GB2546444A

GB2546444A - Electrode assembly, electrode assembly product, electrode assembly system and method for installing electrode assembly

Info

Publication number: GB2546444A
Application number: GB1706619.2A
Authority: GB
Inventors: Jones Colin; Lamont-Black John
Original assignee: Electrokinetic Ltd
Current assignee: Electrokinetic Ltd
Priority date: 2014-11-20
Filing date: 2014-11-20
Publication date: 2017-07-19
Anticipated expiration: 2034-11-20
Also published as: GB2532483A; GB2532483B; GB201706619D0; GB2546444B; GB201420651D0

Abstract

An electrode assembly 20 for installation and electrokinetic treatment of the substrate. The electrode assembly comprises a tube 22 for collecting and draining fluid from the substrate said tube having a sidewall comprising openings (fig. 1; 14) for allowing fluid to enter the tube from the substrate a filtration membrane 24 surrounding the tube for preventing at least some particulate matter from entering the tube; and a plurality of conducting members 26, 28 surrounding or associated with said filtration membrane, the filtration membrane (24) extending transversely away from said tube to form an extended collection region 30, comprising two adjacent spaced-apart portions of the filtration membrane for collecting fluid from the substrate for drainage by the tube . A further electrode assembly where a first longitudinal section and at least one second longitudinal section are configured such that the sections are operable for conducting electrical current independently each other is also claimed. Claims for an electrode assembly product and system comprising an electrode assembly and a method of installation are also contained. The electrode assembly may be flexible.

Description

electrode assembly,

ASSEMBLY "sYETSM AND. yETHOD EOR INSTALLING ELECTRODE ASSEMBLY

Th@: present invention relates to: an e Lectrode assembly, a produet and system comprising said electrode assembly, and a metbed for installing said electrode assembly, and relates particular!*, but set exclusively, to a cathofc assembly far use in an eiectrokinetic systern for treatinq a ground: substratel

Electrokinetic processes can be used for ground improvement and reinforcement and slope stabilisation. In particular, eleetrokiueUc treatments can be used to improve the strength of the. soil material, reduce pore water pressure, reinforce the soil mass and provide drainage. Anode and cathode electrodes are installed into the ground and connected to a power supply to set up electric fields within the soil mass. This causes water to flow away from: the; anodes and towards the cathodes, which collect and drain the water from: the treated ground. Soft and disturbed soils1 may experience a large pore water suction resulting in consolidation g| the soil and an increase in. its cohesion. After completion of the active electrokineti© treatment, the anodes; may be completed as soil hails and the cathodps may remain in the ground as drams.

Slope stabiiisatfon is an important application of :el ed t mil net ic ground treatments. Instable embankments and cuttings represent a major problem for railway and highway authorities. Ih the majority of oases slopes in soils fall or become unstable owing to a number of factors, including weak soils, excessive pore water pressures, over-steepened s1 opes, and: excessive external loadings,: A recurrent issue in ground engineering is a generally large degree of uncertainty about the composition, distribution and engineering characteristics of the materials in the ground. Simula r Ly, variations in groundwater composition, quantity and flow in spatial and temporal dimens 1 oris ! requenliy introduces additional complexitf and uncertainty in geomechanical, hydraulic, e .1. e c t r o k me t i c a η o elect, rical characteristics . Under -such uncertainties it is necessary that any engineering intervention, used to improve or stabilise the ground should be inherently adaptable to ground and groundwater conditions that may change and change rapidly with respect to space and or time.

Electrokinetic ground improvement and slope stabilisation,, for example using e.l ectrokinet ic geosynthetic (EKG) materials, is adaptable to a large range of ground conditions. The approach comprises up to .four different treatment components, namely: (i) ground improvement by electro-osmosis, (i 1 } ground st.rengthening using reinforcement (ill:} drainage and, optionally, (iv) soil modification using chemical conditioners,

In the active phase, that is, during the application of the electric field, water is transported by electre-osmosis through the soil, mass towards: the cathodes,:: in the treatment of slopes:, the cathodes may be installed rising a few degrees above the horizontal in order to encourage drainage of water out of the slope. During: the passive phase, that is, after the voltage has been removed from the elect rode:?, the installed, cathodes continue to intercept and drain zones of groundwater,

Electro “©smotic flow of water and the" development" of increased effective stress ip driven by a combination1 of the electro··osmotic characteristics of the ground and the electric field generated in the g round by the arrangement Of the electrodes and the voltages applied to the electrodes. The functions required from anode and calbode electrodes are dissimilar and therefore: their structure and deployment are different.

Preferred embodiments of the present Invention seek: to overcome; one or more disadvantages of the prior art,:

According to a fijg&t aspect of the invention, there is provided an electrode assembly, for installation in a substrate for use in e iectrokinet iu treatment; of the substrate, the:: electrode: assemb!y comprising: a tube for collecting and draining fluid from the supshrafe,: said tube having a sidewall comprising openings for allowing1 fluid to enter the tube from the substrate; a filtration membrane surrounding the tube, for preventing at least some part.·, enlace matter from entering the tube through said openings; and a plurality of conducting members surrounding or associated with said if. It rat ion membrane; wherein said electrode assent.Iy is :flex 1bid,

Being flegible, the electrode assembly is able to adapt to non ··linear alignments in the ground:. These: map arise as a result of design in t en t ion ,: f or example bp the employment of directional drilling techniques, which set out with the intention of creating a curved borehole, or an anticipated deviation from linearity during service owing to ground movements cause# by consolidation or shear deformation.

For example,: an electrode assembly may be installed1 in a trench having1 a rough mt uneven profile as a result op obstructions such as boulders. A flexible electrode assembly may accommodate bending and flexing without cracking or fracturing when the trench is backfilled. Flexible electrodes may also bend to accornmodate small ground movements without the risk of cracking or rupturing.

