|
(11) | EP 0 011 429 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||||||
| (54) | Treating soils by injecting grout |
| (57) Apparatus for treating soil by injecting grout into the soil at different levels
sequentially, the apparatus comprising a pipe (10) having pistons (19,20, 21, 22)
slidable therein, the pistons being apertured and means extending through the apertures
of the pistons longitudinally of the pipe and being movable longitudinally of the
pipe to close the apertures of the piston in sequence thus allowing each piston to
be moved downwardly by the hydraulic pressure of the grout thus to open apertures
(11, 12,13,14) in the pipe in sequence and allow grouting at the different levels
in sequence. |
[0001] This invention relates to apparatus for treating soils by injecting grout into the soil. The grout solidifies and thus stabilizes or consolidates the soil. The grout may, for example, comprise a mixture of sodium silicate solution with a hardener such as ethyl acetate. The ethyl acetate hardens the grout after it has been injected into the soil but the time of solidification can be controlled so that the grout is liquid at the time of injection.
[0002] It is necessary in practice in many cases to inject grout into a soil mass sequentially at different levels starting at the lowermost level in the soil to be stabilized. Thus a hole is bored in the soil and an injection pipe is lowered into the hole, the pipe having a series of circumferentially spaced apertures, the series being spaced apart along the length of the pipe. Each series of apertures is closed by a flexible collar, the collar surrounding the pipe in alignment with the series of apertures.
[0003] The usual way of controlling the injection is by the provision of what is known as a double packer in the pipe. This packer comprises two interconnected pistons which can be moved along the pipe so that the space between the pistons is aligned with a series of apertures in the pipe. Grout under pressure is then supplied to the space between the pistons which prevent the grout flowing up or down the pipe so the grout deforms the collar which closes the apertures, flows out of the apertures, cracks the bentonite cement which fills the space between the bore hole and the pipe and flows into the soil. The collars form one-way valves and prevent the ingress of soil into the pipe. The double packer is then moved up until it is aligned with the next series of apertures and the operation repeats itself and so on until the required levels of soil have been stabilized.
[0004] This apparatus which is in use has a number of dis- advantages. The first is that it normally requires two operators to move the double packer from one position to another within the pipe. This means that two operators can usually only operate about three injection pipes simultaneously. There are other disadvantages as well which are as follows:-
1. When the pipe is lowered into the bore hole the collars shift thus allowing soil to enter the pipe and prevent proper seating of the packer so that clearing becomes necessary. When the grout is thus supplied to the space between the pistons it can return up in the pipe instead of flowing into the soil and it can solidify in the pipe and cause problems.
2. The pipe can deform in service and this can cause difficulties in moving the packer.
3. Sometimes, even without the ingress of soil, the packer will leak so that one will get solidified grout above and/or below the packer.
4. In practice it is difficult accurately to determine the position of the packer within the pipe so that one may either grout twice through the same apertures or miss out one set of apertures altogether, therebeing only 33 cm normally between adjacent series of apertures. This inaccuracy is due to the way in which the packer is supported by threaded rods, the total length of which can differ depending on how they are screwed together.
[0005] It has also been proposed in U.S. Patent No. 3,243,962 to have a pipe as described above with series of apertures spaced along the pipe but to have movable, apertured pistons therein. Before the pipe is lowered into the bore hole, each piston is set to close the series of apertures. When it is desired to open this series of apertures a ball is passed down the pipe and seats in the aperture in the piston so that the hydraulic pressure of the grout can then move the piston down against stops provided in the pipe to open the apertures and allow grouting to take place. The apertures in the pistons decrease in size from the top to the bottom of the pipe so that a ball which closes, say, the lowermost piston will pass through the apertures in the pistons above it. This apparatus would have a very limited use in practice because the outside diameter of the pipe would have to be kept to about 1
" and therefore the number of different size apertures one could have in the pistons would be limited to three or four so that the apparatus could only be used over a short depth of grouting area.
