Textiles: weaving – Fabrics – Multiweft planes
Patent
1989-01-24
1991-08-20
Cannon, James C.
Textiles: weaving
Fabrics
Multiweft planes
405 18, 405 19, D03D 1100, E02B 312
Patent
active
050405721
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a novel, improved revetment fabric and to its use as a revetment mattress, in erosion control.
Revetment fabric consists of two layers of fabric either woven, in part, together or held in parallel relationship by spacer threads. The three types of revetment mattress are: spaced points through which the water in the concrete slurry is expelled giving a cobblestone appearance to the mattress; parallel relationship by spacer threads giving a pillow or buttoned appearance to the mattress; and woven together in longitudinal strips with optional transverse weaving to give a parallel column or pillow appearance to the mattress. Longitudinal threads extend through the woven sections and through any transverse weaving and allow the column or pillow to collapse or fold about the adjacent column or pillow, should ground subsidence occur.
All of the above types of revetment mattress come in a range of sizes of about 50 mm to about 600 mm, being the approximate set thickness of concrete within the revetment mattress.
Revetment mattresses are used in a wide range of erosion control applications from ocean breakwaters to lining drainage channels and ditches; and to be effective, the revetment mattress must be able to withstand nature's forces such as wave action, ice formation and soil movement. The weakest part of a revetment mattress, and the place where cracking or breakage of the concrete will occur is obviously where the concrete is at its thinnest.
Regardless of the type of revetment mattress chosen, and this will depend on the particular site requirements, there will always be parts of the concrete mass which are thinner than surrounding parts. This is particularly marked on steep corners of a ditch or culvert where the fabric is folded and the pillow or buttoned appearance is extreme, as shown in attached FIG. 1.
In addition, as the strength of the overall mattress is not dependant on the thickest cross-section of concrete in the mattress but rather on achieving a uniform cross-section; it follows that any substantial pillowing or buttoning appearance to the mattress is only excess concrete.
In previous attempts to achieve a uniform cross-section a 100 mm uniform cross-section revetment fabric was used. However, this had the major disadvantage that it was impossible to pump concrete into the mattress without first cutting several spacer threads every few meters to form a large enough hole in the mattress to insert the pump nozzel. Often around these cut sections, concrete was not set and water could under-flow the mattress defeating its very purpose.
The present invention seeks to substantially overcome the above disadvantages and provide a substantially uniform cross-section of concrete within a revetment mattress.
In one broad aspect of the present invention there is provided a revetment fabric comprising two layers of flexible pervious material characterised in having at least one lengthwise spacer thread intermittently and alternatively woven in each layer, to form an angled connection between each layer and maintain the layers in a parallel relationship.
Preferably there are six lengthwise spacer threads intermittently and alternatively woven in each layer to form a scissor connection between each layer. More preferably, the woven section of spacer threads is in staggered relationship with an adjacent row of spacer threads. In known revetment fabrics the woven section is linear and cracking of the concrete could occur. The staggered woven sections act to prevent cracking by giving a more linear appearance to the mattress.
The present invention will now be described with reference to the attached drawings in which:
FIG. 1 is a schematic view of a known uniform cross-section revetment mattress fabric in situ;
FIG. 2 is a schematic perspective view of a preferred revetment fabric illustrating the spacer threads;
FIG. 3 is an actual cross-section view of a revetment mattress made with the preferred revetment fabric; and
FIG. 4 shows a plan view of the revetment mattress of FIG. 3
REFERENCES:
patent: 3008213 (1961-11-01), Foster et al.
patent: 3048198 (1962-08-01), Koppelman et al.
patent: 3517707 (1970-06-01), Hages et al.
Bissell Henry M.
Cannon James C.
Foreshore Protection Pty Limited
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