Flexible electrode assemblies may be i>. t e n tο n a 11 y installed in an Intentionally curvilinear arrangement, which may provide various advantages, including improving the uniformity Of an electric field, generating an electric field which follows a curved a hear sari ace or failure zone,, optimisation of bhe se i f-draining furct:; cn of the cathodes, and improvement of the installation process. For example, this may allow electrodes to be installed in a desired location from a position of relative ease (compared to, for example, slope climbing! and thereby reduce costa.

Using flexible: electrode assemblies, long electrodes may be installed as a continuous, non-modular electrode, and may be conveniently transported as a coil or on a reel.

The electrode assembly may be flexible to thS: extent that; at least a portion of the electrode assembly 1s reconfiguraOl e between a substantially straight, configuration and a curved conflguration haying a radius Of curvature substantially equal to hr less than; 10 mitres;,

Said curved configuration may have a radius of curvature substantially: equal;; to of less than 5 metres, or substantially equal to or less than 1 metre.

According to a second aspect of the: invention, there is provided an electrode assembly,: for installation in a. substrate fbr use cn electrokinetic; treatment o f t h e substra Le, the electrode assembly comprising; a tube for collecting and a raining fluid frorti the substrate, saro tube haying a sidewall comprising openings fox allowing fluid to enter the tube; from the substrate; a ii 11.ration membrane surrounding the tube, for preventing: at j,east some pari", . curate matter from entering the tube: through said openings;: and a mesh surrounding said filtration membrane, xesh comprising a plurality of conducting members,:

The mesh of conducting members surrounding the filtration membrane .reduces the likelihood of puncture or other damage: to the f i. .1 t- rat. lou membrane, which may result from Intenaction w 11h roots and she.' ?:P stones or other sharp objects in tne ground, p&rclcu.larly during the i nstallation process or due to subsequent ground movements. Damage may allow the ingress of silt, which would, clog the tube and recuce drainage.

The mesh may compr ise at least one metal.

Meters advantageous1y provi de both strength and good electrical conductivity.

Tne mesr. may comprise two or mo re different metals:.

This enables the individual properties of different rnetals, for example conductivity, corrosion resistance and strength, to be combined. In particular, the metals in the mesh may be selected to achieve both the desired strength and tne resistance necessary to avoid unacceptably high, voltage drops.

The mesh may comprise copper.

Tne mesh may Comprise: stainless steel. in particular, a blend of copper and stainless steel provides a mesh which rs both strong and has high co;:duc... rv a i.y.

The mesh may be oraxded.

Branding gives good mechanical strength, and ensures that the conduct.;.no members of the mesh are firmly associated with each other, improving voltage transmission to the distal end of the electrode.

Accordinc to a third aspect of the invention, there is provided an electrode assembly, for installation in a substrate for use in electroKinetic treatment of the substrate, the electrode assembly comprising: a tube for collecting and draining fluid from the substrate, said: tube: having a Sidewall comprising openings for allowing fluid to enter the tube from the subffrate; a filtration membrane surrounding the tube, for preventing at least some pfrtlculete patter Ifop entering the tube through .said openings? snd a plurality of conduct n rig members associated with said filtration membrane; 'wherein said filtration membrane extends transversely away from said tube to form an attended Collection region Comprising two adjacent spaced-apart portions of the filtration membrane, lor collecting fluid from the substrate for drainage by the tube.

The extended collection region provided by the: electrdllnetic filtration membrane provides a larger electrode surface area for driving ei ectro-osmotic flow and a larger filtration surface over which fluid is collected;:. In use, the extended collection region extends upwardly: from the tube, so that fluid entering the collection region mibnes downwards under gravity to the tube, enters the tube through the openings and then drains along the tube.

The electrode assembly may further comprise a spacer element located between: said adjacent spaced-apart portions of the filtration membrane.

The spacer element may hold the two portions of the filtration membrane apart to improve drainage item the space between them to the tube,:

The: collection region may be substantially planar.

The: plurality of conducting members may comprise substantially transversely-oriented conducting members and substantially long], tudinall y-ori ented conducting members.

This arrangement may improve conduction of electric current through the filtration membrane to ensure that ail parts of the id itration membrane are able to act as an electrode.

The plurality of conducting triorabers may be substantially evenly Spaced in the transverse and/or 1 ongi tudinar direct:ions .

The electrode assembly may further camp rise" a: plural-ty of closely--spaced, longitudinally-orrented conducting members at an edge of the1 filtration membrahe distal from the tube.

In use, these conducting members can im used t© provide a relatively .1 ow- res i s t ance path for conducting electricity -ut;> parts Of the electrode assembly distant from the power supply so that; the voltage drop along the electrode assembly mini in: sed.

The el-. c:: rode assembly defined above may further comprise at least one first longitudinal section and: at least" one second longitudinal section, configured: such that:, in use, said first longitudinal section is operable for conducting electrical current to pr: from, said suestrate independently of said second longitudinal section,

According to a fourth aspect of the invention, there ip provided an electrode assembly, for Installation in a substrate for use in e lect rok inet ic. treatment of the substrate? the electrode assembly comprising: a tube for collecting and draining fluid from the substratei:, said tube having a sidewall comprising openings fob allowing fluid to enter fet|e: tube from the substrate; a filtration membrane surrounding the tube, for preventing at least some particulate matter from entering the tube1 through said openings; ana a plurality of conducting members surrounding or" associated with said fllrratidh membrane; wherein the electrode assembly comprises at least one first long·; tudinal section and at least one second longitudinal sectibh:, configured such that, in use, said first longitudinal· sectior. Is operable for conducting electrical current fo or r.com. said substrate independently of said second lougitudi rial section.