[0006] The invention aims to provide apparatus for use in injecting soil with grout which overcomes the above disadvantages.
[0007] According to the invention we provide apparatus for treating soil by injection comprising a pipe having apertures spaced apart along the length of the pipe, a plurality of pistons slidable within the pipe in sealing relation thereto, each piston having an aperture therein which places the parts of the pipe above and below the piston in mutual communication, means for introducing grout into the pipe above the uppermost piston therein, limit means between adjacent apertures to limit movement of each piston between adjacent limit means along the pipe and means extending longitudinally of the pipe and passing through the central apertures of the pistons which can be moved along the pipe to effect closing of the apertures in the pistons in sequence thus to allow the hydraulic pressure of the grout to move each piston downwardly against a limit means.
[0008] Initially, before the pipe is lowered into the bore hole as described above, the pistons will be arranged in the pipe to seal the apertures in the pipe and the means for closing the apertures will extend through the apertures in all the pistons. Grout will then be supplied and will pass to the bottom of the tube and out through the lowermost set of apertures below the lowermost piston, all the other apertures being closed by the pistons. When the grouting at the lowermost level has been effected, said means is lifted and is allowed to close the aperture in the lowermost piston which is then moved downwardly by the hydraulic pressure of the grout to expose the apertures which were initially closed by the piston and thus to allow injection to take place through the apertures. Preferably, as described above, each set of apertures is closed by a flexible collar surrounding the pipe thus to prevent the ingress of foreign matter although no foreign matter can pass into the pipe initially when the pistons are in position. The means may then be lifted up the pipe to close the next piston which will then .be.moved to open its associated apertures and so on until injection has taken place at all the desired levels in the soil.
[0009] Said means for closing the' apertures in the pistons can comprise means to inject hardener into the grout so as immediately to solidify the grout in a piston aperture thus to close the aperture. In this arrangement the apertures in the piston may be conical and converge downwardly so that a conical plug of the solidified grout is formed in each piston.
[0010] Alternatively, said means may comprise a pipe having an inflatable member at the lower end thereof, the inflatable member being arranged to be inflated to temporarily close the aperture in each piston in turn.
[0011] In a still further arrangement, said means may comprise a rod passing through the apertures in the piston together with a ball arranged between each set of pistons. Initially, the rod will hold the balls out of the apertures in the pistons but as the rod is sequentially moved upwards, as it clears the apertures in any given piston the ball above the piston can fall into the aperture thus closing the aperture so that the piston can then be moved downwardly by the hydraulic pressure of the grout.
[0012] Also, in this last arrangement, since the balls are already in position between adjacent pistons, the apertures in all the pistons can be of the same size so can the balls be of the same size because the ball does not have to pass through a number of pistons and seal the lowest as in the arrangement of the U.S. patent mentioned above so that one can have an indefinite number of pistons involved and therefore this arrangement can be used to inject grout over any practicable depth without exceeding a pipe diameter of 12".
[0013] The invention will now be described in detail by way of example with reference to the accompanying sketches in which:-
FIGURE 1 is a vertical section through a pipe having means for sealing the pistons according to one embodiment of the invention;
FIGURE 2 is a view similar to Figure 1 showing how the aperture in a piston is closed by a solidified mass of grout;
FIGURE 3 is a vertical section showing means for closing the apertures in the pistons by an inflatable member;
FIGURE 4 shows how the piston is moved downwardly after closing of the aperture by hydraulic pressure;
FIGURE 5 is a vertical section through another arrscge- menu snowing how the pistons can have their apertures closed by balls controlled by a rod;
FIGURE 6 is a section on the line 6-6 of Figure 5;
FIGURE 7 is a view similar to Figure 5 but showing the red having been moved upwardly; and
FIGURE 8 is a view showing the sealing means at the top of the pipe.
