TECHNICAL FIELD

This invention relates to a vertical drain, and more particularly to a vertical drain for use in consolidating weak or soft soils.

BACKGROUND

Before infrastructure or buildings can be developed in an area, the ground upon which the development is to take place must be adequately consolidated in order to take the load of the infrastructure or building. This is especially true where construction is to take place on reclaimed land. Large amounts of clay, silty clay, or marine clay may be found in many areas inland and onshore where land is to be reclaimed. Before construction can take place, the high water content of such weak and soft soils must be reduced to consolidate the ground.

An early approach to ground consolidation involves the use of sand drains. Sand drains are vertical bores filled with sand which extend down into the layer of weak and soft soil to be consolidated. A surcharge load such as a large volume of soil is deposited over the bores on the ground to be consolidated. The pressure exerted by the sand on the ground forces water in the weak and soft soils to flow up and into the sand drains, thereby consolidating the ground.

In another approach, sand drains are replaced with pre-fabricated vertical drains (PVD). FIG. 6a illustrates a cross-section of a corrugated core PVD 1. As illustrated in FIG. 6a, the known PVD 1 comprises an elongate plastic corrugated core 2 surrounded by a filter cloth 3. Water permeates through the filter cloth 3 directly into the corrugations of the plastic core 2. The corrugations define a series of open channels in the core. The open channels are next to and exposed to the filter cloth 3. When installed into the ground, the open channels are oriented substantially vertically and form a substantially vertical path along which fluid flows up along and out of the PVD 1. The water in the PVD 1 is forced up through the open channels to the surface by the pressure of the surcharge load placed on the ground being consolidated or can be drawn up the PVD 1 by use of a vacuum suction system. Additionally, an electro-osmotic consolidation process may be used with the PVD. FIG. 6b illustrates a cross-section of a corrugated core PVD 1 with filter 3, electrically conductive strips 4, and open channels 5. Electrically conductive strips 4 used as electrodes can be attached or embedded to the corrugation core 2 along the length of the corrugated core 2 to effectuate electro-osmotic consolidation of the ground. Electrical potential between the electrodes attracts fluid to the PVD 1. The electrically conductive strips 4 run continuously from one end of the PVD 1 along the length of the plastics core to other end of the PVD 1. Instead of utilising electrically conductive strips, the corrugated core 2 can be electrically conductive. When installed into the ground, fluid is attracted to the corrugated core 2, passing through the filter, and flows up and out of the PVD 1 via the vertically-oriented open channels 5 of the corrugated core 2. The corrugated core PVDs may be placed in an array, with some corrugated core PVDs used as cathodes, and other PVDs used as anodes. Each of the cathode PVDs is paired with an anode PVD. The anode vertical drains may comprise solid cores without corrugations.

Unfortunately, the main pathways through which fluid flows upwards in the corrugated core PVDs are the open channels of the corrugated core, which are exposed to the filter and soil pushing against the filter. Soil pushing against the sides of the vertical drain may force the filter into the open channels of the corrugated core. The open channels may thereby become obstructed. The upward passage of fluid along the open channel may be inhibited, reducing the efficiency of fluid removal.

SUMMARY One aspect of the present invention provides a vertical drain for draining fluid from ground soil, comprising: a tubular structure defining a circumferential wall of an internal fluid conduit; a filter surrounding said tubular structure; and a conductive element extending within and along said internal fluid conduit and having a terminal for connection to a power supply; and wherein said tubular structure comprises a plurality of openings for passage of fluid filtered by said filter into said internal fluid conduit.

The tubular structure of said vertical drain may include corrugations that define channels circumferentialiy surrounding an exterior side of said tubular structure to allow filtered fluid to flow circumferentialiy around said tubular structure. The plurality of openings of said vertical drain for passage of fluid filtered by said filter into said internal fluid conduit may be located on said channels defined by said corrugations.

The vertical drain of said vertical drain may have one end attached to an anchor shoe.

