Underground drainage

Abstract: A drainage component comprises a flexible panel having a water permeable surface 9 and an interior 1, 3, 5 providing for flow of water from the permeable surface 9 to an outlet 11. In use, the outlet 11 communicates with a drainage pipe 45, for example. Means 21, 17 are also provided for connecting the drainage component to the pipe. The drainage component can also be used for stabilising and/or ventilating ground, as well as draining ground.

Description: This invention relates to underground drainage, and in particular to subsoil drains and the like, and for draining off water from the surrounding ground. Conventionally, subsoil drains comprise slotted or perforated pipes laid in a suitable bed of granular material which acts as a collector and filter. It has also been proposed (see f.i. US-A-4,898,494) to use geotextiles mounted on a suitable support, e.g. in the form of a panel, as drainage means, the textile material (for example moulded plastics mesh) acting as a filter to permit entry of ground water from the surrounding ground. In our UK Patent Specification GB-A-2208465 we have proposed drainage means comprising a drainage pipe or duct to be laid generally horizontally, and at least one upright hollow pillar defining a space communicating with the interior of the drainage pipe, and provided with one or more openings for entry of ground water. A filter medium enclosing or contained in the pillar permits the flow of ground water while preventing solid particles entering the drain pipe from the ground. With such drainage means, the usual granular bedding material can be wholly or partly dispensed with, as the upright pillar will pick up percolating water from the surrounding ground over a range of levels corresponding to the panel or the pillar or pillars. It has however been found that, depending on the nature of the ground, there may be insufficient contact between the drainage components and the back-filled soil, which impairs the effectiveness of the drainage system. It will be understood that, in conventional back filling, the back fill material is placed between the drainage system and both walls of the trench, breaking the continuity of flow from the ground to the drain. With the foregoing in mind, the invention provides a shoe for connecting a drainage component, a system for connecting a drainage panel and a drainage system as set out in the claims. The invention will be further described with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a panel core Figure 2 shows a modified drainage panel core Figure 3 shows a drainage panel comprising the core of figure 1 and a filter cloth covering Figure 4 shows components of a drainage system incorporating the panel of figure 3, for use with clay pipes Figure 5 shows the drainage panel used with a corrugated plastics drainage pipe Figure 6 shows a connecting shoe and cap Figure 7 shows a seat or socket for the connecting shoe Figures 8 to 13 show schematically the present drainage system in use Figure 14 shows a side elevation of the panel core of figure 1 fitted with an alternative type of connector Figure 15 is a cross-section on the line Z-Z in Figure 14; and Figures 16 and 17 are elevations of the left and right hand ends of the panel core shown in Figure 14 respectively. The illustrated panel comprises a plurality of parallel narrow stringers 1. These are interconnected by transverse webs 3 moulded integrally with the stringers. Each web is a rectangular plate with its plane perpendicular to the stringers and extends only between two adjacent stringers. The webs are staggered, so that they are spaced from one another in the longitudinal direction of the stringers and also in the direction of the length of the webs viz. transverse to the stringers. Each web stands proud of the stringers on both sides of the common plane of the stringers. The free edges of the webs therefore define a pair of parallel planes spaced apart on opposite sides of the common plane of the stringers. The outermost stringers have projecting lugs 5 corresponding in position and height to the inwardly staggered webs. At one end, the stringers are interconnected by a female connector 7 comprising a channel having a width equal to the overall height of the webs and communicating with the spaces between the stringers. The female connector is integral with the stringers or connected to them in any convenient way. At the other end the stringers are interconnected by a male connector unit 11 transverse to the stringers, integral with these or connected to them in any convenient way. The male connector 11 is provided with an aperture or apertures for fluid flow. By means of resilient hooked tabs 8 in the female connector, and a corresponding aperture or apertures in the male connector, two