Track Bed Structures

Abstract

A track bed composite structural element issued in railway track engineering, and has an upper water permeable layer, a lower water permeable layer and a filter material layer provided between the upper and lower water permeable layers. The upper and lower layers may comprise geotextile layers and the filter material may be sand or glass, for example.

1 . A track bed composite structural element for use in railway track engineering, the structural element comprising:
 an upper water permeable layer,   a lower water permeable layers and   a filter material layer provided between the upper and lower water permeable layers.   
   
   
       2 . A track bed structural element according to  claim 1 , wherein the upper and lower water permeable layers comprise geo-textile materials. 
   
   
       3 . A track bed structural element according to  claim 1 , wherein the filter layer comprises a filter material encapsulated within the structural element. 
   
   
       4 . A track bed structural element according to  claim 1 , wherein:
 i) the filter material comprises a particulate filter material; and/or   ii) the filter material comprises a sand filter material.   
   
   
       5 . (canceled) 
   
   
       6 . A track bed structural element according to  claim 1 , wherein the filter layer is effective to filter out clay or silt, whilst permitting liquid water to pass across the element between the upper and lower water permeable layers. 
   
   
       7 . A track bed structural element according to  claim 1 , wherein the filter layer inhibits migration of the filter material to spaced zones of the structural elements. 
   
   
       8 . A track bed structural element according to  claim 6 , wherein the filter layer includes a dividing structure arranged to inhibit migration of the filter material to spaced zones of the structural element. 
   
   
       9 . A track bed structural element according to  claim 7 , wherein:
 1) the dividing structure divides the filter layer into separate zones or compartments; and/or   ii) the dividing structure comprises a permeable material; and/or   iii) the dividing structure comprises an impermeable material.   
   
   
       10 . (canceled) 
   
   
       11 . (canceled) 
   
   
       12 . A track bed structural element according to  claim 7 , wherein:
 i) the dividing structure comprises a flexible material structure; and/or   ii) the dividing structure comprises a relatively rigid material structure; and/or   iii) the dividing structure divides the filter layer into a plurality of elongate compartments; and/or   iv) the dividing structure divides the filter layer into a grid array of cells.   
   
   
       13 . (canceled) 
   
   
       14 . (canceled) 
   
   
       15 . (canceled) 
   
   
       16 . A track bed structural element according to  claim 1 , in the form of an envelope or panel having opposed major surfaces and a relatively shallow depth dimension. 
   
   
       17 . A track bed structural element according to  claim 1 , further comprising an elongate sealing flap extending from an edge of the structural element. 
   
   
       18 . A track bed structural element according to  claim 17 , wherein:
 i) the sealing flap is secured to the lower water permeable layer; and/or   ii) a sealing flap is secured to the upper water permeable layer; and/or   iii) the sealing flap is water impermeable; and/or   iv) the sealing flap extends along substantially an entire edge of the structural element.   
   
   
       19 . (canceled) 
   
   
       20 . (canceled) 
   
   
       21 . (canceled) 
   
   
       22 . (canceled) 
   
   
       23 . (canceled) 
   
   
       24 . (canceled) 
   
   
       25 . (canceled) 
   
   
       26 . (canceled) 
   
   
       27 . A railway track bed comprising:
 a sub-grade layer;   a track bed composite structural element including an upper water permeable layer,   a lower water permeable layer, and a filter material layer provided between the upper and lower water permeable layers; and   a ballast layer above the track bed structural element.   
   
   
       28 . A railway track bed according to  claim 27 , wherein the structural element is laid on top of the sub-grade layer and the ballast is laid on top of the structural element. 
   
   
       29 . A method of construction of a railway track bed, the method comprising;
 laying a track bed composite structural element on a sub-grade layer and subsequently laying a ballast layer above the track bed structural element, wherein the track bed composite structural element includes an upper water permeable layer, a lower water permeable layer, and a filter material layer disposed between the upper and lower water permeable layers.