METHOD AND APPARATUS FOR CONSOLIDATING EARTH STRATA

Abstract: Method for consolidating an earth stratum situated in a subgrade by withdrawing water that is present in there from it, comprising the stepwise arrangement from the surface of the soil, at some depth, of vertical draining means, such as drainage strips, in the earth stratum, the arrangement of horizontal drainage means, such as drainage pipes, in the upper area of the earth stratum and connecting them to the vertical drainage means for water transfer between them, the arrangement of an air sealing layer directly over the horizontal drainage means and the closing of the surface of the soil, as well as the connection of the horizontal drainage means to a pump for discharge of the water.

Description: Method and apparatus for consolidating earth strata The invention relates to a method and apparatus for consolidating earth strata. When the bearing capacity of a soil is insufficient for (carrying out) a civil engineering project, such as the construction of a rail road or a motorway, it may be increased by forcedly driving out/withdrawing water from the weak earth strata (clay, peat). By withdrawing water the soil material will be pressed against each other and thus obtain an increased bearing capacity. As a consequence, the volume of the soil body will decrease. Forced consolidation techniques have been known for a long time. Nowadays drainage ribbons are often used, which are driven vertically into the ground with great force by means of a drive-in lance. On top of the ground level, incorporating the projecting end portions of the ribbons, a sand body is placed over which an airtight membrane is arranged. In the sand body a drainage pipe has been accommodated, to which a pump is connected, with which water and air is withdrawn from the sand body and thus from the drainage ribbons and the areas surrounding it. The weight of the sand body increases the pressure of the water to be withdrawn, in order to accelerate the process. However, an objection is that during the forced consolidation process the terrain, due to the presence of the membrane, is not available for (preparations for) construction activities. A membrane moreover has to be bought, arranged and guarded and mostly be removed and discharged in a flow of waste material. It is an object of the invention to improve on this, to which end -from one aspect- a method is provided for consolidating an earth stratum situated in a subgrade by withdrawing water that is present in there from it, comprising the stepwise arrangement from the surface of the soil, at some depth, of vertical draining means, such as drainage strips, in the earth stratum, the arrangement of horizontal drainage means, such as drainage pipes, in the upper area of the earth stratum and connecting them to the vertical drainage means for water transfer between them, the arrangement of an air sealing layer directly over the horizontal drainage means and the closing of the surface of the soil, as well as the connection of the horizontal drainage means to a pump for discharge of the water and air. In this way the upper load relatively increases to the atmospheric pressure and the terrain is made available again for other activities. The pump may be very effectively active, as the sealing prevents drawing in of air from above the drainage means, at least reduces it to a large degree. Preferably a trench is made from the ground surface and the vertical drainage means are arranged from the bottom of the trench. As a result the drainage means need not be pressed through an upper layer, and their length may be limited to the minimum necessary. In an advantageous embodiment the trench is being made by means of a plough that is arranged on a device, a vertical drainage means being arranged by means of said device as well, and the horizontal drainage means are each time arranged after that until the next vertical drainage means has to be arranged. Thus both the vertical and horizontal drainage means are arranged in a continuous progress of a process. Preferably simultaneously with the arrangement of the horizontal drainage means or immediately after that, the air sealing layer is being arranged by means of the device as well, as a result of which the time of processing is further minimized. Preferably the air sealing layer is being arranged by removing soil material from the trench walls and pressing it on the horizontal drainage means. In this way use is made of sealing material that is already present, which is particularly possible in cases of clay or loamy soil. Alternatively the air sealing layer can be arranged by arranging a sealing foil layer or plastic material such as for instance bentonite, on the