[0014] Referring first to Figures 1, 2 and 8 a pipe is indicated at 10 and is shown as lowered into a bore hole in soil to be stabilized. The pipe is in fact made in sections which are screwed together although it is not shown in the drawing. Each section has formed therein a circumferential series of apertures which are indicated at 11, 12, 13 and 14 respectively. Closing each series of apertures is a flexible collar made, e.g. of rubber, these collars being indicated at 15, 16, 17 and 18. Slidable in the pipe is a number of pistons which are indicated at 19, 20, 21 and 22. These pistons are identical and have apertures therethrough indicated at 23, the apertures being conical and converging downwardly. A pipe 24 extends through the central apertures of the pistons 19, 20 and 21 and is shown in position above the aperture in the piston 22. Referring now to Figure 8, the pipe is sealed at the top by means of a sealing means 25 through which the pipe 24 passes. Limit means, indicated diagrammatically at 26 are positioned between adjacent pistons. These limit means may be provided by locally constricting the pipe which may be made of plastic material.
[0015] It will be appreciated that grout is supplied to the interior of the pipe 10 adjacent the top thereof such as for example through the radial pipe junction shown in Figure 8 of the drawings. Grout supplied to the top of the tube 10 will then flow downwardly through the apertures 23 in the pistons 19, 20, 21 and 22 to the desired position in the pipe 10 at which grouting is required to be commenced into the soil.
[0016] Assuming that grouting has taken place below the piston 22 and it is now desired to open the apertures 14, a dose of hardener is delivered from the bottom of the pipe 24 and this solidifies the grout in the vicinity of the bottom of the pipe as shown at 27. As shown in Figure 2 this mass 27 forms within the aperture 23 in the piston 22 and the piston is thus moved downwardly by the hydraulic pressure of the grout so as to expose the apertures 14. Injection can thus now take place through the apertures 14. Figure 2 shows the next stage in which the pipe 24 has been moved upwardly so as to be above the aperture 23 in the piston 21 and the dose of hardener has been injected from the pipe so as to form a mass 28 in the aperture 23 in the piston 21 and has allowed the piston 21 to be moved downwardly by hydraulic pressure to expose the apertures 13 to allow grouting to take place. As ,explained above, the collars 15-18 will be deformed and act as one way valves during grouting when the apertures which they cover are exposed. It will be seen that the pipe 24 has moved downwardly with the piston 21.
[0017] It is easy to mark the pipe 24 so that one knows exactly where it is so that each piston can be sealed in turn as the pipe is lifted up through the apertures in the pistons.
[0018] Referring now to Figures 3 and 4, this shows a somewhat different arrangement in which there is a tube 30 similar to the tube 10 having series of apertures 31, 32, 33 and 34 closed by flexible sleeves 35, 36, 37 and 38. Pistons 39, 40, 41 and 42 are positioned so as to close the apertures 31 to 34 respectively. A pipe 43 passes through the apertures 44 provided in the pistons and carries, at its end, an inflatable member 45. It will be understood that the actual flow of grout down the tube 30 is as indicated by the arrows i.e. the grout is supplied adjacent the top of the tube and flows downwardly through the apertures 44 in the pistons to a position in the tube 30 at which grouting is required to be commenced into the soil.
[0019] As shown in Figure 3, the inflatable member is in the top of the aperture 44 in the piston 42. When it is desired to expose the apertures 34, fluid (e.g. air or water) under pressure is passed down the pipe 43, to expand the inflatable member 45 as shown in Figure 4. The pressure of the fluid is higher than the grouting pressure so as to avoid deformation Qf the member 45 by the grout. This effectively closes the aperture 44 in the piston 42 thus allowing the piston 42 to be moved downwardly as shown in Figure 4 to expose the apertures 34 so that grouting can take place through these apertures as described above. The air pressure is now cut off and the pipe 43 lifted until the inflatable member is in the aperture 44 in the piston 41 and then the inflatable member can be inflated to close the aperture in the piston so that the latter may be moved down. Limit means 26 will be provided between adjacent series of apertures 35-38 to limit the downward movement of the piston precisely as described in relation to Figures 1 and 2.
