| 摘要 |
<p>Bentonite, and other water-sensitive materials in granulate form, are introduced into boreholes. The material is borne into the borehole through a conduit, in which a flow of air (or nitrogen) not only transports the material but also keeps water that may be present in the borehole from entering the conduit. The materials are contained, above ground, in hoppers arranged to feed in parallel into the conduit. Material from a selected hopper enters via a respective valve into the conduit. The hoppers are pressurized to ensure the moving gases in the conduit do not enter the fall pipe. Having turned the air on, the technician lowers the conduit to the bottom of the borehole; then he opens the valve to admit the selected filler material; then he withdraws the conduit gradually and progressively up the borehole, depositing the material. The conduit is of flexible material, and can be held in the hand, to assist in sensing the flow of material.</p> |