By a.'i Lowing; operation of the first longitudinal section tor conducting electrical current to or: £ rom said substrate;, independently of said second longitudinal section, costs and duration of. treatment may be reduced, by se l ectiveiy targeting the electrokinetic. treatment. For example, a voltage may be applied only to sections of the electrode assembly proximal to the slope surface, or to a speak zone of the ground, or another region vhere e.1.ectrok.1 neCic ground improvement is particularly beneficial. the passive: drainage function of non-electrifled sections of the electrode assembly may still be beneficial in other regions where electrokinetic ground improvement is; of 1 cwg.r ben ©fit.

In one embodiment, the conducting members in said first longitudinal: section ape electrically isolated from conducting members in said second longitudinal sect.i.o;:·.

In. another embodiment, the electrode assembly further; comprises an insulating layer for insulating conducting members; ih said second long; tcarnal section from said substrate,;

In another embodiment, said conducting members surround or are associated with said1 filtration membrane only in said: first 1OhgiLudinaI section.

The electrode assembly according to: the second, third c.r fourth aspects of the invention may be flexible.

The: electrode assembly may be flexible to the extent thai;. :at least a portion of the electrode assembly is rbconfigurab]e between a substantially straight configuration and a curv« conixguration having a .radius of curvature substantially eqUaj. to or less than 10 met res.

Said. carved conf.1 guration may have a radi<·53 v* -urvatu..e substantia 11y equal to or leas than 5 metres, or sa^ta^Uallv equal to or less than 1 metre, lid electrode assemla i y according to any °:· t;:,.. abovo aspects of the invention may be a cathode as semis.1-1>

The electrode assembly is par tree';ariy suited for electrokinetic dra;nage of water from, ground subs-rates, during which process water drains towards the cathodes,: However, .one skilled person will:: appreciate: that any of the elec-rode assemblies described above may be operated as an anode deoenaincf on the application.

The substrate may be a ground substrate.

The fluid may comprise water.

The filtration membrane may comprise: a geosynthetic material *

The filtraticn membrane: may comprise a geotextiie.

The filtration membrane comprises an electrokinetic: geosyhthe tic material.

According to a fifth aspect of the invention, there is provided an electrode assembly product comprising: an electrode assembly according to any of the first to fourth aspects of the invention, where in said electrode assembly is arranged as a coil. A coiled electrode assembly is p a r t) c u I a r .1 y convenient for transport and installation. This enables long electrodes to be manufactured and transported t.o site as a single, non - .modular electrode, improving manufacturing efficiency, reducing installation time and reducing space requirements at the installation site.

The electrode assembly product may further comprise a reel around which said electrode assembly is wound.

This may improve ease of instaliation, particularly where access is limited,, as the electrode assembly may be gradually unwound as it is installed.

According to a sixth aspect: of the invention, there is provided an eie<...Lrokinei in.: system, comprising: m plurality of electrodes installed in a substrate for use in electrokinetic treatment of the substrata, the plurality of e i ectrodes corrpris ing at least one: f irst electrode:, and aleast pne second electrode spaced apart from said first electrode; and at least :bne power supply for applying a potential difference between at least one said first electrode and at least pnei said second electrode for driving an electroki.netic process within the substrate; wherein at least one said e1ectrode comprises an electrode assembly according to any of the first to fourth aspects of the invention,

At least a portion of at least one said electrode may be substantially curved.

The portion of said at least one sold electrode may have a radius of curvature substantially equal to or less than ID metres.

The portion of said at least one said electrode may have a radius of curvature substanfaaily equal to or less than Γ metro. A~ elect.roki netic system including one or more: curved or curvi-linear electrodes may generate electric fields better adapted ta:; the peculiarities of the substrate to be treated,:: for example to adapt the electric field to a curved shear surfaces,: or to improve; uniformity of the field generated.

At least one said electrode may comprise n electrode assernb ly wherein the elect rode assembly comprises11 at least one first longitudinal section and at least one second longitudinal section, configured Such that, In use, said first longitudinal section is operab.1 e for conducting electrical current to or from said substrate i n dependent i y of said second longitudinal section, wherein conducting members in said first longitudinal section are e1ectrically~cοηnected to at least one said power supply, and wherein conducting members in said second longitudinal section are not electrlea11y“connected to a power supply.

This allows eieotrokinet.i.c treatment to be:: targeted:: at the ddnies^ where it is mbit beneficial, while allowing passive drainage at other zones, resulting in a re duel, ion in costs -

According to a seventh aspect of the invention, there is provided a method for installing an electrode assembly i-n a substrate, for use in electrokinetic treatment of the substrate, the method comprising: providing an electrode assernbIy; forming a trench or borehole; and inserting said: electrode assembly into said trench or borehole:; wherein said trench or borehole is substant ial.'; y curved1*

At least a portion of the trench or borehole may have a radius: of curvature substantially equal to or less than 10 metres·:

At least a portion of the trench or borehole may have a radius of curvature substantially equal tg or less than 5 metres .

The electrode assembly may be provided: as a coil; said: method further: compel sing the: step of Unwinding the electrode assembly from the coll as it is fed into the trench or borehole*

The electrode assembly may comprise an electrode assembly according to any of the first to fourth aspects of the invention. Ά preferred embodiment of the present invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which:

Figure 1 shows an armoured electrode assembly according to an embodiment of the present invention;

Figure 2 shows an electrode assembly according to another embodiment of the invention;

Figure 3 schematically illustrates an electrokinetic system according to a further embodiment of the invention;

Figure 4 schematically illustrates another electroki.net.ic system according to a further embodiment, of the invention;

Figure 5 schematically illustrates another electrokinetic system according to a further embodiment of the invention;

Figure 6 schematically illustrates another electrokinetic system according to a further embodiment of the invention;

Figure 7 schematically illustrates another electrokinetic system according to a further embodiment of the invention; and

Figure 8 schematically illustrates another electrokinetic system according to a further embodiment of the invention. A first embodiment of an electrode assembly 10 according to the present invention is shown in Figure 1, in the form of a cathode assembly 10 for installation in a ground substrate for use in electrokinetic treatment of the ground. In electrokinetic ground treatment, a cathode has two primary functions. Firstly, it. acts as a negatively charged electrode and thus collects current .f rorn the ground and conoucts It to the surface where it is connected via a cable array to a power supply, "Secondly, it collects: iWatsf: from the ground and conducts it to the star face arid thus but of the ground.