horizontal drainage means. Preferably the air sealing layer is arranged by means of the device. It is further preferred that the trench is finally closed off with soil material up to approximately the original surface. Then as well no supply of extra soil material will be necessary. In a further development of the method according to the invention the vertical drainage means are taken from a supply and after having been arranged are separated by cutting through at a level above the trench bottom, so that the upper portion is available for contact with the - preferably elongated or tubular- horizontal drainage means. The cutting through preferably takes place in the device, so that a good performance is ensured. From another aspect the invention provides an apparatus for use in forced consolidation, comprising a device provided with means for moving them in horizontal direction, over the ground surface, with means for making a trench from the ground surface down to at least just below the upper side of the earth stratum to be consolidated, with means for the stepwise supplying of a vertical drainage ribbon from a supply and driving it into the earth stratum, and means for supplying a horizontal drainage means in the trench bottom. Preferably the device is further provided with means for cutting trough the drainage ribbon at a level above the trench bottom. The means for cutting- through preferably comprise a movable blade and an anvil for said blade, said blade preferably having been arranged on an arm of a lever rotatable about a horizontal centre line, the other arm of said lever being connected to a vertically active hydraulic cylinder, preferably accommodated in the trench-making means. In this way a high cutting power can be achieved with low (horizontal) occupation of space, as the stroke length of the cylinder is not limited by horizontal limitations. The trench-making means preferably form a plough, which at its rear side is provided with means for removing soil material from the trench walls and for pressing it downward, for forming an air sealing layer over the horizontal drainage means, or with means for arranging foil or bentonite, at least (initially) plastic sealing material. Preferably, at its rear side the plough is provided with means for supplying the horizontal drainage means, particularly from a supply roll, in the trench, so that they are situated, as it were, at the free shadow side. It is furthermore preferred that means are provided for pivoting the plough about a horizontal axis of rotation, between a trench-making active position and an upwardly tilted moving position and vice versa. On the one hand this facilitates transport, on the other hand it can promote initial penetration of the plough. The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which: Figure 1 is an example of a partial arrangement for an apparatus according to the invention, extending to below the ground level; Figures 1A-C show several possible states of the apparatus according to figure 1 , amongst others a fully collapsed state (figure 1 C); Figure 2 shows a side view on a plough part of an apparatus according to the invention; Figures 2A-H show several details and cross-sections, partially and schematically, of the plough part of figure 2; Figures 3A and 3B schematically show the portion in the plough part of figure 2 with which a drainage ribbon can be cut through; Figures 4A and 4B illustrate a possible way of connecting the drainage ribbon to the lance of the apparatus of figure 1 ; and Figure 5 schematically shows a project carried out with an apparatus according to the invention. Figure 1 shows a preferred embodiment of an apparatus 1 according to the invention coupled to a hydraulic (excavating) machine 40 in order to form a kind of driving rig, which is common in driving vertical drainage ribbons into a ground. The hydraulic machine 40 is supported on ground level 41 , and has an arm or boom 1 10 which is hinged to the machine at 70a. At the outer end, the arm 1 10 is connected to a U-shaped bracket 12 at hinge 71 . A second connection between machine 40 and bracket 12 consisting of a piston/cylinder assembly 4a that extends between hinge 70c on the machine 40 and hinge 73 on the bracket 12. Hinge 73 is located above hinge 71. A further connection is provided between the arm 1 10 and the machine 40, in order to move the arm 1 10 up and down by means of hinge 70b, piston/cylinder assembly 4d and hinge 72. A kings post 2 is connected to both ends of the U-shaped bracket 12 by means of a first connection, consisting of a hinge 75, a piston/cylinder assembly 4c, a hinge 74 and a bracket 3a, located at a distance above the lower end of the post 2, and by means of a second