GB1566096A

GB1566096A - Method of and means for driving and sinking piles

Info

Publication number: GB1566096A
Application number: GB1994478A
Authority: GB
Original assignee: DOO KWOK CHUEN
Current assignee: DOO KWOK CHUEN
Priority date: 1978-05-16
Filing date: 1978-05-16
Publication date: 1980-04-30

Description

(54) AN IMPROVED METHOD OF AND MEANS FOR DRIVING AND SINKING PILES (71) 1, Doo KWOK CflUEN, a British subject, of 14 Man Fuk Road, 4th Floor G Flat, Kowloon, Hong Kong, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particu marly described in and by the following statement This invention concerns a modification of the improved method of and means for driving and sinking piles as claimed in Patent Specification No. 1,457,125.

According to said Patent Specification No.

1,457,125 there is provided a method of and means for driving and sinking a pile that consists in forming the pile from a required number of hollow co-axial units of concrete or other suitable material arranged end-to-end about an inner tube of metal or other suitable material that is closed at its upper outer end by a removable lid and left open (i.e. not provided with a closure) at its lower end, the said inner tube having an outside diameter slightly less than the inside diameter of said units so as to leave an annular space between the units and said inner tube whereby said tube is allowed to make a floating or cushioning movement when pile driving during which displaced material of the penetrated ground crushed by the tube and loosened by contained liquid passes into the tube through the lower open end of the latter as the units enter the ground and compresses air trapped in the inner tube between the said displaced material and the closed top of the tube, removing said tube together with the contained ground material and filling the resulting hollow interior of the units with concrete.

The primary object of the modification provided by the present invention is to relieve any excessive air pressure that may occur during pile driving in the inner tube between the displaced material that enters the open lower end of the inner tube and the lid closing the upper end of said inner tube thereby enabling a pile to be driven in an efficient manner without changing equipment to suit different characteristics of different levels of strata.

According to the present invention there is provided a method of and means for driving and sinking a pile as claimed in Patent No.

1,457,125 that is characterised in that said lid is fitted with a valve that permits air at a predetermined pressure compressed below said lid to pass therethrough to the space the lid so as not to resist continued sinking of the pile.

To enable the invention to be clearly understood preferred embodiments thereof will now be described by way of example with reference to the accompanying drawings wherein Figure 1 is a vertical section of the apparatus, Figure 2 is an enlarged sectional view of the upper end of the apparatus having the said lid and valve.

Figure 3 is a view to a greatly enlarged scale illustrating said valve, Figures 4, 5, 6 and 7 are diagrammatic views illustrating a sequence of operations performed with the apparatus of Figures 1 to 3 during which a reduced displacement of the soil is achieved, Figures 8, 9, 10, 11, 12 and 13 are diagrammatic views illustrating another sequence of operations performed with the apparatus of Figures 1 to 3 during which a greater displacement of soil is achieved, and Figures 14 to 21 are diagrammatic views illustrating a sequence of operations performed with the apparatus of Figures 1 to 3 that enables a plurality of closely related piles to be sunk to form collectively a permanent screen-like part of a building without lateral displacement of soil occurring that would normally have an adverse effect on the stability of the piles.

Referring firstly to Figures 1 to 3, the pile comprises a required number of precast circular hollow concrete units 1 of a length that will enable them to be handled easily.

These units 1 are arranged co-axially end-toend so as to constitute in effect a continuous hollow structure within which is located a steel tube 2 having an outside diameter which is about one half-an-inch less than the inside diameter of the circular concrete units 1 so as to leave between itself and said units an annular space 3 into which ground material or liquid contained by said material can pass to produce a floating or cushioning effect. A lid 4 is screwed into the upper end of the tube 2 to facilitate said floating or cushioning effect.

Preferably, the length of the tube 2 is about eighteen inches longer than the aggregate length of three of four concrete units 1.

A helmet 5 of mild steel provided with an impact cushion 6 is fitted over the upper end of the uppermost concrete unit 1. This helmet 5 serves chiefly to transmit the impact load of a driving hammer to the uppermost hollow concrete unit and this load is also transmitted to the upper end of the tube 2 when the latter touches the underside of said said helmet.