The anchor shoe of said vertical drain may comprise a substantially flat anchor plate with a handle such that said vertical drain can be securedly attached to said handle.

The tubular structure of said vertical drain may include channels that are located on an exterior side of said tubular structure to allow fluid to flow to said plurality of openings, and said conductive element of said vertical drain is located within said tubular structure.

The tubular structure of said vertical drain may have a substantially cylindrical shape.

The tubular structure of said vertical drain may surround and separate said internal fluid conduit from said filter.

The conductive element of said vertical drain may be covered by electrical insulation starting from a point of said conductive element that is above ground, extending along said the conductive element to also cover a segment of said conductive element below ground.

The vertical drain of said vertical drain may include a vacuum suction connector that is fitted into said internal fluid conduit.

A further aspect of the present invention provides an array of vertical drains and conductive strips comprising: a plurality of vertical drains, as described above, connected to a selected terminal of a power source, and a plurality of conductive strips connected to another terminal of said power source. Each vertical drain of said array may be paired with a conductive strip.

A further aspect of the present invention provides an array of vertical drains comprising: a plurality of vertical drains, as described above, connected to a power supply to form alternating rows of cathode vertical drains and anode vertical drains.

A further aspect of the present invention provides a method of consolidating soft soil comprising using a vertical drain as described above. The method may be performed with the application of vacuum suction onto the vertical drain directly or indirectly.

A further aspect of the present invention provides a method of consolidating soft soil comprising using an array of vertical drains and conductive strips as described above. The method may be performed with the application of vacuum suction onto the vertical drains directly or indirectly.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which:

FIG. 1a illustrates a vertical drain with a tubular structure defining a circumferential wall of an internal fluid conduit, according to an embodiment.

FIG. 1b illustrates the filter wrapped around the tubular structure, according to an embodiment. FIG. 2a illustrates a cross-sectional view of the corrugated tubular structure defining a circumferential wall enclosing an internal fluid conduit, according to an embodiment. FIG. 2b illustrates a partial cutout view of the tubular structure, according to an embodiment.

FIG. 3a and FIG. 3b illustrate the anchor shoe with a top view and a side view, according to an embodiment.

FIG. 3c, FIG. 3d, and FIG. 3e illustrate a vertical drain with the anchor shoe, according to an embodiment. FIG. 4a and FIG. 4b illustrates an array of vertical drains and conductive elements, according to an embodiment.

FIG. 4c illustrates an array of vertical drains, according to an embodiment. FIG. 5a illustrates an installation of an array of vertical drains and conductive elements, according to an embodiment. Figure 5b illustrates execution with a power supply, and Figure 5c illustrates end results of ground consolidation after treatment.

FIG. 6a illustrates a cross-section of a known corrugated core PVD.

FIG. 6b illustrates a cross-section of a known corrugated core PVD with electrically conductive strips.

FIG. 7 illustrates a vertical drain coupled with drainage pipes and connectors of a vacuum suction system, according to an embodiment.

FIG. 8a illustrates an array of vertical drains and conductive elements connected by both the electrical connections and drainage pipes, according to an embodiment. FIG. 8b illustrates an array of vertical drains connected by both the electrical connections and drainage pipes, according to an embodiment.

FIG. 9a illustrates an installation of an array of vertical drains and conductive elements, according to an embodiment. Figure 9b illustrates execution with a power supply and vacuum pump, and Figure 9c illustrates end results of ground consolidation after treatment.

DETAILED DESCRIPTION

Embodiments of the invention will be discussed hereinafter with reference to the figures.

FIG. 1a illustrates a vertical drain 100 with a tubular structure 102 defining a circumferential wall 104 of an internal fluid conduit 106, according to an embodiment. A filter 108 surrounds the tubular structure 102. The tubular structure 102 is substantially cylindrically shaped. A conductive element, in the form of rod or wire or any solid material with any cross-sectional shape 110 extends within and along the internal fluid conduit 106. Openings 112 located on the tubular structure 102 allow water filtered by the filter 108 to pass through the tubular structure 102 into the internal fluid conduit 106. The circumferential wall 104 defined by the tubular structure 102 surrounds, along the axial length of the tubular structure 102, both the conductive element 110 and the internal fluid conduit 106, with an exposed opening 1 1 at one end of the tubular structure 102 for fluid to leave the vertical drain. The tubular structure 102 advantageously surrounds and separates the internal fluid conduit 106 from the filter 108. The tubular structure 102 also provides the stability of internal fluid conduit against the pressure of soil that may push against filter 108, when vertical drain 100 is installed in the ground.