connection, consisting of a hinge 79 and a bracket 3b located at the lower end of the post 2. A lance 5 is supported by the post 2 and can be moved up and down along the post 2 in the directions P by means of means that are known per se and not further shown. By way of background information, as illustrated in figures 4A,B , the lower end of the lance 5 is connected to an end of drainage ribbon 9, which is unwound from a supply roll (not shown) arranged on the post 2. The lower end of the ribbon 9 is passed in the direction J through a U- bracket 38 fixed to a plate 37, and then the plate 37 is moved against the lower end of the lance 5 in the direction K. When the lance 5 is urged into the ground (direction L) , the plate 37, which laterally extends from the lance 5, will bend according to arrows M to form inclined anchoring lips 39. When a length of drainage ribbon has been pressed into a ground to be consolidated by means of the lance 5, the lance 5 " is lifted again. Due to the anchoring lips 39, the lower end of ribbon 9 will be held in the ground and stay in its place. The drainage ribbon will be cut through at ground level or above it after letting the lance pass upwards along the kings post, after which the new end of the drainage ribbon is connected again to the lance, for instance by means of an anchor, for a subsequent processing step. The U-shaped bracket 1 2 forms a support for a plough 6 too. This plough 6, which will be described in detail, is hinged to the bracket 1 2 at 77, spaced apart from hinge 79. In addition, the plough 6 is connected to the bracket 1 2 by means of a piston/cylinder assembly 4b, which is hinged to the bracket 12 at 76 and to the plough 6 at 78, between hinges 77 and 71 . Hinge 76 is located between hinges 75 and 73. The plough 6 has a front edge 7 and a rear side 8. At its lower end, the front edge 7 may be provided with a nose, but it is left out in the figures. Due to the various hinges 70-79 and the piston/cylinder assemblies 4a-d, the machine 40, the arm or boom 1 10, the post 2 and the plough 6 may be set at different angles with respect to each other, as illustrated in figures 1 A-C. In the upright position of figure 1 A the piston/cylinder assembly 4d has been extended somewhat, and assembly 4a has been operated to maintain the orientation of bracket 1 2 as compared to figure 1 . Two other positions have been indicated in figure 1 A, that is for the post 2 a lying orientation by swinging the post 2 in direction S, realized by extending assembly 4c, and for the plough 6 a halfway swung back (direction T) orientation, realized by extending assembly 4b, all while maintaining the orientation of bracket 1 2. In figure 1 B the post 2 has been left out, and the plough 6 has been swung to a horizontal orientation, while maintaining the orientation of bracket 1 2. In figure 1 C, piston/cylinder assemblies 4a and 4d have been operated to swing the post 2, the bracket 1 2 and the plough 6 as a unity from the orientation of figure 1 into a horizontal, transportation orientation. Turning now to figure 2, at its front edge 7, the plough has a sharp front edge with flanks 7a, 7b. These flanks merge into side plates 1 13a,b, defining an inner space shielded from the soil and providing strength to the plough 6. In this inner space, the plough 6 is provided with a vertical passage 1 5, at the lower end of which a schematically indicated ribbon cutter 1 6 has been arranged, which in an exemplary embodiment is shown in detail in the figures 3A and 3B. The cutting mechanism 1 6 shown in figure 3A and 3B is arranged to be active at the lower end of vertical passage 1 5, near its lower opening 1 5a. Figure 3A schematically shows a drainage ribbon 9 vertically extending through the passage 15, at the moment the lance has already been drawn and the drainage ribbon 9 therefore has been inserted into the ground sufficiently deep. The ribbon cutting mechanism 16 comprises an anvil 22 attached in a holder 23 fixedly arranged on the plough 6, against which anvil a blade 21 can be brought with great force for cutting the drainage ribbon 9. The blade 21 has been attached to a lever 24, which is hingedly attached in the plough 6 at the location of pivot pin 30, and which by means of pin 29 has been attached to the end of a piston rod 27 of cylinder 26, which itself has been attached with the other end to an attachment block 28 fixedly arranged on the plough 6. When a drainage ribbon 9 has to be cut through, the cylinder 26 is excited with means that are not further shown, so that the piston rod 27 is urged downwards in the direction A. As a result the pin 29 is moved downwards, in which as a result of the hinging attachment of the upper end of the cylinder 26 to the block 