SETT ATT FRAMSTELLA EN FILTERBRUNN

摘要

1484702 Wells &c FERDINAND AUFSCHLAGER KG 26 Nov 1974 [28 Nov 1973] 48395/74 Heading E1F A filter well for water comprises a plurality of vertical boreholes overlapping along the whole of their lengths and containing gravel. The boreholes may be formed along straight (Figs. 1 and 3 not shown), curved or closed lines, as viewed from above. The boreholes may be formed by a dry drilling method in which a casing is inserted into the borehole simultaneously with drilling and the casing is subsequently removed as the borehole is filled with gravel. A filter pipe F provides a water collection space and the gravel surrounding the pipe is of a coarser grade K2 than the gravel of the other boreholes. The boreholes may alternatively be formed without the use of a drilling device and in the presence of a borehole-wall-stabilizing slurry.