AU680296B2 - Piling bell - Google Patents

Description

1 PILING BELL Field of the Invention The current invention relates to devises for driving piles and posts into the ground, and in particular relates to a piling attachment designed to replace the moil or mandrel in an hydraulic hammer attachment of an excavator or similar.

Background of the Invention In modern engineering practice, the use of piles in the ground is an expedient method used to improve a naturally poor foundation. By the use of piles, structural loads are transmitted to lower levels of ground strata, generally via friction, but sometimes by bearing or a combination of both. A piled foundation is often a requirement of the building codes where unsuitable ground strata fails to provide the required level of support to foundations and footings. This is done to prevent the settling or collapse of structures due to insufficient foundation support and ensure even and equal settling of a structure after construction.

There are several distinct types of piles used in construction; timber, precast concrete, cast-in-place concrete, steel piles and sheet piles. Two ether types of piles less frequently used are screw piles and disc piles.

Piles are the conventional and economical method of providing the level of support required for the foundations and footings of various structures when ground Sstrata support is found to be deficient.

So There are two common ways to utilise piles on a building site. The first is to °use the cumbersome drop hammer system to drive a few large piles into place to 0o support foundations and footings. This method requires much heavier foundations and o 25 footings because of the small number of large piles usually placed, creating the need to structurally span between piles with the structure of the footings or foundations, oo .0 The second method is to use numerous small piles in all areas of the foundations and footings. This method is more economical because of the integrated support provided by numerous piles and therefore requires far less engineering and materials in S 30 foundations and footings.

o Piles are usually driven into place by the application of force to the head of the pile in a manner similar to that of hammering in a spike. That is, a large amount of kinetic energy is applied to a small area, the head of the pile, for a short period of time, :0.00 usually fractions of a second. This energy is transferred along the length of the pile, resulting in the pile forcing its way into the ground strata by a combination of impact, vibration and fluid movement of the particles of soil or sand comprising the ground.

By applying a measured or known quantity of kinetic energy to the pile, once the pile ceases to advance into the ground strata a known and suitable level of -foundation support can be achieved.

[N:\LIBLLOO829:JVR 2 Methods of applying this kinetic energy to the pile are varied and include, drop hammer, diesel hammer, compressed air or steam hammer, tractor or vehicular mounted hydraulic hammer with jury rigged plate, and hydraulic ram.

The drop hammer is the original form of pile driving and is basically a large weight raised to a height on a constructed tower above the head of the pile, then released. The gravitational effect upon the weight causes it to gain speed, kinetic energy, as it drops towards the head of the pile. At the moment of contact with the head of the pile, the weight instantly ceases to travel in a downward motion, and most of the kinetic energy accumulated through the gravitational effect upon the weight is transferred to the pile, resulting in that pile being driven into the ground strata. The disadvantages of a drop hammer are, it is slow and cumbersome to use and to move to a new pile site once a pile has been successfully driven. It imposes a severe shock loading to the head of the pile and frequently damages piles during this process.

A diesel hammer gains kinetic energy from the compression of diesel fuel oil and air within a chamber in the head of the hammer to the point that spontaneous combustion ignites the mixture creating energy between the hammer head and the head of the pile. The physical action upon the pile is the same as for the drop hammer.

Additional disadvantages are that the operation of a diesel hammer creates environmentally unacceptable fumes and noise and is therefore unsuited to urban areas where the need for pile driving is greatest. It too is cumbersome to operate and to move from pile head to pile head on a construction site.

j A compressed air or steam hammer creates the required driving energy by the 0 0 injection of compressed air or steam into the hammer chamber, the rest of the operation is the same as with the drop hammer and the diesel hammer. It too suffers from the o 00o 0 00 25 same environmental problems as does the diesel hammer and has the added problem of 0 a noisy compressor or steam generator. It too is cumbersome to operate and move from pile head to pile head. Most compressed air or steam hammers are constructed on 00 floating barges and used extensively in bridge or harbour construction.

A tractor or vehicular mounted hydraulic hammer is actually a jury rigged steel o 0000 30 plate attached to the hydraulic hammer moil and attached with steel chains This type of operation is easier to move from pile head to pile head, but is very dangerous to operate because of the failure rate of the jury rigged components. It has the advantage of manoeuvrability and flexibility and is relatively efficient on level sites. The danger factor increases dramatically on uneven building sites.

Hydraulic rams and drivers are usually used on screw and disc piles, or to drive very small piles. This equipment is not very effective with the normal range of pile sizes used on construction sites and the basic equipment cost is high.

IN:\LIBLL100829:JVR 3 More stringent building codes, tougher budgetary requirements and the ever increasing building height, even in small communities, has highlighted the need for an efficient, economical method for Jihe driving of piles on building sites.