28 some deflection to the rear is possible, so that a fluent rotational movement about the pivot pin 30 is possible. Thus the lever 24 is rotated anti-clockwise in the direction B, until the blade 21 , as can be seen in figure 3B, has separated the drainage ribbon 9 into a portion 9a that is left behind in the ground and a portion 9b that can be arranged at another location. The arrangement shown with vertical operation cylinder 26 and lever 24 for converting a vertical movement into a more or less horizontal cutting movement is efficient as regards occupation of space and power transmission. At its upper side the plough 6 is provided with attachment eyes 77a and 78a, serving to accommodate hinges 77 and 78, respectively. At the rear side 8, the plough 6 is provided with a pipe 10, having an entrance 19 at its upper end and a smoothly curved portion 10a at its lower end, which curved portion 10a is cut open in the upper portion of its circumference and ends in portion 10b, where also the lower portion of its circumference has been cut away (notice the cross sections of figures 2C and 2D) . The end portion 10b is horizontally oriented and defines exit 20 which is oriented horizontally rearwards. Parallel to pipe 10, directly rearwards of it, extends a supply for an air-tight sealing foil strip or sheet 99, when the application of such a foil would be needed. The supply comprises a support 90 for a supply roll 98 of a foil strip 99. The strip 99 is guided over idle roll 97 into a downward direction, where it engages about a pipe 91 having a circular cross-section. A small distance below pipe 91 a pipe 93 has been arranged about the pipe 91 to form an annular channel therewith for the foil strip 99 (see figure 2B). As can be seen in figure 2A, the lower ends of the circular pipes 91 ,93 are received in plate 1 20 which forms a part of bracket 1 21 that is fixed to the plough 6. Only the inner pipe 91 continues, and this pipe gradually merges into a U-shaped profile 94 realized at the lower end of bracket 1 21 , just above the curved track 95. As can be seen in figures 2A and 2F, the space around profile 94 is sidewardly bounded by plates 14a,b, to the rear by plate 14c and to the fore by plate 14d (vide also figure 2A). The U-shaped profile 94 has a bottom 80 and two side walls 84a, b, as can be seen in the cross-section of figure 2C. The side walls 14a,b are downwardly continued in curved downward extension plates 82a, b in curved track 95 to form a U-shaped channel 83 for the foil strip 99. As can be seen in figure 2C, this channel is delimited at its bottom by the pipe 10a, or, at pipe 1 0b, by the drainage pipe travelling through pipe 10 at the same speed. Thus, in the downward direction of travelling, the foil 99 is transferred from a more or less circular shape into a U-shape, the legs of the U-shaped foil strip 99 being folded about the bottom 80 and the side walls or legs 84a, b and being laterally confined by the downward extensions 82a, b of the plates 14a,b. As can be seen in figures 2, 2A, 2E and 2H, the plough 6 is provided with a pair of scraping blades 101 , 102, forming part of an inverted U-shaped scraper 100, attached to the lower end of the bracket 1 21 and defining a horizontal, upwardly confined passage Y (figure 2E). The scraper 100 has two inclined scraper blades 101 /102a and 101 /102b and upper wall 103/104, wherein the blades 102a,b and wall 1 04 converge towards each other and urge the soil flowing rearwards through the scraper 1 00 downward. The scraping blades 101 a,b have slanted front edges 105a,b (figure 2A, 2H) which project sidewards from the plates 1 1 3a,b to cut soil from the walls (45a, b in figure 2E) of the trench made by the plough. This cut out soil will then be able to fall on the foil strip 99 that travels just below it. The scraper 1 00 may be left out in case no foil strip 99 is applied. Below the scraper 100, the plough 6 is provided with a pair of blades 86a, b extending obliquely upwards and sidewards and having front edges 106a,b that are inclined upwards and rearwards and upper edges 87a, b (figures 2A, 2E and 2G). These blades 86a, b make a cut into the walls of the trench made by the plough in order to make an incision or discontinuity in these walls, so that the stability of the walls below the incision may not be affected by the soil scraper and presser 1 1 yet to be described, which is active on the soil above the incision. Reference is made to figures 2 and 2A, in which the soil scraping and pressing and soil filling blades 1 1 attached to the rear 8 of the plough 6 has been illustrated. The blades 1 1 are positioned behind the scraper 100 and the blades 87a, b. It regards a substantially inverted U-shaped pressing profile 