Water detention system incorporating a composite drainage membrane

摘要

A water detention system comprises a sub-base of crushed rock or stone overlying an impermeable layer which may be naturally-occurring, as in an impermeable sub-grade, or may be formed by an impermeable membrane laid over the sub-grade prior to the sub-base layer. Over the sub-base layer is an incompletely impermeable layer the impermeability of which is compromised by openings in the form of slits or by spacing between adjacent strips forming the layer. These openings allow water to percolate downwardly through the layer into the sub-base, but substantially inhibit the escape of moisture by evaporation thereby serving to retain the collected water. Above the incompletely impermeable layer may be a laying course of finer particulate material such as pea gravel over which may be laid a wear surface of slabs or blocks to form an area for traffic, such as a roadway or parking area.

主权项

1. A water detention system comprising a sub-base of particulate material in a layer having a substantial number of voids over an at least substantially impermeable sub-grade or a preliminarily positioned at least substantially impermeable membrane, with an overlying substantially unidirectionally porous layer able to allow water to infiltrate from above into the sub-base but which is such as substantially to resist loss of water from the sub-base by evaporation such that water collecting on its upper surface can infiltrate into the sub-base to be retained therein, wherein said substantially unidirectionally porous layer comprises a membrane having an upper nonwoven textile material component the fibres or filaments of which are heat bonded and a lower woven textile component the filaments of which are composed of flat plastics strips, wherein said woven and non-woven components are bonded together, the weave of the flat plastic strips of the lower woven textile component being sufficiently tight so as to provide interstices between adjacent woven filaments to allow water to pass therethrough but which prevent water vapour from escaping whereby to resist evaporative loss from the sub-base.