The conductive element 110 is preferably manufactured from steel, copper, or some other material that allows an electrical current to flow. The conductive element 110 preferably has a diameter that ranges from 0.5 to 25 mm, or any cross- section with dimensions that ranges from 0.1 to 30 mm. The conductive element 110 may have variable cross-section size throughout the length of the conductive element 110. The conductive element 110 substantially extends at least from one end of the tubular structure 102 to the other end, and the conductive element 110 is surrounded by the tubular structure 102 substantially along the length of the conductive element 110. One end of the conductive element 110 can be attached to and tied to an anchor shoe 114. The other end of the conductive element 110 is attached to a terminal of a power source. Electrical insulation (not illustrated) can be used to cover a portion of the conductive element 110. Preferably, the electrical insulation covers the conductive element 1 0 starting from a point of the conductive element 110 that is above ground, extending along the conductive element 110 to also cover a segment of the conductive element 110 below the ground.

The tubular structure 102 is corrugated such that channels 116 are circumferentially formed around the tubular structure 02 for the flow of fluid around the sides of tubular structure 102. The channels 116 encircle the tubular structure 102 such that the direction of fluid flow along each of channels 116 is substantially orthogonal to the length axis of tubular structure 102. Filtered fluid advantageously travels substantially along the circumferential wall 104 within the channels 116, until the filtered fluid encounters one of openings 112. The filtered fluid enters the internal fluid conduit 106 through one of openings 12. The fluid then moves up and out of the tubular structure 102. The channels 1 16 are substantially horizontal when the tubular structure 102 is installed in the ground. The corrugations also advantageously provide stability for the tubular structure 102 when installed in the ground.

FIG. 1b illustrates the filter 108 wrapped around the tubular structure 102, according to an embodiment. The corrugations 1 5, when not covered by filter 108, are clearly visible in FIG. 1 b. The filter 108 may include filter cloth that is manufactured from a geotextile material. The filter cloth is preferably manufactured from polypropylene or polyethylene or other synthetic fibres. Preferably, the filter cloth is sufficiently porous to allow water to permeate through the filter cloth, flow along the channels 116, and into the internal fluid conduit 106. Preferably, the average pore size of the filter 108 is approximately 50 to 200 microns.

FIG. 2a illustrates a partial cross-sectional view of the corrugated tubular structure 102 defining a circumferential wall 104 enclosing an internal fluid conduit 106, according to an embodiment. The corrugated tubular structure 102, as depicted in the cross-sectional view of FIG. 2a, is depicted as two concentric rings 204, 206. The inner concentric ring 204 represents a valley of the corrugations 5 (FIG. 1 b). The outer concentric ring 206 represents a peak of the corrugations 115. The peaks and valleys of the corrugations form the channels 1 6 that encircle tubular structure 102.

FIG. 2b illustrates a partial cutout view of the tubular structure 102, according to an embodiment. Peaks 210 and valleys 212 are clearly visible in this figure. The channels 116 are defined by the peaks and valleys of the corrugations 115. The channels 116 are each of the valleys surrounded by two peaks. The peaks of the corrugations advantageously prevent the filter from sagging into the channels 116. The openings 112, of any dimension, are located along the valleys 212. The corrugations 115 (including the channels 116) are preferably made from a non-conductive material, such as plastic. The channels 116 that are located on the exterior side of tubular structure 102 allow filtered fluid to flow to openings 112. The conductive element 110 is located within the interior side of tubular structure 102.

