US20100028079A1

US20100028079A1 - Fascines

Info

Publication number: US20100028079A1
Application number: US12/444,033
Authority: US
Inventors: Philip John Brown; Douglas Hugh Jones; Colin Peter Morgan
Original assignee: Qinetiq Ltd
Current assignee: Qinetiq Ltd
Priority date: 2006-11-08
Filing date: 2007-10-26
Publication date: 2010-02-04
Also published as: WO2008056102A1; EP2079879A1; GB0622233D0

Abstract

Inflatable members for incorporation into a fascine are linked together at their ends by chains or other such flexible tension members, the tension in which is such as to cause at least local compression and flattening of the inflatable members where they are in contact with adjacent members. The forces so generated between adjacent members can prevent their tendency to rotate under the action of traffic crossing the fascine.

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, WO2004/099505, WO2006/027555 and WO/2006/027559. 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 to 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.
More particularly WO2004/099505, WO2006/027555 and WO2006/027559 disclose fascines comprising an assembly of parallel inflatable members each of generally cylindrical form. That is to say the cross-section of such members has an outer periphery that is generally circular when inflated (at least when not exposed to external forces). These members may be “solid” inflatable members in the sense that substantially the whole of the gross volume encompassed by the outer periphery of the member must be pressurised to achieve inflation, its walls being akin to a closed sausage skin, or they may comprise chambers with double walls configured to define hollow tubes when inflated, so that the pressurised volume at any section along the length of the member is of annular rather than solid disc-like form. They may also be of hybrid forms as described in WO2006/027559.
A problem that can arise in use of fascines comprising cylindrical inflatable members is the tendency of the cylinders to roll about their longitudinal axes when contacted or otherwise loaded by the tracks or wheels of vehicles driving over the fascine. At worst, particularly in the case of wheeled vehicles, this can prevent the crossing, and in any event can led to undesirable relative movement and the opening of gaps between members and undesirable forces in any connections or anchorages to the same.
In one aspect the present invention seeks to address this problem and accordingly resides in a fascine comprising an assembly of parallel inflatable members of generally cylindrical form, wherein such members at least in the region of the crossing surface of the fascine are linked to adjacent members by flexible tension members at each end thereof, and wherein the effective lengths of the flexible tension members between their points of connection to the inflatable members are so related to the dimensions of the inflatable members as to cause at least local compression of adjacent such members when inflated and the generation of forces between those members sufficient substantially to resist their relative rotation when the fascine is crossed by vehicular traffic.
The “crossing surface” of such a fascine means the surface that is presented to traffic for crossing when the fascine is deployed.
The invention also resides in an assembly of three parallel inflatable fascine members of generally cylindrical form linked together in a triangular pattern by flexible tension members at each end thereof, wherein the effective lengths of the flexible tension members between their points of connection to the inflatable members are so related to the dimensions of the inflatable members as to cause at least local compression of those members when inflated and the generation of forces between them sufficient substantially to resist their relative rotation when the assembly is crossed by vehicular traffic.
The flexible tension members may be chains, cables, strops or any other such members capable of carrying the requisite tension to link and locally compress the respective inflatable members in use of a fascine or assembly as defined above.
The invention also resides in the combination of a plurality of inflatable members of generally cylindrical form and a plurality of flexible tension members to link adjacent such inflatable members together at each end thereof, all adapted to be assembled into a fascine or assembly as defined above.
The invention also resides in a method of constructing a fascine comprising an assembly of parallel inflatable members of generally cylindrical form, which comprises linking at least such members intended to be in the region of the crossing surface of the fascine to adjacent members by flexible tension members at each end thereof and inflating the inflatable members, the effective lengths of the flexible tension members between their points of connection to the inflatable members being so related to the dimensions of the inflatable members as to cause at least local compression of adjacent such members when inflated and the generation of forces between those members sufficient substantially to resist their relative rotation when the fascine is crossed by vehicular traffic.
The invention also resides in a method of constructing an assembly of three parallel inflatable fascine members of generally cylindrical form, which comprises linking those members together in a triangular pattern by flexible tension members at each end thereof and inflating the inflatable members, the effective lengths of the flexible tension members between their points of connection to the inflatable members being so related to the dimensions of the inflatable members as to cause at least local compression of those members when inflated and the generation of forces between them sufficient substantially to resist their relative rotation when the assembly is crossed by vehicular traffic.