Referring to Figure .1., the electrode assembly 10 comprises a tube 12 for coileotinf and draining water from the ground:.

Tide c.u.be 12 has......openings 14 along the length of its sidewail, through which fluid; from the substrate can enter the tube 12. The openings 1,4 may be holes or slots, formed for example by perforating tbs sidewall. A11ernative 1 y, the sidewall of the: tube 12 may hay® a mesh or grid-1 ike structure. Cathodes are generally installed rising: & few degrees above the horizontal sio that any water entering the tube 12 can drain along the tu.oe and out gf the ground. The materials and size of the: tube may joe selected according to the application. In one example, the; tube 12 is a plastic tube approximately SO - 6Omrn in aiamoter„ The tube 12 may be rigid or flexible:;.: The size of the holes or openings 14 in the tube 12 may, for example, be in the range of

Qi, 5 to 8 mi 11 ime t r e s * A filtration membrane 16 surrounds the tube 12, for preventing at least some particulate matter, i.e. fine grained mater 1 a1, from entering the tube 12 through the openings 14 and potentially clogging tne drainage tube M, The filtration membrane: 16 is selected by air pernieability and: pore size to be most appropriate for the:; particle si ze distfibutidh Of the substrate in which it is to be installed. Sui’..able materials for the filtration membrane 16 include geosynthetic materials such as geo text iMs, for example woven of non ~ v/ov e η po 1 y me r 1 c fabrics such as polyester, polypropylene polyamide, polyacrylamide and nylon etc. The pore size associated with the f il trav. ion membrane 16 may range from approximately 5Θ micrometres to approximately micrometres::. A metallic mesl 18 surrounds the filtration membrane 16. In use, the rnesh 16 is connected to a power supply so that the e.lecerode assembly acts as a cathode. The conducting mesh IS .has a sufficiently low e Lectricai resistance to conduct the anticipated current to the distal end of the cathode (i.e. the end deepest in the ground or furtnesL from the connection to the power supply) without suffering large voltage drops. This becomes particularly important if the cathodes is long, for example in excess of 12m, Furthermore, the cathode needs to resist: diametrical brushing, tear: or puncture damage to filtration membrane 16 due to roots, sharp stones or other sharp obj ects in the ground - This is particularly likely during the installation process. xt has 536611 found that a conductive mesh 18 Gin provide the necessary conductivity while offering sufficient protection f° the filtration membrane 11. The electrode assembly stay be referred to as ah 'srτπo,.!rod, electrode assembly due to the prdtdctibh provided by the metallic mesh 18. In this embodiment, th© aesn 18 Is a braided metallic: mesh. Braiding ensures good dontact between the multiple conducting members of the mesh 18' thereby ensuring good electrical conductivity along the ien^h of the electrode assembly 10, even: if it suffers minor d^age. Metallic conducting members:: may Pi6-M.de. feed strength, 0«Ι=ϋ«Υ and electrical conductivity. The mesh 18 may CompUse «MMss steel, sapper, mild steel, aluminium or other" elec'tI:icalIf seductive material..... The numeer, density, comp®^tlSnal Μβηά and ai*fcter of the metals ·>· he mesh 18 are selected to achieve the or other materials in '' „ . . r0 avoid unacceptably high voltage drops resistance necessary 1 ., electrode 1Θ, For exampl e, the mesh 18 along the length of f.ne ·:,.-.nd of two dif ferent metals, for example may bp .termed from a bi ^ed copper or other conductive fibre, to stainless steel and th- c .5ct ivit v. The mesh 18 may be configured provide the desired coJ> . welded structure. As an example, the as a woven, braided b" ,., f rhe: mesh 18 may have diameters in the diameter of the wires ^ range from; approximately ©.1 millimetres to approximately 0.7 millimetres. The mesh 18 may be: configured with a square, hexagonal, rhomboidal or: ocher polygonal pat tern, with: a character is t id Spacing between the v;i res being in the range 0.2 to 10 millimetres. The mesh 18 may be flexible, enabling the electrode assembly 10 to be formed rigid of flexible, depending also on the composition and structure of material used for the drainage tube .1.2.

With reference to Figure 2, an embodiment of ah elect rode assembly 2C for use in e 1 e c t r o k. :i r. s t i. c treatment of a subs trace, according tp another embodiment of the invention comprises a tube 22 for collect! ng and draining fluid from the substrate,: a filtration membrane 24, and a plurality" of conducting members 26, 28 associated with said filtration membrane 24. As in the previous embodiment, the tube 22 comprises openings (not visible in Figure 2} for allowing fluid: to enter the tube 22 from the substrate, and the filtration membrane 24 surrounds the tube 22 to prevent fine-grained particulate matter from entering the tube through the openings, to prevent clogging Of the tube 22,

The conducting members 26, 28 include transverse conductors 26 and longitudinal conductors 28, distributed throughout the filtration membrane 24, fob collecting electrical current from the substrate end: transmitting it through the filtration membrane 24 to a power supply. The filtration membrane 24 may comprise a geosynt heic material, irf particular" ah. electrokinetic geggynthetif material or textile , Ihe cοnducting members 26, 28 may be woven, sewn or otherwise integrated into the: fabric of the: filtration membrane: 24. As an example, the conductifg members 26, 28 may be wires haying diameters in the range from approximately 0,1 millimetres:: to approximately 0.7 millimetres, spaced apart by around 0,2 to 10 millimetres.