The partial cutout view (FIG. 2b) of tubular structure 102 includes openings 112 as seen on both interior and exterior sides. The rectangular shape openings 112 runs along the channels 116. In some embodiments, the openings 1 12 may be other shapes, such as round holes.

FIG. 3a and FIG. 3b illustrate the anchor shoe 1 14 with a top view (FIG. 3a) and a side view (FIG. 3b), according to an embodiment. The anchor shoe 114 is used in installation of a vertical drain, such as vertical drain 100 (FIG. 1 ). Prior to installation of the vertical drain 100 into ground, the vertical drain 100 is securedly attached to anchor shoe 114. That is, the filter, tubular structure, and conductive element of vertical drain 100 are fastened to the anchor shoe 114. The vertical drain 100 is inserted into and enclosed within an installation mandrel (not illustrated). The vertical drain 100 and installation mandrel are inserted into the ground. The installation mandrel is then retrieved by pulling the installation mandrel up and out of the ground, leaving behind the vertical drain 100. The vertical drain 100 remains immobile in the ground, staying approximately at the same depth where the installation mandrel is retrieved from. The anchor shoe 1 14 advantageously prevents the vertical drain 100 from being pulled out of the ground, since the filter, tubular structure, and conductive element are fastened to the anchor shoe 114.

The anchor shoe 114 has an anchor plate 304 that advantageously resists upward pulling when the installation mandrel is retrieved, and a handle 306 to securedly attach the filter, tubular structure, and conductive element of vertical drain 100 to the anchor shoe 114. In some embodiments, only a subset of the filter, tubular structure, and conductive element of vertical drain 100 need be securedly attached to the anchor shoe 114. The anchor shoe is preferably manufactured from steel. The length of the anchor shoe 114 is approximately 160 mm. The width of the anchor shoe 114 is approximately 70 mm. The height of the handle is approximately 10 mm. The thickness of the material used to manufacture the anchor plate 304 and the handle 306 is approximately 1 mm.

FIG. 3c, FIG. 3d, and FIG. 3e illustrate a vertical drain 100 (FIG. 1) with the anchor shoe 114, according to an embodiment. In FIG. 3c, a segment 308 of the vertical drain 100, including portions of the tubular structure 102, conductive element 110 (FIG. 1), and filter 108 (FIG. 1), are slipped through the handle 306 of the anchor shoe 114. In FIG. 3d, the segment 308 of the vertical drain 100 is folded around handle 306 back towards the vertical drain 100 and stapled to the tubular structure 102. Other types of fasteners can also be used to fasten the folded segment to the tubular structure 102. In FIG. 3e, the vertical drain 100 with the anchor shoe 114 is depicted in an upright position.

FIG. 4a illustrates an array 402 of vertical drains and conductive strips, according to an embodiment. The conductive strips can be made of any conductive material in the form of a strip, of about 10 to 150 mm width and 0.1 to 5 mm thickness, that can be inserted into the ground using the same installation mandrel as vertical drain 100. The array 402 may preferably include alternating rows of vertical drains 404 and conductive strips 406. Preferably, the number of vertical drains 100 in each row of vertical drains 404 is the same as the number of conductive strips in each row of conductive strips 406. The distance between a vertical drain 404 of one row and a conductive strip 406 of a neighbouring row may be approximately one (1 ) metre. Other separation distances are also possible. In the depicted example, the spacing between each row of vertical drains and a neighbouring row of conductive strips is approximately one (1 ) metre. The distance between two conductive strips 408, 410 in the same row of conductive strips is approximately one (1) metre. Likewise, the distance between two vertical drains 414, 416 is also approximately one (1) metre. Preferably, the distance between a conductive strip of one row and a corresponding paired vertical drain of a neighbouring row is approximately 0.5 to 3.5 metres, the distance between two conductive strips of the same row are approximately 0.5 to 3.5 metres, and the distance between two vertical drains of the same row are approximately 0.5 to 3.5 metres.