Due to the provision of said annular space 3 which becomes filled with ground material or liquid contained thereby, the tube 2 has a tendency to float as the pile sinks during a pile driving operation. The said hollow concrete units 1 may be formed with dowel bars.

The construction referred to in the previous four paragraphs is that described and claimed in my said prior Patent Specification No.

1,457,125.

It is found that the capacity of a pile is chiefly dependent on the amount of friction that exists between soil and the pile. The greater the displacement, the better the friction. In certain cases, however when the soil has been compacted nearly to its greatest limit, an excessive amount of additional displacement by the pile driven would probably destroy the structure of soil and reduce the friction. On the other hand, if the soil is so loose a constant amount of displacement made by a constant section pile does not compact the soil sufficiently to create an effective friction for the desirable total resistance.

As previously explained the primary object of the present invention is to adapt the pile driving apparatus in such a manner that according to different characteristics of stratums of the soil the apparatus can be adapted to effect instead of constant displacement of the pile; (a) a less displacement or (b) a greater displacement. The object of the present invention is achieved by fitting the lid 4 with an adjustable non-return one-way valve 7 that can be set to relieve excessive internal air pressure in the inner tube in the space 8 between the underside of said lid 4 and soil and water 9 and 10 respectively that enters the lower end of the tube 4 during pile driving.

When adapting the apparatus to effect less displacement of a pile (as illustrated by Figures 4 to 7) by a hammer 11, the valve 7 is adjusted to allow trapped air 8 to escape upwardly past the lid at a lower pressure to suit the porosity of soil encountered before closing the upper end of the steel tube 2 by the helmet 6. The air 8, water 9 and soil 10 within the tube 2 are under increased pressure while the pile 1 is continuously sunk by the impact of the external hammer 11 as a result of the penetration of soil into the bottom of the tube 2 and the reduction of the air space 8.

As soon as the air pressure reaches a predetermined pressure to which the valve has been set the valve will release excessive pressure so that the displacement thus made by the pile being driven is under control. Of course the soil has to be removed from within the tube 2 (Figure 6) from time to time, as explained in my prior Patent Specification No. 1,457,125 if the tube has been filled to a certain limit or plugged at the bottom end, by extracting it from the outer tube 1. Repeating this sinking of the pile, extracting soil andadjusting the valve when it becomes necessary, the pile can be driven in a controlled manner according to the porosity of soil penetrated.If the valve is closed or adjusted to its maximum resistance and the air space 8 becomes completely filled with water, or the bottom end of this space is plugged, no soil can penetrate into the tube 2 while continued sinking of the pile is effected. The pile then acts as an ordinary constant displacement pile. In the course of pile driving, the outer tube 1 can be driven together with the steel tube 2 or separately if necessary with an external hammer. Water 9 inside the steel tube 2 is used as a water column for softening the soil, as a filler for transmitting the pressure to the valve 7 and lubricating agent for easy discharge of soil within the tube, (see Figure 1). After the inner tube 2 has been withdrawn the column of concrete outer tube 1 is filled with a concrete mix 15 and reinforcing bars introduced as this takes place.

When the apparatus is adapted to effect a greater displacement as illustrated by Figure 8 to 13, this is commenced after the sequence of operations illustrated by Figures 4 to 6 by compacting the soil at the bottom by an internal hammer 12 to form a cavity 13. This cavity 13 is then filled with aggregate 14 and this aggregate is compacted by the internal hammer 12 (Figures 9 and 11) to enlarge the displacement.

The inner tube 2 together with the concrete units 1 constituting an outer tube are driven into the aggregate (Figure 10) the said valve 7 being adjusted so that the displacement is not excessive.

The helmet 6 is again removed and the inner tube 2 withdrawn and the aggregate plugging the lower end thereof is removed and the tube replaced and the internal hammer 12 again used (Figure 11) so as to enlarge the cavity 1 to a lower level.

Figure 12 illustrates the final stage of the pile driving determined by the settlement load as a result of the final blow of the hammer 11.

The inner tube 2 is then removed leaving the outer tube comprising the concrete units 1 empty to receive and protect concrete 15 cast therein and in which metal reinforcing bars 16 are progressively introduced.