The filtration membrane 24 extends transversely away from, the tube 22 to form an extended collection region 30 comprising two adjacent, portions of the filtration membrane M, which are held apart by an internal spacer 32, and the space between chem. In use, the extended collection region or 'drainage fin* 30 extends substantially vertically upwards above the drainage tube 22. Water collected In the drainage fin 30 is conducted, vertically downwards under gravity and enters the tube 22 for drainage out of the substrate:. To connect: the transverse and longitudinal conductors 26., 28 to a power supply, a plurality of close]y-spaced, longitudinally-oriented: conducting member® 34 are provided at the edge of the filtration membrane 24, at the upper edge of the drainage fin 30. These conducting members 34 form a conductive strip which ensures good electrical connection between the power supply connector 36 and all: of the transverse conductors 26, to minim i se any voltage drop along the longitudinal length of the electrode assembly. 20. The 'drainage fin' 30 may extend up to around 3 metres or so from the drainage tube 22. The

The electrode assemblies IQ, 20 shown in Figures; 1 and 2 •respectively may be flexible. Flexible electrodes offer additional advantages in that they are able to be» installed along curved paths, for example 1o adapt the shape; of electric field produced by the; electrodes to the; shape, of a; sheer surface (failure surface} in the ground.: Directional drilling techniques may be used to create; an intentionally curved borehole. Flexible electrodes; may also adapt during service to ground movements caused by consol ids ϊ. ion or shear deformation. The curvature of a borehole formed by direct Iona l. drilling techniques may be limited to a radius ocurvature of around 10 metres:, depending on the site and length of the borehole. A flexible electrode is roqui red fop insertion into such a curved borehole. However, the electrodes may be sufficiently flexible to adapt to more abrupt changes: in direction, for example due to deformations or movements ip the ground, or a sharp change in direction where a borehole meets the surface. For example. the electrode assemblies may be sufficient Ly flexible to adapt tb a radius of curvature of around 1 metre or less,

Another convenience of flexible electrode assemblies is that they may be provided as a product in a coiled form. This saves space and makes transport of the electrode assemblies more straightforward. In addition,, it enables the electrode assembly to foe installed on site from a coil or reel. This can be useful for installing long electrodes, particularly where access Is difficult, since these might otherwise need to he installed in sections which would then need to be electrically arid mechanicaliy connected tb each other. In electofeinetio installations, a typical length of the cathodes is in the range l.J to IS metres, but cathodes longer:: than 20 metres have been installed at some sites and it is likely that some applications Wifll regufte significantly longer cathodes,: By providing a flexible electrode assembly wound in a coll or on a reel, the electrode assemoiy can foe Unwound from the coil or reel as It is fed into the trench ©t borehole, saving space at the: installation site;. The inner portion of the coil, or the core of a reel on which the boil is wound,: may typically have a diameter from around 20 centimetres up to around 2 metres, this requires sufficient flexibility that the; electrode assembly can: be curved to a radius of curvature of around 1 metre or less,:

Examples of installed electrdkrnetie systems incorporating flexible cathodes are if lust rated .:. n Figures 3 to 7.

Figure 3 shows an electrokinftic system 4f> comprising a plurality of electrodes 42, 48 installed in a substrate 41, in the form of a slope 4 r, for Usd In alec troki ret.ic treatment of the substrate 41. The electrodes 42, 48 comprise multiple first electrodes 0 add multiple second electrodes 4:8 spaced apart from::: said fir at electrodes 42,, Here, the first electrodes; 42 arc cathodes ana tne second c iectrodes 4 8 are anodes. The electrskinetic system, 40 also corripri ses one or more; power ,. applies and: associated cableo (not shown; -tor applying «. pctenlral difference betvein thl anodes 48 and cathodes 42 for giving an electrokinctic process within the substrate 41.

In this embodiment, the cathodes 42 amn formed using flexible cathode assemblies 10 as described above with reference no Figure 1. lie cathodes pi are installed in trenches 46 or slits firmed using, for example:, a narrow bucket excavator,, a drag iine or mole plough. The tfinches 46 may have a rough or uneven profile as a result oi obstructions e.g. beulders. A flexible cathode 42 is placed in the bottom of: a respective trench 46, thereby taking In a curved It curvilinear profile according to the profile of the bottom of the trench 42. The trenches 4 6 and cathodes 4 2 arid also:: curved at the "base, of the installation so that......the lower einidu 42a of the1 cathodes return to the surface of the slope iiThis allows wafer collected in ihe drainace tubes 12 of the cathode assemblies If to drain out of the slope 41.

The cathodes 4 2 are then surrounded with a porous particulate material which is selected to have:: a suitable particle size distribution for retaining water within its pore spaces for transmission of the electric field between the anodes 48 and the cathodes 42. The flexible cathodes 42 are able to accommodate bending and flexing without era eking of fracturing when the trenches 4 6 a re bflkflildd:,: either with the originally1 excavated material or granular drainage material such as clean gravel:. The mesh 18 of the cathode assemblies 10 of the cathodes 42 prevent damage to t::|®::: f lit ration: membrane: 16 du r i na installation or subsequent ground movements:.

In the embodiment shown in Figure 3, the anodes 4 8 are installed substantially orthogonal to the cathodes 42. The ends 48a of the anodes 48 are accessible at the surface of the slope 41 to allow connection to a power supply.

Figure 4 shows another eieccrokineLic system 50 comprising a plurality of electrodes 52, 58 installed in a substrate |1,; in the form of a slope 5.1, for use in e i ectrokrneti-C treatment of the::: subst ra te 51. As in the previous embodiment;, the electrodes 52, 58 comprise multiple cathodes 52 and anodes 58 spaced apart from each other and connected to one or more power supplies (not shown).