The vertical drains and conductive strips are connected to a power supply to form cathodes and anodes respectively. Each vertical drain is connected to one terminal of the power supply through electrical connections that connect rows of vertical drains to the power supply. Each conductive strip is connected to the other terminal of a power supply through electrical connections that connect rows of conductive strips to the power supply. The conductive strips are preferably manufactured from conductive material. Each of the vertical drains is paired with a conductive strip or placed between two conductive strips. FIG. 4b illustrates an example vertical drain 412 that may be used in quantity for constructing the array of vertical drains. The arrow extending from FIG. 4b to FIG. 4a shows that each circular representation in FIG. 4a is representing a vertical drain 100.

In another embodiment, an array 418 may include only vertical drains 100 as illustrated in FIG 4c. In array 418, rows of vertical drains may be connected to the power supply such that they form alternating rows of cathode vertical drains 420 and anodes vertical drains 422. In this embodiment, the alternating rows of cathode vertical drains 420 and anodes vertical drains 422 are analogous to the alternating rows of vertical drains and conductive strips in the array 402.

While the arrays 402 and 418 in the embodiments described above are shown as square arrays, different array patterns are possible. For example, the array pattern can be a triangular grid pattern in which a row of vertical drains forms a zigzag pattern. Each of the rows of conductive strips can also form a zigzag pattern. Embodiments of the invention are not limited to the array patterns described herein. The example array patterns are provided for illustration only, and the array pattern in an embodiment may be of other different patterns to suit different circumstances.

FIG. 5a illustrates an installation of an array of vertical drains and conductive elements, according to an embodiment. FIG. 5b illustrates execution with a power supply, and FIG. 5c illustrates end results of ground consolidation after treatment.

As depicted in FIG. 5a, rows of vertical drains 504 are inserted into the ground to be consolidated. Each of the vertical drains may be, for example, the vertical drain 100 as described with respect to FIG 1a-FIG 1b and FIG 2a-FIG 2b. In FIG. 5a, six (6) rows of vertical drains 504 are depicted as inserted into the ground. Five (5) rows of conductive strips 506 are depicted as inserted into the ground. The rows of vertical drains 504 alternate with rows of conductive strips 506. That is, each row of vertical drains 504 is installed between rows of conductive strips 506. Thus, the array may include alternating rows of vertical drains and conductive strips, similar to the array 402 illustrated in FIG 4a. FIG. 5a, FIG.5b and FIG. 5c are provided for illustration only, the array 418, including only vertical drains illustrated by FIG 4c, may also be installed in similar manner.

A surcharge load, such as sand 508, can optionally be placed over the area of ground to be consolidated. Placing the surcharge load on the ground begins the hydraulic consolidation process for the ground beneath the surcharge load. Water passes through the filter wrapped around each tubular structure into the internal fluid conduit of the vertical drains, and the water flows up and out of the vertical drains.

As part of the electro-osmotic consolidation process, a power source connected to the vertical drains is switched on. During the electro-osmotic process, the flow of water is induced by the application of an electric potential created by the electrically connected alternating rows of vertical drains and conductive strips in array 402, or alternating rows of cathode vertical drains and anode vertical drains in array 418. Furthermore, during the electro-osmotic consolidation process, a certain amount of hydraulic consolidation continues to occur. Thus, water flows to the vertical drains both through the optional hydraulic consolidation process and the electro-osmotic consolidation process. Advantageously, using the vertical drains with the tubular structure and conductive element described herein, the surcharge load process may be skipped entirely to directly start the electro-osmotic process.

As depicted in FIG. 5b, the array 502 is attached to a power source by means of connector terminals which are exposed above the surface of the ground. The power supply can be, for example, high capacity wet cells, an on-site generator or a connection to a grid supply.

FIG. 5c depicts the soft soil after consolidation. The soft soil from which water is extracted and removed can be any kind of soil, such as marine clay, silty clay, peaty soil, sludge, trailings or any other kind of weak soil with undesirable high water content. The types of ground that may be consolidated by means of extracting water is not limited to the examples presented herein.