Referring lastly to Figures 14 to 21, these illustrate a method of arranging a plurality of piles, as best illustrated at P in dotted outline in Figure 21, to form what can be termed a screen wall that becomes a permanent part of a building and resists lateral pressure of surrounding soil.

The first step as shown by Figure 14 consists in partly sinking the inner tube 2 into the soil and partly filling this tube with a grouting fluid 17 consisting of cement and water to control the displacement. The valve 7 may be made detachable from the lid 6 to permit this to be done, or the lid together with the valve may be detached from the tube 2.

Figure 15 shows how the upper portion 18 of the surrounding soil becomes well grouted but without causing failure, i.e. collapsing of the soil due to excessive displacement.

After the inner tube 2 is sunk by the hammer 11 to a greater depth (Figure 16) the bottom of the tube becomes plugged with soil 19 and outer concrete units 1 are then driven successively (Figure 17) using the inner tube 2 as a guide and the tube 2 is then withdrawn (Figure 18).

The resulting outer concrete tube 1 then has metal reinforcing bars 16 progressively inserted therein and filled with cast concrete 15 (Figures 19 and 20).

The resulting row of side-by-side piles combine to resist lateral pressure and bending as well as to support the vertical load of a building structure.

A second and closely related row of piles as illustrated in Figure 21 can then be formed in exactly the same manner as the first row without risk of disturbing one another because the displacement of soil that may vary with different stratas is always under control by appropriately adjusting the valve 7. In addition, grouting of the upper portion of the soil serves to resist any detrimental disturbance of the surrounding soil. As shown, the piles in the second row are positioned opposite the spaces between the piles of the first row.

The piles and grouted soil in combination form a screen if the soil at one side thereof is excavated and a concrete mass 20 (Figures 19, 20 and 21) at the upper end of the piles constitute a horizontal strengthening beam bridging the piles.

It is to be appreciated that the particular arrangement of piles illustrated by Figures 19, 20 and 21 is given merely by way of example and that the piles may be arranged in any required formation to suit different lay outs.

Any suitable form of non-return valve 7 may be fitted to, or incorporated, in, the construction of the lid 4, that illustrated in Figure 3 comprising a pair of springs 7a acting respectively one below the lid 4 and the other above a closure disc 7b that co-acts with a seating 7c. The required force exerted by the springs 7a can be preset by adjusting a nut 7d.

The terms "displacement of the pile" used herein means displacement of the soil the pile has made and "a displacement pile" means a kind of pile of which the resistance depends on the displacement of soil it has made.

The said valve can be said to have a "high yield" when the spring of the valve is set to a high valve so that it can contract or expand only under high pressure, and "low yield" when it is set to a low value so that it can contract or expand easily under low pressure.

When dealing with loose soil the valve can be set to a low yield because the displacement of soil is easily achieved, whereas when the soil has already been well displaced and compacted the valve must be set to a high yield if a further small displacement is required.

Thus the valve is set to high yield for making high internal pressure and low yield for low pressure, the amount of displacement depending of course both on the pressure exerted and the physical properties of the soil.

WHAT I CLAIM IS;- 1. A method of and means for driving and sinking piles as claimed in Patent Specification No. 1,457,125, characterised in that said lid is fitted with a valve that permits air at a predetermined pressure compressed below said lid to pass therethrough to the space above the lid so as not to resist continued sinking of the pile.

2. The method and means claimed in Claim 1, wherein said valve is an adjustable one-way non-return valve.

3. The method and means claimed in Claims 1 and 2, that consists in adjusting said valve to reduce the displacement of the pile and soil at each impact of the pile driving hammer substantially as herein described with reference to and as illustrated by Figures 4 to 7 of the accompanying drawings.

4. The method and means claimed in Claims 1 and 2, that consists in adjusting said valve to increase the displacement of the pile and soil at each impact of the pile driving hammer substantially as hereinbefore described with reference to and as illustrated by Figures 8 to 13 of the accompanying drawings.

