GB2128233A - Method of and apparatus for constructing a water-tight underground pile wall - Google Patents

Abstract

A water-tight pile wall is formed by boring a first series of spaced apart bores in the ground, filling these with weak mortar and allowing to set to provide a series of first piles 15, and subsequently boring, between each pair of adjoining piles 15 of the first series, a respective bore of a second series of such a diameter that parts of the adjoining piles 15 are also cut away, then further cutting in the opposing, already cut away sides of the piles 15, which bound each hole of the second series, opposing longitudinal grooves, and filling the holes of the second series, and said grooves, with mortar to form second piles 16. Apparatus for use in performing the method is disclosed which comprises parallel, transversely spaced augers each of which is hollow to allow the passage of mortar therethrough and each having retractable blades in a cutting head for cutting said grooves. <IMAGE>

Description

SPECIFICATION Method of and apparatus for constructing a water-tight underground pile wall This invention relates to a method of and apparatus of constructing a water-tight underground pile wall in the form of a row of piles, in which method piles of a first series are first installed, spaced apart from each other at intervals and thereafter piles of a second series are subsequently installed, each pile of the second series being installed between a respective pair of piles of the first series the piles of said two series being interconnected with one another.

The accompanying Figure 1 illustrates, in idealised form, a known method of the above noted kind. In Figure 1, which is a view in crosssection through a pile wall, the piles of the first series are indicated at 1 and the piles of the second series at 2. In the known method illustrated in Figure 1 , the piles 1 and 2 are formed by boring holes in the ground then filling these holes with mortar. During the installation of piles 2 between previously formed piles 1, in this known method, cement paste is jetted under high pressure towards the previously formed piles 1 from the respective pile hole disposed between the piles 1 on either side of that hole, during the filling of that hole with mortar to form the respective pile 2.By means of such jetting of cement paste, the earth in the regions between that hole and the adjoining piles 1 is cut away and replaced by the cement paste which hardens to form webs 3, of width d, between each pile 2 and the adjacent piles 1.

In this known process, it sometimes happens that the previously formed piles 1 and the subsequently formed piles 2 are not formed truly vertically, and thus parallel with one another, or the piles are not formed accurately in line with one another, or the mutual spacing between piles is not accurateiy maintained, and consequently the cement paste jetted towards the adjoining piles 1 from the hole in which a pile 2 is being formed does not reach the side of one or other of the previously formed piles 1, or fails to reach it at some particular level, thus failing to form a complete web 3.

Also, it sometimes happens that because of the condition of the earth, the earth between the piles 1 is not cut away sufficiently by the jetted cement paste and a defect such as illustrated in Figure 2 arises, in which the cement paste is spread along the earth layer around the side of the previously formed pile 1 failing to form a complete web 3 connecting the piles.

Moreover, even if the earth is cut away by the jetted cement paste, it may occur that the web 3 is thin and discontinuous in places as shown in Figure 3, which is again an unsatisfactory state of affairs.

It is an object of the present invention to eliminate the disadvantages noted above with respect to conventional processes and to provide a method by which it is possible to ensure that a reliable and continuous connection is always obtained between the piles of the two series, and which nevertheless is not greatly dependent on the execution accuracy of the pile holes or upon the condition of the earth.

According to one aspect of the invention, there is provided a method of constructing a water-tight underground pile wall, in the form of a row of laterally connected piles, wherein a first series of piles is installed, then a series of bores is formed, each bore having a central axis lying between a respective pair of piles of the first series and each bore cutting into the two piles of the first series between which said axis thereof lies, each said bore, after the formation thereof, being filled with mortar to form a respective pile of a second series and to connect the adjoining piles of said first series.

Preferably, after the formation of a said bore longitudinal slots are cut in the walls thereof at diametrially opposite positions, each said slot cutting into a respective one of the two piles of the first series between which the axis of the respective bore is disposed.

Thus, in a preferred embodiment, the watertightness of a pile wall formed by a row of piles does not depend on the provision of webs extending between the piles but the row of piles is unified by the direct connection of piles with each other and by the interlocking of connected portions to enhance the water-tightness.

In this preferred embodiment, the aforesaid direct connection of the piles with each other is accomplished by subsequently installing, between piles of the first series having a low strength previously installed two by two in spaced apart relation, the piles of the second series, which overlap the previously formed piles. The interlocking of the connected portions is accomplished, in the installation of the subsequent piles, by mechanically and vertically cutting grooves in the opposing sides of the previously formed piles on either side of each pile of the second series being formed and introducing a part of the mortar filling used to form the respective pile of the second series into grooves formed in the piles on either side.