A major disadvantage of conventional single blow pile hammers as described above, are the stresses created during driving. The single blow, or hammer type of pile driver, which represents most pile drivers with the exception of hydraulic rams, vibration drivers and the piling bell, the subject of this patent document, is that the action of applying a single blow to the head of the pile to drive it creates destructive forces with in the pile which can actually destroy the pile. Because the length of the pile is many times larger than its diameter, stress waves travel longitudinally. The pile too does not behave as a concentrated mass, but more as an elastic bar which is capable of compression and expansion as the waves of energy transverse the length of the pile.

When these energy waves are compressive, they cause the pile to penetrate the ground, but when the soil at the tip of the pile is soft, the energy wave instead of travelling out into the surrounding ground, can be reflected back up into the pile away from the pile soil interface in the form of a tensile wave, which if not cancelled out by a compressive energy wave, a net tension or compression may develop for an instant which can be sufficient to crack or splinter a pile.

Thus the behaviour of the pile both as a structurally sound entity, and its ability to penetrate soil during driving are intimately related to the mechanics of stress wave transmission within the pile and also at the pile soil interface. The creation of these stress waves are a direct result of the mechanical action of the pile driver which 0 0 aare linked to or dependant upon the ability of its operator to control those energy waves 0 and stresses.

0 0 Summary of the Invention 0 It is the object of the present invention to overcome or substantially ameliorate 0 the above disadvantages.

There is disclosed herein a piling attachment adapted to replace a moil or mandrel in an hydraulic hammer attachment, or other vibrating or hammering device o operatively associated with an excavator or other suitable mechanical device, thereby enabling utilisation of an hydraulic or mechanical or vibrating action of said mechanical device to drive piles or posts into the ground, said piling-Jtcomprising: a shaft adapted to be secured at least partially within a moil or mandrel recess of said vibrating or hammering device, a piling head integrally formed with or fixedly secured to an end of said shaft and adapted to engage a head of a said pile or post.

IN:\L8ILL00829:JVR 0 00 00 0 o0 noo aooo o b Q o e o1 a o o o os a oor Do oc oo a u Io k 4 The piling head is typically adapted to envelope said head of said pile or post, said piling attachment head having a closed end from which said shaft extends and an open end for enveloping said pile or post head..

The enveloping piling head may be generally cylindrically, Lox or semispherically shaped.

The piling head may further comprise slots adapted to receive sheet piles which are wider than a width of said piling head open end.

Alternatively, the piiing head may comprise a flat plate.

The piling attachment, or piling bell, of the preferrec embodiment, when attached to an excavator, is a versatile pile or post driver, capable of driving in excess of 100 piles per day on level terrain, compared to about 30 piles per day by a drop hammer pile driver, used on the same level terrain. When operated on uneven or sloping terrain, the efficiency difference between the preferred piling bell and other pile driving equipment is even greater, because of the mobility and flexibility of the excavator equipment in moving around r,,ost construction terrain, which, when combined with the designed ease of operation and efficiency of the piling bell, delivers efficiency and cost savings of some magnitude to the operator or contractor.

The piling bell of the preferred embodiment is a much safer pile driving mechanism to use than other pile driving equipment currently available, because there are no moving or attached parts to break off or disintegrate. The operator has no need to be near the driving head during operation, and even if the operator or an assistant were to approach the equipment during the operating cycle, it is almost impossible to place hands or limbs or objects between the driving platen and the head of the pile because the piling bell completely envelopes the pile head.

25 The driving action of the piling bell of the preferred embodiment is different from other pile drivers because it utilises the rapid hammer action of the hydraulic hammer attachment of an excavator, which, because of the short duration between impacts, 1/10 of a second to 1 second on average, vibrates the pile into the ground as well as driving it, a unique combination of forces which enhance the pile driving 30 process and cance out the dangerous build up of tensile and compression stress waves reflected back from the pile ground interface, a major problem with slower hammer and X diesel hammer pile drivers, resulting in the pile being driven more smoothly into the ground with less damage to the piles in the process, and maintaining better suspension of ground particles instead of compacting them and causing less vibration to surround ground strata and nearby standing structures, resulting in less ground heave at the pile sites, a major consideration when clusters of piles are required.

The piling bell of the preferred embodiment, when used on an excavator, allows piling to be performed on construction sites after all excavation trenches have been dug, a major benefit over other systems, which require that all excavations be [N:\LIBLLIOO829:JVR -h I i. i made after pile driving has been completed, a task requiring that the major digging effort be performed by manual labour because machinery cannot manoeuvre between pile heads easily. The preferred piling bell, however, can perform pile driving on sites after excavations have been completed by excavators, thus saving a significant amount of time and labour over other pile driving systems.

The piling bell of the preferred embodiment is capable of being used over swampy ground, water, sand, mud, or on barges directly over water, and can be positioned into difficult access areas, such as unstable ground structures, steeply sloping ground, and can work over and around obstacles or existing structures, inside trenches or holes and can be operated below the level of the excavator or other supporting machinery.

The preferred piling bell can drive piles at angles other than vertical and is capablc of driving piles horizontally, a task that no other conventional pile driving equipment known to the current inventor is capable of.