or more of the illustrated frames can be connected together end to end with the hooked tabs of one snap-fitted into the apertures of another, with a silt-tight joint, to form a longer panel. Figures 14 to 17 show the same core frame but fitted with a second type of connector. At one end, the stringers are interconnected by a female connector 157 comprising a bar or frame having a thickness equal to the overall height of the webs and provided with apertures 159 corresponding in position to the spaces between the stringers. The female connector is integral with the stringers or connected to them in any convenient way. At the other end the stringers are interconnected by a male connector unit 61 transverse to the stringers, integral with these or connected to them in any convenient way. The male connector 61 is provided with a plurality of projecting tabs 63 each corresponding in position to a respective aperture 159, these tabs being staggered and being provided with hooks 65 at their tips, the hooks on alternate tabs being oppositely directed. By means of the hooked tabs and corresponding apertures 159, two or more of the illustrated frames can be connected together end to end with the hooked tabs of one snap-fitted into the apertures 159 of another. The entire core frame is made, for example by injection moulding, of a flexible plastics material, for example of a polypropylene copolymer or recycled polyolefin waste. The design of the frame is such that it can flex about axes parallel to the stringers and perpendicular to them, and indeed also about diagonal axes. Figure 2 shows an alternative frame in which the webs 13 extend longitudinally instead of transversely, again in a longitudinally and transversely staggered arrangement. Webs 13 are present at the edges of the frame, therefore there is no need for lugs corresponding to the lugs 5 of figure 1. The core, has an intermittent gate-like structure which allows free passage of water down its length but provides high crushing strength across the width under normal and angled (shear) loading conditions. The flexibility allows the panel to fit properly against uneven trench walls or structures to ensure the intimate contact necessary between the covering 9 and the soil. The core is covered (except at its ends) with a flexible filter cloth covering 9 through which ground water can percolate. The filter medium may be a so-called geotextile, of a mesh size suitable to prevent passage of ground particles without becoming clogged or unduly resisting the flow of ground water. Such materials are now quite well known. They may comprise woven or non-woven material, or moulded or extruded material, of appropriate porosity, for example so-called needle punched geotextiles. The geotextile material is selected to have the correct pore size, flow characteristics, chemical resistance and mechanical properties to allow the free flow of water from the soil into the cores whilst preventing soil movement or clogging. According to one specification, the material may be so selected that the 95% level of its hole size distribution corresponds to the 50% dimension of the particle size distribution of the surrounding soil. More specifically, by way of example only, the filter medium may be a non-woven needle-punched continuous filament polyester or polypropylene fabric. The filter medium is welded, glued, or heat-bonded to all of the raised web surfaces and edge lugs 5 of the frame skeleton, to form a panel 15 covered with the filter medium 9 on all surfaces except at the ends, that is to say at the male and female connectors. This covering does not impair the above-described flexibility. The geotextile material is attached to the core at all the intermittent webs (gates) which ensures that there is very little local stretch or apertures becoming reduced and ensures the maintenance of a high flow capacity for a relatively thin panel. Typically the panel may be 500mm x 150mm x 15mm. In use, the complete panel is connected to a land drain pipe and installed for example in a drainage trench. It will be understood that the panel frame provides a large hollow space and almost unimpeded water flow past and between the webs 3 within the panel. Panel ends remaining open after installation can be closed by suitable caps fitted onto the exposed connectors 7, 11, 157 or 61, if desired. The pipe can be of any convenient kind. It may for example be a plastics pipe, preferably a corrugated plastics pipe, or a clay pipe. In the case of plastics pipe, entry holes for receiving water from the panels can be provided, distributed along the length of the pipe, as a factory operation for example by drilling, punching, or in the moulding of the pipe. In the case of clay pipe, holes may be provided distributed along the length of the pipe