In. this embodiment, the cathodes 52 are formed using flexible cathode assemblies 20 as described above! with reference to Figure 2. As in the previous embodiment, the cathodes 52 a re installed in trenches 56, and their flexibility allows them. %o adapt to the profile of the trenches 56. .1 n particular, the upper portions of the cathodes 52 are substantially parallel to the slope 52, but the Cathodes 52 are bent or curved close to the base of the slope 51 so that the lower ends 52a of the cathodes '52 emerge at the base of the s Lope 51. The anodes 58 are installed substantially orthogona L to the slope 51, with their ends 58a accessible sat the surface of the slope 51. The extended collection region Or drainage! fin 54, 30 of each cathode assembly 52, 20 extends upward from the drainage tube 52, 22 so that water collected id the dPilnapp fin 54, 30 is conducted downward to the tube 52, 2.2 for draining out of the! ground 51*

Figure 5 shows a further electrokinetic system 60 comprising a plurality of electrodes 62, 68 installed in a substrate 61, in the form of a slope 61:,: for use in eiectrokinetic treatment of the substrate 61. As in the previous embodiments, the electrodes 62, 68 comprise multiple cathodes 62 and anodes 68 spaced apart from each other and:: connected to One at more power supplies (pot shown) . The cathodes 62: are formed using flexible cathode assemblies, for example the flexible! cathode assemblies: 10, 20 as described above With reference to Figures 1 and 2*

In tills embociment, the: f lexible cathodes 62 are installed is boreholes, formed; by drilling into the slope 61 from the surface of the slop®; hi. The boreholes are drilled into the slope 61 rising a tew degrees above" horizontal so that water" collected by the cat nodes 62 drains towards the surface of the slope 61. The proximal ends 62a of the cathodes 62 emerge at the surface of the s;ope 61 to ailow the water to drain out of the qround and to allow electrical connection of the cathodes 62 to the power supply. i|s in. the previous embodiments, the anodes 58 are Installed substantially orthogonal to the slope :51., with their etas 58a accessible at the surface of the slope 51 for connection to the power supply.

The slope 61 illustrated in Figure 5 has a circularly shaped failure indicated by shear surface 66. Relative movement of the ground on each side: gf the shear surface 66 has caused a step in the profile of the cathodes @2 at the- location of the shear surface 6¾ The flexibility of the: cathodes 62 permits the accommodation of small ground movements m this manner w1thout the; risk of cracking or rupturing. Indeed, such movement is antic; paten due to consolidation and volume; change of the ground due to the electrokinetic treatment. Moreover, such movement is required by the combined treatment, in order that the anodes may take up the desired restraining load as part of their longterm passive reinforcement function.

Figure 6 illustrates a further el ectroki.net ic system 70 in Which directional drilling is used to install the cathodes 72 parallel to a curved shear surface:: 76 in a sipping ground substrate .7.1* Directional drilling ohn he used to create; boreholes which are intentionally curved; or curve1inear, The anodes 78 are installed substantially orthogonal to the; surface of the slope 71 as in the previous embodiments. This technique hah be used to tailor the shape of the electric field created ®y the e 1 cc'Lrocle3 72, 18 1.0 spec.·’: > .lc 31λ.q;qjf·qr.r<3 in the ground to be treated. &s can be seen from Figure 6, directional drilling also enables electrodes to be Installed from -p] at ground above the olope ilf wnich is often muon more accessi!>i<| fir equipment and personnel than drilling on the slope: itself and therefore reduce costs. The tipper ends 3m of the cathodes 72 are accessible above tie slope 71, and the lower ends ?ta 0f the cathodes 72 emerge :¾% various points down the surface ©f the slope 7.1 for drainage.

Figure 7 Illustrates another electrokinetic system 80, similar to that shown in Figure 6, in which directional drilling is used to install cathodes 82 parallel to a curved shear surface 86 in i Sloping ground substrate 81. ghe anodes 88 are installed substantially orthogonal to the surface of the slope 81, as in the previous: embodiments.

In tn is emboaimeht> access to the slope 81 is particu1 ariy difficult due to the presence of a cliff 83 at the foot of the slope SI. It is particularly benefloral ;n this situation tb install the cai. nodes 82 from trie flat ground above the slope 81. Ihe upper ends 82b of the cathoaes 82 are therefore accessible above the slope 81. The curved cathodes 82 are drilled into the bedrock beneath the sediments which are failing, such that the lower ends 82a of the cathodes 8? emerge in the cliff surface 83 below the slope 81 for draining water collected by the cathodes 82.

Figure 8; illustrates a furth,,r elect rokinetic system 9C comprising a plurality of eioctrodes 92, 98 installed in a substrate 91.. in the form of a giope 91, for use --n elect rokinetic treatment of the* S3Jhstrate 91. m irx embodiment described above with mmmm& to Figure: 5, the electrodes 9/, 98 comprise m.uitipie cathodes 92 and anodes spaced apart from each other and connected to one or more power supplies (fiop shown) . The cathodes 92 may formed using rigid or flexible cathode assemblies, for examples the cathode assemblies 10, 20 as described above with reference to Figures 1 and 2y and are ms failed in bore holes formed; fey drilling into the slope 9; from the; surface of the slope It. The proximal::: ends 92a bf the cathodes 9)2 emerge at the surface of the s 1 ope 91 to allow the water to drain out of the ground and to allow elect;; lea L connect ion of the cathodes 92 to the power supply. The anodes id are installed substantially orthogonal to the s loos 9.., with their ends 98a accessible at the surf ace of the slope 91 fqr gonrigpt ion to the power supply.

The slope ii illustrated in Figure 8 has a circularly-shapnd failure indicated by shear surface 96. Elegtpokinetic treatment: of the ground ll in the region 100 proximal the shear surlat:e iig and the surface of the slope 91 may be highly beneficial. in some circumstances, drainage of the ground 91 in tde region 102 further (or deeper) from the surface of the: slop6 91 may still be advantageous, but ground improvement, by xeeurblihetie treatment may be of lower value.