The vertical drain can be manufactured in coiled lengths of several hundred metres or more. The vertical drain 100, including the conductive element 110, the filter 108, and the tubular structure 102, can be manufactured for any length that is appropriate for the depth of the ground to be consolidated. Preferably, the tubular structure is manufactured from plastics material such as polypropylene or polyethylene or other extrudable plastics. The tubular structure 102 can be manufactured by extrusion. In another embodiment of the invention, the array 402 of vertical drains and conductive strips illustrated in FIG 4a are configured to combine with a vacuum suction system to form a hybrid electro-osmotic and vacuum suction consolidation system. Fig 7 illustrates a vertical drain 100 coupled with drainage pipes and connectors of a vacuum suction system, according to an embodiment. A vertical cylindrical connector 702, in the shape of a hollowed cylinder with a flange on one end, is connected to the tubular structure 102 of a vertical drain 100 such that the external cylindrical surface of the vertical cylindrical connector 702 is tightly fitted to the internal surfaces of the tubular structure 102. A vertical drainage pipe 704 is in turn fitted into the vertical cylindrical connector 702 such that the external surface of the vertical drainage pipe 704 is tightly fitted into the internal walls of the vertical cylindrical connector 702. In this arrangement, the vertical cylindrical connector 702 may allow the drainage pipe 704 to be tightly coupled to the tubular structure 102.

On the other end of the vertical drainage pipe 704, a cross-shaped connector 706 is connected. The cross-shaped connector 706 has three symmetrical cylindrical end 708, 710, 712 and a fourth smaller cylindrical end 714 with screw threads on the internal wall. The vertical drainage pipe 704 is connected tightly to the cross-shaped connector 706 via the cylindrical end 708, which is the end opposite to the smaller cylindrical end 714. With this arrangement, a conductive element 110 may then run from the smaller cylindrical end 714 of the cross-shaped connector 706 to the tubular structure 102 via the vertical drainage pipe 704 coupled to the cylindrical end 708 of the cross-shaped connector 706.

On the smaller cylindrical end 714 of the cross-shaped connector 706, a plug 716, with the conductive element 110 running through a through-hole in its center, is screwed in into the screw thread on the internal wall. Between the tip of the plug 716 and the internal base of the smaller cylindrical end 714, an O-ring 718 is placed such that the plug 716 may sealed tightly together the cross-shaped connector 706 and the conductive element 110 when the plug 716 is screwed in.

The remaining two cylindrical ends 710, 712 of the cross-shaped connector 706 are connected to horizontal drainage pipes 720, 722 linking up this vertical drain 100 with other vertical drains 100. FIG 8 illustrates an array 802 of conductive strips and vertical drains connected by electrical connections as well as drainage pipes, according to an embodiment. The array 802 may preferably include alternating rows of conductive strips 806 and vertical drains 804. Preferably, the number of vertical drains 100 in each row of vertical drains 804 is the same as the number of conductive strips in each row of conductive strips 806.

The vertical drains and conductive strips are connected to a power supply to form cathodes and anodes respectively. Each conductive element 110 of the vertical drain 100 is connected to one terminal of the power supply through electrical connections that connect rows of vertical drains 804 to the power supply. Each conductive strip is then connected to the other terminal of a power supply through electrical connections that connect rows of conductive strips 806 to the power supply. Each vertical drain 100 is paired with a conductive strip or placed between two conductive strips.

Each row of vertical drains 804 is also linked up by the drainage pipes 808. The drainage pipes 808 at the terminal of each row of vertical drains 804 then converge and link up to a vacuum pump. In this arrangement, vacuum pump may provide vacuum suction to the individual vertical drains 100. Therefore, vertical drains in this embodiment may perform the consolidation process by both electro- osmotic and vacuum suction methods independently or in combination.

