Guidelines for the design and construction of soil embankments are sufficiently developed so that unsatisfactory performance of these fills is relatively rare. The same is true for rock fills. However, there are transition materials or "soft rocks" for which placement in large chunks may lead to highly unsatisfactory embankment performance. Shales are a prominent example, for the large pieces may degrade (slake) into soil in service. This soil may in turn sift down into the large voids, resulting in large settlements and even slope instability. The harder and more durable shales can probably be placed as rock fills if certain precautions are taken. The shales of very low durability must be thoroughly degraded at the end of compaction; i.e., they must be treated as soil fills. And a full spectrum of durabilities exists between these limits. The engineer obviously needs a classification system that will establish where, in the possible range of relative durabilities, a potential embankment shale lies. Such a classification for Indiana shales was developed by sampling materials and subjecting them to a battery of durability, stability, and other tests. The durability tests were the standard ones used for mineral aggregates, but were modified in severity to account for the soft rock being evaluated. It was concluded that the desired classification into four groupings, soil-like, intermediate-1, intermediate-2, and rock-like shales, could be accomplished with four simple tests: one-cycle slaking in water, slake-durability on an initially dry sample, slake-durability on a soaked sample, and a modified sodium sulfate soundness test. The paper describes the Indiana shales tested, the tests, and the response of the shales to the tests. It concludes with a flow chart showing how the tests are used to accomplish the shale classification.

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  • Accession Number: 00080984
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Mar 26 1975 12:00AM