The cathode drains 92 shown in Figure: 8 have been adapted {;o target elect roki netlc treatment in the region ΙΘ0 proximal the shear surface 9 6, while allowing passive drainage lit the; j.-egi°r· 10? farther from the surface of the;; slope 91. The cathodes 92 comprise a first longitudinai section 92c and a second longitudinal section 92a, configured such that,, in use, gaj.d first., longitudinal section lie is operable fob conducting e Ie-otrical current to or from the' substrate;:: 91: independently of tpe second longitudinal, segtign lid, The; sections 92c of the c:3thodes 12 proximal to the surface of the: slope 91 are ^ j. e o t r i c a i 1 y ~ c ο η n e c t e a td:: a power supply so as tb act as an e].ectrode, i. e. without the application of a voltage. The sCctdons lid; of the cathodes 22 distal from the surface: of the slope @1 are not e i ecrricaily-ccnnected to a power supply s© act as passive drains, i.e. without the application of a voltage.: By targeting the eioctrokii netic treatment of the ground 91 in this way, power consumption may be reduced, leading to lower costs, and/or a shorter electpokinetic treatment phase. Further costs savings may be made due to the lower rating required for the cabling between the electrodes 92, 98 and the power supply,;

Although this concept of. targeted treatment is illustrated; using straight cathodes 92, which may be rigid or flexible, it is equally applicable to curved cathodes 92.

Electrical isolation between the fir sip and second longitudinal sections of the cathodes 92 may be achieved in several ways .

In one embodiment, the conducting members:; 18, 26, 28 surrounding or associated with the filtration membrane 16, 24 in the first longitudinal section 92c of the cathode 92 are f lectricalily isolated from those:; in the second; i ongi tudlnal section 92d of the cathodes :92. This may be achieved by a break in the conducting members ;e.g„ by a break in the mesh 18 shown in Figure 1, or: a break in the longitudinal conduct'dng members 28 and concuctive strip 34 shown in Figure 2). The conducting members 18, 2 6, 28 in each section; 92c, 92d b£ rhe cathode 92 may be Independently powerea, for example they pay each be operated at different voltages, or those in one section may be disconnacted from the power: supply io be complete 1y passive.

In another embodiment, the cathodes" §2 comprise an insulating layer surrounding the second longitudinal: section 92d of the Cathode 92, preventing electrical current from flowing from, the substrate to the cathode 92 in the region 102 in which the second longitudinal section: 92d of the cathode 92 is located.

Ih another embodiment, the second longitudinal section 92d of the cathode may be formed without any conducting members surrounding or as.soc.iar.ed with the filtration membrane 16, 24, Nonetheless, the drainage tube M, 22 and filtration membrane 16 f 24 may be oont inuous between the first and second longitudinal sections 92c, 92d.

In all three embodiments, the first and second longitudinal sections 92c, 32d nay be formed as separate cathode assemblies:, and:; Connected tog ethers by means Mfc couplets (not shown) which provide mechanical connection between the first and second longitudinal sections 92c, 92d. The couplers enable fluid to flow continuously between the; tubes of the first and second longitudinal sections 9%, 92d, but prevent ingress of fine particulate matter into the tube between the 1.1^. ^rabrob membranes of the two adjoining sections. Tne: couplers may connect adjoining sections by means of a screw tnread.

The couplers may bo configured to provide either electrical isolation or electrical connection between the first and second longitudinal sect .ions 3 2 c, 9 2d. By e .1. e c t r i c a.;. 1 y i so iat mg t.he first and second longitudinal sections 9ac, 920, they may be independently powered.

The couplers described above may also be used .tor connecting Identical or dissimilar cathode: assemblies to create a long cathode powered from a single power supply.. This may be useful for maintaining mechanical integrity, for the purposes of ease of installation and preventing fine jarticmate matter entering the tube by bypassing the filter, while maintaining electrical continuity along the length of Lhe cathode. in sucn applications,: the couplers; would be eonrif ured to provide electricaI connection between the coupled sections.

Although the above embodiments have been described .m. terms of cathode assemblies: for use as cathodes in electro.kinetj_c systems, it will be appreciated that the; described eiectroap assemblies may also be usee as anodey*

Applications of the electrode assemblies for electrokinetic treatment of slopes, namely slope stabilisation, have been described. However, the skilled person will appreciate the applicability of the above described electrode assemblies and installation techniques to horizontal ground.

The skilled person will appreciate that the features of the above-described electrode assemblies may be combined in various combinations .

It will also be appreciated that the above-described electrode assemblies may be operated as either cathodes or anodes depending on the nature of the material to be dewatered and the result to be achieved.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limitative sense, and that various alterations and .modifications are possible 'without departure from the scope of the invention as defined by the appended claims .