In a further embodiment, an array 810 may include only vertical drains 100 as illustrated in FIG. 8b. In array 810, rows of vertical drains may be connected to the power supply such that they form alternating rows of cathode vertical drains 814 and anodes vertical drains 812. Further, each row of cathode vertical drains 814 is linked up by the drainage pipes. The drainage pipes at the terminal of each row of cathode vertical drains 814 then converge and link up to a vacuum pump. Similarly, the cathode vertical drain 814 in this embodiment may perform the consolidation process by both electro-osmotic and vacuum suction methods independently or in combination.

Embodiments of the invention are not limited to the array patterns described herein. The example array patterns are provided for illustration only, and the array pattern in an embodiment may be of other different patterns to suit different circumstance. FIG. 9a illustrates an installation of an array of vertical drains and conductive elements, according to an embodiment. FIG. 9b illustrates execution with a power supply and a vacuum pump, and FIG. 9c illustrates end results of ground consolidation after treatment.

As depicted in FIG. 9a, rows of vertical drains 904 are inserted into the ground to be consolidated. Each of the vertical drains may be, for example, the vertical drain 100 with drainage pipes and connectors as described with respect to FIG 7. In FIG. 9a, six (6) rows of vertical drains 904 are depicted as inserted into the ground. Five (5) rows of conductive strips 906 are depicted as inserted into the ground. The rows of vertical drains 904 alternate with rows of conductive strips 906. That is, each row of vertical drains 904 is installed between rows of conductive strips 906. Thus, the array may include alternating rows of vertical drains 904 and conductive strips 906. The arrays illustrated in FIG. 9a, FIG.9b and FIG. 9c are provided for illustration only. Additionally, the array may include only vertical drains illustrated by FIG 8b, which may also be installed in a similar manner as discussed above.

A surcharge load, such as sand 908, can optionally be placed over the area of ground to be consolidated. Placing the surcharge load on the ground begins the hydraulic consolidation process for the ground beneath the surcharge load. Water passes through the filter 108 wrapped around each tubular structure 102 into the internal fluid conduit 106 of the vertical drains 100, and the water may flow up and out of the vertical drains 100.

As part of the hybrid electro-osmotic and vacuum consolidation process, a power source connected to the vertical drains is switched on. The application of an electric potential created by the electrically connected alternating rows of vertical drains and conductive strips in array 802, or alternating rows of cathode vertical drains and anode vertical drains in array 810, may induce the flow of water through the electro-osmotic process. In addition, as the vacuum pump is switched on, the application of vacuum suction in the vertical drains may further induce the flow of water. During the electro-osmotic and vacuum consolidation process, a certain amount of hydraulic consolidation may continue to occur. Advantageously, using the vertical drains 100 with the tubular structure 102, conductive element 110 and vacuum suction apparatus described herein, the consolidation process may be more effective and efficient. As depicted in FIG. 9b, the array 902 is attached to a power source by means of connector terminals which are exposed above the surface of the ground. The power supply can be, for example, high capacity wet cells, an on-site generator or a connection to a grid supply. At the same time, rows of vertical drains are also connected to a vacuum pump by means of drainage pipes.

FIG. 9c depicts the soft soil after consolidation. The soft soil from which water is extracted and removed can be any kind of soil, such as marine clay, silty clay, peaty soil, sludge, trailings or any other kind of weak soil with undesirable high water content. The types of ground that may be consolidated by means of extracting water is not limited to the examples presented herein.

Embodiments of the invention also include a method of consolidating soft soil including using a vertical drain as substantially described herein. An embodiment of the invention includes a method of consolidating soft soil including using the vertical drain as described above. The methods of consolidating soft soil including using a vertical drain may be performed with the application of vacuum suction onto the vertical drain directly or indirectly.

Embodiments of the invention also include a method of consolidating soft soil including using an array of vertical drains and conductive strips as substantially described herein. An embodiment of the invention includes a method consolidating soft soil including using an array of vertical drains and conductive strips as described above. The methods of consolidating soft soil including using an array of vertical drains and conductive strips may be performed with the application of vacuum suction onto the vertical drains directly or indirectly.

It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. For example, it will be appreciated that embodiments are not limited to the example materials, shapes, and dimensions described herein.