WO2020091689A1

WO2020091689A1 - A dischargeable electric vertical drain

Info

Publication number: WO2020091689A1
Application number: PCT/SG2019/050513
Authority: WO
Inventors: Richard Douglas Sandanasamy
Original assignee: Richard Douglas Sandanasamy
Priority date: 2018-11-01
Filing date: 2019-10-17
Publication date: 2020-05-07
Also published as: SG11202103416QA; SG10201809736YA

Abstract

An electrically conductive and elongate Cathode Vertical Drain (Cathode EVD) for draining fluid from ground soil, featuring means to introduce vertical suction of fluid from above ground, along its embedded length in soil; permeable around its circumference and flexible in form; which is capable of manufacture in coil lengths, suitable for continual installation to varied depths.

Description

A Dischargeable Electric Vertical Drain

DESCRIPTION

The most common method used in the consolidation of soft soils in the last five decades or so, is the use of Prefabricated Vertical Drains (PVDs) with a surcharge load, or with vacuum suction, or a combination of both.

An electrically conductive vertical drain (EVD) for the consolidation of soft soils by means of electro-osmosis, has been disclosed in Singapore Patent No. 76511.

In the field application of the referred invention, EVDs are typically manufactured in coils of at least a 100m in length to be mounted on an installation rig for rapid and continual installation, just as in the case of PVDs. Due to the large volumes needed in consolidation projects, such a rapid and continual installation technique is preferred for commercial viability.

During treatment of soft soils by electro-osmosis, each EVD of an array or a grid of EVDs is connected to a positive or a negative terminal of a Direct Current (DC) source. The electric field, induced into the soft soil through the EVDs, attracts clay particles towards the EVDs connected to the positive DC (anodes) and water towards the EVDs connected to the negative DC (cathodes). In the referred Patent, no difference is identified between an EVD acting as an anode, and that as a cathode. They are identical. At the same time, there is no disclosure or claim(s) that the embodiment of the singular form of EVD in the Patent, provides means for the introduction of suction into and around the core of the cathode EVD, along its length.

During the process of electro-osmosis, a column of fluid builds-up at the cathode EVD that acts as a gravitational back pressure against the electro-osmotic pressure induced by the voltage gradient between the anodes and cathodes. When the two opposing pressures equate, the treatment ceases to have any further consolidation effect. This phenomenon significantly retards the performance of EVD type electro-osmotic consolidation in practice. The downside of an identical anode and cathode EVD, in the form disclosed in Singapore Patent No. 76511, is that it does not provide means to introduce suction within its core and around its length to remove the fluid build-up at the cathodes.

Laboratory studies and field trials have been made to combine consolidation pressures by physical load, vacuum and electro-osmosis with drainage or suction at the cathodes. However, the cathodes used in the field trials are individually fabricated steel or copper tubes which are not commercially viable beyond a plot trial.

This invention then relates to a varied form of a cathode EVD, that features means for introduction of suction into its core and around its length, while being permeable and flexible, capable of continual manufacture in coils of at least 100m, and which may be mounted on and installed by the same installation rig as used for PVD and/or EVD, rendering it commercially viable. Electro-osmotic strengthening of soft clays can then be implemented with suction at the cathode EVDs, making possible a rapid consolidation that has never so far been achieved in commercial scale.

1

SUBSTITUTE SHEET RULE 26 In order that the present invention may be more easily understood, the embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1A is a cross-section through a schematic representation of a conventional ground consolidation system using PVDs with surcharge load;

FIG. IB is a cross-section through a schematic representation of a conventional ground consolidation system using PVDs with vacuum or surcharge with vacuum;

FIG. 1C is a cross-section through a schematic representation of a ground consolidation system using conventional EVD with voltage potential;

FIG. ID is a cross section through a schematic representation of an installation rig mounted to an excavator to install PVD and/or EVD from mounted coils of at least 100m;

FIG. IE is a cross section through a schematic representation illustrating the gravitational fluid back-pressure acting against the induced electro-osmotic pressure;

FIG. IF is a cross-section through a schematic representation of a ground consolidation system using conventional anode EVD coupled with one embodiment of the present invention providing for the introduction of suction at the Cathode EVDs concurrently with voltage potential.