60, which at its front at the location of 53 is hingingly attached to the plough 6, in particular bracket 1 21 . At its upper side, the profile 60 is provided with a block 50 with stop 51 which abuts against a stop bolt 52 threadingly attached to bracket 1 21 by means of a pair of nuts 54. By adjusting the nuts 54 the length of projection of bolt 52 can be adjusted, and therewith the angle of orientation of the profile 60 with respect to the plough 6. The profile 60 has two legs 61 /62a and 61 /62b and an upper wall 66, wherein the upper wall 66 is inclined rearwards and downwards, and the leg portions 62a, b converge to each other, so as to define a narrowing passage or tunnel for the soil. As can be seen in figures 2A and 2E, the edges 64,65 of the legs 61 /62 are downwardly and rearwardly inclined. The level of the edges 65a, b is just below the level of the lower edges of blade legs 1 01 , 102. The wall 66, and therewith the legs 61 /62, however, extend laterally beyond the blade legs 101 /102 and the blades 86a, b. Moreover, the level of the edges 65a, b is slightly higher than the level of the upper edges 87a, b of the blades 86a, b. In figure 5 a picture at a given moment is given of a project in which the apparatus according to the invention is being used. The excavating machine 40 holds the kings post 2 straight up and provides the necessary power and operation lines. The project was started on the left-hand side in the drawing. The hydraulic machine 40 has moved itself over the ground level 41 , underneath which a sand layer 42 is situated. At larger depth a sand layer 44 is situated between relatively weak -for instance clay or loamy- earth strata 43 and 45. In order to be able to carry out a project, such as the construction of a rail road or motorway, at the ground level it is necessary to reinforce the earth stratum 43, which takes place by accelerated consolidation, by letting water present in the layer 43 escape from it. This technique is known per se. One starts by rotating (direction T) the plough 6 from the position shown left in figure 1 B to a vertical position, during which movement the plough is able to penetrate the soil. A plough nose may be an aid here. If required a small excavation may be made locally. The plough may have a height of several meters (for example 2 meters or more), in any case sufficient to amply extend into the earth stratum 43. When the plough 6 has been brought on the right location for arranging a vertical drainage ribbon, the apparatus is operated to press a drainage ribbon 9a in the earth stratum 43 by means of a lance, in the direction E, down to the wanted depth. The lance 5 need not penetrate the sand layer 42 here, but instead easily penetrates the free passage 1 5 within the plough 6. After the lance 5 has been lifted again and the drainage ribbon 9 has been cut through by the cutting mechanism at about the level of line X in figure 5, the machine 40 is driven one step backwards, in which the plough 6 is pulled along in the direction D, while making a trench. During that movement a bendable drainage pipe 36 is supplied from a supply that is not further shown on king post 2, in which the pipe moves through the passage 10, 10a, 10b and exits from the horizontally oriented opening 20 in the direction H (figure 2A) . The end of the -perforated- drainage pipe 36 is connected to an unperforated pipe portion 36a, which leads to a deep well pump 31 above ground level, which later on is able to discharge water (and air) in the direction F. The supplying of the drainage pipe 36 at the rear side of the plough 6 is relative: the drainage pipe that is already in the trench remains there, and the plough moves in the direction D. At the next location where a drainage ribbon has to be arranged, one proceeds as with drainage ribbon 9a and thus the drainage ribbons 9b, 9c, 9d, 9e etc. are arranged stepwise. With all interim movements in the direction D the horizontal drainage pipe 36 is extended stepwise, until the situation shown in figure 4 has been reached. During the movements, the part of the drainage ribbon that extends between the cutting mechanism 1 6 and the lower side of the plough 6 is horizontally spread on the trench bottom as a result of engaging against the outer bend 10a of the passage 10, and on the thus horizontally turned portion 9a' (see figure 5) the horizontal drainage pipe 36 has come down, as a result of which a direct contact between both drainage elements is possible for quick passing on of water. When the wanted end of the horizontal extension of the pipe 36 has been reached, the pipe can be cut at depth and sealed at the end or connected to a perforated pipe portion that is connected to a second pump, so that in case