In the pile wall in the form of a row of piles constructed as described hereinbefore, the watertight properties are greatly increased by the connection of piles with each other by the overlapping interlocking arrangement of the piles described. Furthermore, since the grooves for the interlocking arrangement are mechanically cut, in any of the piles of the first series the grooves are cut with the same form and high accuracy and thus the piles are tightly and uniformly interconnected to exhibit a water-tightness that may not be obtained by the aforementioned conventional process.

It is an object of the invention, in another aspect, to provide apparatus by which the formation of the piles of the first and second series may be easily and positively accomplished.

According to another aspect of the invention, there is provided an apparatus for use in constructing an underground pile wall by the method of the invention, comprising two similar augers mounted in a common support and extending therefrom in parallel, transversely spaced relation, the spacing between the adjacent parts of the two augers being less than the diameter of each auger, each auger being mounted for rotation about its axis in said common support.

In a preferred form, the apparatus comprises two augers each having spiral flights connected around a hollow shaft of the auger, each auger having a head on both sides of which are spreadably provided cutting blades for cutting grooves in the sides of a hole formed by means of the auger In the formation of the piles of the second series, said blades are spread, and the augers are raised so that the sides of adjacent, previously formed piles of the first series are vertically cut by the blades to form grooves.

An embodiment of the invention is described below with reference to the accompanying drawings.

In the drawings, Figure 1 is a view in horizontal cross-section of a pile wall comprising a series of vertical piles interconnected by webs, formed by a method of the prior art and discussed above, for explanation of a conventional process for constructing a pile wall in the form of a row of piles; Figures 2 and 3 are respective similar views in horizontal cross-section showing defects which may arise in this conventional process; Figure 4 is a schematic front elevation view of an apparatus embodying the invention for constructing a pile wall in the form of a row of piles by a method embodying the present invention;; Figures 5, 6 and 7 are views in horizontal crosssection showing successive stages in the formation, by said method embodying the invention, of a pile wall comprising a row of vertical piles, Figure 8 is a view in longitudinal vertical section showing part of a pile wall formed by the method illustrated in Figures 5, 6 and 7, Figure 9 is a side view of the foremost end of an auger, forming part of the apparatus of Figure 4, and Figure 10 is a view in longitudinal section, and to an enlarged scale, of the end of the auger of Figure 9.

Referring first to Figure 4, reference numeral 11 denotes a construction device in which a pair of identical augers 12, having spiral flights 22 (Figure 9), extending around hollow shafts thereof, extend parallel with one another from a common driving device 13. The augers 12, mounted in device 13 for rotation about their longitudinal axes, are spaced apart transversely by an amount less than the diameter of a said auger, the diameter of a second auger being the diameter of the imaginary cylinder in which lies the outer edge of the spiral flight and the spacing between suche augers being the spacing between the surfaces of such cylinders. Blades 14, 14 are spreadably provided on both sides of each said auger head.

Figures 9 and 10 show the foremost end of a said auger 12. Reference numeral 20 denotes the auger shaft, and 21 denotes a head member joined to the lower end of the shaft and providing the auger head. The shaft 20 and the head member 21 have said spiral flights 22 disposed around the circumference thereof, and excavation bits 23 are mounted on the foremost end of the head member 21.

The shaft 20 and the head member 21 are internally provided with a longitudinal, lowpressured mortar feeding passage (not shown) having an opening port 24 located in the side of the head member 21, at the foremost end thereof.

The shaft is also internally provided with a longitudinal high pressure fluid flow passage 25, and a cylinder 26 communicating with the flow passage 25 is provided internally in the head member 21.

This cylinder 26 accommodates, sealingly slidable therein, a piston 30, a chamber defined within the cylinder 26 on the side thereof remote from the passage 25 being filled with an appropriate hydraulic fluid and being in communication with actuating cylinders 32 of plungers 31, acting on pistons in cylinders 31 and which operate the blades 14. The blades 14 are disposed at diametrally opposite sides of head 21 and each is in the form of an elongate body pivotally mounted at one end via a respective pivot pin 28 on respective bearings 27 projecting from the respective side of the head member 21 adjacent the lower end of number 21. The piston 30 is normally biased upwards by means of a spring member 29. The cylinders 32 are in the form of casings 32 inserted in the head member.

The plungers 31 engage the blades 14 on their radially inner and lower sides, at positions below the pivotal mountings 28. A communication hole 33 is provided between the plungers 31, and the cylinder 26. When the passage 25 is unpressurised, the piston 30 is urged by spring 29 into its uppermost position, the plungers 31 are retracted, and the blades 14 hang down in the positions shown in dotted lines, in which they lie within the imaginary cylinder defined by the radially outermost edge of the flights of the auger.