The invention will now be more particularly described, by way of example, with reference to the accompanying schematic drawings in which:

FIG. 1 is an end view of an assembly of inflatable fascine members linked together in accordance with one preferred embodiment of the present invention; and

FIG. 2 is an end view of an assembly of inflatable fascine members linked together in accordance with another preferred embodiment of the present invention.

Referring to FIG. 1 there is shown an assembly of three parallel sausage-like inflatable fascine members 1 linked together in a triangular pattern which constitutes a useful sub-assembly or “building block” for incorporation in an overall fascine structure comprising other such sub-assemblies and/or individual inflatable members, and in which structure each member or sub-assembly may also be linked to its neighbour(s), if required, in a similar fashion to that described below. A trio of members of this kind may also serve in itself as a ramp-like fascine to facilitate the passage of vehicles over a vertical step, ridge or other sharply rising discontinuity.
Each member 1 of the illustrated assembly comprises an inflatable bladder, typically of a polyurethane-coated nylon fabric, which may have an outer covering of wear-resistant or sacrificial material, such as a fabric of aramid fibres e.g. Kevlar®, and is closed at each end by a central fitment 2 of metal, fibre-reinforced polymer or other such engineering material. The fitment 2 at at least one end of the respective member 1 may be fitted with a valve for inflation from an external gas source and/or with a pressure relief valve and/or may mount an internal compressed gas cylinder for inflation (not shown). The fitments 2 are also equipped at each end with rings, eyes, shackles or the like fixtures 3 aligned with the central axis of the respective member 1, which serve as mounting points for the connection of chains 4 or other such flexible tension members which link each member 1 of the trio to its neighbours. The effective length of each chain 4 between the points of connection 2 to neighbouring members 1 is less than the unconstrained fully-inflated diameter of each member 1. Consequently when the members 1 are fully inflated the chains 4 are placed under tension and cause local compression of the members 1 at their end regions. More particularly the neighbouring members 1 are pulled together at their ends and their nominal cylindrical form is forced to flatten where they contact each other, as indicated by the three contact regions 5 in the Figure. The tight contact between neighbouring members 1 over the regions 5—which are shown, for ease of illustration, somewhat exaggerated in extent in the Figure as compared to the degree of flattening which may obtain, and is sufficient, in practice—provides a high level of frictional resistance to relative rotation of the members, and may also provide some degree of mechanical resistance to their relative rotation due to the non-circularity of the members where they are in contact, and has been found to be successful in eliminating the tendency of such members to rotate when a fascine in which they are comprised is crossed by tracked or wheeled vehicles.
Prior to deployment of such an assembly the members 1 may be linked by the chains 4 while deflated or partially inflated. In order to keep the members 1 together in the desired arrangement prior to inflation or full inflation the effective lengths of the chains 4 can be shortened by connecting non-adjacent links together, e.g. by means of plastic cable ties, to form a loop in the chain. During the course of inflation the tension in the shortened chains generated by expansion of the members 1 breaks these ties and permits the chains to attain their full length.
In any event, if it is desired to adjust the tension in the chains 4 and consequent compression of the members 1 when in the fully inflated condition this may be achieved by adjusting the effective lengths of the chains e.g. by means of turn buckles or the like provided at the connection points 3 or within the chains themselves.
Referring to FIG. 2, this shows a variant of the assembly of FIG. 1, where like parts are denoted by like reference numerals increased by ten. In this case the inflatable fascine members 11 are closed at each end by fitments 12 having pairs of connection points 13 for chains 14 diametrally offset from the central axis of the respective member 11. This embodiment works in a similar way to the embodiment of FIG. 1 in producing high resistance to relative rotation of the members 11 due to the tension in the chains 14 and local compression of the members 11 where they contact each other when fully inflated. The resistance to rotation may however also be enhanced by moments generated in the fitments 12 by the offset connection of the chains in FIG. 2 as compared to FIG. 1 where the chains are connected centrally of the inflatable members.
Fascine members as described above may typically have a nominal diameter in the range 300-1000 mm and an inflation pressure of 40-50 PSI (2.8-3.5 bar). The effective lengths of the chains 4,14 or other such flexible tension members may typically be in the range 80-98% or more preferably 88-95% of the unconstrained distance between their points of connection 3,13 to neighbouring members. Put another way, the degree of local reduction of the diameters of the members where they are flattened together as at 5 may typically be in the range 3-8% or more preferably 5-6%.

