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Overall requirements for TMFs

Each stabilisation or modification method and formulation must be classified with an equivalent to one of the four defined classes of backfill material permitted in A1, as follows:
  1. Class A TMF Material – equivalent to Class A Graded Granular Backfill Material,
  2. Class B TMF Material – equivalent to Class B Granular Backfill Material,
  3. Class C TMF Material – equivalent to Class C Cohesive/Granular Backfill Material,
  4. Class D TMF Material – equivalent to Class D Cohesive Backfill Material.
The TMF material classification must be based on the soaked % CBR or equivalent value proven during the development and laboratory testing, in accordance with Table A9.2.
The CBR value must be determined by laboratory testing in accordance with the principles of BS 1377 (soil) or BS1924 (material with hydraulic binder), with the following requirements:
  1. Conventional steel test moulds may be unsuitable for some TMF materials (owing to the requirement to remove coarse aggregate >20 mm in size) and in-situ testing may therefore need to be considered. The preparation of TMF test samples may include test cores extracted from site.
  2. Following preparation, the test samples are stored at ambient temperature for up to 90 days after the placement of the material on site.
  3. The laboratory CBR test is performed on samples in a soaked condition (soaked for 4 days before testing).
  4. The tests are carried out by a UKAS accredited laboratory unless mutually agreed otherwise.
  5. On site, a recognised appropriate direct or indirect equivalent test method may be used.