The efficiency of the piling bell of the preferred embodiment is only equalled by hydraulic rams and vibrating machinery, both of which are dedicated purpose machinery costing hundreds of thousands of dollars Australian, whereas the piling bell is an attachment implement to existing machinery and cost would represent only a small fraction of the cost of a dedicated machine.

The piling bell of the preferred embodiment is capable of being used as an efficient and cost effective method of driving posts used retaining walls or fences into place.

The piling bell of the preferred embodinment is restricted in the pitch length of the pile being driven only be the physical dimensions of the excavator or other machinery being used, and the capacity of the piles driven is only restricted by the driving energy of the hydraulic hammer used.

The piling bell of the preferred embodiment is capable of being modified, without changing or affecting the basic concept, to suit larger or smaller powered and sized machinery as and when they become available.

Brief Description of the Drawings In order that this invention, the piling bell, may be more clearly understood, reference is hereto made to the accompanying drawings which illustrate particular preferred embodiments of the invention by way of example, and in which: Fig. 1 is a perspective view showing the external layout of the piling bell in accordance with the invention, and it is important to note that the details of the shaft can be changed to suit particular models of hydraulic, mechanical or vibratory hammers without in any way affecting the operating principle of this invention, the piling bell.

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o D u o o 0 au [N:\LIBLLIO0829:JVR Ii 6 I Fig. 2 is a view showing the piling bell installed in position in place of the moil in the hydraulic hammer attached to the excavator boom, and positioned in a normal operating position on top of a vertical pile.

Fig. 3 is a view showing a cut-away section of the helmet piling bell showing the platen area with the head of a pile in place.

i i Description of the Preferred Embodiment Referring first to Fig. 1, the piling bell of the preferred embodiment comprises a bell like piling head I with an attached shaft 2, with retailning rebates towards the head of the shaft 3. At the open end of the piling head 1 is a lip 4. Inside the open end of the piling head 1 is a flat platen area 5 which acts as a pile/piling head interface.

Another platen area 6 is provided at the top of the shaft 3 acting as the shaft/hydraulic hammer interface.

The piling bell may be machined and formed integrally as a single piece or constructed of separate shaft and piling head pieces and fixedly secured by joining at the junction 7 by means of a strong and fixed joint such as threads and sockets, welding or other adhesive or joining methods so at to form a single piling attachment.

In Fig. 2, a perspective view of the piling bell is shown, with the piling bell in situ in the moil recess in an hydraulic hammer 9 attached to the boom 12 of an excavator. Wedges 8 lock the shaft 2 into place at the bottom of the hydraulic hammer 9 which is attached to the excavator boom 12, and is connected to the excavator machinery via the hydraulic hoses and rams 10. The assembly is depicted at the top of a pile 11 which is being driven into the ground 13. Kinetic energy created within the pile works against the pile/ground interface 14.

In Fig. 3 a cut-away view of the piling bell is shown, with the platen area defining the pile/piling head interface visible with the head of a pile 11 in place in contact with the platen area 5 such that the bell shaped piling head envelopes the pile 11 head. Other similar enveloping shapes such as a cylinder, box or semi-spherical shape may be used in place of the bell shape to accommodate different types of piles and posts or situations. Alternatively, the piling head may be in the form of a flat plate engaging a pile on a flat surface of the plate.

The piling bell is here machined from a forged and heat treated alloy with properties which will tend to resist fracturing, metal fatigue, distortion, wear and tear and the stresses involved in pile driving. Other suitable materials with similar proerties may also be utilised.

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Claims (9)

1. A piling attachment adapted to replace a moil or mandrel in an hydraulic hanmmer attachment, or other vibrating or hammering device operatively associated with an excavator or other suitable mechanical device, thereby enabling utilisation of an hydraulic or mechanical or vibrating action of said mechanical device to drive piles or posts into the ground, said pilingeidl comprising: a shaft adapted to be secured at least partially within a moil or mandrel recess of said vibrating or hammering device, a piling head integrally formed with or fixedly secured to an end of said shaft and adapted to engage a head of a said pile or post.

2. The piling attachment of claim 1 wherein said piling head is adapted to envelope said head of said pile or post, said piling attachment head having a closed end from which said shaft extends and an open end for enveloping said pile or post head.. 4) o 'o o p p0a

3. The piling attachment of claim 2 wherein said piling head is generally bell shaped.

4. The piling attachment of claim 2 wherein said piling head is generally cylindrically shaped.

The piling attachment of claim 2 wherein said piling head is generally box shaped.

6. The piling attachment of claim 2 wherein said piling head is generally semi-spherically shaped.

7 The piling attachment of any one of claims 3 through 6 wherein said piling head further comprises slots adapted to receive sheet piles which are wider than a width of said piling head open end.

8. The piling attachment of claim 1 wherein said piling head comprises a flat plate.

9. A piling attachment substantially as hereinbefore described with reference to the accompanying drawings. Dated 7 April, 1997 Mihen Constructions Pty Ltd O oo a Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON [N:\LIBLLIO0829:JVR