Fascines

Abstract

A fascine for filling ditches or smoothing other discontinuities in or on the ground to facilitate the passage of vehicles across the discontinuity is composed of inflatable members wrapped with one or more fabric sheets extending back along the ground from the respective discontinuity in the path of oncoming vehicles. The overwrapping sheet(s) assist in maintaining the integrity of the fascine and provide an improved surface particularly for wheeled vehicles to cross the fascine, obviating the risk of wheels falling into gaps between individual fascine members.

Description

The present invention relates to fascines and more particularly to fascines comprising inflatable members.

Fascines are structures comprising at least one, and usually several, elongate members which are used to fill ditches or to level or smooth other discontinuities in or on the ground sufficiently to facilitate the passage of personnel or vehicles across the discontinuity, and sets of such members are commonly carried by tanks and other military vehicles when in the field for the temporary levelling of such discontinuities which would otherwise halt or impede the passage of the vehicles and/or of others which follow. Fascines comprising bundles of high density polyethylene or similar pipes are known from U.S. Pat. No. 4,312,601 and U.S. Pat. No. 4,566,821 and fascines including inflatable members are known from U.S. Pat. No. 5,122,400, U.S. Pat. No. 5,215,401, U.S. Pat. No. 5,406,662, GB2401640 and WO2006/027559.

Inflatable fascine members have the advantage over rigid pipes of reduced weight and of much reduced bulk whilst uninflated; they can be stored and carried uninflated and need be inflated only when required for use, e.g. by a suitable compressor or from cylinders of compressed air or other gas (such as an inert mixture of carbon dioxide and nitrogen) carried for the purpose.

While it is generally possible to traffic fascines composed of inflatable members with tracked vehicles, the ability to traffic with wheeled vehicles is more problematic due to the presence of discrete wheels, axle separation and the potential for tyre slip on the surfaces of the inflated members. The lightweight nature of inflatable fascine members together with their inherently low inertia makes them extremely susceptible to movement as a consequence of dynamic trafficking loads. Depending on how many fascine members are deployed to smooth a given ditch profile or other discontinuity and how efficiently they are anchored, large gaps can open up between adjacent members. These gaps make trafficking with wheeled vehicles very difficult because wheels can drop down between different fascine members and the inflated members can become trapped between adjacent axles. This can immobilise wheeled vehicles and prevent successful crossing of the fascine. It can also result in damage to the fascine members from contact with the undersides of vehicles attempting to cross.

FIG. 1 is a side view of a deployed fascine with a fabric overwrap in accordance with the invention; and

FIG. 2 is a plan view of the fascine of FIG. 1, to an enlarged scale.

In the example illustrated in the Figures, two bundles each of three conventional sausage-shaped inflated fascine members 1 have been deployed in a ditch 2 and encircled with a sheet 3 of flexible reinforced or geotextile fabric—typically a PVC coated polyester base fabric. The overwrapping sheet 3 can extend across the full width of the fascine or can comprise two separate strips of material as shown in FIG. 2. These strips will be wide enough and positioned such that they can easily accommodate the width and location of the crossing vehicles' tyres or tracks. The or each sheet is attached along one of its shorter (end) edges to one of the fascine members located at the bottom of the ditch nearest the “home” bank side, e.g. as indicated at 4 in FIG. 1, such that the sheet is trapped between the fascine and the bottom of the ditch profile. This attachment may be continuous across the full width of the sheet or intermittent with connections at several discrete points. The method of attachment of the overwrap is demountable and can interface with whichever of the fascine members is located at the desired position, all being of similar design. The remainder of the or each sheet 3 is not physically attached to any of the other fascine members, however. This allows some relative rotation or other movement of the fascine members during trafficking if required.

From the attached end, the or each sheet 3 is draped over the top surface of the whole assembly of members 1 deployed in the ditch. This provides the eventual trafficking surface. The material is wrapped over the fascine following the direction from home bank to far bank, returning underneath the complete fascine assembly and back up onto the home bank surface, all as indicated by the direction of the arrows in FIG. 1.

As an alternative to wrapping the members 1 with the sheet 3 in situ in the ditch, deployment of a pre-wrapped fascine into the ditch may be achieved by use of a lightweight mechanical handling device mounted on a vehicle, with the sheet 3 being pulled back onto the home bank surface as the vehicle withdraws and before opening the fascine to traffic.

Laying the second end portion of the sheet onto the home bank allows it to be anchored by the weight of a vehicle approaching to cross, exemplified as a wheeled vehicle 5 of which the front portion is seen in FIG. 1. The length of the sheet returned onto the home bank surface is preferably at least as long as the length of the vehicle to be crossed (or at least as long as the distance between its foremost and rearmost ground-engaging portions). This will ensure that the sheet is restrained by the entire number of axles of a wheeled vehicle or by the complete track length of a tracked vehicle and will remain restrained on the bank by the trailing portion of the vehicle as its leading portion encounters the ditch. As an addition or alternative to using the weight of the vehicle, however, the sheet could be anchored on the home bank along its two longer edges using ground anchor pegs/spikes or similar.

As the approaching vehicle engages the overwrapped fascine, there is a tendency for the inflated members 1 to be pushed forwards. Local distortion of the fascine members coupled with this forward movement tensions the fabric of the sheet(s) 3 which is consequently pulled tight around the fascine member bundles. The greater this tension the tighter the members 1 are pulled together. This maintains the integrity of the fascine, prevents wheels from falling into gaps between different fascine members and provides an improved surface which facilitates speedier crossing of the fascine by vehicles of all types.

The surface of the or each sheet 3 also serves to provide a sacrificial wear surface which protects the fabric of the inflated fascine members 1 from direct contact with the wheels or tracks of passing traffic. As such these sheets can be treated as disposable items which can be replaced when specified limits of wear and tear have been reached.

Claims

1. A fascine adapted to facilitate the passage of a vehicle across a discontinuity in or on the ground comprising an assembly of inflated fascine members and a flexible sheet wrapped around that assembly, said sheet extending back along the ground from the discontinuity in the intended path of the vehicle and providing a surface over which the vehicle can cross the fascine.

2. A fascine according to claim 1 wherein the sheet is attached to said assembly of inflated fascine members in the region of the near side of the discontinuity (in the sense of the intended direction of crossing) and extends from the attachment forwardly over the top of said assembly and rearwardly below said assembly.

3. A fascine according to claim 1 comprising two such sheets in parallel and spaced apart in accordance with the widthwise wheel or track spacing of the vehicle.

4. A fascine according to claim 1 wherein the or each said sheet extends back along the ground from the discontinuity by a distance at least as long as the distance between the foremost and rearmost ground-engaging portions of the vehicle.

5. A plurality of inflatable fascine members and a flexible sheet or sheets adapted to be wrapped around an assembly of inflated such members to form a fascine according to claim 1.

6. A method of crossing a discontinuity in or on the ground with a vehicle which comprises deploying a fascine according to claim 1 and directing the vehicle to pass over the surface of the or each said sheet.