When fluid under pressure is supplied to passage 25, the piston 30 is urged downwardly to the position shown in full lines in Figure 10 and the hydraulic fluid below the piston 30 correspondingly pressurised, to urge the plungers 31 outwardly to act on the blades 14 and swing the blades outwardly, into the positions shown, in which their free, cutting ends project radially outwardly beyond the imaginary cylinder defined by the outer edges of the flights 22.

A pair of nozzles 34 in communication with the high pressure flow passage 25 in the shaft is incorporated into the spiral flights 22 around the shaft, the nozzles 34 extending radially, in opposite directions from the shaft 20 in the same vertical diametral plane in which the blades 14 are extendable. Thus when, as explained below fluid mortar under pressure is fed to the flow passage 25 the piston 30 is depressed, to project blades 14 and at the same time pressurised mortar is jetted out of the edges of the spiral flights through the nozzle members 34.

In use of the apparatus described to form a pile wall by a method embodying the invention, a first series of pile holes is excavated by the apparatus 11, with passage 25 being unpressurised and the blades 14 retracted. The holes of this first series of holes are formed two at a time, by the device 11, so that the spacing between adjacent holes in the series corresponds to the spacing between the two augers 12 of the device. During the drilling of each pair of holes using the device, when the augers have reached the required depth, they are withdrawn upwardly whilst mortar in a fluid condition is introduced, via the low pressure mortar passage and port 24 into each of the two holes, the mortar being of such a composition as to form, when set, piles of relatively low strength.

In this fashion a series of pile holes, and a series of piles 1 5 of said first series therein, is formed two by two.

Next, the apparatus 11 is applied, in turn, to successive pairs of regions between adjoining piles 1 5 of said first series. To this end the apparatus is positioned so that the central axes of the augers 12 extend in the common plane of the axes of three adjoining piles 1 5 with the axis of each auger 12 lying midway between the axis of the central pile 1 5 of that group of three and a respective outer pile 1 5 of the group and is lowered vertically, while rotating the augers, to form further bores in the earth along the axes of the augers.It will be appreciated that because of the spacing of adjacent a piles 15, during this phase, the adjacent sides of the two piles 1 5 on either side of each hole being formed are partially cut away, along with the earth being excavated by the respective auger, because the auger overlaps the two adjoining piles 1 5 as illustrated in Figure 6. During drilling of these holes, as before, the blades 14 are kept retracted.

After the excavation has been finished, both the augers are stopped, the apparatus incorporating means (not shown) to ensure that the augers are stopped in such positions that the blades 14 lie in the common plane of the axes of the two augers and of the adjoining piles 1 5, so that when projected the blades extend towards the centres of the adjacent piles 1 5. The blades 14 are then spread apart by supplying pressurised mortar to passage 25 as described so that the free ends of the blades are forced into the adjacent piles 1 5.

After the aforesaid preparation has been completed the device 11 is raised while mortar fed into the shafts 20 under low pressure is poured via the ports 24 into spaces formed by raising the auger heads while mortar under high pressure issues from jets 34. In this way, the piles 1 6 are installed. At this time, the aforesaid blades 14 further cut the central portions of the sides of the previously formed piles 1 5 already cut into a circular configuration as shown in Figure 6 to form vertical grooves 1 7 (Figure 7 and Figure 8) therein.

The depth of the cut grooves 1 7 varies with the spreading angle of the blades 14 and can be readily changed.

Mortar forced out of the auger heads for forming the piles is partly poured into the mechanically cut grooves 1 7 as described above as the augers 12 move upward, and the subsequently formed piles 16 and the previously formed piles 1 5 overlap one another and are connected in a water-tight manner and united by the interlocking engagement between the cut grooves 1 7 and parts 1 6a of the subsequently formed piles formed therein.

After the piles 1 6 have been installed, the device 11 is moved to the next pair of spaces between piles 15, and immediately, inserts 1 8 such as H-section steel girders are forced into the newly poured piles 1 6 before they have set. The aforementioned steps are repeatedly carried out to complete a pile wall in the form of a row of piles 1 9 having the inserts 18 in every other pile.

During raising of device 11 and forming of the piles 1 6, the sides of the previously formed piles 1 5 are primarily cut by jetting said mortar under high pressure through the nozzles 34, and the regions thus cut away by jetting are thereafter further cut by the blades 14 to form said cut grooves 1 7 having predetermined dimensions.

The high pressure mortar may be cement paste or other coagulating agent.