of larger drainage lengths water can be discharged in two directions. Alternatively this connection can be realised in a casing of granular material. To that end, simultaneously with either the drainage pipe or with a separate pipe, a granular material is supplied via pipe 10 to a space formed by lower side plough, bend 10a and the vertical ribbon. In order to let the drainage arrangement be as efficient as possible, use is made of an underpressure system in which according to the invention it is prevented that false air is being drawn in, particularly in the area above the drainage pipe. In order to let the drainage pipe be active as much as possible in downward direction, the contact area with the drainage ribbons, first an incision is made in the trench wall by means of the blades 86a, b, after which the U-blade 60 extends with horizontal portion 66 in those incisions made and soil material below there in the trench wall is cut vertically by the legs 61 a, b and after that is removed from the trench wall by the converging legs 62a, b and urged downwards by wall 66. During the movement steps in the direction D of the plough 6, the material is thus pressed and compacted on and around the upper half of the circumference of the horizontal drainage pipe 36 by the pressing blade 60, so that an as it were airtight layer 46 is situated on the pipe 36. The reversed U-shape of blade 60 and the stop 52 here promote the realization of the airtight sealing. When the work has been completed the plough 6 can be removed from the trench by tilting about hinge 77. alternatively, the assembly of plough 6, bracket 12 and post 2 can be lifted. In that case, the hinged connection of the scraper/presser 1 1 /60 at 53 permits the scraper/presser to rotate towards a more vertical orientation in which the lifting movement is facilitated. In addition, by such an orientation it is avoided that the walls of the trench are severely damaged, which would otherwise result in local collapse of these walls and loosened soil falling on the drain, due to which a leakage path might be realized. In case the type of soil is less cohesive or substantially granular, the foil 99 can be used to provide an air tight seal on the pipe 36. Here, the scraper 100 and the parts for the supply of the foil strip 99 are used, the strip 99 being supplied at the same speed as the drainage pipe 36 in the direction I and H, respectively (figure 2 and 2A). The scraper cuts the soil from the trench walls, crumbles it and urges it downwards to let it fall on the foil strip 99 which is then already more or less horizontal. Thus it is ensured that the strip has a proper position on the upper side of the drainage pipe before the pressing and filling blade 60 becomes active in the area concerned. The foil 99 used can be a composite one, such as a sandwich foil of an upper layer and a lower layer of polypropylene for strength, and an air tight foil in between these layers. When making the trench the plough can be hindered by high density types of soil, or by obstacles of a natural or artificial nature. In order to remove or minimize that hinder the plough can be equipped with means known per se for breaking off the cohesion of the soil and/or obstacles or displacing them. In one embodiment the plough at its front edge 7 is provided with one or several blades that are vertically movable over the entire height of the cut surface. When necessary these blades make an upward and downward movement. Alternatively for making the trench, the trench-making device can be provided with a ground cutter in the portion in front of a vertical passage of the lance/the ribbon. It strongly resembles a chain saw and may consist of an endless chain which may or may not be provided with teeth and/or scrapers. A chain here runs in the centre of the device about a drive wheel at the upper side of the device to a turn wheel at the lower side of the device. The shafts of the chain wheels are perpendicular to the direction of travel of the device whereas the chain runs in the plane of the direction of movement of the device. Here the device is furthermore provided with the means described earlier on for supplying the pipe and possibly the U- shaped soil closing blades. The movement of the chain may take place in continuous rotating movement or in an up and downwardly oscillating movement. In a special embodiment several chains may run side by side possibly having an opposing direction of movement. Alternatively the plough can be provided with one or several vibrating mechanisms to let the plough make a pulsating movement in the propelling movement as well as transverse to it. It is noted that the methods discussed can also be used from a pontoon on a subaqueous soil.

