GB2159842A - Reinforcing net - Google Patents

Abstract

A reinforcing net 2 for a bituminous composition such as a plate 1 for a revetment of a dam or bank comprises longitudinally extending cords 3 and cross elements 4. The cords 3 engage around the elements 4 and are thus secured thereto at the nodes of the net 2. The meshes of the net are substantially constant in size, the dimensions of the meshes being in the range 8cmx8cm to 30cmx30cm. <IMAGE>

Description

SPECIFICATION Reinforcing net The invention relates to a net for reinforcing for example bituminous compositions such as asphalt plates and such reinforced plates for use e.g. as revetments of banks, dams, watercourses or the like to protect them against erosion.

It is known, e.g. from NL-A 67.07673, to reinforce water permeable asphalt plates by means of steel wire netting. However it is an object of this invention to combine an even and effective reinforcing effect throughout for example an ashphalt plate with a desired overall flexibility of the reinforced plate. Such a reinforcing net should be capable of supporting a bituminous composite material over a substantial plate length-e.g. 20m or even 60m and more.

By bituminous composition is meant here the well known water permeable mixtures of tar with broken stones, boulders, gravel and/or sand or other filler material wherein the tar is the binder between the grains and stone pieces. The load to be supported by the net is typically the weight of the reinforced plate in a vertical suspended position thereof combined with tensile forces exerted on the net during deposition of the asphalt plates against the slopes of the banks. These tensile forces can generally amount to about 15%-30% of the plate weight.

Viewed from one aspect the invention provides a reinforcing net comprising a plurality of longitudinally extending cords interconnected by a plurality of cross elements, wherein the cords engage around said cross elements and are thereby secured thereto at each node of the net, and wherein the meshes of the net are substantially constant in size, the dimensions of the meshes being in the range 8cm x 8cm to 30cm x 30cm.

Viewed from a second aspect the invention provides a bituminous plate having therein a reinforcing net, such net comprising longitudinally extending elements and cross elements interconnected at the nodes of the net, wherein the net has a substantially constant mesh having dimensions in the range 8cm x 8cm to 30cm x 30cmm, and wherein the flexibility of the net is not less than that of said plate, the longitudinal elements being adapted to distribute the load of the plate.

Thus, the net comprises substantially equal meshes with dimensions between about 8cm X 8cm and 30cm X 30cm so that a bituminous composition can easily penetrate through the meshes. Larger meshes would generally impair the evenness and effectiveness of the reinforcing effect throughout the plate. The meshes may be square. When suspending the plates vertically, the longitudinal elements are likewise oriented vertically so that they are effective to support the load of the plate whereby the load is evenly distributed over the longitudinal elements. The load is transmitted via the cross elements to the cross over points or nodes. These nodes should therefore be sufficiently secure to form rigid anchoring points for the partial loads transmitted to the longitudinal elements. The flexibility of the net should further not be less than that of the non reinforced asphalt plate.

In general. the net with mesh dimensions as mentioned before can consist of longitudinal ropes linked to each other by means of wires, strands or strips running in cross direction and whereby the load is evenly distri- buted over the longitudinal elements. Fixation at the cross over points or nodes of a net in accordance with the second aspect of the invention can be anchored by knotting. interweaving, welding, glueing, by binder threads or by mechanical clips or by any suitable combination thereof as desired.

In a preferred embodiment of the invention, the longitudinal elements in the net comprise steel wire strands or cords. According to another feature. the cross elements are steel wires which are crimped.

The invention will now be further described by way of example with reference to an embodiment thereof shown in the accompanying drawings. wherein: Figure 1 is a plan view of an asphalt plate comprising a reinforcing net structure: Figure 2 is a cross section view along lines Il-Il in Fig. 1; Figure 3 iliustrates methods of interconnecting the longitudinal edges of adjacent nets: Figure 4 shows atop end arrangement for supporting and handling the reinforced plates during their deposition.

Figure 5 shows an asphalt plate reinforced by two parallel nets In Figs. 1 and 2, an asphalt plate 1 is shown comprising a reinforcing net 2 embedded therein. The net 2 comprises longitudinal load carrying elements 3 linked to each other by cross elements 4. The net may be located in the lower part. i.e. below the neutral axis a-a of the plate (see Fig. 2).