Claims

CLAIMS .:-. %ΐ eject rode assembly,, for installation in a, substrate for use in e 1 ectrokinetic i.reatment of the substrate, the electrode; assembly comprising: # tube for collecting and draining fluid from the substrate, sard tube having a sidewall comprising openings for sllowing tiuid uo enter the: tube from the s.ubsIrate; a firtration membrane surrounding the tube, for preventing at least some particulate matter from entering the tube through said open 1 n.gs; and a plurality of conducting members associated with said filtration memorane; therein said filtration membrane extends transversely away from said tube to form an extended collection region comprising two adjacent spaced-apart portions of the filtration membrane, for collecting fluid from the substrate for drainage by the tube,
2.,. An electrode assembly according to claim 1, further comprising a spacer element located between said adjacent spaced-apart portions of :the filtration membrane.
3. An elec-..rode assembly according; to claim 1 or 2, wherein said plurality of conducting members comprises substantially trar.sverse 1 y-oriented conducting members and sufos tantia 1iy longitudinally-oriented conducting members.
4. An eieptrode assembly according to any of claims 1 to 3, wherein said plurality of conducti ng members are substantrally evenly spaced in the transverse and/of longi tudmal dir ©ex. iorts.
5. An electrode assembly according to any of claims 1 to 1, further comprising a plurality of cm osery-spaced;, .1 ongit udinaily-oriented conducting members at an edge οι tne filtration membrane distal from the tube,:
6. An electrode as serai:: i.y accord, ---, < . ..... .. . , etug LO any ore of claims .1 to 3, wherein the e Lectrocle assembly ;--.-,rr.y.,.,.,. , y -^mpr ;.ses at least one first longitudinal sedition and at least _____„ , . ., , rfdo1· one second longitudinal sectidii, ©dnfigured such that, fn ^ ^ £i:ist lonaltud nal section is operable for conducting e:leotriBal ourrent t(> or froffi said substrate independently oi sald lBftgitudinal .section.
7. An electrode assembly; for . .......J ration m a substrate for uae in e Lect.roliner ie treatment or ,. ,.,,, ,,,,,, ; ,,,,,,,,,,,, r,, . , .. ..,..........,.... - L:«e suoscrate, the electrode a ss embiy corr.p rising: a tube for collecting and draining fluid fern, the substrata, said Mbs lading a, sidesau comprising openings for allowing; fluid to enter the tube Iron, the substrate; a filtration me*» aBrroaaa.log the tubB> fox pr.evefffelng at Hast some particulate matter from el«ing the tube through said openings; and a plurality of conducting merabe,8 sd„Blmdij5g «- associated with.....said fi Ltralion membrane; wherein the electrode assembly comprises: ai least one first longitudinal section and ::at least one second longitudinal seel.i.o% coniigured such tha..? iu use, said first longitudinal sect iot"i is oper ab j. e lot condwoLi.ng electrical current to or from said substrate;: independently of said second longitudinal section.
8. An electrode assembly according to claim 6 or claim Ί, wherein conducting members in sarc· first longitudinal section ate electrica 12.y isolated from oonauct. ir.g members in. said, second I ongil. udinul sec I 'i on . 9:. An electrode:: assembly accord ;.ng to claim 6 or alarm /, further comprising an insulating layer fgr ing-jiafmg conduct'i ng members in said second 1 οngitudi nau. section from sard sub si rate. 10i·' Mi electrode;: assembly according to claim Φ or claim 7, wherein said conducting members surround or are associated with said filtration membrane only in said first longitudinal Section. 11. in electrode assembly according to any of claims 1 to 1Θ, wherein said electrode assembly is flexible. 12. at electrode assembly according to claim 11, wherein said electrode apscmbly is flexible to the extent that at least a portion of the electrode assembly may he reconfigured between a subscantia1ly straight configuration and a curved configuration having a radius of curvature substantially equal to or less than 10 metres:.
13. An electrode assembly according any of the preceding claims, wherein said electrode assembly is a cathode assembly.
14. An electrode assembly according any of the preceding claims, wherein said Substrate is a ground substrate. li. An electrode assembly according any of the preceding Claims:, wherein said fluid comprises water.
16. An electrode assembly according any of the preceding claims, wherein said filtration membrane comprises a geosynthetiC material.
17. An electrode assembly according any: of the preceding claims, wherein said filtration membrane comprises a geotextile,
18. An electrode assembly according to any of the preceding claims, wherein said filtration membrane comprises an electrohinefic geosynthetic material.
19. An electrode assembly product comprising1* an electrode assembly according any* of fhe preceding claims:,: wherein said electrode:: assembly is arranged as a coil.
20. An electrode assembly product according to claim If, further comprising a reel around which said electrode assembly is wound.
21. Ah electrokrnetic system, comprising: a plurality of electrodes installed in a substrate: for use in electrokinetie treatment of the substrate, the plurality of electrodes comprising at least one first electrode, and at least one second electrode spaced apart from said first electrode; and at least one power supply for applying a potential difference between at least one said first electrode and at least one said second electrode for driving an electrokinetie process within the substrate; Wherein at least one said electrode comprises an electrode assembly according to any of claims 1 to 18.
22. An electrokinetie system according to claim 21, wherein at least & portion Of at least one said electrode is substantially curved.
23. Ah eleccrokinetic system according to claim ii;, wherein said portion pf said at least one said; electrode haS:: a radius of curvature substantially egual to or less than 10: metres;. 2¾. Ah electrokinetie system according to claim 23, wherein said portion of said at least one said electrode has a radius1 Of curvature: substantially sepal tq or less than 1 metre.
25. An electrokinetie system according to any one of claims 21 to 24, wherein at least one said electrode comprises an electrode assembly according to any of claims 1 to 6, wherein said collection region extends upwards from Said tube,
26. An electrokinetie system according to any of claims 21 to 25, wherein; at least one said electrode comprises an electrode assembly according to claim 8 of claim 9, wherein said conducting members of said first longitudinal section are electrically- connected to at least one said power supply, and wherein said conducting members of said second longitudinal section are not electrically-connected to a power supply,

21, A method for installing an electrode assembly in a substrate, for use in electrokinetic treatment of the substrate, the method comprising: providing an electrode assembly according to any one of claims 1 to 18; forming a trench or borehole; and inserting said electrode assembly into said trench or borehole; wherein said trench or borehole is substantially curved. 2^'. A method according to claim 27, wherein at least a portion of said trench or borehole has a radius of curvature substantially equal to or less than 10 metres.
29. A method according to claim 27 or 28, wherein said electrode assembly is provided as a coil; and said method comprises the step of unwinding the electrode assembly from the coil as it is fed into the trench or borehole.