FIG. 2A is a cross-section of one embodiment of the present invention comprising of a flexible core with permeable tubes, made from an electrically conductive polymer;

FIG. 2B is a cross-section of FIG. 2A with a conductive element encapsulated within its core;

FIG. 2C is a front view of a close-fitting suction tube inserted into a permeable tube of embodiments 2A and 2B (immediately upon installation), past the impermeable layer of the soil strata;

FIG. 2D is a cross-section of another embodiment of the present invention where the Cathode EVD comprises of a flexible and permeable tube, electrically conductive along its length;

FIG. 2E is a cross-section of an embodiment such as in FIG. 2D incorporating an electrically conductive element along its length;

FIG. 2F is a front elevation of an electrically conductive metallic element in tubular form that is flexible and permeable along its length;

FIG. 2G is FIG. 2F with a coating of conductive polymer;

FIG. 2H is a front view of a close-fitting suction tube 3 inserted into embodiments such as 2D, 2E, 2F and 2G, past the impermeable layer of the soil strata;

2

SUBSTITUTE SHEET RULE 26 FIG. 21 is a front view of an alternative embodiment of the present invention comprising an assembly added to a conventional EVP, functioning as a Cathode EVD, to allow means for introduction of suction into its core and along its length, while maintaining a sealed electrical connection.

Referring to FIG. 2A, a Cathode EVD 1 embodying the present invention comprises an electrically conductive profiled polymer core with a pair of permeable tubes 2 at each end that would provide means to insert a close-fitting tube 3 (in FIG. 2C) up to some length to introduce vacuum suction along its length. The functional arrangement is illustrated in FIG. 2C.

Referring to FIG. 2B, a Cathode EVD 1 embodying the present invention comprises an electrically conductive profiled polymer core, encapsulating a conductive element, with a pair of permeable tubes 2 at each end that would provide means to insert a close-fitting tube 3 (in FIG. 2C) up to some length to introduce vacuum suction along its length. The functional arrangement is illustrated in FIG. 2C.

Referring to FIG. 2D, another embodiment of the present invention comprises an electrically conductive and permeable flexible tube 2 that would provide means to insert a close-fitting tube 3 (in FIG. 2H) up to some length to introduce vacuum suction along its length. The functional arrangement is illustrated in FIG. 2H.

Referring to FIG. 2E, such an embodiment as FIG. 2D may feature a conducting element 4 to enhance its electrical conductivity along its length. The functional arrangement is illustrated in FIG. 2H.

Referring to FIG. 2F, another embodiment of the present invention comprises electrically conductive metallic element in tubular form 2 that is permeable and flexible along its length. The functional arrangement is illustrated in FIG. 2H.

Referring to FIG. 2G, another embodiment of the present invention comprises a metallic element in tubular form 2 with a conductive polymer coverage, that is permeable and flexible along is length. The functional arrangement is illustrated in FIG. 2H.

Referring to FIG. 21, an alternative embodiment of the present invention of a Cathode EVD is the use of an assembly of fitments to facilitate the introduction of suction into a conventional EVD featuring an air-tight electrical connectivity 5. Although various forms of connecting suction tubing to PVDs are known in vacuum consolidation, there is no disclosure on any means to add concurrent electro-osmotic treatment.

3

SUBSTITUTE SHEET RULE 26

Claims

CLAIMS What is claimed is:

1. A permeable and flexible cathode Electric Vertical Drain (EVD), for consolidation of soft soils by electro-osmosis, providing means to introduce suction into its core and along its length.

2. A cathode EVD as in Claim 1 where it comprises or includes at least one permeable and flexible tube, featuring a hollow internal core;

3. A cathode EVD as in Claim 2 where the elongate permeable tube deployed for suction, is not an integral part of the cathode EVD.

4. A cathode EVD as in Claim 2 and 3 where the elongate tube may not be circular in its cross-section;

5. A cathode EVD as in Claim 2, 3 and 4, where the tube is made of at least a conductive polymer or a conductive metal or a combination of both;

6. A cathode EVD as in the preceding Claims, provided with a filter fabric;

7. A cathode EVD made with fitments attached to a conventional EVD, as described in Singapore Patent No. 76511, to receive suction into its core whilst providing means for air-tight electrical connectivity.

4

SUBSTITUTE SHEET RULE 26