As the width of the net making machines is generally limited to e.g. 3 m, adjacent nets will be mechanically attached to each other in their longitudinal border areas to provide a net with the desired width and before combining them with the bituminous composition. As shown in Fig. 3, longitudinal elements in the border area of each of two nets can be joined and fixed to each other by means of a number of suitable clips or clamps 5 which are attached at regular intervals along the length of the elements 3. In another manner, cross elements 4 can be fixed to each other as suggested by clamp 6. A combination of clamps 5 and 6 is also possible. Other attachment means can of course be used.

The head end arrangement shown in Fig. 3 is basically formed by an extension of the reinforcing net. The net end is folded over itself in a loop and fixed by means of clamps 7. A tube 8 is then inserted in the loop which tube can be gripped by a crane for supporting the reinforced asphalt plate.

When asphalt plates with a substantial thickness (e.g. over 20 cm) have to be reinforced, it will sometimes be preferred to use two reinforcing nets 2 as shown in Fig. 4.The nets can then have either the same or a different construction, elasticity and load bearing capacity. The nets can be disposed against each other if desired.

A preferred fixing arrangement of the elements 3 and 4 at their crossing points is obtained by providing a suitable crimp distortion in the cross wires 4. In the troughs 9 of said crimp wave the longitudinal elements 3 can be locked e.g. when they comprise two subelements 10 and 11 which enclose or entwine the wire 4. Such an arrangement can be reached by twisting the two subelements together and inserting the cross wires between them at the appropriate place. The twist in the consecutive sections 12, 1 3 of an element 3 between consecutive cross elements 4 can be the same or alternately differ.

When consecutive sections 12, 1 3 have alternatively differing twists, then a section 1 2 can have a twist in Z-direction, whereas the adjacent sections 1 3 can then have a twist with S-direction and the next sections 1 2 again a Z-twist etc. The number of torsions per m in the Z-twisted sections 1 2 can thereby either correspond to, or differ from said number of torsions in the S-twisted sections 13.

Alternatively the twist direction can be the same in each section of the same element 3.

The number of torsions per m can then be the same throughout the length of the element.

The number of torsions can however differ whereby only every first section 14 has the same number of torsions and every second section 1 5 has another number of torsions.

The number of torsions in every section 1 5 is of course the same.

Sections of adjacent elements 3 located between the same pair of cross elements 4 will preferably have a different twist direction.

Example 1 A net was made comprising galvanized steel cords as longitudinal elements and gear crimped galvanized steel wires with a diameter of 3 mm as cross elements. The crimp wave length was 1 8 mm, the crimp amplitude 2 mm and the breaking load 4240 N. Each longitudinal element was composed of two steelcords with the same twist (direction and number of torsions per m) as subelements 10 and 11. Each steelcord had a thickness of 2.7 mm, a breaking load of 10.100 N and consisted of 1 9 wires which were twisted together with a lay length of 27 mm. The distance between consecutive cross elements 4 was about 85 mm and between adjacent longitudinal elements 3, it was about 1 50 mm.Each two subelements 10, 11 were further twisted together in each section between consecutive cross elements 4 with about 30 torsions per m (2.5 torsions per section). Consecutive sections 1 2 and 1 3 had different directions of twist. Sections of each two adjacent elements 3 situated between the same cross elements 4 had likewise a different direction of twist. The subelements 10 and 11 clamped themselves around the cross element 4 thereby fixing the crossing area.

The net was made on a weaving machine with a width of 1 20 cm. Such machines are known. Six or seven elements 3 were used as warp elements and the crimped wires as weft elements. The length of the net was 20 m. A net with seven elements 3 was joined at both its longitudinal edges with a net comprising six elements 3 and the cross elements were fixed to each other by means of mechanical clamps 5. The net offered a longitudinal strength of 88 kN per m of net width. The net is suitable for reinforcing a bituminous composition to form a water permeable asphalt plate with a thickness of about 1 5 cm and a weight of about 300 kg/m2.

Example 2 A similar net can be made whereby the cross element 4 is a crimped wire as in example 1. The longitudinal subelements 11 and 1 2 have a thickness of 3 mm (steelcord construction 1 9 X 0.60 mm; lay length 27 mm) and a breaking load of 11 320 N.

