| 摘要 |
<p>The system controls the amount of moisture in a plot of land, such as a tennis court, in the open air, and below which a number of drainpipes are laid. The ground is excavated to a depth below the topsoil, and material impervious to water is laid to form a bowl. The drainpipes are then placed in position, and covered in turn with a sand mixture and the topsoil, after which the pipes are connected to a system delivering and extracting water. The sand mixture can be 75 per cent by weight of coarse sand and 25 per cent by weight of stealite (S1C). Gravel can be used as the top covering and a plastics for the impervious material.</p> |