As described above, in the present invention, the piles 1 6 are installed between the previously formed piles 1 5 in an overlapped fashion, the vertical cut grooves 17 are formed in the opposing sides of the previously formed piles 1 5 in the regions of overlap, and the grooves 1 7 and parts of the subsequently formed piles 1 6 are connected in the engaging condition and unified, and therefore, adequate water-tightness of the pile wall may be obtained even if the piles are somewhat inaccurately formed.Moreover, since the grooves are mechanically cut, the form of the grooves is not affected by the condition of the earth and it is possible to form reliable grooves having predetermined dimensions and to ensure pouring of the desired mortar into the grooves in each pile, thus completely preventing water leakage through the finished pile wall.

Moreover, with respect to the apparatus 11, because the zone of operation of each auger is spaced substantially from that of the other, and the flights thus wholly separated, interference of the flights of the two augers, with difficulty in discharge of excavated soil cannot possibly occur even if the rotary movements of the two augers are not synchronised or the pitches of the flights of the two augers are not exactly the same. These things may, of course, occur with twin auger devicesin which the flights overlap and intermesh. Moreover, there are further advantages in that geared motors used for driving the two augers can be formed as two systems.and it is not necessary to have such motors synchronized with each other. In all, the formation of a pile wall is easily accomplished using the apparatus described.

Claims (12)

1. A method of constructing a water-tight underground pile wall, in the form of a row of laterally connected piles, wherein a first series of piles is installed, then a series of bores is formed, each bore having a central axis lying between a respective pair of piles of the first series and each bore cutting into the two piles of the first series between which said axis thereof lies, each said bore, after the formation thereof, being filled with mortar to form a respective pile of a second series and to connect the adjoining piles of said first series.

2. A method according to claim 1 wherein after the formation of a said bore longitudinal slots are cut in the walls thereof at diametrially opposite positions, each said slot cutting into a respective one of the two piles of the first series between which the axis of the respective bore is disposed.

3. A method according to claim 1 or claim 2 wherein said first series of piles is formed by forming a first series of bores spaced apart laterally by an amount less than the diameter of a bore of said first series, and filling said bores of the first series with a mortar fill to form said piles, and wherein said bores in which the piles of the second series are formed are of the same diameter as those in which the piles of the first series are formed.

4. A method according to any of claims 1 to 3 wherein the bores for the piles of the first series are formed in pairs of adjacent bores, the two bores of each said pair being formed at the same time as one another.

5. A method of constructing a water-tight underground pile wall in the form of a row of piles wherein first piles having a low strength are first installed pair by pair at intervals of every other pile, second piles are subsequently installed between said first formed piles while overlapping the latter, and a pile wall is constructed by said piles, characterised in that in installation of said subsequently formed piles, vertical grooves are cut at diametrally opposite positions in diametrally opposite said previously formed piles, and a part of a mortar filling forming each of said subsequently formed piles is introduced into said grooves to connect the subsequently formed pile with the adjoining first formed piles in a watertight manner.

6. An apparatus for use in constructing an underground pile wall by the method of claim 1, comprising two similar augers mounted in a common support and extending therefrom in parallel, transversely spaced relation, the spacing between the adjacent parts of the two augers being less than the diameter of each auger, each auger being mounted for rotation about its axis in said common support.

7. An apparatus according to claim 6 wherein each of said augers comprises a head and flights extending around the auger axis from said head towards said common support, each said auger head having blades movable between projected positions in which they extend radially outwardly beyond the radial limits of said flights and retracted positions in which they do not, the apparatus including means for moving said blades remotely between their projected and retracted positions and means for arresting said augers in angular positions in which said blades of the two augers extend along a common diametral line.

8. An apparatus of constructing a water-tight underground pile wall in the form of a row of piles, the apparatus comprising two augers, each having flights connected around a shaft of the auger and each auger having a head on both sides of which are spreadably provided blades for cutting sides of adjacent piles to form grooves, said augers being capable of installing a pair of piles, said two augers being provided on a driving device in a spaced relation which makes it possible using the apparatus, to install subsequent piles which overlap such piles formed previously.

9. A method of constructing a water-tight underground pile wall, substantiaily as hereinbefore described with reference to Figures 4 to 10 of the accompanying drawings.

10. Apparatus for use in constructing a watertight underground pile wall, substantially as hereinbefore described with reference to, and as shown in, Figures 4, 9 and 10 of the accompanying drawings.

11. A pile wall constructed by the method of any of claims 1 to 5 or 9 or using the apparatus of any of claims 6 to 8 or 10.

12. Any novel feature or combination of features described herein.