5. The method of and means claimed in Claim 4, that further consists in compacting

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. pile driving determined by the settlement load as a result of the final blow of the hammer 11. The inner tube 2 is then removed leaving the outer tube comprising the concrete units 1 empty to receive and protect concrete 15 cast therein and in which metal reinforcing bars 16 are progressively introduced. Referring lastly to Figures 14 to 21, these illustrate a method of arranging a plurality of piles, as best illustrated at P in dotted outline in Figure 21, to form what can be termed a screen wall that becomes a permanent part of a building and resists lateral pressure of surrounding soil. The first step as shown by Figure 14 consists in partly sinking the inner tube 2 into the soil and partly filling this tube with a grouting fluid 17 consisting of cement and water to control the displacement. The valve 7 may be made detachable from the lid 6 to permit this to be done, or the lid together with the valve may be detached from the tube 2. Figure 15 shows how the upper portion 18 of the surrounding soil becomes well grouted but without causing failure, i.e. collapsing of the soil due to excessive displacement. After the inner tube 2 is sunk by the hammer 11 to a greater depth (Figure 16) the bottom of the tube becomes plugged with soil 19 and outer concrete units 1 are then driven successively (Figure 17) using the inner tube 2 as a guide and the tube 2 is then withdrawn (Figure 18). The resulting outer concrete tube 1 then has metal reinforcing bars 16 progressively inserted therein and filled with cast concrete 15 (Figures 19 and 20). The resulting row of side-by-side piles combine to resist lateral pressure and bending as well as to support the vertical load of a building structure. A second and closely related row of piles as illustrated in Figure 21 can then be formed in exactly the same manner as the first row without risk of disturbing one another because the displacement of soil that may vary with different stratas is always under control by appropriately adjusting the valve 7. In addition, grouting of the upper portion of the soil serves to resist any detrimental disturbance of the surrounding soil. As shown, the piles in the second row are positioned opposite the spaces between the piles of the first row. The piles and grouted soil in combination form a screen if the soil at one side thereof is excavated and a concrete mass 20 (Figures 19, 20 and 21) at the upper end of the piles constitute a horizontal strengthening beam bridging the piles. It is to be appreciated that the particular arrangement of piles illustrated by Figures 19, 20 and 21 is given merely by way of example and that the piles may be arranged in any required formation to suit different lay outs. Any suitable form of non-return valve 7 may be fitted to, or incorporated, in, the construction of the lid 4, that illustrated in Figure 3 comprising a pair of springs 7a acting respectively one below the lid 4 and the other above a closure disc 7b that co-acts with a seating 7c. The required force exerted by the springs 7a can be preset by adjusting a nut 7d. The terms "displacement of the pile" used herein means displacement of the soil the pile has made and "a displacement pile" means a kind of pile of which the resistance depends on the displacement of soil it has made. The said valve can be said to have a "high yield" when the spring of the valve is set to a high valve so that it can contract or expand only under high pressure, and "low yield" when it is set to a low value so that it can contract or expand easily under low pressure. When dealing with loose soil the valve can be set to a low yield because the displacement of soil is easily achieved, whereas when the soil has already been well displaced and compacted the valve must be set to a high yield if a further small displacement is required. Thus the valve is set to high yield for making high internal pressure and low yield for low pressure, the amount of displacement depending of course both on the pressure exerted and the physical properties of the soil. WHAT I CLAIM IS;-

1. A method of and means for driving and sinking piles as claimed in Patent Specification No. 1,457,125, characterised in that said lid is fitted with a valve that permits air at a predetermined pressure compressed below said lid to pass therethrough to the space above the lid so as not to resist continued sinking of the pile.

soil at the lower end of said tubes by an internal hammer to form a cavity for the reception of an aggregate which itself is compacted by said hammer and into which the inner and outer tubes are driven and the former tube subsequently removed.

6. The method of the means claimed in Claims 1 and 2, that consists in introducing grouting fluid into said inner tube so that said grouting fluid is forced into the surrounding soil to reinforce the latter and prevent collapsing thereof due to lateral pressure.

7. The method of and means claimed in Claims 1, 2 and 6 wherein a plurality of closely related piles are sunk in a required formation to form a permanent screen-like part of a building substantially as hereinbefore described with reference to and as illustrated by Figures 14 to 21 of the accom panying drawings.