[0020] Referring now to Figures 5 to 7, there is a pipe 50 having a series of apertures 51, 52, 53 and 54 spaced along the pipe. The pistons 55, 56, 57 and 58 initially close the apertures 51 to 54 respectively. A rod 59 passes through the apertures 60 in the pistons and there is a ball above each piston which is dimentioned to seat in the aperture 60 as shown for the ball 61 seating in the aperture 60 in the piston 54. It will be noted that the upper end of each aperture 60 diverges upwardly. There is a ball 62 above the piston 57, a ball 63 above the piston 56 and a ball 64 above the piston 55. As previously described with reference to Figures 1 to 4 the grout is supplied to the top of the pipe 50 and will flow down the tube through the apertures 60 in the pistons to a position in the pipe at which grouting is required to be commenced into the soil.
[0021] As shown in Figure 5, the'rod 59 has been lifted so as to allow the ball 61 to seal the aperture 60 in the piston 58 with the result that the piston can be moved downwardly as shown in Figure 7 to expose the apertures 54 so that grouting can take place. Figure 7 shows a further stage in that the rod has been withdrawn from the aperture 60 and the piston 57 so that it also is moved downwardly with its aperture closed by the ball 62. As described in relation to Figure 1, means will be provided for limiting the downward movement of the pistons between adjacent apertures. The divergent apertures 60 in the pistons ensures that, even if the pipe is not precisely vertical, the balls will seal the apertures as the rod is withdrawn.
[0022] The advantage of the arrangement shown in Figures 5 to 7 over that described in the U.S. patent mentioned above is that the apertures in each of the pistons can be of the same diameter as can the balls and so one can have an unlimited number of pistons and balls and therefore one can grout to any practicable depth using this apparatus.
[0023] It will be seen that the invention provides an improved apparatus for grouting soil in stages at different levels. Where there is a rod as in Figures 5 to 7, this may be suspended at the end of a cable or in fact the cable may be used instead of the rod. In all the embodiments it is easy accurately to locate, from ground level, the precise position of the bottom of the pipe or rod so that one knows accurately that each piston is being closed in turn and grouting will take place from each series of apertures, no series of apertures has been missed and no series of apertures will have material injected through them twice.
[0024] Moreover, it is less laborious to lift the rod or pipe in this arrangement than in the double ยท packer arrangement initially described. We have found, therefore, that less labour is required and one operator can tend a greater number of pipes than heretofore. A significant saving in cost can be achieved.
1. Apparatus for treating soil by injection com-prising a pipe having apertures spaced apart along the length of the pipe, a plurality
of pistons slidable within the pipe in sealing relation thereto, each piston having
an aperture therein which places the parts of the pipe above and below the piston
in mutual communication, means for introducing grout into the pipe above the uppermost
piston therein, limit means between adjacent apertures to limit movement of each piston
between adjacent limit means along the pipe, and means extending longitudinally of
the pipe and passing through the central apertures of the pistons and which can be
moved along the pipe to effect closing of the apertures in the pistons in sequence
thus to allow the hydraulic pressure of the grout to move each piston downwardly against
the limit means.
2. Apparatus according to claim 1 wherein said longitudinally extending means is arranged
to inject material to solidify grout in a piston aperture thus to close said aperture.
3. Apparatus according to claim 2 wherein said aperture is conical and converges downwardly.
4. Apparatus according to claim 1 wherein said longitudinally extending means comprises
a pipe having an inflatable member at its lower end, the inflatable member being capable
of being positioned in an aperture in a piston and inflated to close said aperture.
5. Apparatus according to claim 1 wherein said longitudinally extending member comprises
a rod or cable and a ball is arranged above each piston and dimensioned to close the
aperture therein, the ball being retained out of the aperture by the rod or cable
but allowed to fall into the aperture to seal it as the rod or cable is moved out
of the aperture in the piston.