Claims: Claims 1 . Method for consolidating an earth stratum situated in a subgrade by withdrawing water that is present in there from it, comprising the stepwise arrangement from the surface of the soil, at some depth, of vertical draining means, such as drainage strips, in the earth stratum, the arran- gement of horizontal drainage means, such as drainage pipes, in the earth stratum and connecting them to the vertical drainage means for water transfer between them, the arrangement of an air sealing layer directly over the horizontal drainage means and the closing of the surface of the soil, as well as the connection of the horizontal drainage means to a pump for discharge of fluid from the horizontal drainage means, in particular the water and air. 2. Method according to claim 1 , in which a trench is made from the ground surface and the vertical drainage means being arranged to extend down- wardly from the bottom of the trench. 3. Method according to claim 2, in which the trench is being made by means of a plough that is arranged on a -preferably mobile- device, a vertical drainage means being arranged by means of said device as well, and the horizontal drainage means each time being arranged after that until the next vertical drainage means has to be arranged. 4. Method according to claim 3, in which simultaneously with the arrangement of the horizontal drainage means or immediately after that, the air sealing layer is being arranged by means of the device as well. 5. Method according to claim 4, in which the air sealing layer is being arranged by removing soil material from the trench walls and arranging it on the horizontal drainage means. 6. Method according to claim 4, in which the air sealing layer is arranged by arranging a sealing foil layer on the horizontal drainage means. 7. Method according to claim 4, in which the air sealing layer is arranged by arranging a sealing layer of plastic material, such as bentonite, on the horizontal drainage means. 8. Method according to claim 5, 6 or 7, in which the air sealing layer is arranged by means of the device. 9. Method according to any one of the preceding claims, in which the trench is finally closed off with soil material up to approximately the original surface. 10. Method according to any one of the preceding claims, in which the vertical drainage means are taken from a supply and after having been arranged are separated by cutting through at a level above the trench bottom, wherein preferably the cutting through takes place in the device. 1 1 . Method according to any one of the preceding claims, in which the horizontal drainage means are arranged in an upper area of the earth stratum. 1 2. Apparatus for use in the method according to any one of the preceding claims, comprising a device provided with means for moving it in horizontal direction, over the ground surface, with means for making a trench from the ground surface down to at least the upper side of the earth stratum to be consolidated, with means for the stepwise supplying of a vertical drainage ribbon from a supply and driving it into the earth stratum, and means for supplying a horizontal drainage means in the trench bottom. 1 3. Apparatus according to claim 1 2, in which the device is further provided with means for cutting trough the drainage ribbon at a selected level above the trench bottom. 14. Apparatus according to claim 1 3, in which the means for cutting- through comprise a movable blade and an anvil for said blade. 1 5. Apparatus according to claim 14, in which the blade has been arranged on an arm of a lever rotatable about a horizontal centre line, the other arm of said lever being connected to a vertically active hydraulic cylinder, preferably accommodated in the trench-making means. 1 6. Apparatus according to claims 1 2-1 5, in which the trenchmaking means form a plough. 1 7. Apparatus according to claim 1 6, in which at its rear side the plough is provided with means for removing soil material from the trench walls and for pressing it downward. 1 8. Apparatus according to claim 1 7, in which the plough is provided with means for making an incision in the trench walls just below the line of engagement of the trench walls with the means for removing soil material from the trench walls. 1 9. Apparatus according to claim 1 6, 1 7 or 1 8, in which at its rear side the plough is provided with means for supplying the horizontal drainage means, particularly from a supply roll, in the trench. 20. Apparatus according to any one of the claims 1 6-1 9, furthermore provided with means for pivoting the plough about a horizontal axis of rotation, between a trench-making active position and an upwardly tilted moving position. 21 . Method according to one of the claims 1 -1 1 , performed on a sub- aqueous soil. 22. Method comprising one or more of the characterizing steps described in the attached description and/or shown in the attached drawings. 23. Apparatus provided with one or more of the characterizing measures described in the attached description and/or shown in the attached drawings.

Inventors: BODEGOM DIRK ALBERTUS, BODEGOM, DIRK, ALBERTUS
Applicants: BODEGOM DIRK ALBERTUS, BOS & KALIS BAGGERMAATSCH, BAGGERMAATSCHAPPIJ BOSKALIS B.V., BODEGOM, DIRK, ALBERTUS
Application year: 2001
Main classification: E02D3
IPC codes: E02D3