SECOND PROGRESS REPORT ON PERFORMANCE OF FILTER MATERIALS

Tentative results of the first phase of the cooperative program indicated that the stability of the filter adjacent to the pipe perforation was not a function of material sorting and consequent bridging of large grain sizes. Further study of this tentative finding was undertaken by means of a series of flow tests in which the filter materials was compacted to six different specific weights. The major conclusions developed during the present phase of the investigation are as follows: 1. There is an optimum compaction of concrete sand when used as a filter material. The optimum compaction is a function of velocity of flow through the filter. The optimum compaction applies to both filter stability and flow capacity. 2. Compaction of the filter in excess of the optimum results in filter destruction, while compaction less than the optimum leads to readjustment of the filter and eventual stability. 3. Readjustment of the filter material is accomplished by the migration of fine particles toward the pipe perforations. This migration continues until the number of fines passing through the coarser material adjacent to the perforations causes physical binding. After binding the filter is stable for all velocities equal to or less than the velocity at the time of binding. 4. Determination of the required size of drain pipe for a hypothetical case indicates that many subdrains are being installed with pipe diameters at least 75 percent oversize.

  • Supplemental Notes:
    • This is a cooperative research program conducted by the Association of American Railroads and the University of Illinois.
  • Corporate Authors:

    Association of American Railroads Research Center

    3140 South Federal Street
    Chicago, IL  USA  60616
  • Authors:
    • Guillou, J C
    • Lanyon, R F
  • Publication Date: 1961-5

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 18 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00083043
  • Record Type: Publication
  • Source Agency: Association of American Railroads Research Center
  • Report/Paper Numbers: #ER-12
  • Files: TRIS
  • Created Date: Mar 26 1975 12:00AM