser thickness than that required in a conventional pile casing subjected to direct blows from a driving head.

Claims

1. A driven piling assembly comprising a hollow pile casing open at its lower end, a transverse annular member aligned across the lower end of the pile casing and a driving head adapted to pass within the casing, wherein the driving head comprises a portion adapted to pass through, close, and engage the annular member during driving, and in which a dolly connected to the driving head via driving rod(s) is arranged to bear on the upper end of the casing with sufficient pressure to maintain contact between the lower end of the casing and the annular member during driving where the annular member is separable from the casing.

2. A piling assembly according to claim 1 in which the annular member is in the form of a separate metal washer.

3. A piling assembly according to claim 1 or 2 in which the annular member extends outwardly of the circumference of the pile casing to form a peripheral shoulder.

4. A piling assembly according to any of claims 1 to 3 in which the pile is formed of plastics or of thin metal (as hereinbefore defined).

5. A piling assembly according to any of claims 1 to 4 in which the pile is formed of a corrosive resistant plastics or another noncorrosive material.

6. A piling assembly according to any of claims 1 to 5, in which the annular member is provided with a central aperture dimensioned to allow access for soil-sampling and assessment of the pile load carrying capacity.

7. A method of forming a pile comprising positioning a piling assembly of any of claims 1 to 6 in the desired position, driving the assembly into the ground to the desired depth, removing the driving head, introducing a sand/cement mixture or concrete mixture into the pile casing, re-introducing the driving head and driving the sand/cement mixture or concrete mixtue downwards to partially exit from the bottom of the pile, again withdrawing the driving head and finally introducing the desired reinforement into the pile.

8. A method according to claim 7 in which a soil sample is taken through the aperture in the annular member prior to the introduction of the said sand/cement mixture or concrete mixture.

9. A method according to claim 7, substantially as hereinbefore described with reference to Figs. 1 to 4 of the drawings.

10. A piling assembly substantially as hereinbefore described with reference to Figs.

1 to 4 of the drawings.