as a factory operation, or standard non-perforated pipe lengths may be interconnected by pipe couplings incorporating connector holes for the panels. Figure 4 shows a panel 15, an injection moulded plastics coupling sleeve 17, for example to fit standard 100mm clay pipe lengths, a plastics connector or entry shoe 19 and a sealing ring 21. A rectangular stopper 23 is provided, which snaps into the open female connector 7 to close the end of the panel. Alternatively, the stopper could be configured to snap into the open male connector, to close opposite end of the panel. The shoe 19 and stopper 23 are shown on a larger scale in figure 6. The shoe has a female connector portion 25 which corresponds to the female connector 7 and, like the latter, has resilient hooked lugs 8 which snap into and retain the male connector 11 of an inserted panel, forming a silt-tight joint between the shoe and the panel. Stopper 23 has apertures 27 in its side walls 29. When the stopper is inserted into a female connector 7 or 25, the apertures 27 receive the hooked tabs 8 to retain the stopper. Alternatively, the shoe could be configured to have a male connector portion, thus making it capable of engaging a female connector of a panel. The shoe 19, which is made of injected moulded plastics for example polypropylene, also incorporates a funnel 31 communicating with the female element 25, and a circular spigot 33 communicating with the funnel and angled at for example 45° relative to the female element 25 and accordingly to the plane of a panel inserted in the shoe. The spigot is typically approximately 40mm in diameter, and is inserted into an aperture provided in the coupling sleeve 17 (or an aperture provided in a pipe). The ring 21 has hooked resilient tabs 35 around its periphery for snap fitting in a hole 37 provided in the coupling sleeve 17, and a skirt 39 shaped to seat against the external surface of the coupling sleeve and to form a silt-tight joint with the latter. The ring is made of a hard elastomeric material. Lugs 41 provided on the exterior of the spigot 33 can mate with slots 43 provided in the seal ring 21, in such a manner that the shoe can be located on the pipe with the female connector 25 either parallel or perpendicular to the axis of the pipe. Figure 4 shows the components arranged so that the shoe, and the width of the panel, are perpendicular to the pipe axis. Because the spigot 33 is angled, the length direction of the panel will then lie at 45° to the length direction of the drainage pipe. Circular plugs may be provided to close apertures 37 or seal rings 21 not used for the attachment of drainage panels. Alternatively, at joints between pipes where connection of a drainage panel is not required, conventional pipe coupling sleeves can be used. Seal rings similar to the rings 21 can also be used for connecting shoes and panels to apertures provided in clay pipe bodies. In the case of a coupling sleeve used with clay pipes, the seat of seal for the connector shoe may be moulded integrally with the coupling sleeve. In the case of seal or seat rings provided directly in clay or other pipes, the rings may be factory-fitted, secured for example by an adhesive or by welding in the case of plastics pipes. In the case of plastics pipes or coupling sleeves, seal and coupling formations corresponding to rings 21 can be provided integrally with the pipes or sleeves. Figure 5 shows an alternative arrangement in which a pair of panels 15, connected end to end for increased length or height, are connected by a shoe 19 to a 110mm twin-wall corrugated PVC-u pipe 45. The pipe 45 has factory drilled connection holes, provided with seal rings identical or similar to the ring 21. In the assembly shown in Figure 5, the shoe 19 has been set so that its length is parallel to the axis of the pipe 45, with the result that the plane of the panels 15 is substantially tangential to the pipe 45. This enables the panels 15 to make complete close contact with the wall of a trench, or a structure. In particular, this arrangement enables the panels to make direct contact with undisturbed ground at one of the excavated side wall surfaces of a trench, the trench being back-filled only on the other side of the panel. The flexibility of the panels enables them to conform closely to the excavated surface or to the surface of the structure, thereby maximising the efficiency with which the panels can collect ground water. The panels can be installed at any desired orientation, for example in a vertical or near-vertical plane, horizontal, or sloping. However, in any arrangement, the panels will normally form a multiplicity of separate localized collectors, rather than an effectively continuous surface as is the case in conventional panel-type drainage devices. These individual