Claims

1. A fascine comprising an assembly of parallel inflatable members of generally cylindrical form, wherein such members at least in the region of the crossing surface of the fascine are linked to adjacent members by flexible tension members at each end thereof, and wherein the effective lengths of the flexible tension members between their points of connection to the inflatable members are so related to the dimensions of the inflatable members as to cause at least local compression of adjacent such members when inflated and the generation of forces between those members sufficient substantially to resist their relative rotation when the fascine is crossed by vehicular traffic.

2. An assembly of three parallel inflatable fascine members of generally cylindrical form linked together in a triangular pattern by flexible tension members at each end thereof, wherein the effective lengths of the flexible tension members between their points of connection to the inflatable members are so related to the dimensions of the inflatable members as to cause at least local compression of those members when inflated and the generation of forces between them sufficient substantially to resist their relative rotation when the assembly is crossed by vehicular traffic

3. A fascine according to claim 1 wherein the flexible tension members are connected to the inflatable members at positions substantially aligned with the central axes thereof

4. A fascine according to claim 1 wherein the flexible tension members are connected to the inflatable members at positions offset from the central axes thereof.

5. A fascine according to claim 1 where the effective lengths of the flexible tension members are in the range 80-98% of the unconstrained distance between their points of connection to adjacent inflatable members.

6. A fascine according to claim 5 where the effective lengths of the flexible tension members are in the range 88-95% of the unconstrained distance between their points of connection to adjacent inflatable members.

7. A fascine according to claim 1 wherein the degree of reduction of the diameters of the inflatable members where they are locally compressed is in the range 3-8%.

8. A fascine according to claim 7 wherein the degree of reduction of the diameters of the inflatable members where they are locally compressed is in the range 5-6%.

9. The combination of a plurality of inflatable members of generally cylindrical form and a plurality of flexible tension members to link adjacent such inflatable members together at each end thereof, all adapted to be assembled into a fascine according to claim 1.

10. A method of constructing a fascine comprising an assembly of parallel inflatable members of generally cylindrical form, which comprises linking at least such members intended to be in the region of the crossing surface of the fascine to adjacent members by flexible tension members at each end thereof and inflating the inflatable members, the effective lengths of the flexible tension members between their points of connection to the inflatable members being so related to the dimensions of the inflatable members as to cause at least local compression of adjacent such members when inflated and the generation of forces between those members sufficient substantially to resist their relative rotation when the fascine is crossed by vehicular traffic.

11. A method of constructing an assembly of three parallel inflatable fascine members of generally cylindrical form, which comprises linking those members together in a triangular pattern by flexible tension members at each end thereof and inflating the inflatable members, the effective lengths of the flexible tension members between their points of connection to the inflatable members being so related to the dimensions of the inflatable members as to cause at least local compression of those members when inflated and the generation of forces between them sufficient substantially to resist their relative rotation when the assembly is crossed by vehicular traffic.

12. A method according to claim 10 wherein the flexible tension members comprise chains which, prior to completion of inflation of the inflatable members, are shortened by connecting non adjacent links together by means which are adapted to break under the tension in the shortened chains generated during inflation.