The square net meshes measure about 1 50 mm X 1 50. The Z-twists in sections 1 2 as well as the S-twists in sections 1 3 by which the sublements. 10, 11 are twisted together amount to 13.33 turns per m (t/m). The crimped wires are satifactorily blocked in their crossing area with the steel cords. This net is again suitable for reinforcing an asphalt plate of 20 m long and a thickness of about 1 5 cm.

The net weighs 0.955 kg/m2 of net width.

Example 3 Another net with the same cross elements and mesh size as in example 2 can be designed for heavier asphalt plates (either longer and/or thicker). The longitudinal subelements (steel cords) can then have the construction 1 9 x 0.80mm with a lay length of 27mm and a breaking load of 1 921 5 N. The Z-twists, resp. S-twists in the sections 1 2 resp. 1 3 can then be chosen at about 1 9 t/m. This reinforcing net has a weight of about 1.41kg/m2 of net width.

It is of course possible to use nets with thinner subelements and with the same or another mesh size, e.g. when theplate is thin ner and/or shorter. The number of Z-twists resp. S-twists in the sections 1 2 and 1 3 can then be increased, depending upon the twist in each cord-subelement and for the purpose of securing a sufficient locking force in the net knots. In general the subelements can be twisted together with between about 5 and 45 t/m.

As a rule, the number T of torsions per M by which the subelements will be twisted together will relate to the diameter D (in mm) of a bundled subelement as T between 15/D and 100/D and preferably T between 20/D and 80/D.

Instead of using preformed cords as subelements 10, 11 it is of course possible to feed bundles of wires as subelment 10 and bundles as subelement 11 and to twist the two bundles together in the sections 12, 1 3 e.g. in Z-respectively in S-direction. Each bundle may then have a low twist with a lay length of e.g. 50cm or more.

Prior to embedding the net in the hot bituminous composition it can be advantageous to coat the net with tar. The net can also be provided with a plastic coating before coating it with tar and/or combining it with the bituminous composition.

Instead of reinforcing a plain asphalt plate by the net it is possible to apply the bituminous composition in a pattern of adjacent blocks or tiles or slabs with intermediate free areas similar to e.g. U.S. patent 3.922.865.

The sheet of slabs can eventually be rolled up.

When desirable a filter cloth can be embedded in the underside of the asphalt plate or slabs.

Claims (14)

1. A reinforcing net comprising a plurality of longitudinally extending cords interconnected by a plurality of cross elements, wherein the cords engage around said cross elements and are thereby secured thereto at each node of the net, and wherein the meshes of the net are substantially constant in size, the dimensions of the meshes being in the range 8cm X 8cm to 30cm X 30cm.

2. A net according to claim 1, wherein the meshes are substantially square.

3. A net according to claim 1 or 2 wherein the longitudinal cords comprise two adjacent subelements twisted together.

4. A net according to claim 3 wherein the subelements comprise steel wire strands.

5. A net according to claim 3 or 4, wherein the consecutive longitudinal sections of each cord defined between said cross elements alternate in their twist direction.

6. A net according to claim 5, wherein the twist direction in consecutive longitudinal sections is alternately in the left and right sense.

7. A net according to claim 6, wherein the number of turns per unit length in the longitudinal sections twisted in one sense differs from the number of turns per unit length in sections twisted in the opposite sense.

8. A net according to claim 6 or 7, wherein laterally adjacent longitudinal sections of the cords defined between a particular pair of cross elements are provided alternately with an S-twist and a Z-twist.

9. A net according to claims 3 or 4, wherein consecutive longitudinal sections of said cords defined between said cross elements are twisted in the same direction and have alternately a higher and a lower number of turns per unit of length.

10. A net according to any preceding wherein the cross elements are crimped.

11. An asphalt plate reinforced with anent according to any of the preceding claims.

1 2. A plate as claimed in claim 11 having a thickness of between 5cm and 20cm.

1 3. A plate as claimed in claim 11 or 12 comprising two nets disposed side by side.

14. A bituminous plate having therein a reinforcing net, such net comprising longitudinally extending elements and cross elements interconnected at the nodes of the net, wherein the net has a substantially constant mesh having dimensions in the range 8cm X 8cm to 30cm X 30cm, and wherein the flexibility of the net is not less than that of said plate, the longitudinal elements being adapted to distribute the load of the plate.

1 5. A reinforcing net substantially as herein described with reference to the accompanying drawings.

1 6. A bituminous plate provided with a reinforcing plate substantially as herein described with reference to the accompanying drawings.