collecting panels are individually connected to an independent drainage pipe at positions spaced along the latter. This has the significant advantage that the numbers and arrangement of panels, and therefore the local drainage rate, can be selected according to the particular requirements of each individual site, and indeed according to different requirements in different regions of a site. The present drainage system is extremely versatile. Some possible applications will be described by way of example only. Figure 8 illustrates the drainage of a retaining wall 51. A stack of three panels 15 is placed vertically adjacent and parallel to the wall, and tangential to the drainage pipe 53. The tangential mounting of the panels on the pipe ensures intimate unimpeded contact between the panels and the wall, so that water cannot build up against the wall and cause damage due to hydraulic pressure. This arrangement can drain the ground fill 55 adjacent the wall extremely efficiently, reducing the risk of flooding and damp, and enabling a lighter wall to be used by eliminating hydraulic pressure of ground water. It may be desirable to provide an impervious membrane between the panels and the wall. Figure 9 shows a similar arrangement of a vertical panel tangential to the drainage pipe, for draining the edge of a carriageway to ensure rapid removal of excess water from the sub-structure 57 of the carriageway; accumulation of water in the sub-structure causes rapid structural damage. The system described herein can also be used for land fill management both to remove liquids, and to vent gases produced for example by the degradation of organic refuse. Figure 10 shows a land fill drainage system comprising multiple panels 15 extending obliquely downwardly through the buried refuse 59, and connected tangentially to the pipe 53. Figure 11 shows the panels 15 arranged vertically, again tangential to the pipe 53, with the upper end 61 of the panel or panel assembly exposed to the atmosphere. Gases generated in the buried refuse 59 are collected by the panels 15, along with liquids. The gases are vented from the upper end of the panels to the atmosphere, or are collected while liquids are drained off through the pipe 53. The stability of embankment slopes can be improved by preventing the build up, and controlling the movement, of water. Figure 12a and 12b show in front and side elevation the use of panels, or assemblies of panels, connected in a sloping herringbone formation to a sloping pipe 63. In this case, the connecting shoes 19 are arranged with the female elements 25 perpendicular to the length of pipe, so that the panels 15 form baffles at 45' across the path of movement of water down the embankment. Because of this arrangement of the panels, the panels can also themselves act as mechanical stabilizing elements for the material of the embankment. The drainage system of the present invention can also be used for general land management and reclamation by sub-soil drainage. The preferred arrangement comprises a herringbone layout of panels and pipes as in figure 12a and 12b, but with the pipes substantially horizontal as shown in plan view in figure 13a and in side elevation in figure 13b. Numerous other applications and layouts will suggest themselves to the skilled reader. The present drainage system has a number of substantial advantages: a) by providing drainage at individual positions spaced along the pipe, the drainage rate can be selected and adjusted, as already described b) the present system has been found to give an efficiency of collection, using thin (15mm) panels, comparable to that achieved by conventional thick-panel drainage elements, c) the panels and all other components can be prefabricated, and simply assembled on site in whatever combination is needed to meet local requirements of drainage area and drainage rate, thereby minimising on-site work, d) the small number of individual components described can be used and combined in a variety of ways, to provide drainage systems capable of coping with substantially all normal drainage requirements, thereby minimising the numbers of components and material to be stocked to meet different requirements. In particular, the described angled connector shoe provides exceptional versatility. Most conventional drainage requirements are currently satisfied by several different conventional methods, i.e. filter (French) drains, fin drains , sand drains and perforated pipe. The present system can satisfy all five market areas with a small number of basic elements used in several different combinations. This can involve the use of different geotextile materials for different applications and the use of alternative shoe/connector arrangements to allow horizontal or vertical use with clay or plastics pipes.

Claims: A shoe for connecting a drainage component comprising a drainage panel (15) to a discharge duct (45), the connector shoe (19) having a first end for engaging a connector (11) of said drainage panel (15) and a second end adapted to engage an aperture in said discharge duct (45) and a funnel (31) located between said first and second ends; said first end of the connector shoe (19) being defined by a first connector (25) for engaging a mating complementary second connector of said drainage panel (15); said second end of the connector shoe (19) comprising a circular spigot (33) for connection with an aperture (37) in said discharge duct (45); characterised in that the connector shoe (19) is further provided with a coupling and/or sealing ring (21) adapted to receive the spigot (33) of the shoe in a central aperture thereof, fit within the said aperture (37) of the discharge duct, and cooperate with the spigot (33) to support a plurality of relative circumferential orientations of the spigot (33) and aperture (37) so as to allow said drainage panel (15) to be selectively located at different orientations relative to said discharge duct (45), the connector shoe (19) being so configured that, in use, it can serve to locate said drainage panel (15) substantially tangential to said discharge duct (45). A shoe as claimed in claim 1 in which the spigot is angled relative to the said first connector (25). A system for connecting a drainage panel (15) to a discharge duct (45) comprising a shoe according to claim 1 or 2 and a stopper (23) adapted to be snap-fitted in the first connector (25). A system for connecting a drainage panel (15) to a discharge duct (45) comprising a shoe according to claim 1 or 2 wherein the coupling ring (21) comprises a plurality of hooked resilient tabs (35) disposed about its periphery for snap-fitting in the said aperture (37) provided in the discharge duct. A system according to claim 4, the said ring 21 further comprising a skirt (39) for seating against an outer surface of the said discharge duct. A drainage system comprising at least one flexible panel (15) having at least one water permeable surface (9) and an interior providing for flow of water from the permeable surface to an outlet, and a connecting shoe or system as claimed in any of claims 1 to 5 for connecting said panel to a discharge duct (45). A drainage system according to claim 6, wherein the panel can flex with respect to both the horizontal and the vertical directions. A drainage system according to claim 6 or 7, wherein the permeable surface (9) is defined by a filter covering and the panel comprises a core (1, 3) in the form of an open-work skeleton comprising a flexible framework with outstanding projections (3, 5) against which the filter covering rests or to which the filter covering is attached. A drainage system according to claim 8, wherein the said skeleton comprises a plurality of elongate stringers (1) interconnected by a series of transverse webs (3); the stringers being aligned substantially parallel to each other and each web extending only between two adjacent stringers; the said webs being staggered, so that they are spaced from one another in the longitudinal direction of the stringers and also transverse to the stringers. A drainage system according to any one of claims 6 to 9, and further comprising connector means (7, 11) for enabling the said component to be connected to a further drainage component of a similar or different type; the said connector means being defined by a female connector (7) at a first end of the panel and a male connector (11) at a second end of the panel, the said male and female connectors having matching configurations, thus allowing the said component to be connected to a component comprising at least a similar female connector or at least a similar male connector. A drainage system according to claim 10, wherein the said female connector (7) comprises a channel which communicates with spaces between the said stringers and/or webs, and the said male connector (11) is adapted to be received within the channel in a female connector similar to the said female connector and comprises at least one aperture for allowing fluid flow. A drainage system according to claim 10 or 11, wherein the said female connector (7) comprises at least one resilient hooked tab (8) and the male connector (11) comprises a corresponding aperture for receiving the hooked tab of a female connector similar to the said female connector in a snap-fit manner. A drainage system according to any one of claims 5 to 12, wherein the said core is made of a flexible plastics material. A drainage system according to any one of claims 6 to 12 wherein the filter covering (9) is formed from a geotextile. A drainage system according to claim 14, wherein the said geotextile comprises non-woven material. A drainage system according to any one of claims 14 or 15, wherein the material of the geotextile is needle-punched. A method of draining ground comprising laying a drainage system according to any of claims 6 to 16 a first side of the said drainage panel (15) in direct contact with essentially undisturbed ground and placing filling or back-filling material only on a second side of the drainage panel. A method of stabilising ground comprising planting within the body of the ground to be stabilised a drainage system as claimed in any of claims 6 to 16 having a plurality of drainage panels (15). A method of ventilating ground comprising planting in the ground a drainage system as claimed in any of claims 6 to 16 and using said drainage panels as venting elements. A method according to claim 19, wherein the said panels are spaced from one another along a discharge pathway (53). A method of sub-soil drainage comprising laying a drainage system as claimed in any of claims 6 to 16 with a plurality of drainage panels (15) in a sloping herringbone formation and connecting them to a sloping drainage pipe (63) by means of a series of respective connecting shoes (19).

Inventors: STANIFORTH GRAEME, STANIFORTH, GRAEME
Applicants: HEPWORTH BUILDING PROD, HEPWORTH BUILDING PRODUCTS LIMITED
Application year: 1992
Main classification: E02B11
IPC codes: E02B11, E02D3